Bioglass (R) stimulation of embryonic long-bones in altered loading environments

The 45S5 composition glass (Bioglass (R), USBiomaterials, USA) contains 45 wt% SiO2, 24.5 wt% CaO, 24.5 wt% Na2O and 6 wt% P2O5. It is a low SiO2 (45 wt%) and a high Na2O content glass that results in rapid ion exchange when exposed to physiological solutions. The change in local solution chemistry results in rapid nucleation (1-3 hours exposure) and subsequent crystallisation of hydroxyl-carbonate-apatite (HCA) identical to naturally occurring bone mineral within a hydrated SiO2-rich layer developed on the glass surface. During HCA layer formation, proteins and other growth factors are absorbed into the layer. The synthetic bone mineral layer bonds to collagen, produced by the host tissue, which leads to a strong interfacial bond that is stronger than the host tissue (hard or soft) (Hench and West. 1996). In this study we show that the chemical effects responsible for enhanced bone cell proliferation and differentiation found in-vitro and in-vivo with Bioglass (R) may be sufficient to prevent the demineralisation of bone tissue that occurs as a result of ageing or exposure to a low loading environment i.e. implant/tissue stress-shielding, space-flight.