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Professore Associato presso: Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche

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2019 - Biodurability and release of metals during the dissolution of chrysotile, crocidolite and fibrous erionite [Articolo su rivista]
Gualtieri, Alessandro F.; Lusvardi, Gigliola; Zoboli, Alessandro; Di Giuseppe, Dario; Lassinantti Gualtieri, Magdalena

Background: The mechanisms by which mineral fibers induce adverse effects in vivo are still not well understood. The mechanisms of fiber dissolution in the lungs and subsequent release of metals in the extracellular/intracellular environment must be taken into account. Aim: For the first time, the kinetics of release of metals during the acellular in vitro dissolution of chrysotile, crocidolite and fibrous erionite were determined. Methods: In vitro acellular dissolution of chrysotile, crocidolite, and fibrous erionite-Na was conducted using a solution mimicking the phagolysosome environment active during the phagocytosis process (pH=4.5, at 37 °C). The kinetics of release of a representative selection of metals were determined over a period of three months. Results: Despite the fact that the difference in Fe content between chrysotile and crocidolite is one order of magnitude, the much faster dissolution rate of chrysotile compared to crocidolite prompts greater release of available active surface Fe in the first weeks of the dissolution experiment and comparable amounts after 90 d. Such active iron may promote the formation of toxic hydroxyl radicals. The fast release of metals like Cr, Ni and Mn from chrysotile is also a source of concern whereas the release of V in solution is negligible. Conclusion: Because chrysotile undergoes fast dissolution with respect to crocidolite and fibrous erionite, it behaves like a carrier that releases its metals’ cargo in the lung environment, mimicking the phenomenon that explains the toxicity of nanoparticles. Hence, the toxicity paradigm of a non biodurable fiber like chrysotile should also take into account the release of toxic metals in the intracellular/extracellular medium during the rapid dissolution process.

2019 - Cytocompatibility of potential bioactive cerium-doped glasses based on 45S5 [Articolo su rivista]
Malavasi, Gianluca; Salvatori, Roberta; Zambon, Alfonso; Lusvardi, Gigliola; Rigamonti, Luca; Chiarini, Luigi; Anesi, Alexandre

The cytocompatibility of potential bioactive cerium-containing (Ce 3+ /Ce 4+ ) glasses is here investigated by preparing three different glasses with increasing amount of doping CeO 2 (1.2, 3.6 and 5.3 mol% of CeO 2 , called BG_1.2, BG_3.6 and BG_5.3, respectively) based on 45S5 Bioglass®(called BG). These materials were characterized by Environmental Scanning Electron Microscopy (ESEM) and infrared spectroscopy (FTIR) after performing bioactivity tests in Dulbecco's Modified Eagle Medium (DMEM) solution, and the ions released in solution were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Optical Emission Spectrometry (ICP-OES). The data obtained clearly show that the glass surfaces of BG, BG_1.2 and BG_3.6 were covered by hydroxyapatite (HA), while BG_5.3 favored the formation of a cerium phosphate crystal phase. The cytotoxicity tests were performed using both murine long bone osteocyte-like (MLO-Y4) and mouse embryonic fibroblast (NIH/3T3) cell lines. The cerium-containing bioactive glasses show an increment in cell viability with respect to BG, and at long times, no cell aggregation and deformation were observed. The proliferation of NIH/3T3 cells increased with the cerium content in the glasses; in particular, BG_3.6 and BG_5.3 showed a higher proliferation of cells than the negative control. These results highlight and enforce the proposal of cerium-doped bioactive glasses as a new class of biomaterials for hard-tissue applications.

2018 - Biomimetic fabrication of antibacterial calcium phosphates mediated by polydopamine [Articolo su rivista]
Forte, Lucia; Torricelli, Paola; Bonvicini, Francesca; Boanini, Elisa; Gentilomi, Giovanna Angela; Lusvardi, Gigliola; Della Bella, Elena; Fini, Milena; Vecchio Nepita, Edoardo; Bigi, Adriana

