Objective: Chitosan was investigated as a coating for local delivery of antimicrobials for prevention of acute implant infection. The objectives of this study were to (1) measure the release of 2 antimicrobials from chitosan coatings, (2) determine efficacy of eluted antimicrobials against bacteria, in vitro, and (3) evaluate toxicity of eluted drugs to host cells/tissues.
Methods: Chitosan coatings (80.7% deacetylated, 108 kDa) containing 20% tetracycline or 0.02% chlorhexidine digluconate were bonded to titanium via silane reactions. After elution in culture medium for 7 days, eluates were tested against model pathogens Actinobacillus actinomycetemcomitans and Staphylococcus epidermidis in turbidity tests and in 24-hour cytotoxicity tests using human osteoblasts and fibroblasts. Finally, antibiotic-loaded chitosan-coated titanium pins were implanted for 7 days in muscle of Sprague-Dawley rats to evaluate the initial tissue response.
Results: Coatings released 89% of tetracycline in 7 days and 100% chlorhexidine in 2 days. Released tetracycline inhibited growth (95%-99.9%) of pathogens for up to 7 days with no cytotoxicity to human cells. Released chlorhexidine was active against pathogens for 1 to 2 days (56%-99.5% inhibition) but was toxic to cells on the first day of elution. Typical acute inflammatory response was observed to antimicrobial-loaded chitosan coatings similar to unloaded coatings.
Conclusion: These preliminary data support the hypothesis that chitosan coatings have the potential to locally deliver antimicrobials to inhibit bacteria without being toxic to host cells/tissues and warrant additional studies to evaluate the ability of the coatings to prevent/resist infection and promote osseointegration.