An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can... more An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can separate from glasses has been developed. The program analyzes the output of molecular dynamics simulations of glasses or glass ceramics, systematically sampling the ratios of the ions in different portions of the simulation box and comparing them to the stoichiometric ratio of compositionally equivalent crystalline phases retrieved from a crystal structure database. The efficacy of the similarity index elaborated has been judged by comparing the results obtained with the crystal phases identified by XRD analysis after thermal treatment in a series of multicomponent potential bioactive glasses and glass ceramics for which the advantages of rational-designed erosion-controlled release is straightforward.
Journal of materials science. Materials in medicine, 2002
The reaction of biological and synthetic hydroxyapatite Ca5(PO4)3OH (HAP) with Zn2+ ions is inves... more The reaction of biological and synthetic hydroxyapatite Ca5(PO4)3OH (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 degrees C), the reaction with Zn2+ ion is fast and takes place without addition of precipitating anion; synthetic HAP (dried at 1000 degrees C) 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 Zn3(PO4)2.4H2O (Hopeite) at the beginning of reaction and CaZn2(PO4)2.2H2O (Scholzite) at the equilibrium.
In vitro bioactivity features of a Ga-modified sol gel Si-Ca-P glass (SGGa) were investigated, in... more 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 Simulated Body Fluids (SBF) and the consequent growth of an ...
ABSTRACT The glass of composition Na2O.CaO.2SiO(2) was modified upon addition of ZnO to obtain th... more ABSTRACT 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.
The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilica... more The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilicate glasses based on Bioglass® 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
Glasses belonging to the Na(2)O-CaO-P(2)O(5)-SiO(2) system and modified by CaF(2) substitution fo... more Glasses belonging to the Na(2)O-CaO-P(2)O(5)-SiO(2) system and modified by CaF(2) substitution for CaO and Na(2)O alternatively, were synthesized and characterized experimentally and computationally. The results of molecular dynamics simulations show that fluorine is almost exclusively bonded to modifier cations (Ca and Na) with coordination number close to 4. A similar mean coordination number value is found in the crystal phases obtained by means of thermal treatment at fixed temperature. Addition of fluorine increases the polymerization of silicate tetrahedra by removing modifiers from the siliceous matrix. No appreciable amount of Si-F bonds are detected.
The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.... more The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature stability field of the crystalline phases with the view of creating a different glass ceramic useful in the field of bioactive materials.
A series of compounds of N-p-tolylsulfonyl-l-glutamic acid with divalent Cu, Zn and Cd are synthe... more 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), [Cd2(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 ZnII ion exhibits a tetrahedral geometry arising from coordination of two carboxylic oxygens of two
A gallium containing glass 45.7SiO2·24.1Na2O·26.6CaO·2.6P2O5·1.0Ga2O3 (referred to as &am... more 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 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5 (hereinafter represented as "H"), corresponding to Bioglass® 45S5, were functionalized with Tetraethoxysilane (TEOS) and (3-Aminopropyl)triethoxysilane (APTS) in order to improve their ability to bond with biomolecules, such as drugs, proteins, and peptides. Functionalization with TEOS and APTS promoted the 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. Moreover, in vitro study of these functionalized glasses was performed in simulated body fluid (SBF) so as to investigate the effect of functionalization on the bioactive behavior of H and Ga1.0. The results showed that the functionalization was obtained along with maintaining their bioactivity. The surfaces of both functionalized glasses were covered by a layer of apatite within 30 days of SBF immersion. In addition, CaCO3 was also identified on the surface of APTS functionalized glasses. However, no gallium release was detected during SBF soaking.