In this work we developed new antibacterial composite materials using polydopamine (PDA) to trigger the deposition of silver nanoparticles (AgNPs) onto calcium phosphates, namely octacalcium phosphate (OCP) and α-tricalcium phosphate (αTCP). Functionalization of OCP and αTCP with a self-polymerized polydopamine layer was obtained by soaking the calcium phosphates in dopamine solution. The PDA surface of functionalized calcium phosphates (OCPd and αTCPd) promoted the deposition of AgNPs by reducing silver ions when soaked in a silver nitrate solution. The amount of deposited AgNPs can be modulated by varying the concentration of silver nitrate solution and the type of substrate. The results of in vitro tests carried out with osteoblast-like MG63 cells indicate that the combination of AgNPs with OCP provides more biocompatible materials than those obtained using αTCP as substrate. In particular, the study of osteoblast activity and differentiation was focused on the samples OCPdAg5 (silver content = 8.2 wt%) and αTCPdAg5 (silver content = 4.7 wt%), which did not show any cytotoxicity, and compared with those obtained on pure OCP and αTCP. The results demonstrate that the AgNPs loaded materials support osteoblast viability and differentiation, whereas they significantly inhibit the growth of relevant antibiotic-resistant pathogenic bacteria.

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 - Synthesis and Characterization of TiO2 Nanoparticles for the Reduction of Water Pollutants [Articolo su rivista]
Lusvardi, Gigliola

The aim of this manuscript was the optimization of the synthesis of TiO2 nanoparticles (TiO2 NPs) with conditions that could be easily reproducible at the industrial level. Several procedures were tested and those with C12H28O4Ti and CO(NH2)2 as precursors seemed the most promising and, consequently, were improved with different molar ratios, lower temperatures and the addition of NH4Cl as a secondary dopant of nitrogen. The obtained samples were studied with analytical techniques such as X-ray powder diffraction (XRPD) and field emission scanning electron microscopy (FESEM). To complete the study, dye degradation and bacteriological tests were also performed. The results indicate that it is possible to obtain TiO2 NPs at lower temperatures with respect to those used in the literature; the best candidate that could satisfy all the requirements was a sample with a molar ratio of C12H28O4Ti:CO(NH2)2 at 2:1 and obtained at 50 °C.

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 - Systematic investigation of the parameters that influence the luminescence properties of photoluminescent pigments [Articolo su rivista]
Lusvardi, Gigliola; Malavasi, Gianluca; Menabue, Ledi; Smargiassi, Marco

The formation and quantification of Sr4Al14O25:Eu2+/Dy3+, responsible of specific luminescent properties, was studied as a function of dopants, flux agents, temperature and time of synthesis; this phase was quantified by means of quantitative phase analysis (QPA), using X-Ray Powder Diffraction and Rietveld method. This kind of study gives the possibility to create a specific protocol to find selected parameters that influence the formation of Sr4Al14O25:Eu2+/Dy3+ and their photoluminescence properties. In particular, the present study put in light that a pigment with a slow afterglow decay (high performance by the point of view of its application) must be prepared using low ratios of dopants and varying the synthesis variables in order to maximize the quantity of Sr4Al14O25 as single crystalline phase and to minimize the amorphous phase. Among the synthesis variables, the use of a commercial flux agent based on NH4Cl is very important if compared with that used in the reference synthesis procedure

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 - Crystal structure of a new homochiral one-dimensional zincophosphate containing L-methionine [Articolo su rivista]
Chouat, Nadjet; Hasnaoui, Mohammed Abdelkrim; Sassi, Mohamed; Bengueddach, Abdelkader; Lusvardi, Gigliola; Cornia, Andrea

catena-Poly[[(L-me­thio­nine-[kappa]O)zinc]-[mu]3-(hydrogen phosphato)-[kappa]3O:O':O''], [Zn{PO3(OH)}(C5H11NO2S)]n, a new one-dimensional homochiral zincophos­phate, was hydro­thermally synthesized using L-me­thio­nine as a structure-directing agent. The compound consists of a network of ZnO4 and (HO)PO3 tetra­hedra that form ladder-like chains of edge-fused Zn2P2O4 rings propagating parallel to [100]. The chains are decorated on each side by zwitterionic L-me­thio­nine ligands, which inter­act with the inorganic framework via Zn-O coordination bonds. The structure displays inter­chain N-H...O and O-H...S hydrogen bonds.

