Nitric oxide-releasing sol–gels as antibacterial coatings for orthopedic implants

To assess the benefits of nitric oxide (NO)-releasing sol–gels as potential antibacterial coatings for orthopedic devices, medical-grade stainless steel is coated with a sol–gel film of 40% N-aminohexyl-N-aminopropyltrimethoxysilane and 60% isobutyltrimethoxysilane. Upon converting the diamine groups in these films to diazeniumdiolate NO donors, the NO release from the sol–gel-coated stainless steel is evaluated at both ambient and physiological temperature. Sol–gel films incubated at 25°C have a lower NO flux over the first 24 h compared to those at 37°C, but release more than five times longer. The bacterial adhesion resistance of NO-releasing coatings is evaluated in vitro by exposing bare steel, sol–gel, and NO-releasing sol–gel-coated steel to cell suspensions of Pseudomonas aeruginosa, Staphylococcus aureus, and Staphylococcus epidermidis at 25°C and 37°C. Cell adhesion to bare and sol–gel-coated steel is similar, while NO-releasing surfaces have significantly less bacterial adhesion for all species and temperatures investigated.