Bioactive behavior of a borate glass

For the past 30 years, the bioactive characteristics of special glass compositions have been demonstrated. Until now, phosphate containing soda-lime-silicate glasses such a 45S5 Bioglass®, were used to stimulate bone repair. Through the formation of an osteoconductive layer of hydroxyapatite (the main inorganic compound of bone) on the glass surface, direct bonding with bone will then occur. The rate of formation of hydroxyapatite was studied for the first silica-free borate glass of composition analogue to 45S5 and for a partially crystallized 45S5 glass. An cell-free process has been modeled to assess the formation of hydroxyapatite on the glass. The process involves the reaction of borate glass particles in phosphate solution of various molarity and starting pH. The formation of hydroxyapatite was observed best in a 0.1 Molar phosphate solution for both glasses. The reaction products have been investigated using X-ray diffraction (XRD), Infrared (IR) spectroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP). The positive outcome of the model lead to further investigation of the borate glass. In vitro experiments were performed using MC3T3-E1 bone cells. The borate glass provided a marginally suitable environment for the growth of cells due to the release of boron. Successful in vivo experiments demonstrated bone growth around the borate glass particles very similar to that for the commercially used 45S5 glass. The successful bioactive response obtained with the first silica-free glass composition opens the way to the development of other compositions for bioactive use. Based on our study, future medical applications of a bioactive borate glass may dramatically reduce the rehabilitation time for patients --Abstract, page iv