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2018 - An atomic-level look at the structure-property relationship of cerium-doped glasses using classical molecular dynamics [Articolo su rivista]
Pedone, Alfonso; Tavanti, Francesco; Malavasi, Gianluca; Menziani, Maria Cristina

Ce-containing bioactive glasses are of great interest in biomedical field since they exert antioxidant properties associated with low toxicity and a broad spectrum of bacteriostatic activities. The results obtained by classical molecular dynamics simulations allow the elucidation of the correlations between the effect of the inclusion of cerium doping ions into the structure of phosphosilicate and silicate bioactive glasses and their properties. The addition of small quantities of Ce to the silicate bioglass favours the depolymerisation of the silicate network with a positive effect on the ability to dissolve in body fluid. Moreover, the under coordination of both the Ce3+ and Ce4+ species in these glasses enhances their catalytic activity towards hydrogen peroxide. Conversely, the formation of cerium phosphate domains in the phosphosilicate glasses leads to detrimental effects for both the solubility and the catalytic activity of the glasses. Finally, a new quantitative view of the structure-activity relationships governing the macroscopic properties of these glasses has been obtained by means of structural descriptor that takes into account the fragmentation of the Si network and the consequent rearrangement of the modifier ions and the network destruction per cerium unit descriptor.

2018 - Highly-Bioreactive Silica-Based Mesoporous Bioactive Glasses Enriched with Gallium (III) [Articolo su rivista]
Sanchez-Salcedo, S.; Malavasi, G.; Salinas, A. J.; Lusvardi, Gigliola; Rigamonti, Luca; Menabue, L.; Vallet-Regi, M.

Beneficial effects in bone cell growth and antibacterial action are currently attributed to Ga3+ ions. Thus, they can be used to upgrade mesoporous bioactive glasses (MBGs), investigated for tissue engineering, whenever they released therapeutic amounts of gallium ions to the surrounding medium. Three gallium-enriched MBGs with composition (in mol %) xSiO₂-yCaO-zP₂O₅-5Ga₂O₃, being x = 70, y = 15, z = 10 for Ga_1; x = 80, y = 12, z = 3 for Ga_2; and x = 80, y = 15, z = 0 for Ga_3, were investigated and compared with the gallium-free 80SiO₂-15CaO-5P₂O₅ MBG (B). 29Si and 31P MAS NMR analyses indicated that Ga3+ acts as network modifier in the glass regions with higher polymerization degree and as network former in the zones with high concentration of classical modifiers (Ca2+ ions). Ga_1 and Ga_2 exhibited a quick in vitro bioactive response because they were coated by an apatite-like layer after 1 and 3 days in simulated body fluid. Although we have not conducted biological tests in this paper (cells or bacteria), Ga_1 released high but non-cytotoxic amounts of Ga3+ ions in Todd Hewitt Broth culture medium that were 140 times higher than the IC90 of Pseudomonas aeruginosa bacteria, demonstrating its potential for tissue engineering applications.

2017 - Cerium-doped bioactive 45S5 glasses: spectroscopic, redox, bioactivity and biocatalytic properties [Articolo su rivista]
Nicolini, Valentina; Malavasi, Gianluca; Menabue, Ledi; Lusvardi, Gigliola; Benedetti, Francesco; Valeri, Sergio; Luches, Paola

The ability of Ce-containing bioactive glasses, based on 45S5 Bioglass®, to inhibit oxidative stress in terms of reduction in hydrogen peroxide and superoxide (O2−), by mimicking the catalase and superoxide dismutase activity is reported in this work. The characterization is performed on the powders of pristine glasses and after the soaking in H2O2solutions and simulated body fluid. The glass samples are analysed by XPS, XRD, UV–Vis and FT-IR. The best catalyst activities are obtained for the glass with the highest content of cerium (H_5.3 = 5.3 mol% of CeO2in the nominal glass composition), and the best Ce3+/Ce4+ratio in terms of catalase mimetic activity is found to be a function of H2O2concentration. Moreover, the detailed study of the surface during the mimic enzymatic activity tests shows the formation of a Ca-P-rich layer on the glass surface, where the presence of Ce ions favours the formation of CePO4. The phosphate in turn inhibits the formation of hydroxyapatite, decreasing the bioactivity of the glass with the highest of CeO2in the glass composition. This work shows the effect of Ce3+/Ce4+ratio towards the catalase mimetic activity and for the first time the superoxide dismutase mimetic activity of Ce-containing 45S5-derived glasses.

2017 - Structure of active cerium sites within bioactive glasses [Articolo su rivista]
Benedetti, Francesco; Luches, Paola; D'Addato, Sergio; Valeri, Sergio; Nicolini, Valentina; Pedone, Alfonso; Menziani, Maria Cristina; Malavasi, Gianluca

The inclusion of small amounts of cerium within the matrix of bioactive glasses, a class of materials used for bone tissue reparation and regeneration, adds a very important antioxidant property. In this work we investigate the local structure around cerium ions in cerium oxide doped bioactive phosphosilicate and silicate glasses, by X-ray absorption fine structure at the Ce K-edge, combined with classical molecular dynamics (MD) simulations. The local structure of the active Ce sites results significantly different from the one in bulk cerium oxide phases. A contracted Ce–O first shell distance with respect to bulk oxides is detected, in full agreement with the results of MD simulations. The cerium environment in the glass matrix at different stages of the reaction with H2O2 does not show significant modifications, in spite of the very high catalytic activity. The accurate description of the active Ce sites within bioactive glasses reported in this work is an important step toward an atomic scale understanding of the material functionalities.

2016 - Abstracts from the X INSTM National Conference on Materials Science and Technology [Abstract in Atti di Convegno]
Malavasi, Gianluca; Nicolini, Valentina; Gambuzzi, Elisa; Menabue, Ledi; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola; D’Addato, Sergio; Valeri, Sergio

The ability of a Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of H2O2, by mimicking the catalase enzyme activity is demonstrated for the first time. The antioxidant properties of bioactive glasses containing CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS, UV-Vis and magnetic measurements allowed us to determine the Ce3+/Ce4+ ratio (bulk and surface) and to correlate it with the ability of the samples to show catalase mimetic activity. We have found that the bioactive glass (23.2Na2O-25.7CaO-43.4SiO2-2.4P2O5-5.3CeO2) immersed in 0.1M H2O2 aqueous solution is able to degrade 90% of it in one week.

2016 - SiO2-CaO-P2O5 bioactive glasses: A promising curcuminoids delivery system [Articolo su rivista]
Nicolini, Valentina; Caselli, Monica; Ferrari, Erika; Menabue, Ledi; Lusvardi, Gigliola; Saladini, Monica; Malavasi, Gianluca

In this paper, we report the study of the loading and the release of curcuminoids by bioactive glasses (BG) and mesoporous bioactive glasses (MBG). Through a detailed spectroscopic study, it was possible to determine the amount and the type of molecules released in water and in simulated body fluid (SBF). In particular, curcumin and K2T21 show a good ability to be released in di-keto and keto-enolic form, depending from the pH. However, after 24 h, the amount of pristine curcumin release is very low with a consequent increment of degradation products derived by curcuminoids. The presence of -OH groups on curcuminoids is a fundamental pre-requisite in order to obtain a high loading and release in polar solution such as water and SBF. The substrate on which we loaded the drugs does not seem to affect significantly the loading and the release of the drugs. The environment, instead, affects the release: for all the drugs, the release in SBF, buffered at pH of 7.4, is slightly worse than the release in water (basic pH values).

2016 - The effect of composition on structural, thermal, redox and bioactive properties of Ce-containing glasses [Articolo su rivista]
Nicolini, Valentina; Varini, Elena; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola

The effect of phosphate on the ability of Ce-containing bioactive glasses to inhibit oxidative stress was studied on compositions based on Hench (46.2%SiO224.3%Na2O26.9%CaO2.6P2O5, mol%) and Kokubo (50.0%SiO225.0%Na2O25.0%CaO) glasses. In particular, the reduction of catalase mimetic activity of Ce-containing glasses due to the presence: i) of P2O5 in the glass compositions, and ii) of phosphate groups in the solution employed for catalase mimetic activity tests was explained and rationalized by combining SEM, XPS, XRD, DTA, FT-IR and UV-vis experiments with Molecular Dynamics simulations.The results suggest that the Ce ions play a different structural role in the two series of glasses. In particular, in phosphate free glasses Ce is coordinated by non-bridging oxygens (NBOs) originated from the disruption of the silicate network, whereas in phosphate containing glasses the NBOs around Ce ions belong to orthophosphate groups. The latter groups stabilize the Ce3+ species subtracting them from the interconversion process between Ce3+ and Ce4+, which is of fundamental importance for the exhibition of the catalase mimetic activity.

2015 - Evidence of catalase mimetic activity in ce(3+)/ce(4+) doped bioactive glasses [Articolo su rivista]
Nicolini, Valentina; Gambuzzi, Elisa; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Lusvardi, Gigliola; Pedone, Alfonso; Benedetti, Francesco; Luches, Paola; D'Addato, Sergio; Valeri, Sergio

The ability of Ce-containing bioactive glasses to inhibit oxidative stress in terms of reduction of hydrogen peroxide, by mimicking the catalase enzyme activity is demonstrated here for the first time. The antioxidant properties of three bioactive glasses containing an increasing amount of CeO2 have been evaluated by following the degradation of hydrogen peroxide with time after immersion in H2O2 aqueous solutions with different concentration. XPS and UV-vis measurements allowed us to determine the Ce(3+)/Ce(4+) ratio in the bulk and on the glass surface, and to correlate it with the ability of the samples to show catalase mimetic activity. Interestingly, we have found that the bioactive glass with composition 23.2Na2O-25.7CaO-43.4SiO2-2.4P2O5-5.3CeO2 immersed in 0.1 M H2O2 aqueous solution is able to degrade 90% of it in 1 week. The reduction in bioactivity of the glasses with increasing CeO2 content is here rationalized in terms of a lower amount of phosphate groups available for the hydroxyapatite layer formation, after binding with cerium ions. In fact, classical molecular dynamics simulations revealed that the addition of CeO2 leads to the formation of cerium phosphate rich regions. The formation of an insoluble CePO4 crystalline phase is also observed by XRD analysis after thermal treatment of the glass samples.

2014 - Biovetri come potenziali drug delivery systems ed impianti con proprietà antiossidanti [Relazione in Atti di Convegno]
Nicolini, Valentina; Malavasi, Gianluca; Ferrari, Erika; Benedetti, Francesco; Luches, Paola; Lusvardi, Gigliola; Castagnetti, Mattia; Valeri, Sergio; Saladini, Monica; Menabue, Ledi

Fra i biomateriali (“materiali progettati per essere usati a contatto con tessuti viventi, organismi o microorganismi”, definizione IUPAC), i biovetri ricevono un interesse sempre maggiore. Tali materiali trovano infatti largo impiego in chirurgia odontoiatrica ed ortopedica, nella produzione di impianti dentali, protesi o riempitivi ossei. Attualmente l’interesse è rivolto soprattutto ai biovetri di seconda e terza generazione: biovetri che oltre a formare un legame chimico coi tessuti che li circondano, sono capaci di indurre una specifica risposta a livello molecolare nei tessuti stessi, come l’osteoinduzione. I biovetri possono essere prodotti con processi ad alte temperature (metodo per fusione) o a basse temperature con i metodi Sol-Gel, ottenendo in questo caso biovetri porosi o con il metodo EISA ottenendo biovetri mesoporosi. Attualmente presso il nostro laboratorio due sono le linee di ricerca sui biomateriali: i) sintesi di biovetri Sol-Gel (BGSG) ed EISA (MBGSG) e verifica della possibilità di impiegarli come drug delivery systems (DDS) di molecole con proprietà antitumorali, quali i curcuminoidi; ii) sintesi per fusione di biovetri a partire dal vetro 45S5, drogati con CeO2 al fine di verificare la Catalase e SOD mimic-like activity di tali sistemi. Sui vetri porosi e mesoporosi, caricati con curcumina ed un suo derivato (K2T21) sono stati effettuati test di rilascio statico e dinamico in SBF. I rilasci sono stati quantificati ed in entrambi i casi le concentrazioni raggiunte dai farmaci nell’organismo sono nell’ordine del micromolare, ovvero sufficienti per manifestare l’attività antitumorale. Per ciò che concerne la valutazione della Catalase mimic-like activity, sono stati condotti test con H2O2 ed è stato verificato che i biovetri ottenuti per fusione manifestano questa proprietà. Sono inoltre in atto misure di rilascio di cerio in acqua e soluzione di SBF.

2014 - Conjugation of amino-bioactive glasses with 5-aminofluorescein as probe molecule for the development of pH sensitive stimuli-responsive biomaterials [Articolo su rivista]
Valentina Aina;Gianluca Malavasi;Claudio Magistris;Giuseppina Cerrato;Gianmario Martra;Guido Viscardi;Ledi Menabue;Gigliola Lusvardi

Bioceramics, such as silica-based glasses, are widely used in bone and teeth restoration. Nowadays, the association between nanotechnology and pharmacology is one of the most promising research fields in cancer therapy. The advanced processing methods and new chemical strategies allow the incorporation of drugs within them or on their functionalized surfaces. Bioceramics can act as local drug delivery systems to treat bone and teeth diseases. The present paper reports data related to the development of a pH-stimuli responsive bioactive glass. The glass conjugation with 5-aminofluorescein (5-AF), through a pH-sensitive organic spacer, allows to produce a pH-responsive bioactive biomaterial: when it is exposed to specific pH changes, it can favour the release of 5-AF directly at the target site. 5-AF has been chosen as a simple, low cost, non toxic model to simulate doxorubicin, an anticancer drug. As doxorubicin, 5-AF contains an amino group in its structure in order to form an amide bond with the carboxylic functionalities of the glass. Raman spectroscopy and thermal analysis confirm the glass conjugation of 5-AF by means of an amide bond; the amount of 5-AF loaded was very high (a parts per thousand 65 and 44 wt%). The release tests at two different pH (4.2 and 7.4) show that the amount of released 5-AF is higher at acid pH with respect to physiological one. This preliminary datum evidenced that a pH-sensitive drug delivery system has been developed. The low amount of 5-AF released (< 1 wt% of the total 5-AF) is due to the very low solubility of 5-AF in aqueous medium. This disadvantage, may be overcome in a dynamic environment (physiological conditions), where it is possible to obtain a drug release system ensuring an effective therapeutic dose for long times and, at the same time, avoiding the drug toxicity.