Bioactive glasses containing gold nanoparticles (AuNPs) have been synthesized via the sol-gel rou... more Bioactive glasses containing gold nanoparticles (AuNPs) have been synthesized via the sol-gel route using HAuCl(4) x 3 H(2)O 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 degrees C presents the best characteristics to be used as a bioactive material, namely high surface area, high amount of AuNPs located at the glass surface, presence of micropores, and abundant surface OH groups. In the case of samples either aged at 60 degrees C or calcined at 150 degrees C, AuNPs just begin their formation, and at this stage the gel is not completely polymerized and dried yet. A thermal treatment at higher temperatures (900 degrees C) causes the aggregation of AuNPs, forming "AuMPs" (i.e., Au microparticles) in a densified glass-ceramic material with low surface area, absence of pores, and low number of surface OH groups. These features induce in the glass-ceramic materials treated at high-temperatures a lower bioactivity (evidenced by SBF reaction), as compared with that exhibited by the glass samples treated at 600 degrees C.
It is demonstrated here that bioactive glasses containing Au nanoparticles (AuNPs) can be selecti... more It is demonstrated here 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. The results evidence the following. (i) At room temperature (RT), no functionalization of Au-free glass occurs, whereas in the case of glasses containing AuNPs, stable linkages form only with amino groups, as in this condition Au does not bind with either thiol or hydroxyl groups. The RT functionalization with cysteine and cystine confirms 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 = 5 and to be hindered by the glass matrix dissolution at pH = 12 (with consequent release of AuNPs), while the best results are obtained at pH = 9. (iii) For the effect of reaction temperature, at 4 °C it is possible to obtain a strong Au-S interaction, whereas at RT, a weak Au-N linkage is formed. These results should allow 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 in protein immobilization).
The results of a quantitative structure-property relationships (QSPR) analysis of multicomponent ... more 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
The synthesis of blue-turquoise V–ZrSiO4 pigment from an aqueous solution of Na2O·2.5SiO2·5H2O (s... more The synthesis of blue-turquoise V–ZrSiO4 pigment from an aqueous solution of Na2O·2.5SiO2·5H2O (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 3h long, Tmax=800°C, can
An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can... more An automatic tool (named CLUSTER) for the prediction of the most probable crystal phases that can separate from glasses has been developed. The program analyzes the output of molecular dynamics simulations of glasses or glass ceramics, systematically sampling the ratios of the ions in different portions of the simulation box and comparing them to the stoichiometric ratio of compositionally equivalent crystalline phases retrieved from a crystal structure database. The efficacy of the similarity index elaborated has been judged by comparing the results obtained with the crystal phases identified by XRD analysis after thermal treatment in a series of multicomponent potential bioactive glasses and glass ceramics for which the advantages of rational-designed erosion-controlled release is straightforward.
Journal of materials science. Materials in medicine, 2002
The reaction of biological and synthetic hydroxyapatite Ca5(PO4)3OH (HAP) with Zn2+ ions is inves... more The reaction of biological and synthetic hydroxyapatite Ca5(PO4)3OH (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 degrees C), the reaction with Zn2+ ion is fast and takes place without addition of precipitating anion; synthetic HAP (dried at 1000 degrees C) 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 Zn3(PO4)2.4H2O (Hopeite) at the beginning of reaction and CaZn2(PO4)2.2H2O (Scholzite) at the equilibrium.
In vitro bioactivity features of a Ga-modified sol gel Si-Ca-P glass (SGGa) were investigated, in... more 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 Simulated Body Fluids (SBF) and the consequent growth of an ...
ABSTRACT The glass of composition Na2O.CaO.2SiO(2) was modified upon addition of ZnO to obtain th... more ABSTRACT 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.
The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilica... more The results of preparation, characterization and in vitro bioactivity evaluation of phosphosilicate glasses based on Bioglass® 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
Glasses belonging to the Na(2)O-CaO-P(2)O(5)-SiO(2) system and modified by CaF(2) substitution fo... more Glasses belonging to the Na(2)O-CaO-P(2)O(5)-SiO(2) system and modified by CaF(2) substitution for CaO and Na(2)O alternatively, were synthesized and characterized experimentally and computationally. The results of molecular dynamics simulations show that fluorine is almost exclusively bonded to modifier cations (Ca and Na) with coordination number close to 4. A similar mean coordination number value is found in the crystal phases obtained by means of thermal treatment at fixed temperature. Addition of fluorine increases the polymerization of silicate tetrahedra by removing modifiers from the siliceous matrix. No appreciable amount of Si-F bonds are detected.
