Comparative biodegradation study of poly(e-caprolactone)-poly(L-lactic acid) scaffolds incubated in aqueous media and cell cultures.

To evaluate in vitro degradation mechanism and kinetics, and the role of cells in degradation, poly(-caprolactone)-poly(L-lactic acid) (PCL-PLLA) scaffolds were immersed in different aqueous media and incubated with stromal cells from bone marrow (MSC) and osteoblasts (HOB) from orthopaedic patients. The PCL-PLLA composites consist of PLLA fibers embedded in a PCL matrix. The in vitro biodegradation was investigated under sterile conditions at 37°C in different media: saline phosphate buffer at pH 7.4 (SPB), esterase in SPB at pH 7.4, 0.01 M NaOH solution and simulated body fluid at pH 7.4 (SBF). The samples were analyzed before and after biodegradation for 8 weeks by polarized micro-Raman spectroscopy, thermogravimetry (TG) and differential scanning calorimetry (DSC). MSC and HOB were isolated from marrow/bone fragments obtained during surgery for total hip replacement and cultivated in -MEM with 10% FBS on the PCL-PLLA samples for 4 weeks. Among the in vitro degradation media, the NaOH solution induced the highest weight loss and the most pronounced composition and morphology changes: thermal and spectroscopic analysis showed an enrichment in the PCL component, suggesting a preferential involvement of the more hydrophilic PLLA component in degradation. At the same time, the crystallinity of both polymeric components increased. In particular, as regards the PLLA component, the observed spectral changes were explained in terms of structural rearrangements and decrease of the polymeric chain length. HOB and MSC also induced significant structural rearrangements on both polymeric components, although to a lower extent than in NaOH solution; MSC were more aggressive than HOB.