2014 - In vitro antibacterial capacity and cytocompatibility of SiO2–CaO–P2O5meso-macroporous glass scaffolds enriched with ZnO [Articolo su rivista]
Sandra Sánchez-Salcedo;Shruti Shruti;Antonio J. Salinas;Gianluca Malavasi;Ledi Menabue;Maria Vallet-Regí

Zn2+ ions exhibit osteogenic, angiogenic and antimicrobial properties. For this reason, they are often added in small amounts to bioceramics being investigated for bone tissue engineering. In this paper, the cytocompatibility and antibacterial properties of 80% SiO2-15% CaO-5% P2O5 (mol%) mesoporous bioactive glass (MBG) scaffolds substituted with 4.0% and 7.0% of ZnO were studied and compared with the Zn-free scaffold. Cell proliferation, morphology, differentiation and cytotoxic effects of Zn2+ ions released from the samples were examined by culturing human osteoblast-tike cells (HOS) osteoblasts both in the presence of sample extracts and on the scaffold surface. The bacterial inhibition capacity of the scaffolds was explored by using Gram-positive Stapylococcus aureus bacteria, responsible for numerous infections in orthopedic surgery, to simulate a severe infection. Our results show that the Zn-MBG scaffolds possess a hierarchical meso-macropore structure suitable for osteobtast growth. Furthermore, the amount of Zn2+ released from the scaffold with 4.0% ZnO was found to be more favorable for HOS cell development than that released from the scaffold including 7.0% ZnO. Zn2+ released to the medium from both scaffolds exhibited antibacterial properties against S. aureus. Thus, the cytocompatibility and the antibacterial ability exhibited by the MBG scaffold containing 4.0% ZnO make it a suitable candidate for bone regeneration applications.

2014 - New Formulation of Functionalized Bioactive Glasses to Be Used as Carriers for the Development of pH-Stimuli Responsive Biomaterials for Bone Diseases [Articolo su rivista]
Valentina Aina;Claudio Magistris;Giuseppina Cerrato;Gianmario Martra;Guido Viscardi;Gigliola Lusvardi;Gianluca Malavasi;Ledi Menabue

The aim of the present contribution is to prepare a functionalized bioactive glass potentially useful as prosthetic material, but also able to release organic molecules in response to a change of the pH environment. By this approach it is possible to develop devices which can be used for a triggered drug release in response to specific stimuli; this is an attractive research field, in order to avoid either systemic and/or local toxic effects of drugs. In particular, in the present paper we report data related to the development of a new formulation of bioactive glasses, their functionalization with organic molecules to obtain a pH-sensitive bond, their physicochemical characterization and in vitro bioactivity in simulated biological fluids (SBF), and organic molecule delivery tests at different pH. The glass functionalization, by means of a covalent reaction, allows us to produce a model of pH-responsive bioactive biomaterial: when it is exposed to specific pH changes, it can favor the release of the organic molecules directly at the target site. Cysteamine and 5-aminofluorescein are used as model molecules to simulate a drug. The materials, before and after the different functionalization steps and in vitro release tests at different pH, have been characterized by means of different experimental techniques such as X-ray powder diffraction (XRPD), Raman, FTIR and fluorescence spectroscopies, N-2 adsorption, thermogravimetric (TGA) and elemental analysis.

2013 - Bioglasses: glasses for medical applications [Abstract in Atti di Convegno]
Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Pedone, Alfonso

bioglasses for medical applications

2013 - Curcumin release from cerium, gallium and zinc containing mesoporous bioactive glasses [Articolo su rivista]
Shruti Shruti; Antonio J. Salinas; Erika Ferrari; Gianluca Malavasi; Gigliola Lusvardi; Antonio L. Doadrio; Ledi Menabue; M. Vallet-Regi

Curcumin is the main component of turmeric which is being used since centuries due to medicinal ben- efits with no side effects. In this paper, 80%SiO2–15%CaO–5%P2O5 mesoporous bioactive glasses (MBGs) containing two different concentrations of Ce2O3, Ga2O3 (1.0% and 2.0%) and ZnO (2.0% and 4.0%) (in mol%) were synthesized by evaporation induced self-assembly (EISA) method to investigate their potential as drug delivery system (DDS) for curcumin. Impregnation method was applied for incorporat- ing curcumin into MBGs and in vitro release was performed in simulated body fluid (SBF) at 37 °C up to 72 h. The substituted MBGs exhibited mesostructure and textural properties good enough for drug deliv- ery. Highest gallium and cerium substituted MBGs incorporated drug more than unsubstituted MBG (B_MBG) due to high affinity of curcumin towards hard Lewis acids. However, during in vitro drug release, B_MBG and lowest cerium, gallium and zinc substituted MBGs showed curcumin release that is capable to exert pharmacological activities. On the other hand, strong interaction between curcumin and substituent caused reduction in drug release from the other set of MBGs with negligible release from 2.0%Ga2O3. Furthermore, MBGs loaded with curcumin showed quick in vitro response except 4.0%ZnO. Hence, lowest Ce, Ga and Zn substituted MBGs can be considered as drug release system for curcumin because they showed higher drug release with quick in vitro bioactivity and the added values of the substituents.

2013 - Gallium-containing phosphosilicate glasses: functionalization and vitro bioactivity [Articolo su rivista]
Lusvardi G.; Malavasi G.; Menabue L.; Shruti S.

A gallium containing glass 45.7SiO2•24.1Na2O•26.6CaO•2.6P2O51.0Ga2O3, referred to as Ga1.0, and a parent Ga-free glass 46.2 SiO2•24.3Na2O•26.9CaO•2.6P2O5, corresponding to Bioglass® 45S5, (H glass) were functionalized with Tetraethoxysilane (TEOS) and (3-Aminopropyl)triethoxysilane (APTS) in order to improve the ability of the glasses to bond biomolecuels. Functionalization with TEOS and APTS promoted increment in OH groups and formation of NH2 groups on the glass surface, respectively. The presence of OH or NH2 groups was investigated by means of IR spectroscopy and elemental analysis. Functionalized glasses were investigated by an in-vitro study in simulated body fluid (SBF) for defining the effect of functionalization on their bioactivity as compared to plain glasses. The results showed that the functionalization was obtained and bioactivity was maintained: the surfaces of both functionalized glasses were covered by a layer of apatite by 30 days of immersion in SBF. In addition, CaCO3 was also identified on the surface of APTS functionalized glasses. No gallium release was detected during the immersion in SBF.

2013 - Gold-containing bioactive glasses: a solid-state synthesis to produce alternative biomaterials for bone implantations [Articolo su rivista]
V. Aina;G. Cerrato;G. Martra;L. Bergandi;C. Costamagna;D. Ghigo;G. Malavasi;G. Lusvardi;L. Menabue

A new melted bioactive system containing gold nanoparticles (AuNPs) was prepared exploiting a post-synthesis thermal treatment that allows one to modify crystal phases and nature, shape and distribution of the gold species in the glass-ceramic matrix as evidenced by UV-visible spectroscopy, transmission electron microscopy and powder X-ray diffraction analysis. In human MG-63 osteoblasts the presence of Aun+ species caused an increase of lactate dehydrogenase leakage and malonyldialdehyde production, whereas Hench's Bioglass HAu-600-17 containing only AuNPs did not cause any effect. In addition, HAu-600-17 caused in vitro hydroxyapatite formation and an increase of specific surface area with a controlled release of gold species; this material is then suitable to be used as a model system for the controlled delivery of nanoparticles.

2013 - Mesoporous bioactive scaffolds prepared with cerium-, gallium- and zinc-containing glasses [Articolo su rivista]
S. Shruti; A.J. Salinas; G. Lusvardi; G. Malavasi; L. Menabue; M. Vallet-Regi.

Mesoporous bioactive glass scaffolds (MBG-Scs), based on 80% SiO 2-15% CaO-5% P 2O 5 (in mol.%) mesoporous sol-gel glasses substituted with Ce 2O 3, Ga 2O 3 (both 0.2% or 1.0%) and ZnO (0.4% or 2.0%), were synthesized by combination of evaporation-induced self-assembly and rapid prototyping techniques. Cerium, gallium and zinc trace elements were selected because of their inherent beneficial biological properties. Fabricated scaffolds were characterized and compared with unsubstituted scaffold (B-Sc). All of them contained well interconnected ultralarge pores (pores >400 μm) ideal for vascular ingrowth and proliferation of cells. Macropores of size 100-400 μm were present inside the scaffolds. In addition, low-angle X-ray diffraction showed that B-Sc and scaffolds with substituent contents up to 0.4% exhibited ordered mesoporosity useful for hosting molecules with biological activity. The textural properties of B-Sc were a surface area of 398 m 2 g -1, a pore diameter of 4.3 nm and a pore volume of 0.43 cm 3 g -1. A slight decrease in surface area and pore volume was observed upon substitution with no distinct effect on pore diameter. In addition, all the MBG-Scs except 2.0% ZnO-Sc showed quite quick in vitro bioactive response. Hence, the present study is a positive addition to ongoing research into preparing bone tissue engineering scaffolds from bioceramics containing elements of therapeutic significance.

2013 - New insights into the bioactivity of SiO2–CaO and SiO2–CaO–P2O5 sol–gel glasses by molecular dynamics simulations [Articolo su rivista]
G. Malavasi; L. Menabue; M. C. Menziani;A. Pedone; A. J. Salinas; M. Vallet-Regı.

The structures of binary xCaO . (100 - x)SiO2glasses with x = 10, 20 and 30 mol-% and ternary(20 - x)CaO . xP2O5 . 80SiO2 glasses with x = 3, 10, 15,17 and 20 mol-% have been studied by means of classicalmolecular dynamics simulations using both the melt-quenchedand the sol–gel protocols. The structural picturederived correlates the bioactive behaviour to the combinedeffects of the connectivity of the extended silicate networkand to the tendency to form (or not to form) non-homogeneousdomains. In this context, a mathematical relationshipthat relates the Ca/P ratio in the Ca phosphatemicro-segregation zones to the P2O5 content in ternaryglasses has been developed and this has been used to finetuningthe optimum amount of P in a glass for its highest invitro bioactivity. The composition with optimal Ca/P ratio,80SiO2 . 14.8CaO . 5.2P2O5 has been synthesized and the results of bioactivity tests have confirmed the prediction.

2013 - Sr-containing hydroxyapatite: morphologies of HA crystals and bioactivity on osteoblast cells [Articolo su rivista]
Valentina Aina; Loredana Bergandi; Gigliola Lusvardi; Gianluca Malavasi ; Flora E. Imrie; Iain R. Gibson; Giuseppina Cerrato; Dario Ghigo

A series of Sr-substituted hydroxyapatites (HA), of general formula Ca(10−x)Srx(PO4)6(OH)2, where x=2 and 4, were synthesized by solid state methods and characterized extensively. The reactivity of these materials in cell culture medium was evaluated, and the behavior towards MG-63 osteoblast cells (in terms of cytotoxicity and proliferation assays) was studied. Future in vivo studies will give further insights into the behavior of the materials. A paper by Lagergren et al. (1975), concerning Sr-substituted HA prepared by a solid state method, reports that the presence of Sr in the apatite composition strongly influences the apatite diffraction patterns. Zeglinsky et al. (2012) investigated Sr-substituted HA by ab initio methods and Rietveld analyses and reported changes in the HA unit cell volume and shape due to the Sr addition. To further clarify the role played by the addition of Sr on the physico-chemical properties of these materials we prepared Sr-substituted HA compositions by a solid state method, using different reagents, thermal treatments and a multi-technique approach. Our results indicated that the introduction of Sr at the levels considered here does influence the structure of HA. There is also evidence of a decrease in the crystallinity degree of thematerials upon Sr addition. The introduction of increasing amounts of Sr into the HA composition causes a decrease in the specific surface area and an enrichment of Sr-apatite phase at the surface of the samples. Bioactivity tests show that the presence of Sr causes changes in particle size and/ormorphology during soaking inMEMsolution; on the contrary the morphology of pure HA does not change after 14 days of reaction. The presence of Sr, as Sr-substituted HA and SrCl2, in cultures of human MG-63 osteoblasts did not produce any cytotoxic effect. In fact, Sr-substituted HA increased the proliferation of osteoblast cells and enhanced cell differentiation: Sr in HA has a positive effect on MG-63 cells. In contrast, Sr ions alone, at the concentrations released by Sr-HA (1.21–3.24 ppm), influenced neither cell proliferation nor differentiation. Thus the positive effects of Sr in Sr-HA materials are probably due to the co-action of other ions such as Ca and P.

