Hydroxyapatite composites designed for antibiotic drug delivery and bone reconstruction: a caprine model

The purpose of this study was to investigate the feasibility of fabricating a drug delivery system that serves a dual function, to eradicate infection as well as to provide a scaffold for osseous integration. Two porous composite systems were fabricated using hydroxyapatite (HA) as the carrier for gentamicin sulfate (GS), an aminoglycoside antibiotic. Structural and mechanical properties of porous HA-GS composites were characterized and the in vitro release behavior of GS from fabricated composites was monitored and compared with the well-known polymethylmethacrylate (PMMA)-GS delivery system. Scanning electron microscopy revealed a macropore range of 150 to 200 microm and 100 to 190 microm for the sintered and unsintered HA-GS composites, respectively. The effect of GS inclusion on bone apposition and ingrowth was assessed using a caprine model. Plugs 10 mm x 6 mm of cylindrical tricalcium phosphate, sintered HA, and sintered HA-GS were implanted in the femoral diaphysis for a period of 6 weeks. Data collected during the in vitro study showed that GS can successfully be incorporated into HA and used as a drug delivery system to eradicate Staphylococcus aureus. In vivo data confirmed that the inclusion of GS within a ceramic matrix did not stimulate or inhibit osteointegration or bone apposition. In conclusion, the fabricated sintered HA-GS composite may be beneficial in the treatment of infected osseous sites as a drug delivery system.