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 - 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 - 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 - 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 - 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 - 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 - In vitro biodurability of the product of thermal transformation of cement–asbestos [Articolo su rivista]
Alessandro F. Gualtieri; Alberto Viani; Giulia Sgarbi; Gigliola Lusvardi

To safely recycle the product of the thermal transformation of cement–asbestos as secondary raw material,its toxicity potential should be assessed by in vitro biodurability tests. In this work, the acellularin vitro biodurability of the products of transformation of cement–asbestos at 1200 ◦C (named KRY·AS)was tested using both inorganic and organic simulated lung fluids at pH 4.5. The dissolution kineticswere followed using chemical, mineralogical and microstructural analyses. The total dissolution timeestimated from the experiments with inorganic HCl diluted solution is one order of magnitude higherthan that determined from the experiments with buffered Gamble solution (253 days vs. 20 days). Thekey parameter determining the difference in dissolution rate turns out to be the solidus/liquidus ratiowhich prompts a fast saturation of the solution with monosilicic acid. The calculated dissolution rateconstants showed that the biodurability in vitro of KRY·AS is much lower with respect to that of standardchrysotile asbestos (total estimated dissolution time of 20 days vs. 298 days, respectively). This proves alow potential toxicity of this secondary raw material.

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 - 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 - Recycling of the product of thermal inertization of cement–asbestosfor various industrial applications [Articolo su rivista]
Alessandro F. Gualtieri;Carlotta Giacobbe;Lorenza Sardisco;Michele Saraceno;Magdalena Lassinantti Gualtieri; Gigliola Lusvardi;Cinzia Cavenati; Ivano Zanatto

Recycling of secondary raw materials is a priority of waste handling in the countries of the Europeancommunity. A potentially important secondary raw material is the product of the thermal transformationof cement–asbestos, produced by prolonged annealing at 1200–1300C. The product is chemically comparableto a Mg-rich clinker. Previous work has assured the reliability of the transformation process. Thecurrent challenge is to find potential applications as secondary raw material. Recycling of thermally treatedasbestos-containing material (named KRY-AS) in traditional ceramics has already been studied withsuccessful results.The results presented here are the outcome of a long termed project started in 2005 and devoted to therecycling of this secondary raw materials in various industrial applications. KRY-AS can be added in medium-high percentages (10–40 wt%) to commercial mixtures for the production of clay bricks, rock-woolglasses for insulation as well as Ca-based frits and glass–ceramics for the production of ceramic tiles. Thesecondary raw material was also used for the synthesis of two ceramic pigments; a green uvarovite-basedpigment [Ca3Cr2(SiO4)3] and a pink malayaite-based pigment [Ca(Sn,Cr)SiO5]. The latter is especiallyinteresting as a substitute for cadmium-based pigments. This work also shows that KRY-AS can replacestandard fillers in polypropylene plastics without altering the properties of the final product. For eachapplication, a description and relevant results are presented and discussed.

2011 - Structural and spectroscopic characterization of anorthite synthesized from secondary raw materials [Articolo su rivista]
Alessandro Francesco Gualtieri; Giovanni B. Andreozzi; Carlotta Giacobbe;Gigliola Lusvardi;Cecilia Viti

Recycling of secondary raw materials is a priority of waste handling in the countries of theEuropean community. A virtual secondary raw material of great importance is the product ofthe thermal transformation of cement – asbestos. This work illustrates the study of calcinationproducts obtained starting from the product of the thermal transformation of cement-asbestosat 1200 °C, added to primary raw materials (kaolin, aluminum hydroxide) and boric acid asmineralizing agent. The calcination has been conducted at 1200 °C for 1 hour. Thecrystallization kinetics has been monitored using in situ high temperature X-ray powderdiffraction. The microscopic characterization of the final product of calcination has beenconducted with SEM and TEM imaging supported by X-ray microanalysis. The structurerefinement was conducted on the powder sample using the Rietveld method. The results arecompared with the spectroscopic characterization including Mössbauer and UV-Visspectroscopies. The final product of the calcination is essentially anorthite (about 89 wt%)with minor spinel (11 wt%). All experimental data converge to support the hypothesis thatthe anorthite is stoichiometric, and the small amounts of iron detected (1.32 wt%) is Fe3+hosted in the structure of spinel

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.

