Studies on enzymatic degradation of multifunctional composite consisting of chitosan microspheres and shape memory polyurethane matrix

Abstract Degradation studies of the multifunctional 3b-PU/CH-M composite consisting of 2.5 (wt.%) chitosan microspheres (CH-M) incorporated into crosslinked poly(caprolactone/lactide-co-glycolide) (PCL/PLGA) - urethane matrix (3b-PU) were performed in vitro in phosphate buffered saline (PBS) with lysozyme (Lys). The degradation process of the composite was monitored and analyzed via scanning electron microscopy (SEM), weight loss, pH measurement, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA-FTIR). FTIR analysis of chemical structure and mechanical properties measurement were also performed. Three stages of degradation were distinguished during 6 months studies: first - lasting the first 4 weeks associated with morphology changes of CH-M embedded in the outer layer of the composite film and 3% mass loss, followed by significant mass loss up to 20% and pH decrease to 6.5 attributed to degradation of PLGA units observed between 4 and 8 weeks of degradation. The last stage that was characterized by lysozyme adhesion on the composite surface and mass loss inhibition. SEM observation revealed that CH-M dispersed in the deeper layer of the polymer matrix preserved 6 months of degradation in PBS/Lys solution. In vitro test on MG-63 cells revealed no significant effect of the degradation products on cell viability and proliferation.