2013 - Study of the Structural Role of Gallium and Aluminum in 45S5 Bioactive Glasses by Molecular Dynamics Simulations [Articolo su rivista]
Gianluca Malavasi;Alfonso Pedone;Maria Cristina Menziani

The structural properties of phosphosilicate glasses based on the 45S5 Bioglass doped with gallium and aluminum (46.2SiO(2)center dot 24.3Na(2)O center dot 26.9CaO center dot 2.6P(2)O(5)center dot 1.0X(2)O(3), X = Ga or Al) are investigated by means of classical molecular dynamics simulations. Structural features of the two compositions are compared with those of the original 45S5 Biog,lass in order to relate them to the different known bioactivities of these materials. Differences in the coordination environments of Ga and Al, network connectivity, and ion aggregation reveal a microscopic model of these glasses which supports the interpretation of the experimental data and provides new insight into the different biological behaviors of Ga- and Al-containing phosphosilicate glasses. Although Ga is found predominantly in a 4-fold coordination environment, small amounts of 5- and 6-fold coordinated atoms have been detected depending on the interatomic potential model employed. This suggests its possible intermediate role in phosphosilicate glasses. On the contrary, Al plays a network former role and leads to glasses with a more polymerized structure. Interestingly, the results show an increased propensity for aggregation of the Ca2+ and PO43- ions in the Al-containing phosphosilicate glasses with respect to the Ga-containing ones. This leads to insoluble calcium-phosphate-rich regions not detected in the bioactive glasses

2013 - Synthesis and Characterisation of Strontium and Magnesium Co-Substituted Biphasic Calcium Phosphates [Capitolo/Saggio]
Flora E. Imrie; Valentina Aina; Gigliola Lusvardi;Gianluca Malavasi; Iain R. Gibson; Giuseppina Cerrato;Basil Annaz

Magnesium and strontium both play important roles in the growth of bone and so are desirable ions for substitution into hydroxyapatite (HA) intended for use as bioinstructive bone substitutes. A range of compositions were prepared by a solid state method based on the nominal composition of HA (Ca10(PO4)6(OH)2), with various levels of strontium and/or magnesium substitution: strontium-substituted HA (Ca8Sr2(PO4)6(OH)2), magnesium-substituted HA (Ca9.8Mg0.2(PO4)6(OH)2 and Ca9Mg(PO4)6(OH)2), and strontium and magnesium co-substituted HA (Ca7.8Sr2Mg0.2(PO4)6(OH)2 and Ca7Sr2Mg(PO4)6(OH)2). Materials were characterised by powder X-ray diffraction, Fourier-transform infrared spectroscopy and Raman spectroscopy. These analyses indicated that the co-substituted materials were composed of mixtures of strontium-substituted hydroxyapatite and magnesium and strontium co-substituted β-tricalcium phosphate. In the magnesium-substituted materials, increased magnesium content was related to increased proportion of β-tricalcium phosphate phase, both with and without strontium co-substitution. The unsubstituted and strontium mono-substituted materials, however, were pure apatite phase, suggesting that magnesium was the destabilising factor in the phase compositions of the magnesium mono-substituted and magnesium and strontium co-substituted materials

2013 - Toward the controlled release of metal nanoparticles from biomaterials: physico-chemical, morphological and bioactivity features of Cu-containing sol gel glasses [Articolo su rivista]
V. Aina; G. Cerrato; G. Martra; G. Malavasi; G. Lusvardi; L. Menabue

Two Cu-containing bioactive glasses were prepared and characterized in order to obtain a detailed description of chemical, morphological and bioactivity proprieties of potential Cu releasing systems. The characterization has demonstrated that by varying the synthesis procedure is possible to obtain two systems with Cu species in two different oxidation states and aggregation: (i) SGCu(ox) - oxidated Cu - (Cu oxidation state +2) homogeneously dispersed in the glass network matrix and (ii) SGCu(red) - metallic Cu - (Cu oxidation state 0) containing nano-particles (5-130 nm range) mainly present on the glass surface. The introduction of Cu maintains the bioactivity of the Cu-containing glasses almost unchanged, inducing a partial delay in the hydroxyapatite/ hydroxy-carbonate apatite (HA/HCA) formation on the glass surface with respect to the reference glass (free Cu glass). During the bioactivity test, Cu is released from both Cu-containing glasses, in particular in the case of the SGCu(red) the presence of Cu nanoparticles (CuNPs) of diameter in the range 5-10 nm has been detected in solution. © 2013 Elsevier B.V. All rights reserved.

2012 - A chemical protocol for the evaluation of potential biogas production from biologically pre-treated agro-industrial wastes [Relazione in Atti di Convegno]
G. Malavasi; A. Rustignoli; O. Francioso; A. Piva; C. Salomoni; E. Ferrari

To date, the types of pre-treatment of agro-industrial wastes use mostly physical and chemical (alkaline hydrolysis, acid hydrolysis, oxidative de-lignification and solvent extraction) methods, which have drawbacks both from the environmental point of view and the energy consumption. In this scenario, BIT4enERgy, an entrepreneurial idea supported by SPINNER2013, has developed an innovative biological pre-treatments based on selected strains of microrganisms capable to decompose the biomass recalcitrant (hemicellulose, lignin - Figure) aimed to biogas production in anaerobic digestion. BIT4enERgy, in partnership with Biotec sys srl, is promoting new concept of integration between feedstock biological pre-treatment and advanced anaerobic digestion processes able to convert efficiently agro-industrial wastes with the conversion of high amount of CO2 for biogas production without additional climate change gas emission, supporting a transition towards a low-carbon economy [1,2]. In the present study we show the results on chemical-physical features of agro-industrial wastes before and after biological pre-treatment by using elemental, thermal (TG-DSC) and spectroscopic (ATR/FT-IR) analyses. Particular attention was paid to lignin structural changes as a consequence of biological pre-treatment. Chemical data suggested that the biological pre-treatment allowed a reduction in mass of biomasses in shorter time, the energetic power of the biomasses rich in lignin was increased, the efficiency of their conversion in bio-methane was improved and finally a considerable reductions of greenhouse gas (GHG) balance was expected.

2012 - Development of new metal-based phyto-radiopharmaceuticals: diagnostic agents derived from Cur(e)cumin [Relazione in Atti di Convegno]
E. Ferrari; M. Asti; G. Malavasi; C. Imbriano; F. Pignedoli; M. Bonavia; D. Daquino; M. Saladini

Curcumin, a yellow pigment extracted from the Indian spice Curcuma longa, has been widely linked with suppression of angiogenesis, inflammation, cardiovascular diseases, tumorigenesis and A-binding activities in the context of therapies for Alzheimer’s disease [1,2]. Besides, Curcumin has shown interesting binding ability towards different metal ions such as Fe(III) and Ga(III) with the involvement of its keto-enolic moiety [3]. Metal complexation triggers an increased kinetic stability and bioavailability of Curcumin in physiological conditions, reducing one of its main drawbacks in therapeutic applications. Anyway biologically active curcuminoids have little been investigated as labelled radiopharmaceuticals for cancer diagnosis or therapy, and they represent a novelty in the field. In this presentation we show an overview of new classes of Curcumin-based ligands with bidentate and tridentate coordinating mode, we investigate their binding ability towards Rhenium and Gallium and report a complete thermodynamic and pharmaco-kinetic study on ligands and metal complexes with the aim of developing new radiopharmaceuticals.

2012 - Evaluation of the behaviour of fluorine-containing bioactiveglasses: reactivity in a simulated body fluid solution assistedby multivariate data analysis [Articolo su rivista]
Marina Cocchi; Caterina Durante; Gigliola Lusvardi; Gianluca Malavasi;Ledi Menabue

Potentially bioactive fluorine-containing glassesof formula 46.2SiO224.3Na2O(26.9-x)CaO2.6P2O5xCaF2 [x = (0), 5, 10, 15] have been studied: the study wascarried out as a function of fluorine percentage, dimensionsand time of soaking in SBF. The results are compared tothose obtained in the same conditions for Bioglass 45S5.Due to the high number and different kind of variables/conditions explored by this set of data, the results arerationalized for the first time by means of multivariate dataanalysis (MDA); in this way it is possible to classify thebehaviour of bioglasses toward bioactivity. The presence offluorine does not inhibit the formation of HA; in particular,for a fast bioactivity (in term of HA crystallization) it willbe better to have large particle size or slabs, while for a fastdissolution fine particle sizes should be preferred.

2012 - First-principles simulations of the 27Al and 17O solid-state NMR spectra of the CaAl2Si3O10 glass [Articolo su rivista]
Alfonso Pedone; Elisa Gambuzzi; Gianluca Malavasi; Maria Cristina Menziani

The local and medium-range structure of the 20CaO·20Al2O3·60SiO2 glass generated by classical molecular dynamics simulations has been compared to NMR experiments by computing the 27Al and 17O NMR parameters and NMR spectra from first-principles simulations. The calculation of the NMR parameters (chemical shielding and quadrupolar parameters), which are then used to simulate solid-state MAS and 3QMAS NMR spectra, is achieved by the gauge including projector augmented-wave and the projector augmented-wave methods on the DFT-PBE relaxed structure. The NMR spectra calculated with the present approach are found to be in excellent agreement with the experimental data, providing an unambiguous view of the local and medium-range structure of aluminosilicate glasses.

2012 - Gallium-containing phospho‐silicate glasses: Synthesis and in vitro bioactivity [Articolo su rivista]
Mirco Franchini; Gigliola Lusvardi; Gianluca Malavasi; Ledi Menabue

A series of Ga-containing phospho-silicate glasses based on Bioglass 45S5, having molar formula 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5·xGa2O3 (x=1.0, 1.6, 3.5), were prepared by fusion method. The reference Bioglass45S5 without gallium was also prepared. The synthesized glasses were immersed in simulated body fluid (SBF) for 30 days in order to observe ion release and hydroxyapatite (HA) formation. All Ga-containing glasses maintain the ability of HA formation as indicated by main X-ray diffractometric peaks and/or electronic scanning microscopy results. HA layer was formed after 1 day of SBF soaking in 45S5 glass containing up to 1.6% Ga2O3 content. Moreover, gallium released by the glasses was found to be partially precipitated on theglass surface as gallium phosphate. Further increase in gallium content reduced the ion release in SBF. The maximum of Ga3+ concentration measured in solution is ~6 ppm determined for 3.5% Ga2O3 content. This amount is about half of the toxic level (14 ppm) of gallium and the glasses release gallium till 30 days of immersionin SBF. Considering the above results, the studied materials can be proposed as bioactive glasses with additional antimicrobial effect of gallium having no toxic outcome.

2012 - Magnesium- and strontium-co-substituted hydroxyapatite: the effects of doped ions on the structure and chemico-physical properties [Articolo su rivista]
V.Aina; G.Lusvardi; B.Annaz; I.R.Gibson; F.E.Imrie; G.Malavasi; L.Menabue; G.Cerrato; G.Martra

Mg(II) and Sr(II) ions were substituted for Ca(II) into the hydroxyapatite structure by means of wet synthesis. The materials were characterizad by X-ray diffractometry, IR and Raman spectroscopy and SEM analysis.The results showed the formation of tricalcio phosphate along with hydroxyapatite with change in cell parameters and crystallinity degree as a function of % substitution.

2012 - Novel smart bio-nanomaterials: Bioactive glasses containing metal nano-particles conjugated with molecules of biological interest ( Conference Paper ) [Relazione in Atti di Convegno]
Malavasi G.; Lusvardi G.; Menabue L.; Ferrari E.; Saladini M.; Aina V.; Martra G.; Bergandi L.; Ghigo D.; Valetti F.

New smart materials based on phospho-silicate bioactive sol-gel glasses have been developed. To meet the ever-increasing demand for performing bio-materials, the surface features of the glasses have been tailored to achieve optimal behaviour in different applications (drug delivery, enzymes activity, chemo-signalling probe, stimuli-sensitive agents). In particular, the introduction on the glass surface of metal nanoparticles (NPs; Au and Cu are the metals) is very useful because the NPs can directly act, for example, as bactericides and imaging agents and can be used to immobilize, via a covalent linkage, an enzyme/protein and/or a drug on the glass surface. This can be achieved through the formation of self-assembled monolayers (SAMs), in order to obtain a stable bio-conjugate system. The systems prototyped in this way could be useful as materials bio-implantable into the human body. In the present contribution we report the development of smart bio-materials. In particular, it is demonstrated that bioactive glasses containing Au nanoparticles (AuNPs) can be selectively functionalized with small molecules carrying either amino or thiol groups by simply varying the temperature and pH of the functionalization batch. These results should allow the production, in a selective way, of different bonds exhibiting different strengths and, consequently, different release times in solution, with a wide range of possible applications. (For instance, weak Au-N bonds in the case of drug delivery, strong Au-S bonds for protein immobilization). Unlike other works, in which a preliminary silanization process has often been used, the introduction of AuNPs in the glass composition allows to exploit the easy SAMs formation process on the AuNPs dispersed in the bioactive glass matrix and, consequently, to immobilize an enzyme (soybean peroxidase, SBP). A thorough characterization of the materials, at different steps of the functionalization process, is also reported, together with in vitro activity tests of immobilized SBP, compared with merely adsorbed SBP, and cytotoxicity tests using human osteoblast (MG-63) cells. Overall, a new bio-conjugate material, able to maintain its activity over time and to decrease the oxidative stress when in contact with MG-63 cells, has been obtained. In the present work we have also prepared and characterized bioactive glasses containing CuNPs in order to prepare antibacterial biomaterials useful in the field of implantation surgery.

