Structural and microstructural studies of zinc-doped glasses from NaCaPO4-SiO2 system

Abstract

Silico-phosphate glasses and glass-ceramics materials from NaCaPO4-SiO2 system have the ability to form strong chemical bonds with living tissue. Their bioactivity is associated with the rapid formation of a thin layer of hydroxycarbonate apatite (similar to biological apatite) on their surface when the materials are implanted or in contact with biological fluids. The bioactive glasses and glass-ceramics have been applied in bone regeneration field, coating of implants and scaffolds. During implantation there is a risk of adherence and colonization of bacteria on the surface of the implants, which may lead to their failure. Bioactive materials containing additions of antibacterial ions can reduce the number of microbes on implants' surface and kill bacteria or inhibit their growth. The choice of zinc was related to its antibacterial properties and fundamental role in bone formation.Several compositions of zinc doped glasses were synthesized by sol-gel method. Using X-ray, Infrared (IR) and Raman spectroscopy, the structure of amorphous state was characterized. It was proved that addition of zinc ions causes depolymerizing influence on phosphate sub-network and the increase of silicate sub-network polymerization level. The morphology and composition of the glasses was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS). Immiscibility takes place in all obtained glasses. The influence of zinc doping on the bioactivity of the glasses from NaCaPO4-SiO2 system was researched. It was noticed that zinc-doped glasses lack bioactive properties. Moreover thermal analysis was carried out to check the thermal properties of the glasses. It was showed that zinc ions introduction provides one step crystallization – the glasses without Zn2+ has three steps crystallization.