Prevention of Murine Subcutaneous Titanium Implant-Associated Infection by Saap-148-Loaded Bioactive Glass S53p4 Putty

Orthopedic implant-associated infections remain a major clinical challenge due to biofilm formation and increasing antimicrobial resistance. Staphylococcus aureus, particularly methicillin-resistant strains, and Acinetobacter baumannii are key pathogens associated with these infections. Bioactive glass S53P4 (BAG) is clinically used for infection management; however, its putty formulation may show reduced bactericidal activity due to limited surface accessibility and slower ion release from the large or poorly dispersed glass particles. In contrast, powder-based formulations offer higher glass surface area and improved dispersion, resulting in more efficient ion release and enhanced antibacterial activity. Nevertheless, BAG alone may still be insufficient for complete bacterial eradication, particularly in complex or biofilm-associated infections. Therefore, incorporation of antimicrobial peptides such as SAAP-148 may further enhance antibacterial efficacy. Aim: To evaluate the bactericidal and biofilm-killing efficacy of BAG S53P4 putty and cream loaded with SAAP-148 against clinically relevant pathogens and assess its capacity to prevent implant infection in vivo. Methods: BAG putty, BAG cream, and their SAAP-148-loaded counterparts (2% w/v) were tested against S. aureus and A. baumannii. Eluates were analyzed for bactericidal activity, pH, and SAAP-148 release. Biofilm killing was assessed using 24 h preformed biofilms. Applicability and efficacy were evaluated in cadaver and in vivo mouse subcutaneous implant infection models. Results: BAG cream showed superior bactericidal activity, achieving complete killing in undiluted eluates, whereas BAG putty eluates caused only a ~3-log reduction. Incorporation of SAAP-148 in BAG cream or putty led to complete bacterial eradication with rapid peptide release (<30 min) and ≥99.9% killing at high dilutions. BAG alone showed limited anti-biofilm activity, while peptide-loaded formulations achieved complete biofilm eradication. In the mouse cadaver model, BAG cream achieved ~2-log reduction, whereas BAG putty showed minimal activity; both SAAP-148-loaded formulations caused complete bacterial eradication on implants and surrounding tissue. In vivo, BAG putty alone showed no reduction in tissue bacterial load and limited activity against bacteria on the implants, whereas SAAP-148-loaded BAG putty achieved complete bacterial eradication on implants and in most tissue samples. Conclusion: SAAP-148 significantly enhances the bactericidal and biofilm-killing efficacy of BAG S53P4 formulations, highlighting a promising strategy for preventing and treating implant-associated infections.