In vitro elution of vancomycin from biodegradable beads

Abstract

The current antibiotics delivery system for orthopedic infection treatment uses polymethylmethacrylate (PMMA) beads as a drug release. However the nonbiodegradable nature of the PMMA necessitates a second operation to remove the beads. This article explores the alternative of using biodegradable polymers as antibiotic beads for a long-term drug release. The effect of different processing factors on the release rate of the beads was investigated. To manufacture an antibiotic bead, polylactide-polyglycolide copolymers were mixed with vancomycin. The mixture was compressed and sintered at 55 degrees C to form beads of different sizes. An elution method was employed to characterize the release rate of antibiotic over a 35-day period at 37 degrees C. Biodegradable beads released high concentrations of antibiotic (well above the breakpoint sensitivity concentration) in vitro for the period of time needed to treat bone infection; i.e., 4-6 weeks. A bacterial inhibition test was carried out to determine the relative activity of the released antibiotics. The diameter of the sample inhibition zone ranged from 6.5-10 mm, which is equivalent to 12.5-100% of relative activity. By changing the processing parameters, we were able to control the release rate of the beads. This provides advantages of meeting the specific antibiotics requirement for patients with various surgical infections.