2012 - Structural and in-vitro study of cerium, gallium and zinc containing sol-gel bioactive glasses [Articolo su rivista]
Shruti S.; Salinas A.; Menabue L.; Lusvardi G.; Malavasi G.; Ferrara C.; Mustarelli P.; Vallet Regi M.

Sol–gel derived glasses comprised of bioactive materials exhibit a high in vitro response, i.e., the capability to form a hydroxycarbonate apatite (HCA) layer that is claimed to be responsible for the bonding between the glass and the host bone. In this paper, the sol–gel bioactive glass 80% SiO2–15% CaO–5% P2O5(B_BG) was modified by adding the biologically relevant elements cerium, gallium and zinc. Structural characterization of the glasses was performed by 29Si MAS NMR and their in vitro response was investigated by soaking them in simulated body fluid (SBF) for up to 15 days at 37 °C. The HCA formation was monitored by XRD, FTIR, SEM-EDS and ICP measurements. Ce3+, Ga3+, and Zn2+can be classified as “intermediate ions”. However, 29Si NMR revealed that Ce3+ions have a more marked role of “modifier ions” than Ga3+ions, while the behavior of Zn2+lies between those of Ce3+and Ga3+. On the other hand, in spite of the decrease in the in vitro response of B_BG by substitution, the glasses show HCA formation after 15 days of soaking. In addition, an increase in substitution of zinc accelerated the formation of HCA along with the formation of the mixed phase CaZn2(PO4)2·2H2O (scholzite) acting as nucleating agent for HCA. Moreover, the therapeutic effect of optimum Zn released as an ionic dissolution product from Zn-glasses could be beneficial to stimulate osteogenesis.

2012 - Synthesis and characterization of bioactive glasses functionalized with Cu nanoparticles and organic molecules [Articolo su rivista]
Alberto Bonici; Gigliola Lusvardi; Gianluca Malavasi; Ledi Menabue; Andrea Piva

Bioactive sol gel glasses, based on the ternary system 15CaO·5P2O5·80SiO2, doped with Cu were synthesized and characterized in order to definethe oxidation state of Cu as a function of thermal treatments. In particular, we were able to optimize the condition to obtain: (i) the reduction ofCu2+ to Cu0 followed by nano-aggregation of metal nano-particles (MeNPs) into glass matrix; (ii) a mixed Cu2+/Cu+/Cu0 NPs-containing glasses;(iii) a Cu2+-containing glasses.Successively, the surface of sol–gel glasses was functionalized by means of organic molecules (amino and mercapto alcohols) to give rise to asystem that can interact with the functional groups of the drugs. The functionalization was carried out as a function of the sol–gel glass composition,organic molecules concentration and temperature of the process; the results indicate a preference for the amino groups. The bioactivity (formationof an apatitic layer after simulated body fluid SBF test) was verified for the functionalized sol–gel Cu2+-containing glasses and they are stillbioactive.

2011 - Ga-Modified (Si-Ca-P) Sol-Gel Glasses: Possible Relationships Between Surface Chemical Properties and Bioactivity [Articolo su rivista]
Valentina Aina; Claudio Morterra; Gigliola Lusvardi; Gianluca Malavasi; Ledi Menabue; Shruti Shruti; Claudia Letizia Bianchi;Vera Bolis

In vitro bioactivity features of a Ga-modified sol gel Si-Ca-P glass(SGGa) were investigated, in comparison with a plain ternary Si-Ca-P system(SG). Reaction/dissolution of the glass at increasing soaking times in simulatedbody fluids (SBF) and the consequent growth of an apatite-like layer, monitoringbioactivity, were studied by employing a variety of chemical and physical techniques.The growth of a crystalline apatitic layer at the Ga-modified-glass/SBFinterface is severely delayed with respect to the Ga-free glass, and the reasons for ithave been looked for in the dramatic changes induced, at the glass/SBF interface, bythe presence of the Ga2O3 component. In situ Fourier transform infraredspectroscopy allowed to describe the nature/structure of surface terminations forthe two glasses and to reveal/quantify the acidic strength of different Ga speciesexposed at the SGGa glass surface. 2,6-Dimethylpyridine and carbon monoxidewere employed as molecular probes to reveal Brønsted and Lewis acidity. At thesurface of the Ga-modified glass, both Brønsted and strong Lewis acidic sites are present. The enhanced surface acitiy of SGGa glass,with respect to the plain glass SG, has been proposed to be responsible for the slower glass dissolution in SBF and for the delayeddeposition/crystallization of an apatite-like layer at the glass/SBF interface.

2011 - Influence of the Chemical Composition on Nature and Activity of the Surface Layer of Zn-Substituted Sol−Gel (Bioactive) Glasses [Articolo su rivista]
Valentina Aina ; Francesca Bonino ; Claudio Morterra; Marta Miola ; Claudia Bianchi; Gianluca Malavasi; Marco Marchetti; Vera Bolis

Two Zn-doped sol-gel glasses with the sameZnO content (5 wt %; 4% mol) but different overall composi-tion have been synthesized and characterized, in comparisonwith a bioactive Zn-free reference glass. The role of ZnO inmodifying the bioactivity of sol-gel glasses was investigated bysoaking the glasses in a simple tris(hydroxymethyl)amino-methane-buffered solution (TRIS-BS), so as to maximize thesolubility and to minimize back-precipitation phenomena, which will depend only on the nature and concentration of dissolved glasscomponents. Glass dissolution/ions release in TRIS-BS was monitored by ion coupled plasma emission spectroscopy, whereasmodifications of surface composition upon reaction were checked by X-ray photoelectron spectroscopy (XPS). The deposition of aCa-P layer and the consequent crystallization to hydroxy-apatite (HA) and/or hydroxy-carbonate-apatite (HCA) at the glasssurface were investigated by X-ray diffraction and Raman, Fourier transform infrared (FTIR), and XPS spectroscopies. Glassdissolution rate, back-precipitation of silica gel, and formation/crystallization of an apatite-like layer on Zn-containing glasses werefound to be either inhibited or delayed, according to the overall glass composition, in that the presence of the network former ZnOcomponent enhances glass reticulation, with the consequent formation of Si-O-Zn units. The presence of a ZnO component hasno effect per se, but its influence depends on the overall composition of the glass and, in particular, on the CaO/SiO2 and ZnO/CaOratios, which determine the nature/structure of Zn and Ca surface species. Glass surface features were investigated by the combineduse of in situ FTIR spectroscopy and adsorption microcalorimetry. The role played by surface Ca species, thought to be the mosthydrophilic sites, was found to be a decisive factor in both glass dissolution mechanism and formation of an apatite-like surface layer:(i) the scarce dissolution in aqueous media of a (non bioactive) low-Ca and high-silica glass is due to the high reticulation caused bythe scarce population of Ca2þ cations in the role of network modifiers; and (ii) the amount of the latter species is, instead, muchlarger in the corresponding (moderately bioactive) high-Ca and low-silica glass, which dissolves more, although exhibiting a largerdurability in aqueous solution than the Zn-free glass.

2011 - Novel bio-conjugate materials: soybean peroxidase immobilized on bioactiveglasses containing Au nanoparticles [Articolo su rivista]
V. Aina; D. Ghigo;T. Marchis; G. Cerrato; E. Laurenti; C. Morterra;G. Malavasi; G. Lusvardi; L. Menabue; L. Bergandi

In the field of implantation, the delivery and/or immobilization of biomolecules developing a specificaction on bone mineralization has attracted great attention in the last few years. In fact, a widespectrum of enzymes and proteins have been grafted with different methods onto/within implantedmaterials. Bioactive glasses and glass-ceramics, due to their tailorable properties in terms of chemicalcomposition, reactivity, and easiness of manufacturing, represent good scaffolds for enzymeimmobilization. These biomaterials are well known for their peculiar surface reactivity promoting,when contacted with real or simulated body fluids, the formation of an hydroxy-carbonate apatitelayer. The aim of the present contribution has been to immobilize, via a covalent linkage, an enzyme onthe glass surface through the formation of self-assembled monolayers (SAMs), in order to obtaina stable bio-conjugate useful as a material bio-implantable into the human body. The innovation of thisstudy resides in the use of a new method of protein immobilization on the glass surface. Unlike otherworks, in which a preliminary silanization process has often been used, the introduction of goldnanoparticles (AuNPs) in the glass composition allowed us to exploit the easy SAMs formation processon the AuNPs dispersed in the bioactive glass matrix and, consequently, to immobilize an enzyme(soybean peroxidase, SBP, in the present case) on the SAMs. A thorough characterization of thematerials, at different steps of the functionalization process, has been also reported, together with invitro activity tests of immobilized SBP, compared with merely adsorbed SBP, and cytotoxicity testsusing human osteoblast (MG-63) cells. Overall, a new bio-conjugate material, able to maintain itsactivity over time and to decrease the oxidative stress when in contact with MG-63 cells, has beenobtained.

2011 - Novel smart bio-materials: bioactive glasses containing metal nano-particles conjugated with molecules of biological interests [Relazione in Atti di Convegno]
G. Malavasi; G. Lusvardi; L. Menabue; E. Ferrari; M. Saladini; V. Aina; C. Monterra; E. Laurenti; L. Bergandi; D. Ghigo

Novel smart bio-materials: bioactive glasses containing metal nano-particles conjugated with molecules of biological interests

2011 - On the dissolution/reaction of small-grain Bioglass 45S5 and F-modified bioactive glasses in artificial saliva (AS) [Articolo su rivista]
V.Aina; L.Bertinetti; G.Cerrato; M.Cerruti; G.Lusvardi; G.Malavasi; C.Morterra; L.Tacconi; L.Menabue

The reaction of small-grain Bioglass® 45S5 in artificial saliva (AS), to produce a layer of hydroxy-apatite(HA) and/or hydroxy-carbonate apatite (HCA), has been studied and compared to the results obtained in asimple buffered solution (TRIS). Some potentially bioactive glasses based on the composition of Bioglass®and containing CaF2 (HCaCaF2 5% and HNaCaF2 5%) have also been studied, in order to analyze theeffects/changes produced when a F-containing glass surface is contacted with AS. The insertion of fluorinehas been proposed to improve bioactive glass bone-bonding ability, and to parallel fluorine-containingglass-ceramics currently used in dentistry. ICP-OES analysis of the solution, and FTIR spectroscopy of thesolid samples provided compositional information on the stages of reaction. These data were integratedwith XRD and the textural and morphological data, obtained by specific surface areas determination andTEM-EDS measurements. In the case of Bioglass® 45S5, a comparison at corresponding reaction timesindicates that the precipitation of an amorphous Ca-phosphate phase is faster in AS, but the crystallizationof HA/HCA is delayed in AS with respect to the TRIS solution. For fluoride-containing glasses, the sampleHCaCaF2 5%, in which CaF2 replaces part of CaO, possesses the fastest rate for HA/HCA crystallization (1week) in AS. Some lines of interpretation for these results are proposed.

2011 - Substitutions of cerium, gallium and zinc in ordered mesoporous bioactive glasses [Articolo su rivista]
A.J. Salinas; S. Shruti; G. Malavasi; L. Menabue; M. Vallet-Regí

Ordered mesoporous glasses based on the 80% SiO2–15% CaO–5% P2O5 system including up to 3.5% Ce2O3,3.5% Ga2O3 or 7.0% ZnO (in mol.%) were synthesized by the evaporation-induced self-assembly processusing Pluronic 123 as a surfactant. An ordered hexagonal mesophase was observed in both the unsubstitutedglass (denoted in this paper as B: blank) and glasses containing <0.4% of substituent by X-ray diffraction,transmission electron microscopy and electron diffraction. The increase in the amount ofsubstituent led to a decrease in the mesopore order. B glass exhibited good textural properties:SBET = 515 m2 g1, DP = 4.7 nm and VP = 0.58 cm3 g1. With the inclusion of cerium, gallium and zinc oxidesthe textural properties decreased, but remained in amounts useful for clinical applications. Zinc-containingsamples showed the highest decrement in the textural properties. Substituted glasses exhibited aquick in vitro bioactive response except when the ZnO content was over 0.4%. Taking into account theordered mesoporosity, the quick in vitro bioactive response and the added values of the substituents, thisnew family of glasses are promising candidates for applications in bone tissue engineering.

2011 - The role of coordination chemistry in the development of innovative Gallium-based bioceramics: the case of Curcumin [Articolo su rivista]
E. Ferrari; G. Lusvardi; V. Aina; G. Malavasi; F. Fantini; C. Morterra; F. Pignedoli; M. Saladini; L. Menabue

Curcumin, an active ingredient in the traditional Ayurvedic herbal remedy [Curcuma longa L.], isnowadays also employed in western medicine for its pleiotropic activities, ranging from anticancer to itsfree radical scavenger ability. These features are related to curcumin’s function as a metal chelator,especially being selective for hard Lewis acids, such as Ga3+ which has interesting pharmacologicalactivities. We report the synthesis and characterization of a bioactive gel and mesoporous Ga-containing phospho-silicate glasses loaded with curcumin, in which, for the first time, coordinationchemistry was taken advantage of in designing novel drug delivery systems. In particular, it was foundthat: (i) there is a direct correlation between the external surface area and the amount of loadedcurcumin; (ii) the presence of Ga3+ species on the surface increases the quantity of drug moleculesuploaded and slows down their release in the biological medium (SBF), hinting at a coordination-likeinteraction between curcumin and the surface metal ions; (iii) curcumin molecules released in the SBFsolution stabilize Ga3+ ions, avoiding their precipitation.