The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.... more The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature stability field of the crystalline phases with the view of creating a different glass ceramic useful in the field of bioactive materials.
A series of compounds of N-p-tolylsulfonyl-l-glutamic acid with divalent Cu, Zn and Cd are synthe... more 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), [Cd2(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 ZnII ion exhibits a tetrahedral geometry arising from coordination of two carboxylic oxygens of two
A gallium containing glass 45.7SiO2·24.1Na2O·26.6CaO·2.6P2O5·1.0Ga2O3 (referred to as &am... more 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 46.2SiO2·24.3Na2O·26.9CaO·2.6P2O5 (hereinafter represented as "H"), corresponding to Bioglass® 45S5, were functionalized with Tetraethoxysilane (TEOS) and (3-Aminopropyl)triethoxysilane (APTS) in order to improve their ability to bond with biomolecules, such as drugs, proteins, and peptides. Functionalization with TEOS and APTS promoted the 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. Moreover, in vitro study of these functionalized glasses was performed in simulated body fluid (SBF) so as to investigate the effect of functionalization on the bioactive behavior of H and Ga1.0. The results showed that the functionalization was obtained along with maintaining their bioactivity. The surfaces of both functionalized glasses were covered by a layer of apatite within 30 days of SBF immersion. In addition, CaCO3 was also identified on the surface of APTS functionalized glasses. However, no gallium release was detected during SBF soaking.
Bioactive glasses containing gold nanoparticles (AuNPs) have been synthesized via the sol-gel rou... more Bioactive glasses containing gold nanoparticles (AuNPs) have been synthesized via the sol-gel route using HAuCl(4) x 3 H(2)O 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 degrees C presents the best characteristics to be used as a bioactive material, namely high surface area, high amount of AuNPs located at the glass surface, presence of micropores, and abundant surface OH groups. In the case of samples either aged at 60 degrees C or calcined at 150 degrees C, AuNPs just begin their formation, and at this stage the gel is not completely polymerized and dried yet. A thermal treatment at higher temperatures (900 degrees C) causes the aggregation of AuNPs, forming "AuMPs" (i.e., Au microparticles) in a densified glass-ceramic material with low surface area, absence of pores, and low number of surface OH groups. These features induce in the glass-ceramic materials treated at high-temperatures a lower bioactivity (evidenced by SBF reaction), as compared with that exhibited by the glass samples treated at 600 degrees C.
It is demonstrated here that bioactive glasses containing Au nanoparticles (AuNPs) can be selecti... more It is demonstrated here 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. The results evidence the following. (i) At room temperature (RT), no functionalization of Au-free glass occurs, whereas in the case of glasses containing AuNPs, stable linkages form only with amino groups, as in this condition Au does not bind with either thiol or hydroxyl groups. The RT functionalization with cysteine and cystine confirms 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 = 5 and to be hindered by the glass matrix dissolution at pH = 12 (with consequent release of AuNPs), while the best results are obtained at pH = 9. (iii) For the effect of reaction temperature, at 4 °C it is possible to obtain a strong Au-S interaction, whereas at RT, a weak Au-N linkage is formed. These results should allow 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 in protein immobilization).
The results of a quantitative structure-property relationships (QSPR) analysis of multicomponent ... more 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
The synthesis of blue-turquoise V–ZrSiO4 pigment from an aqueous solution of Na2O·2.5SiO2·5H2O (s... more The synthesis of blue-turquoise V–ZrSiO4 pigment from an aqueous solution of Na2O·2.5SiO2·5H2O (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 3h long, Tmax=800°C, can
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Papers by Gigliola Lusvardi