Preparation of porous composite implant materials by in situ polymerization of porous apatite containing -caprolactone or methyl methacrylate

Biodegradable and biostable composite foams were formed from porous apatite cement infiltrated with -caprolactone (CL) or methylmethacrylate (MMA) using a high over vacuum. For CL composites in situ polymerization was induced using trace water as an initiator and heating at 120°C for up to 10 days or at 80°C for 60 days. MMA composites were polymerized using AIBN initiator at 70°C for 8 h. CL preparations gave composites with a polycaprolactone (PCL) number average of molecular weight (Mn) up to the maximum of 7.1×103 g/mol after 10 days and 16.8×103 g/mol after 60 days. The PCL and PMMA contents were close to 50 and 40 wt%, respectively, polymer was present as a thin coating on the apatite crystal plates and was evenly distributed throughout the samples. Re-evacuation of apatite saturated with monomer during preparation ensured that the upwards of 200 nm microchannels within the apatite cement were largely free of polymer, and the overall macroporous structure of the apatite foams was partly retained. Maximum compressive strengths increased from 9 MPa to 37 and 64 MPa for PCL and PMMA composites, respectively. The water drop contact angle of the PCL composite was 64°, and therefore suitable for cell attachment. PMMA composite surfaces were more hydrophobic. Composites were subjected to corona discharge to induce suitable moderate hydrophilicity at the surface.