Structural characterization by x-ray methods of novel antimicrobial gallium-doped phosphate-based glasses

Antimicrobial gallium-doped phosphate-based glasses of general composition (P2O5)(0.45)(CaO)(0.16)(Na2O)(0.39-x)(Ga2O3)(x) (where x=0, 0.01, 0.03, and 0.05) have been studied using the advanced synchrotron-based techniques of Ga K-edge x-ray absorption spectroscopy and high-energy x-ray diffraction to provide a structural insight into their unique properties. The results show that the Ga3+ ions are octahedrally coordinated. Furthermore, substitution of Na2O by Ga2O3 strengthens the phosphate network structure because the presence of GaO6 octahedra inhibits the migration of the remaining Na+ ions. The results are discussed in terms of the use of Na2O-CaO-P2O5 glasses as controlled-delivery devices for antimicrobial Ga3+ ions in biomedical applications. We are thereby able to relate the atomic-scale environment of the Ga3+ ions beneficially to the glass dissolution, and thus to their ability to disrupt bacterial cell activity by usurping the role of iron.