2011 - The toxic effect of fluoride on MG-63 osteoblast cells is also dependent on the production of nitric oxide [Articolo su rivista]
L. Bergandi ; V. Aina; G. Malavasi; C. Morterra; D. Ghigo

Some soda-lime-phospho-silicate glasses, such as Hench’s Bioglass® 45S5, form bone-like apatite ontheir surface when bound to living bone. To improve their osteointegration for clinical purposes, thefluoride insertion in their structure has been proposed, but we recently showed that fluoride causesoxidative damage in human MG-63 osteoblasts, via inhibition of pentose phosphate oxidative path-way (PPP) and its key enzyme glucose 6-phosphate dehydrogenase (G6PD). In the same cells we havenow investigated the role of nitric oxide (NO) in these effects. Fluoride-containing bioactive glasses andNaF caused, as expected, release of lactate dehydrogenase in the extracellular medium, accumulation ofintracellular malonyldialdehyde, inhibition of PPP and G6PD: we have now observed that these effectswere significantly reverted not only by superoxide dismutase (SOD) plus catalase (scavengers of reactiveoxygen species), but also by N-monomethyl l-arginine (l-NMMA, a NOS inhibitor) and 2-phenyl-4,4,5,5,-tetramethylimidazoline-1oxyl 3-oxide (PTIO, a NO scavenger). Moreover the two highest concentrationsof both fluoride-containing bioglasses and NaF caused increase of nitrite (a stable derivative of NO) levelsin the culture supernatant, which was inhibited by l-NMMA, erythrocytes, PTIO and SOD/catalase, andincrease of intracellular NO synthase (NOS) activity. The incubation with bioglasses or NaF increasedalso the phosphorylation of Ser1177 in the endothelial NOS isoform. Furthermore, the NO donor spermineNONOate was able to inhibit G6PD activity in vitro, and this effect was partly reverted by PTIO. Thereforeour results suggest that most cytotoxic effects of fluoride are mediated by the production of NO: reactiveoxygen species are important, causing NOS phosphorylation. We also observed, for the first time, thatTempol, but not SOD/catalase, besides inhibiting the oxidative stress induced by fluoride, also scavengesfluoride ions. For this reason it is not a selective inhibitor of the oxidative effects of fluoride.

2010 - Bioactive Glasses Containing Au Nanoparticles. Effect of Calcination Temperature on Structure, Morphology, and Surface PropertiesDOI:10.1021/la100472p [Articolo su rivista]
Gigliola Lusvardi; Gianluca Malavasi; Valentina Aina; Luca Bertinetti; Giuseppina Cerrato;Giuliana Magnacca; Claudio Morterra; Ledi Menabue

Bioactive glasses containing gold nanoparticles (AuNPs) have been synthesized via the sol-gel route usingHAuCl4 x 3H2O as gold precursor. The formation process of AuNPs was studied as a function of the thermal treatment,which induces nucleation of Au particles and influences their nature, optical properties, shape, size, and distribution.The physicochemical characterization indicates that the sample treated at 600 °C presents the best characteristics to beused as a bioactive material, namely high surface area, high amount of AuNPs located at the glass surface, presence ofmicropores, and abundant surface OH groups. In the case of samples either aged at 60 °C or calcined at 150 °C, AuNPsjust begin their formation, and at this stage the gel is not completely polymerized and dried yet. A thermal treatment athigher temperatures (900 °C) causes the aggregation of AuNPs, forming “AuMPs” (i.e., Au microparticles) in adensified glass-ceramic material with low surface area, absence of pores, and low number of surface OH groups. Thesefeatures induce in the glass-ceramic materials treated at high-temperatures a lower bioactivity (evidenced by SBFreaction), as compared with that exhibited by the glass samples treated at 600 °C.

2010 - Fluoride-containing bioactive glasses inhibit pentose phosphate oxidative pathway and glucose 6-phosphate dehydrogenase activity in human osteoblasts [Articolo su rivista]

Bioactive glasses such as Hench's 45S5 (Bioglass®) have applications to tissue engineering aswell as bone repair, and the insertion of fluoride in their composition has been proposed to enhancetheir bioactivity. In view of a potential clinical application, we investigated whether fluoride-containingglasses exert toxic effects on human MG-63 osteoblasts, and whether and how fluoride, which isreleased in the cell culture medium, might play a role in such cytotoxicity. A 24 h incubation with 50μg/ml (12.5 μg /cm2) of fluoride-containing bioactive glasses termed HCaCaF2 (F content: 5, 10 and15% mol) caused the release of lactate dehydrogenase in the extracellular medium (index ofcytotoxicity), the accumulation of intracellular malonyldialdehyde (index of lipoperoxidation), and theincrease of glutathione consumption. Furthermore, fluoride-containing glasses inhibited the pentosephosphate oxidative pathway and the glucose 6-phosphate dehydrogenase activity. These effects areascribable to the fluoride content/release of glass powders, since they were mimicked by NaF solutionsand were prevented by dimethyl sulfoxide and tempol (two radical scavengers), by superoxidedismutase (a superoxide scavenger), and by glutathione (the most important intracellular antioxidantmolecule), but not by apocynin (an inhibitor of NADPH oxidase). The presence of fluoride-containingglasses and NaF caused also the generation of reactive oxygen species, which was prevented bysuperoxide dismutase and catalase. The data suggest that fluoride released from glasses is the cause ofMG-63 cell oxidative damage and is independent of NADPH oxidase activation. Our data provide a newmechanism to explain F ̅ ions toxicity: fluoride could trigger, at least in part, an oxidative stress viainhibition of the pentose phosphate oxidative pathway and, in particular, through the oxidativeinhibition of glucose 6-phosphate dehydrogenase.

2010 - Functionalization of sol gel bioactive glasses carrying Au nanoparticles: selective Au affinity for amino and thiol ligand groups [Articolo su rivista]
V. Aina; T. Marchis; E. Laurenti; E. Diana; G. Lusvardi; G. Malavasi; L. Menabue; G. Cerrato; C. Morterra

It is demonstrated here that bioactive glasses containing Au nanoparticles (AuNPs) can be selectively functionalizedwith small molecules carrying either amino or thiol groups by simply varying the temperature and pH of thefunctionalization batch. The results evidence the following. (i) At room temperature (RT), no functionalization ofAu-free glass occurs, whereas in the case of glasses containing AuNPs, stable linkages form only with amino groups, as inthis condition Au does not bind with either thiol or hydroxyl groups. The RT functionalization with cysteine and cystineconfirms the preferential functionalization through the amino groups, while the -SH groups are oxidized to S-S bridges.(ii) The functionalization with cysteine and cystine, compared at pH = 5, 9, and 12, is shown not to take place at pH = 5and to be hindered by the glass matrix dissolution at pH = 12 (with consequent release of AuNPs), while the best resultsare obtained at pH = 9. (iii) For the effect of reaction temperature, at 4 °C it is possible to obtain a strong Au-Sinteraction, whereas at RT, a weak Au-N linkage is formed. These results should allow production, in a selective way, ofdifferent bonds exhibiting different strengths and, consequently, different release times in solution, with a wide range ofpossible applications (for instance, weak Au-N bonds in the case of drug delivery, strong Au-S bonds in proteinimmobilization).

2010 - Molecular Dynamics Simulations of Sodium Silicate Glasses:Optimization and Limits of the Computational Procedure [Articolo su rivista]
Pota, Marco; Pedone, Alfonso; Malavasi, Gianluca; Durante, Caterina; Cocchi, Marina; Menziani, Maria Cristina

The performance of the molecular dynamics (MD) simulations to obtain the structure of silica glasses containing different concentrations of alkali oxides has been tested. An optimal MD simulation procedure (including cooling cycle, MD constants and ensemble used) has been developed by means of experimental design methodologies (DOE), firstly restricting the study to the 30% Na2O silica glass for which experimental data are available to allow the comparison of the results. The optimization procedure led to simulations that well predict experimental density and short-range structure of glasses with different sodium content. On the contrary, the medium-range structure has been badly reproduced and it was not possible to determine a reliable correlation with the parameters of the simulation procedures used. Therefore, the correlation of medium-range properties with the structure has been studied by means of the PLS methods. The results showed to be useful to highlight the relationships among structural elements, such as radial distribution functions of specific bonds and angles, and Qn species, suggesting possible directions in order to improve the force field.

2010 - New Insights into the Atomic Structure of 45S5 Bioglass byMeans of Solid-State NMR Spectroscopy and AccurateFirst-Principles Simulations [Articolo su rivista]
A. Pedone; T. Charpentier; G. Malavasi;M. C. Menziani

An integrated computational method that couples classical molecular dynamics simulations withdensity functional theory calculations has been used to simulate the solid-state 17O and 23NaMQMAS, 29Si, 31P, and 23Na static and MAS NMR spectra of the 45S5 Bioglass structural modelswith up to 248 atoms. Comparison with the experimental spectra collected in this work (the 17OMQMAS spectrum of the 45S5 Bioglass is reported for the first time in the literature) shows anexcellent agreement. The results provide deep insights into fundamental open questions regarding theatomic-scale structural details of this glass of great medical interest. In particular, the host silicanetwork, described by theQn distribution (aQn species is a network-forming ion bonded to n bridgingoxygens), consists of chains and rings ofQ2Si (67.2%) SiO4 tetrahedra cross-linked with Q3Si (22.3%)species and terminated by a low quantity of Q1Si (10.1%) species. No Si-O-P bridges have beendetected by both 31P NMR and 17O MQMAS experiments, and therefore isolated orthophosphateunits are able to form nanodomains that subtract sodium and calcium cations from their networkmodifying role into the silicate network. Finally, both the experimental and theoretical results show amixture of dissimilar cations (Na,Ca) around NBO, according to a nonrandom distribution of thesespecies.

2010 - Synthesis and characterization of Ga-containing silicate based sol-gel and mesoporous sol-gel bioactive glasses loaded with curcumin [Relazione in Atti di Convegno]
F. Fantini; E. Ferrari; G. Lusvardi; G. Malavasi; L. Menabue

1.Introduction Silicate based bioactive glasses are synthesized with the aim to obtain materials usable as bone fillers for orthopedic and maxillo facial surgery1. The studied glasses are sol-gel and mesoporous sol-gel based on molar composition 15CaO-5P2O5-80SiO2 modified with Ga2O3; moreover, curcumin was loaded on these glasses. In fact, these materials may be also used as vehicles for the release of metal ions (Ga with anti-bacterial and anti-cancer properties2) and bio-molecules (curcumin, an anti-oxidant and anti-cancer agent3). 2.Results and Discussion Different techniques (UV-Vis, XRD, SEM, NMR, DTA, AE, ICP) are used to characterize glasses, the absorption and release of curcumin. The results showed that, due to higher external surface, sol-gel glasses adsorb more curcumin with respect to mesoporous; in this last case, another possibility of adsorption is by means of mesoporous, but its diameter is smaller than the dimension of curcumin molecules. The amount of curcumin uptaken is higher for Ga-containing glasses. All these materials, tested in water for 72 hours, show an initial (6 hours) fast and almost complete release of curcumin; afterwards the release is more slow. The amount of curcumin released from Ga-containing glasses is lower than the Ga-free ones. The amount of gallium present in solution is greater for the systems with curcumin, in this way Ga ions in solution could be act as antibacterial and antioxidant agents.

2009 - Bioactive phospho-silicate glasses containing CaF2: bioactivity test in simulated body fluids and behaviour towards osteoblast cells [Relazione in Atti di Convegno]
V.Aina; L.Bergandi; F.Bonino; D.Ghigo; G.Lusvardi; G.Malavasi; L.Menabue; C.Morterra

In this work it is reported a study, in vitro (DMEM), of some potentially bioactive glasses based on the composition of Bioglass® 45S5 bioactive glass, in which CaF2 substitutes alternatively CaO and Na2O. Using a multi-techniques investigation, it is possible to explain in detail the glasses degradatation and the mechanism of formation of an apatitic layer between inorganic material and biological medium. The behaviour of doped glasses is differs from that proposed by Hench for Bioglass® 45S5 bioactive glass, however, these doped glasses have capability of developing bio-activity.A preliminary cellular test is also performed in view of a potential clinical application

2009 - Computational insight into the effect of CaO/MgO Substitution on the Structural Properties of Phospho-Silicate Bioactive Glasses. [Articolo su rivista]
A. Pedone; G. Malavasi; M.C. Menziani

The effect of the replacement of CaO for MgO on the structural properties of the 45S5 Bioglass with composition 46.2SiO2·24.3Na2O·(26.9 − x)CaO·2.6P2O5·xMgO where x = 0, 5, 10, 15, 20, and 26.9 mol has been studied by means of molecular dynamics simulations. The results confirmed the complexity of the local environment of Mg ions which are coordinated by 5 nonbridging oxygens of different TO4 tetrahedra (T = Si/P) leading to large rings in the structures. A rough correlation between the average dimension of the rings found in the structure and the computed Young’s modulus is obtained. The Young’s modulus decrease at low Mg-content reaching a minimum for the 46.2SiO2·24.3Na2O·16.9CaO·2.6P2O5·10MgO glass. At this composition, Mg is homogeneously distributed in the silica rich region together with Ca and Na ions but is almost totally absent from the Ca−Na-phosphate rich regions. The results suggest that the ideal glass composition for lowering the Young’s modulus preserving a specific bioactivity can be found below 10% of MgO content.