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 - Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line [Articolo su rivista]
Federica, Giantomassi; Gualtieri, Alessandro; Lory, Santarelli; Marco, Tomasetti; Lusvardi, Gigliola; Guendalina, Lucarini; Mario, Governa; Armanda, Pugnaloni

Asbestos fibres can be transformed into potentially non-hazardous silicates by high-temperature treatmentvia complete solid-state transformation.A549 cells were exposed to standard concentrations of raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200C (Cry_1200 and KRY-AS, respectively),raw commercial grey cement (GC). Cell growth rate and viability (MTT test) were detected in vitro. RCA and KRY-AS subjected to comprehensive microstructural study by electron microscopy were furtherin vitro assayed to compare their cytotoxic potential by morphostructural studies, proliferation index (Ki-67 antigen), apoptosis induction (AO/EB staining) assays and detection of intracellular reactive oxygen species (ROS) with the fluorescent DCFA dye. More severe cytotoxic damage was induced by RCA than by KRY-AS after each incubation period. Exposure to KRY-AS and GC resulted in comparable cell growth rates and cytotoxic effects. Cells incubated with RCA showed greater apoptotic induction and ROS production and a lower cell proliferation index than those exposed to KRY-AS. Chrysotile asbestos and RCA subjected to heat treatment underwent complete microstructure transformation. The final productof heat treatment of cement asbestos, KRY-AS, was considerably more inert and had lower cytotoxic potential than the original asbestos material in all in vitro tests

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 - 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 - 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.

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 - 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 - 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 - Nuovi vetri bioattivi contenenti zinco. [Abstract in Rivista]
Bertoldi C.; Zaffe D.; Lusvardi G.; Pellacani C.; Consolo U.

Vedi allegato

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 - Vetri bioattivi con elementi stimolanti l’osteogenesi: primi risultati nel ratto [Articolo su rivista]
Bertoldi, Carlo; Zaffe, Davide; Consolo, Ugo; Lusvardi, Gigliola; A., Lucchi; Menabue, Ledi

Introduzione e scopo: Numerose composizioni di vetri bioattivi sono state proposte dopo l'iniziale biovetro di Hench presentato negli anni '70. In realtà il range di variazione della composizione di un vetro bioattivo è abbastanza ridotto soprattutto in rapporto ai suoi elementi pesanti si vuole mantenere l'effetto osteoinduttivo. Ciò in particolarmente in rapporto allo zinco che ne costituisce una fase critica sia da un punto di vista chimico che biologico.Un problema manifestato dal vetro di Hench era quello di agire con buona performance ma di esaurire in fretta la sua azione. Scopo della nostra ricerca preliminare è di studiare il comportamento di vetri contenenti zinco a seguito di impianto degli stessi su modelli biologici standardizzati (muscoli paravertebrali e calvaria di ratto) e di confrontarlo con quello conseguito all’innesto del biovetro di Hench. Materiali e metodi: Vetri bioattivi modificati, derivanti dal bio-glass ® 45S5 di Hench sono stati prima testati chimicamente al fluido biologico somulato con spettroscopia al plasma e analisi diffrattometrica X. Impiantati in 10 ratti maschi Sprague Dawley in forma di polvere e cilindri nei muscoli paravertebrali ed in forma di placchette in difetti critici prodotti sulla calvaria. Sono state analizzati a split-back e su calvaria vetri con concentrazioni al 5% e 20% di zinco e vetro di Hench. Gli animali sono stati sacrificati a 30 giorni dall’intervento e sono state eseguite analisi microradiografiche, al microscopio elettronico a scansione ed istologiche. Risulatati: La diffusione degli ioni zinco si dimostrava assolutamente contenuta allo studio spettroscopico e diffrattomentrico mentre clinicamente gli animali non presentavano reazioni patologiche rilevanti all’innesto. I campioni contenenti un maggior contenuto di zinco parevano essere meno soggetti a degradazione rispetto agli altri e le forme granulari erano degradate con maggior velocità rispetto a quelle compatte. La presenza di uno strato positivo alla fosfatasi alcalina in rapporto alla superficie del biovetro assieme alla deposizione di strati di connettivo presumibilmente osteogenico uniformano sostanzialmente il comportamento dei vetri testati ed il loro potenzaile osteogenetico. Conclusione: La presenza di zinco (almeno fino alle concentrazioni testate) nel vetro pare essere inversamente proporzionale alla reattività dello stesso per cui l’utilizzazione di questo ione pare essere funzionale nel regolare i tempi di bioattività dello stesso vetro senza pesare significativamente sulla biocompatibilità degli stessi preparati.

