B2O3-CaO-ZnO sol-gel glasses: Effect of Zn on glass structure and ion release behavior

In this study, we examined the effects of ZnO incorporation on the structural and elemental release properties of calcium borate sol-gel glasses [60B 2 O 3 - (40- x )CaO- x ZnO, where x = 0, 5, 10, and 15 (mol%)]. The glasses were prepared by adding boric acid, zinc lactate trihydrate, and calcium lactate pentahydrate in methanol, followed by drying and calcination. X-ray diffraction patterns showed that all glass samples were successfully prepared. According to the nuclear magnetic resonance and Fourier transform infrared analysis, the ratio of BO 4 decreased with increasing ZnO content. In addition, the formation of diborate was enhanced with increasing ZnO content. The amounts of B and Ca released from the glasses in tris-HCl buffer solution at pH 7.4, decreased with ZnO incorporation, particularly within a few hours after immersion. The substitution of CaO with ZnO strengthened the borate glass structure owing to an increase in the field strength, and the formation of diborate, particularly zinc diborate with central symmetry, may contribute to the increased structural stability. Fibrous glass with a diameter of approximately 350–400 nm was successfully prepared by adding polyvinylpyrrolidone to the sol and using electrospinning. They also exhibited controllable ion release upon ZnO incorporation, suggesting the potential of flexible glasses with the releasability of therapeutic ions, that is, borate, calcium, and zinc ions.