In vitro elution of antibiotic from antibiotic-impregnated biodegradable calcium alginate wound dressing

Objective: The authors investigated the calcium alginate dressing as a drug-delivery system for the treatment of various surgical infections. Methods: Cytotoxicity of the calcium alginate dressing to fibroblasts and HeLa cells was evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) colorimetric assay. The calcium alginate dressing was mixed with vancomycin, and lyophilized or not lyophilized to form two types of antibiotic dressings. The antibiotic dressings were placed in 2 mL of phosphate buffered saline (PBS) or in PBS containing 0.01% calcium ions, and incubated at 37°C. The PBS was changed daily, and the removed solutions were stored at - 70°C until the antibiotic concentration in each sample was determined by high performance liquid chromatography assay. Results: The results suggested that the antibiotic dressings present no obvious toxic risk to their use as a drug-delivery system. The concentration of vancomycin in each sample was well above the breakpoint sensitivity concentration (the antibiotic concentration at the transition point between bacterial killing and resistance to the antibiotic) for more than 14 days. The release was most marked during the first 48 hours. The concentration of calcium ions in PBS and the lyophilization of the manufacture process of antibiotic dressings prolonged the antibiotic diffusion duration. The diameter of the sample inhibition zone ranged from 10 to 11 mm, and the relative activity of vancomycin ranged from 62.88% to 92.18%. Conclusion: All antibiotic dressings released bactericidal concentrations of the antibiotics in vitro for the period of time needed to treat surgical infections. This study offers a convenient method to meet the specific antibiotic requirement for different patients.