Vancomycin release from bioresorbable calcium phosphate–polymer composites with high ceramic volume fractions

Bioresorbable calcium phosphate–polymer composite implants are a desirable alternative to the traditional metal bone-healing devices. Incorporation of antimicrobial drugs into the composite material and their sustained delivery may dramatically reduce the risk of implant infections. The paper reports the fabrication of drug-incorporated bioresorbable CaP–polymer nanocomposites that can be used for fracture fixation devices and at the same time function as local delivery systems. Vancomycin was incorporated into β-tricalcium phosphate (β-TCP)- and biphasic CaP (BCP)-based composites containing ≤30 vol.% polycaprolactone (PCL) or polylactic acid (PLA), during their high pressure consolidation at 2.5 GPa and room temperature. The antibiotic release was studied in Tris buffer solution at 37 °C. Up to 5 wt% vancomycin could be included without compromising material’s integrity upon immersion into Tris solution. Vancomycin release profile was found to depend on the specific surface area of the test specimens and on the composite porosity. β-TCP–30 vol.% PLA composites were found to have the best combination of compression strength and drug release pattern. Complete drug release was accompanied by only negligible material dissolution suggesting a diffusion mechanism of release. In the context of bone-healing applications, such a release-dissolution pattern will allow local prophylaxis against implant-related infection at the early stages after implantation followed by a much more slow dissolution of the load-carrying device.