In vitro rifampicin release and antimicrobial activity of biodegradable polymer coatings

Implanted medical device infections represent a significant clinical challenge. Infections, often caused by staphylococcal species, are extremely difficult to treat due to challenges in targeting the infection site whilst avoiding systemic toxicity. This study reports on the development of a novel implant coating to provide controlled, local drug-release, for the inhibition of infection. The release of the broad-spectrum antibiotic rifampicin from a range of biodegradable poly (lacticacid) (PLA) and poly (lactic-co-glycolic acid) (PLGA) polymer formulations was analysed. Increasing the fraction of polymer in a formulation provided control over release; e.g. increasing the PLGA:rifampicin ratio from 25:75 to 75:25 significantly (p ≤ 0.001) slowed release of rifampicin from >99%, to <2% after 7 days. The antimicrobial activity of PLGA:rifampicin based formulations (25:75, 50:50, 75:25) against Staphylococcus aureus revealed that all formulations retained antimicrobial activity over 7 days in disk diffusion tests. The 50:50 formulation produced significantly (p ≤ 0.05) larger zones of growth inhibition than the 25:75 or 75:25 formulations. This investigation confirms rifampicin can be released from biocompatible, polymer-based coatings, and reveals potential for engineering both the release rate and level of antimicrobial efficacyClinical Relevance- This research demonstrates the potential of synthetic polymer coatings for the prevention of medical implant infections.