2007 - Biocompatibilità di nuovi vetri bioattivi contenenti zinco. [Abstract in Rivista]
Bertoldi C.; Zaffe D; Lusvardi G.; Consolo U.; Menabue L.

Vedi allegato

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 - 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 - 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.


Chem. investigations have been performed on deflocculated suspensions of kaolinite previously treated with two widely employed dispersants: sodium hexametaphosphate (NaHMP) and sodium disilicate (NaDIS). F. Andreola et al. (2006) showed remarkable differences in the rheol. behavior between untreated and treated samples. The release of ions by kaolinite dispersed in deflocculant solns. results strongly affected by the nature of the treatment. The chem. anal. of the soln. phase sepd. from the suspensions of treated and untreated kaolinite provides relevant information about the deflocculation mechanism of HMP and DIS and gives reason of the obsd. differences in the rheol. responses.

2007 - Valutazione delle proprietà fisiche e chimiche dei camici anti-X reperibili sul mercato italiano” Atti Convegno Nazionale di radioprotezione: Sicurezza e Qualità in Radioprotezione [Relazione in Atti di Convegno]
M. Cecchini; G. Lusvardi; D. Acchiappati

Dispositivi di Protezione Individuali (DPI)come i camici anti-X sono stati studiati al fine di verificarne le proprietà schermanti che dipendono sia dal tipo e spessore di materiale, che dallo spettro di energia della radiazione RX incidente.Storicamente erano costituiti di piombo, ma a causa dei problemi ambientali e del peso eccessivo del DPI, si cercano materiali alternativi. Lo scopo del presente lavoro è di analizzare nuovi camici reperibili sul mercato, vericare l'assenza di piombo ed analizzare le proprietà fisiche e chimiche

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

2006 - Nickel ions release in patients with fixed orthodontic appliances [Articolo su rivista]
L.Levrini; G. Lusvardi; D. Gentile

AIM: The extent to which orthodontic appliances can cause contact allergies due to nickel release is a controversial matter. Since the data provided by literature are contrasting, the Authors think that it is important to analyse nickel ions released in organic tissues by means of a plasma spectrometer. METHODS: About 100 intact hairs were taken from 15 patients wearing fixed orthodontic appliances. The hairs had been washed 12 to 24 h before, in order to limit environmental contamination. The same procedure was carried out on a control group corresponding in sex, age and abode. The samples of hair were taken from at least 3 different scalp sites: frontal, vertex and occipital areas. RESULTS: According to the spectrophotometric analysis of the hair, there were no differences in nickel concentrations between the test group (0.50 mg/g on average) and control group (0.64 mg/g) (*P<0.005). The mean value was reduced even further if minimum and maximum values were excluded (test group 0.46 mg/g, control group 0.52 mg/g). Even though there was a slight difference (0.14 mg/g), it showed that more nickel concentration was found in the control sample (without orthodontic appliances) to a maximum of 2.20 mg/g. This suggests that environmental contamination, in particular diet, has an influence on ion concentration. Other studies also confirm that gut absorption of nickel released in the mouth by orthodontic appliances is much lower than the absorption of nickel release through diet. CONCLUSIONS: It can be assumed that orthodontic appliances do not release significant values of nickel to be a risk factor to the patient's health

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 - Role of the surface treatment in the deflocculation of kaolinite [Articolo su rivista]
F. Andreola; M.C. Romagnoli; E. Castellini; G. Lusvardi; L. Menabue

Suspensions of untreated and properly treated Na-exchanged kaolinite have been subjected to rheological investigations using sodium hexametaphosphate (NaHMP) or sodium disilicate (DIS) as deflocculants. The treatment of the clay consisted of a 24 h contact with solutions of NaHMP or DIS and separation of the resulting solid phase. This was then used to form the suspensions subjected to the rheological measurements. The results indicate that the dispersion ability of each deflocculants is remarkably influenced by the type of treatment. In particular, with respect to the untreated kaolinite, the efficiency of DIS is dramatically increased when the clay has been previously treated with a NaHMP solution. On the other hand, a decrease in the dispersant ability of NaHMP is observed from the untreated kaolinite to the one previously treated with DIS.

