Structure and Stability of High CaO- and P2O5-Containing Silicate and Borosilicate Bioactive Glasses


The present work elucidates about the structure of bioactive glasses having chemical compositions expressed as (mol %) (50.0 - x)SiO2-xB(2)O(3)-9.3Na(2)O-37CaO-3.7P(2)O(5), where x = 0.0, 12.5, 25, and 37.5, and establishes a correlation between the structure and thermal stability. The structural modifications in the parent boron-free glass (BO) with the gradual substitutions of B2O3 for SiO2 are assessed by Raman and Si-29, P-31, B-11, and Na-23 magic angle spinning (MAS)nuclear magnetic resonance (NMR) spectroscopies. The structural studies reveal the presence of Q(Si)(2) and Q(Si)(3) structural units in both silicate and borosilicate glasses. However, Q(Si)(4)(3B) units additionally form upon incorporating B2O3 in BO glass. B-containing silicate glasses exhibit both three-coordinated boron (B-III) and fourcoordinated boron (B-IV) units. The P-31 MAS-NMR studies reveal that the majority of phosphate species exist as isolated orthophosphate (Q(p)(0)) units. The incorporation of B2O3 in B0 glass increases the cross-linking between the SiO4 and BO4 structural units. However, incorporation of B2O3 lowers the glass thermal stability (Delta T), as shown by differential scanning calorimetry. Although both silicate and borosilicate glasses exhibit good in vitro apatite-forming ability and cell compatibility, the bactericidal action against Escherichia coli bacteria is more evident in borosilicate glass in comparison to silicate base glass. The controlled release of (BO3)(3-) ions from boron-modified bioactive glasses improves both the cell proliferation and the antibacterial properties, making them promising for hard tissue engineering applications.



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Prasad, S; Gaddam, A; Jana, A; Kant, S; Sinha, PK; Tripathy, S; Annapurna, K; Ferreira, JMF; Allu, AR; Biswas, K

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The authors thank Dr. K. Muraleedharan, Director, CGCRI, and Dr. Ranjan Sen, Head, Glass Division, CGCRI, for their support and motivation. The authors are grateful to Dr. Vamsi Krishna Balla, Bioceramics Division, for help in animal cell culture studies. They are also grateful to Dr. Rajib Majumder, IICB, for his help in designing the antibacterial test protocol. The authors also appreciate CSIR Extramural Research Fund for Young Scientists (P81-113) and CSIR-HRDG Extramural Research GATE-JRF fellowship for financial support. The NMR studies carried out by A.G. and J.M.F.F. were supported by the project CICECO-Aveiro Institute of Materials, FCT ref UID/CTM/50011/2019, financed by national funds through the FCT/MCTES.

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