Biodegradable alginate antibiotic beads

The authors investigated the poly-L-lysine-coated alginate beads as an antibiotic delivery system for the treatment of various surgical infections. The sodium alginate was mixed with vancomycin, coated with poly-L-lysine, and lyophilized to form five types of the biodegradable antibiotic beads. Type I, 2.5% alginate, nonpoly-L-lysine coated and nonlyophilized; Type II, 2.5% alginate, poly-L-lysine coated but nonlyophilized; Type III, 2.5% alginate, poly-L-lysine coated and lyophilized; Type IV, 5% alginate, poly-L-lysine coated and lyophilized; and Type V, 7.5% alginate, poly-L-lysine coated and lyophilized. Cytotoxicity of the alginate beads to fibroblasts and HeLa cells was evaluated by the MTT [3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide] colorimetric assay. A study of in vitro elution of vancomycin of the alginate antibiotic beads was performed. The results suggested that the alginate antibiotic beads present no obvious toxic risk to their use as a drug delivery system. The concentration of vancomycin in these five types of beads was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial killing and resistance to the antibiotic) for 9,11,12, 14, and 17 days respectively. The release was most marked during the first 3 days. The duration of antibiotic release was prolonged by using techniques of poly-L-lysine coating, lyophilization, and by increasing the content of alginate. This study offers a biodegradable delivery system of antibiotics to treat various surgical infections.