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 - Preliminary experiments of in situ atomic force microscopy observation of hydroxyapatite formation on bioactive glass surface [Articolo su rivista]
Leonelli, C.; Lusvardi, G.; Menabue, L.; Tonelli, M.

This paper demonstrates the use of atomic force microscopy (AFM) to image the bioactivity of phosphate glasses that are well-known to react rapidly in simulated body fluid. The present study demonstrates that the hydroxyapatite (HAP) crystalline layer found via AFM in the examined samples coincides with that identified using scanning electron microscopy. Moreover, the effect of a notorious bacteriostatic cation-tetravalent cerium, Ce(IV)-on the kinetics of the HAP layer is investigated in CeO2-doped bioactive glasses.

2002 - Reactivity of biological and synthetic hydroxyapatite towards Zn(II) ion, solid-liquid investigations [Articolo su rivista]
G. Lusvardi; L. Menabue; M. Saladini

The reaction of biological and synthetic hydroxyapatite Ca-5(PO4)(3)OH (HAP) with Zn2+ ions is investigated as a function of Zn2+/Ca2+ molar ratio, time, temperature and electrolyte type (NaCl, NaHCO3, Na2HPO4) by means of pH, pZn, pCa measurements, in aqueous solution. Biological powdered HAP invariably affords an almost quantitative reaction, while Zn2+ precipitated only partially by reaction with cubelets of biological HAP. Using powdered biological HAP and synthetic HAP (dried at 100 degreesC), the reaction with Zn2+ ion is fast and takes place without addition of precipitating anion; synthetic HAP (dried at 1000 degreesC) reacts if free phosphate ions are present. The solid phases separated after different reaction times are investigated by means of X-ray diffraction (XRD), IR, SEM techniques and elemental analysis (C,H,N). The solid phases contain Zn-3(PO4)(2) . 4H(2)O (Hopeite) at the beginning of reaction and CaZn2(PO4)(2) . 2H(2)O (Scholzite) at the equilibrium.

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.

2001 - Influence of small additions of Al2O3 on the properties of the Na2O center dot 3SiO(2) glass [Articolo su rivista]
Leonelli, Cristina; Lusvardi, Gigliola; Montorsi, Monia; Menziani, Maria Cristina; Menabue, Ledi; P., Mustarelli; L., Linati

Changes in the structural properties of sodium alumine-silicate glasses of general formula Na2O . xAl(2)O(3). (3-x)SiO2 were investigated as a function of Al2O3 concentration. The experimental evidences provided by density, elastic modulus, glass chemical resistance measures, Si-29 and Al-27 MAS NMR investigations were complemented by molecular dynamics simulations. While neither of the experimental techniques or computational investigation utilized in this study were able to furnish unequivocable responses for the rationalization of the measured properties of sodium alumine-silicate glasses, the synergistic application of experimental and computational techniques showed that the anomalies observed in bulk properties like density and elastic modulus find their origin in medium-range structural features.

1999 - Coordination properties of N-p-tolylsulfonyl-L-glutamic acid toward metal(II) - Part 1. Crystallographic study on Zn-II and Cd-II complexes [Articolo su rivista]

A series of compounds of N-p-tolylsulfonyl-L-glutamic acid with divalent Cu, Zn and Cd are synthesized and characterized. For the complexes [Zn(tsgluO)(H2O)(2)]. H2O (1), [Cd-2(tsgluO)(2)(H2O)(6)] (2) and [Cd(bipy)(tsgluO)] (3) the crystal and molecular structure have been determined by X-ray diffraction (tsgluO=N-p-tolylsulfonyl-L-glutamate dianion, bipy=2,2'-bipyridine). In compound 1 the Zn-II ion exhibits a tetrahedral geometry arising from coordination of two carboxylic oxygens of two amino acid molecules and of two water molecules. In compound 2 each Cd-II ion of the dimeric unit is coordinated by oxygen atoms of tsgluO(2-) and water molecules in a distorted octahedral environment. In compound 3 the Cd-II ion is coordinated by 2,2'-bipyridine nitrogens and four oxygen atoms from three different tsgluO(2-) in a distorted octahedral geometry. (C) 1999 Elsevier Science Ltd. All rights reserved.


