Delayed degradation of poly(lactide-co-glycolide) accelerates hydrolysis of poly(ε-caprolactone) in ternary composite scaffolds

Currently available biodegradable scaffolds do not ensure mechanical stability combined with degradation profile needed for an optimal support of bone tissue regeneration. In the present study a step towards scaffolds with tuned degradation rates was made by correlating the lactide to glycolide ratio of the PLGA part of ternary composite scaffolds with the resulting hydrolysis kinetics. The scaffolds were composed of a poly(ε-caprolactone) (PCL) matrix containing 5 wt% of tricalcium phosphate and 25 wt% of PLGAs with three different lactide to glycolide ratios. The scaffolds were fabricated using Fused Deposition Modelling and subsequently incubated in phosphate buffered saline and simulated body fluid for up to 81 weeks. Degradation was analysed by taking change of mass of the samples, water absorption, pH, molecular weight, mechanical properties, surface morphology and crystallinity as indices. Our findings suggest that the degradation rate of the ternary composite scaffolds was inversely correlated to the degradation rate of the PLGA: slower degrading PLGAs were retained longer in the PCL matrix and caused its more advanced hydrolysis. The release of acidic degradation products of the PLGA hindered precipitation of calcium phosphates (CaPs). A late-reinforcement phenomenon was observed simultaneously with precipitation of the CaPs. Thus the ternary composite system represents a suitable tool to tune degradation rate of polyesters for applications as biodegradable implants or tissue engineering constructs.