2009 - Fluoride-containing bioactive glasses: surface reactivity in simulated body fluids [Articolo su rivista]
V.Aina; G.Lusvardi; G.Malavasi; L.Menabue; C.Morterra

The issue of the contribution of the addition of F to glass bioactivity is not well resolved. This work reports on the surface reactivity in different solutions (DMEM and Tris) for some potentially bioactive glasses based on the composition of 45S5 glass, in which CaF2 is substituted alternately for (part of) CaO and Na2O. The reactivity of F-containing glasses has been compared with that of the reference 45S5 system. The aim of this study is to explain in detail the mechanism of formation of an apatitic crystalline phase at the interface between the inorganic material and simulated biological media. A multi-technique investigation approach proposes a set of reactions involving Ca-carbonate formation, which are somewhat different from that formerly proposed by Hench for 45S5 bioactive glass, and which occur when a F-containing glass surface is in contact with a SBF. The usefulness of IR spectroscopy in recognizing the starting step of apatite (and/or FA) formation with respect to XRD technique is well established here.

2009 - Fluoride-contaning bioactive glasses:surface reactivity in simulated body fluid [Abstract in Atti di Convegno]
G. Lusvardi; G. Malavasi; L. Menabue; V. Aina; C. Morterra

The contribution to bioactivity of F-addition to bioactive glasses seems not well resolved. In this work is reported the surface reactivity in different solutions (DMEM and TRIS) of some potentially bioactive glasses based on the composition of 45S5 bioactive glass, in which CaF2 substitutes alternatively (part of) CaO and Na2O, as compared to the reactivity of 45S5 bioactive glass. This study is aimed at explaining in some detail the mechanism and the rapidity of formation of an apatitic crystal phase at the interface between the inorganic material and simulated biological media.Using a multi-technique investigation approach, we propose a set of reactions, involving Ca-carbonates formation, that is somewhat different from that proposed by Hench for 45S5 bioactive glass, and occurs when a F-containing glass surface is contacted with a simulated body solution. The usefulness of IR spectroscopy in recognizing the starting step of apatite (fluoro-apatite) formation, with respect to XRD technique, is well established.

2009 - In vitro and in vivo behaviour of zinc-doped phosphosilicate glasses [Articolo su rivista]
Lusvardi G.; Zaffe D.; Menabue L.; Bertoldi C.; Malavasi G.; Consolo U.

The aim of this work was to study the behaviour of zinc-doped phosphosilicate glasses based on Bioglass 45S5. In vitro (in simulated body fluid), the reactivity was analysed by means of inductively coupled plasma spectrometry, environmental scanning electron microscopy–energy-dispersive spectroscopy (ESEM–EDS) and X-ray diffraction. In vivo (a rat implanted with glass), the reactivity and the tissue behaviour were analysed by conventional histology, histochemistry, microradiography and ESEM–EDS. The in vivo behaviour matches that in vitro perfectly; they show comparable glass degradation processes and rates, ruled by the amount of zinc in the glass.The reaction mechanism for the formation of a polymerized silica layer superimposed with a peripheral calcium phosphate layer is clearly substantiated by ESEM–EDS investigations. The crystallization of a biologically active hydroxyapatite (HA) layer is observed in both cases; the in vitro experiment shows the presence of HA after 4 days. IDS Number: 386ZV PMID: 18701362

2009 - Quantitative Structure−Property Relationships of Potentially Bioactive Fluoro Phospho-silicate Glasses [Articolo su rivista]
G. Lusvardi; G. Malavasi; F. Tarsitano; L. Menabue*; M.C. Menziani; A. Pedone

In this work, the glass transition temperature and chemical durability of bioactive phospho-silicate glasses were experimentally determined and correlated to the structural descriptor Fnet derived from classical molecular dynamics simulations. The replacement of CaF2 for Na2O in the parent glass 45S5 enhances both chemical durability and density, while the replacement of CaF2 for CaO lowers chemical durability. The proposed descriptor, Fnet, provides satisfactorily correlations with glass transition temperature and chemical durability over a wide range of compositions.

2009 - Zinc-containing bioactive glasses: surface reactivity and behaviour towards endothelial cells [Articolo su rivista]
Aina, V.; Malavasi, Gianluca; FIORIO PLA, A.; Munaron, L.; Morterra, C.

This paper reports on a physico-chemical study devoted to reactivity towards hydroxo-carbonate apatite (HA) formation of bioactive glass 45S5 (H glass; commercially known as Bioglass) and of two preparations of zinc-doped 45S5-derived systems (HZ5, HZ20),immersed in Tris(hydroxymethyl)aminomethane (Tris) and Dulbecco’s modified Eagle’s medium (DMEM) buffer solutions. The activity/toxicity of the glasses was also tested using endothelial cells (EC). Zn caused a drastic reduction in the overall leaching activity of glasses and, at high Zn concentration (HZ20), the formation of HA on the glass surface was thoroughly inhibited. The presence of Zn also decreased the increment of pH after glass immersion in both Tris and DMEM solution. EC are known to be very sensitive to pH changes and, for this reason, the rapid increase in pH brought about by H glass dissolution is likely to affect cell adhesion and spreading, whereas the high zinc release from HZ20 causes a drastic reduction in cell proliferation after a long contact time (1 week). This study shows that only HZ5 glass containing 5 mol.% Zn presents at the same time: reduced solubility, bioactivity (monitored by HA formation) and conditions allowing EC growth over a 6-day period.

2008 - A combined experimental-computational strategy for the design, synthesis and characterization of bioactive zinc-silicate glasses [Capitolo/Saggio]
Lusvardi, G.; Malavasi, G.; Menabue, L.; Menziani, M.C.

This review presents a combined experimental-computational strategy for the development of potential bioactive zinc–containing silicate glasses and shows how sound relationships among the structural role of some key elements that appear to control bioactivity can by established and exploitfor rational glass design.

2008 - Deflocculant effect on the surface properties of kaolinite investigated through malachite green adsorption [Articolo su rivista]

The adsorption of malachite green (MG) on sodium-exchanged kaolinite and on the same clay treated with two widely used deflocculants, sodium hexametaphosphate (NaHMP) and sodium disilicate (NaDIS), was investigated. The results indicate that the deflocculants affect the adsorption process. In particular, DIS treatment increases physisorption, whereas HMP treatment almost completely prevents it. The Frumkin isotherm accurately describes MG adsorption for all of the adsorbents investigated and the Frumkin inter- action parameter is found to be repulsive, in keeping with the cationic nature of the adsorbed species. TheKeywords: temperature dependences of the adsorption constant and the related thermodynamic parameters H◦ adsAdsorption and S◦ ads were also determined and discussed.

2008 - Elastic and dynamical properties of alkali silicate glasses from computer simulations techniques [Articolo su rivista]

This paper shows recent progresses in the field ofcomputer simulations of inorganic glasses. Moleculardynamics simulations and energy minimization methods havebeen applied to calculate the elastic and transport proper-ties of alkali silicate glasses of compositions xM2 O · (100 −x)SiO2 (with x = 0, 10, 15, 20, 25, 30 % mol for M = Li,Na and K) and of a soda-lime glass with composition 15Na2 O·10CaO · 75SiO2 , which has been employed to ascertain theeffect of the replacement of CaO for Na2 O. The excellentagreement of the computed results with the experimentaldata highlights the important predictive and interpretativerole reached by computer simulations techniques.

2008 - Elucidation of the Structural Role of Fluorine in Potentially Bioactive Glasses by Experimental and Computational Investigation [Articolo su rivista]
G. Lusvardi; G. Malavasi; M. Cortada; L. Menabue; M. C. Menziani; A. Pedone; U. Segre

Glasses belonging to the Na2O-CaO-P2O5-SiO2 system and modified by CaF2 substitution for CaO and Na2Oalternatively, were synthesized and characterized experimentally and computationally. The results of moleculardynamics simulations show that fluorine is almost exclusively bonded to modifier cations (Ca and Na) withcoordination number close to 4. A similar mean coordination number value is found in the crystal phasesobtained by means of thermal treatment at fixed temperature. Addition of fluorine increases the polymerizationof silicate tetrahedra by removing modifiers from the siliceous matrix. No appreciable amount of Si-F bondsare detected.

2008 - FFSiOH: a New Force Field for Silica Polymorphs and Their Hydroxylated Surfaces Based on Periodic B3LYP Calculations [Articolo su rivista]

A partial charge shell-ion model potential for silica polymorphs and their hydroxylated surfaces(FFSiOH) was parametrized in a self-consistent way using periodic B3LYP results for bulk R-cristobaliteand the (100) and (001) hydroxylated surfaces. The reliability of the new potentials was checked bycomparing structures, vibrational frequencies and relative phase stabilities of dense bulk silica polymorphs,namely R-quartz, R-cristobalite, R-tridymite, and Stishovite with both experimental and B3LYP data.The FFSiOH was also checked for computing structural and vibrational features of representative all-silica microporous materials, namely edingtonite, chabazite, and faujasite. As a last step, FFSiOH wasadopted to predict OH stretching vibrational frequencies and relative thermodynamic stability of themost common fully hydroxylated surfaces of the dense silica polymorphs, the (100) and (001) facesof all-silica edingtonite, the features of the local Si-defect in chabazite and sodalite known as (SiOH)4hydrogarnet and the geometries of H-bonded silanol groups of an amorphous silica surface. In all casesexcellent agreement resulted between FFSiOH and B3LYP periodic data and experimental data, whenavailable. The new FFSiOH force field opens up the molecular simulation of materials in which thesurface hydroxyl groups play a key role, as is the case for amorphous silica surfaces, all-silica zeoliteexternal surfaces, and the internal walls of mesoporous materials.

2008 - Fluoride-containing bioactive glasses: some aspects of reactivity in simulated body solutions [Articolo su rivista]

Bioactive glasses are used in medical field as bone regenerativematerials. They promote the growth of bone tissue on their surface, and establishinterconnections in order to form a continuum with the tissue. The bioactivity of thisclass of materials, immersed in a real or simulated biological medium, is monitored bythe ability to form at its surface a layer of Ca-phosphate, which ought to crystallizein the form of either hydroxy-apatite (HA) or hydroxy-carbonate-apatite (HCA).The present contribution deals with the activity/reactivity of some oxidic materials(to be possibly used as bio-active glasses) that: i) have been produced throughthe conventional melt-quench-grind method; ii) belong to the family of Hench’sBioglass (H-glass); iii) have been modified, in respect of H-glass composition, bythe introduction of variable amounts of Ca-fluoride. In assessing the bioactivity oftwo families of F-modified glasses, it is herewith shown that the use of some physico-chemical methods, typical of surface chemistry (e.g., surface area determination, IRand Raman vibrational spectroscopic analysis), gives indeed access to what happensat the interface between a complex oxidic material and the surrounding biologicalmedium.

2008 - Medium-range order in phosphosilicate bioactive glasses: Insights from MAS-NMR spectra, chemical durability experiments and molecular dynamics simulations [Articolo su rivista]
L.Linati; G.Lusvardi; G. Malavasi; L.Menabue; M.C.Menziani; P. Mustarelli; A Pedone;U. Segre

The medium-range order of phospho-silicate bioactive glasses (with compositions (2 p)SiO2 Æ 1Na2O Æ 1.1CaO Æ pP2O5, in whichp = 0.10, 0.20, 0.26) has been studied by means of a combined-experimental (MAS-NMR, chemical durability measurements) and computational(classical molecular dynamics (MD)) approach. The structural model obtained by MD is showed to be helpful in the interpretationof the NMR spectra. A small amount of Si–O–P link units has been detected in glasses with low P2O5-content, but at high P2O5concentration the percentage of Si–O–P bridges becomes important. However, Qn distributions show that the HP5 (p = 0.20) glass structureis less polymerized with respect to the H (p = 0.10) and HP6.5 (p = 0.26) glasses. These results provide useful explanation of thebehavior of these glasses in water and highlight the influence of the medium-range order on a very important property of potentialbioactive glasses such as the chemical durability.

2008 - Molecular dynamics of stress-strain behaviour of silica glass under tensile load. [Articolo su rivista]

Molecular dynamics (MD) simulations were carried out to study the stress-strain diagrams of crystallineand amorphous silica under different nonequilibrium conditions. The responses of a tensile load wererecorded in two cases. In one case, the system was not allowed to relax along the transverse direction(null Poisson’s ratio), while in the other case, the deformations were allowed in directions perpendicularto the strained one. The higher strength of crystalline silica as compared to amorphous silica resultedfrom a different distribution of ring sizes. The results obtained for the inert failure strains and intrinsicstrength of the silica glass were in good agreement with the experimental data, and the nonlinear elasticbehavior of the glass was reproduced along with the effects of strain rate and temperature variation.Elastic properties extracted from stress-strain diagrams also were compared with the properties calculatedby means of static methods and with experimental data.

2008 - PRIN [Partecipazione a progetti di ricerca]
M.C. Menziani; G. Malavasi; A. Pedone; P. Saxena; M Del Cadia

SCOPO: Lo scopo principale del progetto di Mo-UR è di sviluppare un approccio multi-scala basato su metodi classici e quantistici per modellare la struttura,proprietà spettroscopiche e di trasporto di sistemi amorfi.Attenzione particolare sarà rivolta a sistemi a più componenti con lo scopo di derivare relazioni quantitative struttura-proprietà utili per l'ottimizzazione diformulazioni con proprietà desiderate. L'originalità del progetto risiede nella combinazione di diverse tecniche computazionali, quali la dinamica molecolareCar-Parrinello in un approccio periodico per studiare processi di rilassamento veloci in fusi di ossidi e nel processo di formazione della fase vetrosa e la metodologianon periodica QM/MM ONIOM per lo studio di clusters di migliaia di atomi ottenuti da simulazioni di dinamica molecolare classica.Inoltre, tecniche di Analisi di Dati a Multivariata saranno utilizzate per aiutare l'interpretazione di spettri NMR 1D e 2D, EPR, IR e RAMAN di fusi e vetri inorganicie per trovare correlazioni e relazioni fra i parametri degli spettri simulati e le caratteristiche strutturali.Simulazioni classiche di dinamica molecolare (MD) saranno usate per studiare processi di rilassamento lenti quali il meccanismo di diffusione ionica a bassa ed altatemperatura, la dinamica del meccanismo di fattura nella superficie di cricche e le prime fasi di processi di nucleazione e crescita cristallina in matrici vetrose el'interfaccia cristallo/vetro.Questo sarà realizzato attraverso un continuo scambio di abilità e conoscenze con le Na-UR e Pd-UR come descritto nel PP3 del MODELLO A, in un ambiente dicalcolo distribuito.