Fluroapatite synthetic powders used as bioceramic coatings onto metallic substrate:the coatings are obtained by plasma spray tecnique ant its high temperature could modify the chemistry of the coating. Thermal behaviour of fluoroapatite is studied by means of diffractometric, infrared study and thermal analysis.After thermal treatment its high crystallinity,chemical and physical properties are maintained.The thermal effect cause a loss of weight due principally to CaCO3 decomposition, present as minor phase in the untreated fluoroapatite

1999 - Microstructure at the interface solution/bioactive glass cerium and silver addition in bioactive phosphosilicate glasses [Articolo su rivista]
Leonelli, Cristina; Lusvardi, Gigliola; Menabue, Ledi

Phosphosilicate glasses added with silver and cerium are studied in order to verify their bioactivity; the study is carried out in vitro and the results indicated that these glass are potentially bioglasses.

1997 - Factors influencing the removal of Pb(II) ion by means of hydroxyapatite [Articolo su rivista]
G. Lusvardi; L. Menabue; M. Saladini

The reaction behaviour of synthetic hydroxyapatite, Ca-5(PO4)(3)OH (HAP) toward the Pb(II) ion is investigated for the Pb/Ca molar ratio range 1-0.01, at different temperature values, surface areas of HAP, pH values and solid/liquid ratio by means of ion concentration and pH measurements, powder diffractometry and I.R. spectroscopy. The Pb-containing solid phase is invariably Pb-5(PO4)(3)OH (PbAP) and in addition, at pH>6, the presence of 3PbO . H2O is also verified. The rate of the reaction depends mainly on pH, Pb/Ca molar ratio and HAP surface area and is due to PbAP precipitation alternated with to HAP dissolution. At a Pb/Ca molar ratio of 0.01 the adsorption Pb(ll) on the HAP surface should also occur. At Pb/Ca molar ratios in the range 1-0.6 the reaction is quantitative only at a high surface area. At Pb/Ca molar ratios in the range 0.2-0.01 the reaction is quantitative irrespective of the surface area. For the molar ratio Pb/Ca = 0.01 the EPA limit level of 0.015 mg/l is reached after 2 days by using HAP with a surface area of 57.80 m(2) g(-1).

1995 - Cadmium(II) N-(p-toluenesulphonyl)-L-glutaminate [Articolo su rivista]

Crystals of [Cd(C12H15N2O5S)(2)] contain dimensional polymeric network in which Cd2+ ions are octahedrally coordinated by O atoms.

1995 - Coordination properties of sulfonyl-N-aminoacids: Crystal and molecular structure of the [Zn(II)(N-(p-toluenesulfonyl)-L-glutaminate)(2)(H2O)(2)] complex [Articolo su rivista]
G. Lusvardi; L. Menabue; M. Saladini

The coordination behavior of N-tosyl-L-glutamine (hereafter abbreviated as tsglnH, tosyl = toluenesulfonyl group) toward the Zn(II) ion is investigated by means of structural and spectroscopic techniques. From aqueous solution, at acidic pH the Zn(II) ion separates a compound of empirical formula Zn(tsgln)(2) . 2H(2)O whose crystal structure is determined. The crystal is monoclinic, space group C2, with cell dimensions: a = 19.775(5), b = 5.3146(3), c = 16.543(8)Angstrom, beta = 119.93(3)degrees, Z = 2. The Zn(II) is tetrahedrally coordinated by two symmetry-related tsgln monoanions acting as monodentate carboxylate Ligands and two symmetry related water molecules. The Zn-O bond distances are similar while the angles at Zn(II) ion differ significantly from those of regular tetrahedron. The side chain amide group does not participate in metal coordination and forms intermolecular hydrogen bonds.

1995 - Crystal structure of lead hydroxyapatite from powder X-ray diffraction data [Articolo su rivista]
Brückner, S.; Lusvardi, G.; Menabue, L.; Saladini, M.

The crystal structure of lead hydroxyapatite, Pb-10(PO4)(6)(OH)(2), is refined on powder XRD data using the Rietveld method. The unit cell is hexagonal, a=b=9.866(3) and c=7.426(2) Angstrom, space group P6(3)/m, Z=1 (relative to the specified formula). Results are discussed and compared with previous structures of hydroxyapatite and partially lead-substituted hydroxyapatites. Now that the entire range of lead substitution is covered, it is possible to detect a coherent trend in the distortions of the crystal packing introduced by the different ability of the two metallic crystal sites to accommodate Pb ions.

