Preventing Infection and Biofilm Formation on Surface Modified Orthopedic Implants

Contamination of combat trauma wounds with environmental residues can lead to bacterial infection of orthopedic fractures, which causes delay and difficulties in patient treatment. The reported infection rate of the improvised explosive devices (IED) injuries is 91%, and biofilm formation on orthopedic implants can lead to chronic infection with a rate of 40% in fracture wounds. Once the biofilm is formed it becomes resistant to antibiotics, so designing orthopedic implants that can self-regulate local infection and biofilm formation is beneficial for these patients. Polytetrafluoroethylene (PTFE) and biodegradable chitosan with local antibiotic (vancomycin) elution were deposited on the stainless steel and titanium implant samples (coupons) to reduce biofilm formation and bacterial infection. Staphylococcus aureus is the most common pathogen associated with orthopedic implant infections. S. aureus Seattle 1945 (ATCC 25923) strain encoding intracellular GFP was used to evaluate the antimicrobial and anti-biofilm properties of the modified metal coupons using methods such as crystal violet analysis, ultrasound water bath with viable cell counts and confocal laser scanning microscopy. The release rate of vancomycin from the coupons was determined by HPLC analysis of collected leachates from surface modified coupons. In vitro studies of antibacterial properties of the coupons showed that PTFE did not provide significant advantages against biofilm formation, but the incorporation of chitosan and vancomycin onto modified surfaces prevented biofilm formation on the coupons. LCSM scanning of the modified surfaces with vancomycin did not detect any GFP signal from these coupons and no bacterial cell was recovered from the vancomycin treated surfaces. Local drug-release profile of antibiotic doped chitosan showed the concentration of local vancomycin released within the first 48 hours was effective in preventing bacterial attachment onto the coupons. Based on data obtained from these in vitro studies, it is concluded that vancomycin treated coupons were able to successfully prevent biofilm formation and bacterial growth on the modified surfaces