Study on a novel double-layered composite membrane of Mg-substituted nano-hydroxyapatite/poly(l-lactide-co-ε-caprolactone): Effect of different l-lactide/ε-caprolactone ratios

Three novel double-layered composite membranes consisted of Poly(l-lactide-co-ε-caprolactone) (P(LLA-CL)) cast layer and Mg-substituted nano-hydroxyapatite/P(LLA-CL) (Mg-n-HA/P(LLA-CL)) composite electrospun layer with different LLA/CL ratios of 70/30, 80/20 and 92/08 were fabricated by combining solvent casting with electrospinning. The effects of different LLA/CL ratios on surface morphology, microstructure, mechanical properties, in vitro degradation and bioactivity of double-layered composite membrane were characterized by SEM, universal testing machine and in vitro soaking in simulated body fluid (SBF) solution, and the relationship between the structural and the properties was investigated. The results showed that Mg-n-HA particles were uniformly distributed on the P(LLA-CL) nanofibers, and the two layers between P(LLA-CL) cast layer and Mg-n-HA/ P(LLA-CL) composite electrospun layer were well combined, and the double-layered membranes had good bioactivity. However, the ratio of L-LA/CL had a significant effect on the mechanical property and degradation rate of double-layered membranes, owing to different elasticity and degradability. That is to say, P(LLA-CL, 70/30) polymer caused a low stress strength and fast degradation, while P(LLA-CL, 92/08) polymer brought about a poor practicability because of the cured appearance during degradation in SBF. Compared to the above two polymers, P(LLA-CL, 80/20) polymer endowed the double-layered membrane with the most appropriate tensile strength and elasticity, and moderate in vitro degradation rate, suggesting that it had the greatest potential in developing the novel double-layered composite membrane for guided bone regeneration membrane.