1995 - Effect of pH and anions on hydroxyapatite-Cu2+ solid-liquid interactions [Articolo su rivista]

The reaction of synthetic Ca-5(PO4)(3)OH (HAP) with CU2+ ions is investigated by means of pH, pCu and pCa measurements as a function of the time, pH and electrolyte type (NaCl, NaHCO3, Na2HPO4). The solid phases separated after different reaction times are investigated with X-ray diffraction (XRD) and IR techniques. The Cu2+ does not form mixed compounds with Ca2+ and does not replace Ca2+ in the HAP structure. The presence, in an appropriate concentration, of anions which form very insoluble Cu2+ compounds favours the precipitation of the latter with no involvement of HAP. If the concentration of the anions is low, the precipitation of Cu2+ also involves HAP and this behaviour is particularly enhanced with Na2HPO4.

1995 - Reaction behaviour of hydroxyapatite toward the Zn2+ ion. [Capitolo/Saggio]

The reaction of synthetic hydroxyapatite, Ca5(PO4)3OH (HAP), with Zn2+ ions is investigated by means of pH, pZn, pCa and pNa measurements as a function of the time, temp. (40 and 60) and salts compn. and at different Zn2+/Ca2+ molar ratios in the range 1 - 0.1. The solid phases sepd. after different times of reaction were investigated with XRD and IR techniques. The Zn2+ ions added to HAP give rise to a soln. with pH >6 which inhibits any reaction involving HAP. No effect is obsd. by addn. of NaCl. At pH <5 Zn2+ forms Zn3(PO4)2.2H2O and does not replace Ca2+ in HAP structure. The addn. of an excess of NaHCO3 or a mixt. of NaHCO3 and Na2HPO4, with a molar ratio NaHCO3/Na2HPO4 = 30 gives rise to the formation ZnCO3 (smithsonite).

1994 - Substituent effect on the coordination ability of the amide group of N-protected amino acids [Articolo su rivista]

The binary system Cu(II)-hydantoic acid (hydaH) and the corresponding ternary systems with 2,2'-bipyridine(bpy) and 1,10-phenanthroline (ophen) were investigated both in the solid state and solution. The crystal and molecular structure of the complex [Cu(ophen)(hyda)2].H2O was also determined. The crystal of the compound C18H20CuN6O7 is monoclinic, space group P2(1)/c, a = 7.601(5), b = 14.647(2), c = 19.714(3) angstrom, beta = 96.57(3), Z = 4, R = 0.049, R(w) = 0.053. The structure consists of discrete [Cu(ophen)(hyda)2] units and lattice water molecules. The Cu(II) atom is coordinated in the equatorial plane by two nitrogens from the ophen molecule and two oxygens from two hydantoate anions; the nitrogen atom of the neutral NH group of a hydantoate anion occupies the more distant fifth position (Cu-N(l) = 2.541(5) angstrom) giving rise to elongated square-pyramidal geometry. In solution the carboxylate species [CuL2] is formed in the binary system and the species [CuAL2], [CuAL(OH)] in the ternary systems with bpy and ophen. Spectroscopic data indicate that any possibility of the NH group being coordinated in solution can be excluded.

1993 - Effect of Cu2+ Ion on the Structural Stability of Synthetic Hydroxyapatite [Articolo su rivista]

The reaction of synthetic hydroxyapatite, Ca5(PO4)3OH (HAP), with Cu2+ ions is investigated by means of pH, pCu and pCa measurements as a function of the time and temperature (30, 40, 45 and 60-degrees-C) and at different CU2+:Ca2+ molar ratios in the range 0.01-1.07. The solid phases separated after different times of reaction were investigated with XRD and IR techniques. The Cu2+ ions give rise to an acidic solution and promote HAP dissolution; HAP does not incorporate the Cu2+ ions and a new phase corresponding to the mineral Cu2(PO4)OH (Libethenite) crystallizes quantitatively. In the course of the reaction, with the ratio Cu2+:Ca2+ in the range 0.1-1, the pH decreases owing to the release of phosphoric acid, whereas it increases for the ratio 0.01. At physiological ionic strength, obtained with NaCl, the solid phase containing Cu is again libethenite, but the process is notably accelerated.