Physical Properties and Antimicrobial Release Ability of Gentamicin-Loaded Apatite Cement/α-TCP Composites: An In Vitro Study

Apatite cement (AC), which has excellent osteoconductive ability, and alpha-tricalcium phosphate (alpha-TCP), which can be used for bone replacement, are useful bone substitute materials. The objective of this study was to clarify the physical properties and antimicrobial release ability of antibiotic-loaded AC/alpha-TCP composites in vitro. Gentamicin-loaded, rapid setting AC/alpha-TCP composites were prepared in 2 mixing ratios (10:3 and 10:6). The cement paste of AC/alpha-TCP composites was prepared in a plastic mold and dried in a thermostatic chamber at 37 degrees C and 100% relative humidity for 24 h. A diametral tensile strength test, powder X-ray diffraction analysis, and gentamicin release test were performed. The diametral tensile strengths of the AC/alpha-TCP composites were significantly less than that of AC alone. Powder X-ray diffraction patterns exhibited the characteristic peaks of hydroxyapatite in the AC/alpha-TCP composites and gentamicin-loaded AC/alpha-TCP composites. The concentration of the released gentamicin was maintained above the minimum inhibitory concentration of Staphylococcus aureus until Day 30 in both the gentamicin-loaded AC/alpha-TCP composites (10:3 and 10:6). Our results suggest that a gentamicin-loaded AC/alpha-TCP composite has potential as a drug delivery system. Further study is essential to investigate the antimicrobial activity and safety of the gentamicin-loaded AC/alpha-TCP composites in animal models.