2008 - Properties of zinc releasing surfaces for clinical applications [Articolo su rivista]

Two series of glasses of general formula (2-p) SiO21.1Na2OCaOpP2O5xZnO (p = 0.10, 0.20; x = 0.0, 0.16, 0.35, and 0.78) have been analyzed for physico-chem. surface features before and after contact with simulated body fluid, morphol. characteristics, and osteoblast-like cells behavior when cultured on them. The resulted good cell adhesion and growth, along with nonsignificant changes of the focal contacts, allow the authors to indicate HZ5 and HP5Z5 glasses as the ones having optimal ratio of Zn/P to maintain acceptable cell behavior, comparable to the bioactive glass (Bioglass) used as a control; results are also rationalized by means of three-dimensional models derived by mol. dynamic simulations, with decompn. and conversion rates optimized with respect to the parent Hench's Bioglass.

2008 - Role of Magnesium in Soda-Lime Glasses: Insight into Structural, Transport, and Mechanical Properties through Computer Simulations [Articolo su rivista]

The role of Mg in soda-lime glasses was elucidated by classical molecular dynamics (MD) simulations. Theeffect of the replacement of CaO for MgO on the structure, transport, and elastic properties of a series ofglasses with compositions 15Na2O · (10 - x)CaO · xMgO · 75SiO2 (x ) 0, 5, and 10 mol) was studied. Differentstructural roles were found for the Ca and Mg ions. The former, coordinated by six oxygen atoms, acts as anetwork modifier, while the latter, four-fold coordinated, participates in the silica network. Consequently, Naion diffusion is favored by the replacement of MgO for CaO in these glasses, as shown by variation in thecomputed diffusion coefficients and activation energy of the process in the series of glasses studied. Moreover,the consequences of these structural modifications on the elastic properties (Young’s modulus, shear modulus,bulk modulus, Poisson’s ratio, and compressibility) of the glasses were evaluated by means of energyminimization techniques carried out on the structures obtained by MD simulations.

2007 - A computational multiscale strategy of the study of amorphous materials [Articolo su rivista]

A first step towards a computational Si–O–P angles, respectively. Other geometrical featuresmultiscale approach has been adopted here to deal with are in excellent agreement within the two approaches.the computational simulation of the Hench bioglass Electronic properties of the Hench bioglass have been45S5, an amorphous material of 48.1% SiO2 , 25.9% reported at B3LYP for the first time and both Mullik-CaO, 22.2% Na2 O and 3.7% P2 O5 composition. Molec- en charges and electronic band structure show a ratherular dynamics simulations based on classical force fields ionic character of the material, whereas a band gap offollowed by static minimizations on quenched structures about 6.5 eV characterizes the bioglass as a strong insu-have been run on a unit cell size suitable for subsequent lator. Work presently in progress will soon allow theab initio calculations. The molecular mechanics opti- information to be transferred from the B3LYP calcu-mized unit cell envisaging 78 atoms of Na12 Ca7 P2 Si13 lations to the molecular mechanics engine in order toO44 composition and P1 symmetry has then been fully refine the presently available empirical force fields foroptimized (both unit cell parameters and internal coor- complex ionic systems and their surfaces.dinates) at B3LYP level in a periodic approach usinggaussian basis sets of double-ζ quality and the devel-opment version of the CRYSTAL03 code. Comparisonbetween the molecular mechanics and B3LYP optimizedstructures shows the latter to give a slightly higherdensity than the former, due to overestimation of theSi–O bonds and underestimation of the Si–O–Si and

2007 - An ab initio parameterized interatomic force field for hydroxyapatite [Articolo su rivista]
A. Pedone; M. Corno; B. Civalleri; G. Malavasi; M. Menziani; U. Segre; P. Ugliengo

A classical interatomic force field for hydroxyapatite has been parameterized from periodicab initio calculations carried out on the hexagonal structure (space group P63). The GULPprogram has been used for fitting geometry and phonon frequencies computed with theCRYSTAL06 program using the B3LYP hybrid functional and Gaussian-type basis set ofpolarized double zeta quality. Polarization effects and covalent bonding have been includedthrough the shell-ion model potential. Excellent agreement has been found in reproducingstructural features, lattice dynamics, the OH stretching vibrations and relative phase stabilitiesbetween the monoclinic structure (space group P21/b) and the hexagonal one. Transferability fromhydroxyapatite to other calcium phosphates has also been demonstrated.

2007 - Crystallization Kinetics of Bioactive Glasses in the ZnO-Na2O-CaO-SiO2 System [Articolo su rivista]
G. Malavasi;G. Lusvardi;A. Pedone;M.C.Menziani;M.Dappiaggi; A. Gualtieri; L. Menabue

The crystallization kinetics of Na2OâCaOâ2SiO2 (x ) 0) and 0.68ZnOâNa2OâCaOâ2SiO2 (x ) 0.68, where xis the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using bothnonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showedthat the first glass crystallizes into the isochemical Na2CaSi2O6 phase, whereas the Na2ZnSiO4 crystallinephase is obtained from the Zn-rich glass, in addition to Na2CaSi2O6. The activation energy (Ea) for thecrystallization of the Na2OâCaOâ2SiO2 glass is 193 ( 10 and 203 ( 5 kJ/mol from the isothermal in situXRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from theisothermal method is 1 at low temperature (530 °C), and its value increases linearly with temperature increaseup to 2 at 607 °C. For the crystallization of Na2CaSi2O6 from the Zn-containing glass, higher values of boththe crystallization temperature (667 and 661 °C) and Ea (223 ( 10 and 211 ( 5 kJ/mol) have been foundfrom the isothermal and nonisothermal methods, respectively. The Na2ZnSiO4 crystalline phase crystallizesat lower temperature with respect to Na2CaSi2O6, and the Ea value is 266 ( 20 and 245 ( 15 kJ/mol fromthe isothermal and nonisothermal methods, respectively. The results of this work show that the addition ofZn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, itcauses an increase of Ea for the Na diffusion process, determined using MD simulations, and consequentlyan overall increase of Ea for the crystallization process of Na2CaSi2O6. Our results show good agreementbetween the Ea and n values obtained with the two different methods and confirm the reliability of thenonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determinationof the temperature stability field of the crystalline phases with the view of creating a different glass ceramicuseful in the field of bioactive materials.

2007 - Cytoxicity of zinc-cotaining bioactive glasses in contact with human osteoblasts [Articolo su rivista]

potential clinical application, we have investigated whether zinc-containing 45S5 (HZ) glasses might be cytotoxic for human rs on Bioactive glasses such as Hench’s 45S5 have applications to tissue engineering and bone repair: the insertion of zinc has been proposed to improve their bone-bonding ability and to slacken their dissolution in extracellular body fluids. In view of a MG-63 osteoblasts. In our experimental conditions, after 24 h of incubation HZ glasses released significant amounts of Zn2+ and induced in MG-63 cells release of lactate dehydrogenase (index of cytotoxicity) and the following indexes of oxidative stress: (i) accumulation of intracellular malonyldialdehyde, (ii) increased activity of pentose phosphate pathway, (iii) increased expression of peheme oxygenase-1, (iv) increased activity of Cu,Zn-superoxide dismutase, (v) decreased level of intracellular thiols. These effects were inversely related to the zinc content of glass powders, were mimicked by ZnCl2 solutions and were prevented by either metal chelators (EDTA, NTA) or the antioxidant ascorbate, suggesting that Zn2+ released fastly from HZ glasses can cause MG-63 cell damage via an oxidative stress. This work highlights the importance of designing Zn-containing bioactive glasses without cytotoxic effects and gives supplementary information about the prooxidant role of zinc in living systems.

2007 - Density of multicomponent silica-based potential bioglasses: Quantitative structure-property relationships (QSPR) analysis [Articolo su rivista]
G. Lusvardi; G. Malavasi; L. Menabue; MC Menziani; A. Pedone; U. Segre

The results of a quantitative structure-property relationships (QSPR) analysis of multicomponent silica-based potential bioglasses (containing Na2O, CaO, P2O5 and/or ZnO) are here presented. A quantitative model explaining the variation of the density data measured for series of glasses with different compositions has been obtained by means of a structural descriptor derived from molecular dynamics (MD) simulations. A descriptor able to rationalize the variation in density caused by the overall packing degree of the structural units in the glasses examined has been defined. It is worth noting that the descriptor used allows the fitting of glasses with different composition (presence-absence Of P2O5, ZnO, Na2O and CaO) in the same correlation. The validity of the QSPR approach, which has recently been introduced for the rationalization and prediction of the technology-related properties of a series of complex multicomponent glasses, is confirmed by this work on a larger series of glasses of various compositions. (c) 2006 Elsevier Ltd. All rights reserved.

2007 - Insight into elastic properties of binary alkali silicate glasses; prediction and interpretation through atomistic simulation techniques [Articolo su rivista]
A. Pedone; G. Malavasi; A.N. Cormack; U. Segre; M.C. Menziani

Molecular dynamics simulations and energy-minimization techniques have been applied for the firsttime to determine the whole set of elastic properties (Young’s modulus, shear modulus, bulk modulus,and Poisson’s ratio) of alkali silicate glasses with different ion modifiers (Li, Na, and K) in the range0-30 mol % alkaline oxide. Excellent agreement has been found between the simulation results and theexperimental data. The peculiar behavior of the Li-containing glasses with respect to the Na and K onesis extensively discussed in terms of the glass structural features. It is found that the elastic propertyvariation as a function of alkali addition can be explained by three concurrent factors: (1) depolymerizationof the silica network; (2) increasing the cohesion of the glass by the establishment of alkali-NBO bonds;and (3) decreasing the free volume with consequent increasing of the glass packing density.

2007 - Multitechnique approach to V-ZrSiO4 pigment characterization and synthesis optimization [Articolo su rivista]
C. Caselli; G. Lusvardi; G. Malavasi; L. Menabue; P. Miselli

The synthesis of blue-turquoise V-ZrSiO4 Pigment from an aqueous solution of Na2O center dot 2.5SiO(2)center dot 5H(2)O (soluble glass) and the citrate complexes of zirconium and vanadium was investigated as a function of V2O5 contents, mineralizers (NaF and/or LiNO3) addition and thermal cycle. Blue V-ZrSiO4 was obtained without mineralizers addition for the (ZrO2)(SiO2)(V2O5)(0.09) composition; QPA analysis shows that a thermal cycle 3 h long, T-max = 800 degrees C, can lead to a 78.0 wt.% of ZrSiO4. The addition of mineralizers gave rise to 73.0 wt.% of ZrSiO4 for the (ZrO2)(SiO2)(NaF)(0.16)(V2O5)(0.09)(LiNO3)(0.09) composition and a thermal cycle 2 h long, T-max = 800 degrees C. LiN03 can favour both ZrSiO4 formation and a fairly blue colour, up to LiNO3 = 0.09 moles; NaF seems effective on ZrSiO4 formation only when mixed with LiNO3 through the formation of LiF HT-XRD analysis of this composition agrees with QPA results at the corresponding temperature; ZrSiO4 was present (64.0 wt.%) at 730 degrees C and good colour parameters were obtained. (c) 2006 Elsevier Ltd. All rights reserved.

2006 - A new self-consistent empirical interatomic potential model for oxides, silicates, and silica-based glasses [Articolo su rivista]
A. Pedone; G. Malavasi; MC Menziani; AN Cormack; U. Segre

A new empirical pairwise potential model for ionic and semi-ionic oxides has been developed. Its transferability and reliability have been demonstrated by testing the potentials toward the prediction of structural and mechanical properties of a wide range of silicates of technological and geological importance. The partial ionic charge model with a Morse function is used, and it allows the modeling of the quenching of melts, silicate glasses, and inorganic crystals at high-pressure and high-temperature conditions. The results obtained by molecular dynamics and free energy calculations are discussed in relation to the prediction of structural and mechanical properties of a series of soda lime silicate glasses.

2006 - Cell configuration for focal adhesions in cells seeded onto Zinc-doped silicate-bioglasses [Capitolo/Saggio]

2006 - Physico-chemical characterization and in vivo evaluation of zinc-glasses biocompatibility [Abstract in Atti di Convegno]
G.Lusvardi; G.Malavasi; L.Menabue; M.C. Menziani; A.Pedone; D.Zaffe

Study of soda-lime-phosphosilicate glasses based on Bioglass® and modified by zinc. "In vitro"(SBF) bioactivity was investigated through apatite forming ability and through a preliminary "in vivo" study. Zinc improves chemical durability but does not inhibit the apatite formation; a mixed-metal (Ca-Zn) phosphate-based crystalline layer is identified on the surface of HP5Z5. The improvement of the observed chemical durability can also be rationalized by Molecular Dynamics simulations

2006 - Towards a quantitative rationalization of multicomponent glass properties by means of molecular dynamics simulations [Articolo su rivista]

This review summarizes the achievements obtained by making use of molecular dynamics (MD) simulations in the elucidation of the structure of multicomponent glasses exerting bioactive properties. Emphasis on critical aspects of MD simulations for oxide glasses treatment is given. The potentiality of the quantitative structure-property relationships (QSPR) analysis as a tool for interpretative and predictive purposes is highlighted.

