Effect of Si and Fe doping on calcium phosphate glass fibre reinforced polycaprolactone bone analogous composites

Reinforcing biodegradable polymers with phosphate-based glass fibres (PGF) is of interest for bone repair and regeneration. In addition to increasing the mechanical properties, PGF can also release bioinorganics, as they are water soluble, a property that may be controllably translated into a fully degradable composite. Herein, the effect of Si and Fe on the solubility of calcium-containing phosphate-based glasses (PG) in the system (50P2O5–40CaO–(10 − x)SiO2−xFe2O3, where x = 0, 5 and 10 mol.%) were investigated. On replacing SiO2 with Fe2O3, there was an increase in the glass transition temperature and density of the PG, suggesting greater crosslinking of the phosphate chains. This significantly reduced the dissolution rates of degradation and ion release. Two PG formulations, 50P2O5–40CaO–10Fe2O3 (Fe10) and 50P2O5–40CaO–5Fe2O3–5SiO2 (Fe5Si5), were melt drawn into fibres and randomly incorporated into polycaprolactone (PCL). Initially, the flexural strength and modulus significantly increased with PGF incorporation. In deionized water, PCL–Fe5Si5 displayed a significantly greater weight loss and ion release compared with PCL–Fe10. In simulated body fluid, brushite was formed only on the surface of PCL–Fe5Si5. Dynamic mechanical analysis in phosphate buffered saline (PBS) at 37 °C revealed that the PCL–Fe10 storage modulus (E′) was unchanged up to day 7, whereas the onset of PCL–Fe5Si5 E′ decrease occurred at day 4. At longer-term ageing in PBS, PCL–Fe5Si5 flexural strength and modulus decreased significantly. MC3T3-E1 preosteoblasts seeded onto PCL–PGF grew up to day 7 in culture. PGF can be used to control the properties of biodegradable composites for potential application as bone fracture fixation devices.