Micrococcal-Nuclease-Triggered On-Demand Release of Vancomycin from Intramedullary Implant Coating Eradicates Staphylococcus aureus Infection in Mouse Femoral Canals

Preventing orthopedic implant-associated bacterial infections remains a critical challenge. Current practices of physically blending high-dose antibiotics with bone cements is known for cytotoxicity while covalently tethering antibiotics to implant surfaces is ineffective in eradicating bacteria from the periprosthetic tissue environment due to the short-range bactericidal actions, which are limited to the implant surface. Here, we covalently functionalize poly(ethylene glycol) dimethacrylate hydrogel coatings with vancomycin via an oligonucleotide linker sensitive to Staphylococcus aureus (S. aureus) micrococcal nuclease (MN) (PEGDMA-Oligo-Vanco). This design enables the timely release of vancomycin in the presence of S. aureus to kill the bacteria both on the implant surface and within the periprosthetic tissue environment. Ti6Al4V intramedullary (IM) pins surface-tethered with dopamine methacrylamide (DopaMA) and uniformly coated with PEGDMA-Oligo-Vanco effectively prevented periprosthetic infections in mouse femoral canals inoculated with bioluminescent S. aureus. Longitudinal bioluminescence monitoring, muCT quantification of femoral bone changes, end point quantification of implant surface bacteria, and histological detection of S. aureus in the periprosthetic tissue environment confirmed rapid and sustained bacterial clearance by the PEGDMA-Oligo-Vanco coating. The observed eradication of bacteria was in stark contrast with the significant bacterial colonization on implants and osteomyelitis development found in the absence of the MN-sensitive bactericidal coating. The effective vancomycin tethering dose presented in this on-demand release strategy was \u3e 200 times lower than the typical prophylactic antibiotic contents used in bone cements and may be applied to medical implants and bone/dental cements to prevent periprosthetic infections in high-risk clinical scenarios. This study also supports the timely bactericidal action by MN-triggered release of antibiotics as an effective prophylactic method to bypass the notoriously harder to treat periprosthetic biofilms and osteomyelitis