2006 - Void size distribution in MD-modelled silica glass structures [Articolo su rivista]

The void distribution of different models of the silica glass have been analyzed in terms of the Voronoi-Delaunay description of the void space into a disordered system. The silica glass has been modelled by making use of different pair-pair and three body potentials, previously proposed. The glass structural parameters (bond lengths and bond angles) are compared with known experimental data. A computer algorithm has been implemented to apply the Voronoi-Delaunay approach to a system of non-uniform spheres, and it is fully described. The algorithm furnishes the size distribution of interstices into the bulk structure. From this result, the solubility of noble gasses into the glass is computed, and the values obtained are successfully compared to known experimental data. The correlation between void size distribution and ring size distribution in silica glass is discussed. Both the glass structure and void distribution give better agreement to the experimental data when the pair pair interaction is modelled with the potential developed by Beest et al. [B.W.H. Beest, G.J. Kramer, R.A. Santen, Phys. Rev. Lett. 64 (1990) 1955].

2005 - A Computational Tool for the Prediction of Crystalline Phases Obtained from Controlled Crystallization of Glasses [Articolo su rivista]
G. Lusvardi; G. Malavasi; L. Menabue; M. C. Menziani;A.Pedone; U. Segre

An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can separatefrom glasses has been developed. The program analyzes the output of molecular dynamics simulations ofglasses or glass ceramics, systematically sampling the ratios of the ions in different portions of the simulationbox and comparing them to the stoichiometric ratio of compositionally equivalent crystalline phases retrievedfrom a crystal structure database. The efficacy of the similarity index elaborated has been judged by comparingthe results obtained with the crystal phases identified by XRD analysis after thermal treatment in a series ofmulticomponent potential bioactive glasses and glass ceramics for which the advantages of rational-designederosion-controlled release is straightforward.

2005 - Qualitative and quantitative structure-property relationships analysis of multicomponent potential bioglasses [Articolo su rivista]

The results of a qualitative and quantitative structure-property relationships analysis of multicomponent potential bioglasses of composition (2 - y)SiO(2)center dot 1Na(2)O center dot 1.1CaO center dot yP(2)O(5)center dot xZnO (x = 0, 0.16, 0.35, 0.78 and y - 0. 10, 0.20, 0.36) are presented. Quantitative models are obtained by means of structural descriptors derived by molecular dynamics simulations and experimental data measured for density, thermal analysis, 21 Si and IT magic angle spinning NMR, and chemical durability in water. Analysis of the crystal species obtained upon glass crystallization helped in the rationalization of the structural role of the different components. Finally, glass surface characterization with scanning electron microscopy, transmission electron micrsocopy, and X-ray diffraction after soaking in acellular simulated body fluid demonstrated the in vitro bioactivity of the newly obtained 1.80SiO(2)center dot 1Na(2)O center dot 1.1Ca center dot 0.20P(2)O(5)center dot 0.16ZnO (HP5Z5) glass, corresponding to x = 0. 16 and y = 0.20.

2005 - Thermodynamic aspects of the adsorption of hexametaphosphate on kaolinite [Articolo su rivista]
E. Castellini; G. Lusvardi; G. Malavasi; L. Menabue

The adsorption of hexametaphosphate ion, an important deflocculant used in the ceramic industry, from aqueous solutions onto kaolinite has been studied at different temperatures. The adsorption isotherm follows the Langmuir model: the thermodynamic parameters Delta G(ads)(0), Delta H-ads(0) and Delta S-ads(0) as were calculated and found to be consistent with an interaction model involving the formation of an inner-sphere complex between HMP and aluminol groups. Also, the dependence of the adsorption behavior on the kaolinite volume fraction has been studied and discussed in term of association processes between the clay particles.

2005 - Zinc-releasing silicate-bioglasses modulated Bone Cells Activity [Relazione in Atti di Convegno]
Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Menziani, Maria Cristina; Segre, Ulderico; V., Aina; C., Morterra; M. F., Cannas

Two series of glasses of general formula (2-p) SiO21.1Na2OCaOpP2O5xZnO ( p ¼ 0.10, 0.20; x ¼ 0.0, 0.16, 0.35, and 0.78) have been analyzed for physico-chemical surface features before and after contact with simulated body fluid, morphological characteristics, and osteoblastlike cells behavior when cultured on them. The resulted good cell adhesion and growth, along with nonsignificant changes of the focal contacts, allow the authors to indicate HZ5 and HP5Z5 glasses as the ones having optimal ratio of Zn/P to maintain acceptable cell behavior, comparable to the bioactive glass (Bioglass) used as a control; results are also rationalized by means of three-dimensional models derived by molecular dynamic simulations, with decomposition and conversion rates optimized with respect to the parent Hench’s Bioglass

2004 - A combined experimental and computational approach to (Na2O)(1-x) (CaO) (ZnO)(x)2SiO2 glasses characterization [Articolo su rivista]

Insight into the Zn structural role in a series of glasses of composition (Na2O)(1-x) (.) CaO (.) (ZnO)(x) (.) 2SiO(2) (x = 0, 0.2, 0.6 and 1) has been obtained by density measurements, analysis of the crystals separated from the glasses, micro-Raman spectra and molecular dynamics simulations. We found that Zn acts as a weak tetrahedral network former independent of the glass Na content.

2004 - CaO and ZnO in soda-silicate glasses: a molecular dynamics simulation study and experimental characterization [Capitolo/Saggio]

CaO and ZnO in soda-silicate glasses: a molecular dynamics simulation study and experimental characterization

2004 - In vitro evaluation of zirconia nanopowders [Capitolo/Saggio]
S. Braccini; C. Leonelli; G. Lusvardi; G. Malavasi; L. Menabue

ZrO2 is used for a long time as biomaterial. Nanopowders of ZrO2 are prepared via a microwave assisted hydrothermal synthesis and morphological studies carried out by TEM. The powders are tested in vitro and this test does not alter the dimension of the particles.

2004 - Synthesis and in vitro studies of phosphosilicate glasses doped with cerium and zinc oxides [Abstract in Rivista]
Lusvardi, G.; Malavasi, G.; Menabue, L.; Menziani, M.C.; Segre, U.

Glasses based on the Bioglass, formula and doped by the addn. of CeO2 (1.5-13.5%) and ZnO (5-20%) were studied. The addn. if small oxide quantities (1.5% for CeO2 and 5-10% for ZnO) did not significantly alter the ability of the in vitro apatite formation on the glass surface. After 15 days, a mixed-metal (Ca-Zn) or (Ca-Ce) phosphate-based layer was identified. High metal contents improved the chem. durability of the glass, the bioactivity was strongly inhibited and there were no hints of apatite formation obsd. even after prolonged soaking in SBF. The SiO2, 39.4; Na2O, 22.6; CaO, 22.6; P2O5, 10.4; ZnO, 5.0% glass compn. seems to demonstrate an optimal ratio of Zn/P to improve the glass strength and simultaneously yield a Ca/P ratio able to preserve rapid apatite formation.

2004 - Vetri bioattivi contenenti zinco: comportamento in viotro ed in vivo [Abstract in Atti di Convegno]
Lusvardi G.; Zaffe D.; Bertoldi C.; Malavasi G.; Menabue L.; Menziani M.C.; Pedone A.

Vedi allegato

2003 - Characterization and thermal behavior of fluoroapatite and Ti-alloy for orthopedic implants [Capitolo/Saggio]
G. Lusvardi; G. Malavasi; L. Menabue; M. Saladini

Characterization and thermal behaviour of fluoroapatite and Ti-alloy for orthopedic implants

2003 - In vitro bioactivity testing of ZrO2 nanopowders prepared by MW-assisted hydrothermal synthesis [Capitolo/Saggio]

Zirconia nanopowders obtaneid by hydrothermal synthesis were tested in vitro at 60°C for 30 days.Elemental analysis,XRD,SEM,TEM techniques were used for this study.Crystallinity and phase identification was performed before and after in vitro test

2003 - Synthesis and characterization of cerium-doped glasses and in vitro evaluation of bioactivity [Articolo su rivista]
Leonelli, C.; Lusvardi, G.; Malavasi, G.; Menabue, L.; Tonelli, M.

The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilicate glasses based on Bioglass(R) 45S5 (SiO2 45; Na2O 24.5; CaO 24.5; P2O5 6 wt%) doped during melting with (1.5-13.5 wt%) cerium dioxide (CeO2), has been reported. The choice of cerium was related to its low toxicity associated with bacteriostatic properties; cerium-doped bioactive glasses could be useful when implantation concerns local infected areas. The maximum value that permitted forming a homogeneous glass was 13.5 wt% and enabled us to get a better insight into CeO2 effect on the chemical behaviour of glasses. The as-quenched glasses were characterized by means of magnetic and spectroscopic measurements that revealed the prevailing presence of cerium (III). The bioactivity of the glasses was tested by soaking them in a simulated body fluid at 37 degreesC, under continuous stirring. ICP measurements were carried out for ion concentration determinations and the solution/glass interface was investigated by scanning electron microscopy equipped with energy dispersive analyzer (SEM/EDS technique) to check morphological modifications; the solids were investigated by means of X-ray powder diffraction and IR techniques. The results indicated that at low cerium content the glass degradation and repolymerization gave rise to an internal silicon-based layer and an external calcium-phosphate-based layer formed on the glass surface; high cerium content retards the glass degradation and gave rise to ceriumphosphate layer instead of calcium one. The cerium was never found in solution. For the reacted glasses, in the external layer, at 10% and 13.5% CeO2 contents the molar ratio Ca/P were approximate to1 and 0.8 respectively and the molar ratio Ce/P was approximate to0.3 in both cases. On the surface of the glasses with the highest cerium content it could distinguish new regular aggregates mainly formed by cerium and phosphate (Ce/Papproximate to3.5, Ca/Papproximate to0.6). In the cerium-free glass and with low cerium content (1.5 wt%) the calculated Ca/P ratio was 1.67, as calculated for pure hydroxyapatite. At low cerium content (BG-1.5 Cc) the glass behaviour was strictly similar to that of Bioglass(R) 45S5. (C) 2003 Elsevier Science B.V. All rights reserved.

2003 - Zinc addition to sodium-calcium-silicate bioglasses. Theoretical vs experimental results [Capitolo/Saggio]
G. Lusvardi; G. Malavasi; L. Menabue; M.C. Menziani

The glass composition Na2O•CaO•2SiO2 was modified upon addition of ZnO to obtain the series of glasses Na2O•CaO•(2-x)SiO2•xZnO (x=0.15 and 0.19), where x= 0.19 is the maximum zinc content which does not produce phase separation. The glasses were investigated by means of density and thermal measurements (glass transition, Tg, and crystallisation, Tc, temperature); moreover the phases separated upon crystallisation were identified. The results of molecular dynamics (MD) simulations combined with the analysis of the crystal structure of the main phases separated [(Na4Ca4(SiO3)6 and Na2ZnSiO4)] provide insight into the structural role of zinc in the glass network, its limits of solubility and its effect on the short- and medium-range order of the glass structure.

2002 - In vitro characterisation of phosphosilicate and silicate glasses doped with zinc oxide [Articolo su rivista]
Lusvardi, G.; Menabue, L.; Malavasi, G.

It has been shown for various types of glasses and glass-ceramic that the essential condition for them to bond to living bone is the formation of an apatite layer on their surface in the body. Here, the in vitro bioactivity of phosphosilicate and silicate glasses doped with zinc ion has been evaluated. The bioactivity of the glasses was tested by soaking them into a simulated body fluid (SBF) at 37. The soln./glass interface was investigated by SEM to check morphol. modifications: the apatite layer formation was monitored by means of XRD and IR measurements. The degrdn. kinetics of doped glasses has been decelerated. Zinc ion was detected on the reacted surface and its simultaneous presence with calcium and phosphorous atoms could indicate a formation of a mixed zinc-calcium-contg. phase.

2002 - Removal of cadmium ion by means of synthetic hydroxyapatite [Articolo su rivista]
G. Lusvardi; G. Malavasi; L. Menabue; M. Saladini

The reaction behaviour of synthetic hydroxyapatite [Ca-10(PO4)(6)(OH)(2)] (HAP) toward cadmium ion was investigated for the Cd/Ca molar ratio in the range 1-0.005, by means of ions, pH measurements and XRD, SEM, IR techniques. The reaction behaviour between HAP and cadmium ion could be explained by a formation of an amorphous phase and/or a sorption mechanism. (C) 2002 Elsevier Science Ltd. All rights reserved.

2002 - Synthesis, characterization, and molecular dynamics simulation of Na2O-CaO-SiO2-ZnO glasses [Articolo su rivista]
Lusvardi, G.; Malavasi, G.; Menabue, L.; Menziani, M.C.

The glass of composition Na2O.CaO.2SiO(2) was modified upon addition of ZnO to obtain the series of glasses Na2O.CaO.2SiO(2).xZnO (x = 0.17, 0.34, 0.68), where x = 0.68 is the experimentally determined maximum zinc content that does not produce phase separation. The glasses were investigated by means of density and thermal measurements (,(glass-transition and crystallization temperatures); moreover, the phases separated upon crystallization were identified. The results of molecular dynamics (MD) simulations combined with the analysis of the crystal structure of the main phases separated (Na2Ca(SiO3)(2) and Na2ZnSiO4) provided insights into the structural role of zinc and its effect on the short- and medium-range order of the glass structures.