Silver multilayer coating on orthopedic implant material of different alloys and surfaces significantly reduces bacterial colonization

Lydia Tara Dewina Speijker^1,2Janine Fechter³Rainer Bargon³Jozef Dingemans^1,4Jacobus J. Arts^2,5,6Paul H.M. Savelkoul^1,2Inge H.M. Van Loo^1,2*

• ¹Department of Medical Microbiology, Infectious Disease and Infection Prevention, Maastricht Universitair Medisch Centrum+, Maastricht, Netherlands
• ²Care and Public Health Research Institute (CAPRHI), Universiteit Maastricht, Maastricht, Netherlands
• ³Department of Research and Development, Aesculap AG, Tuttlingen, Germany
• ⁴Laboratory clinical biology and Center of Molecular Diagnostics, Jessa Ziekenhuis vwz, Hasselt, Belgium
• ⁵Laboratory for Experimental Orthopaedics, Department of Orthopaedic Surgery, Maastricht Universitair Medisch Centrum+, Maastricht, Netherlands
• ⁶Department of Biomedical Engineering, Orthopaedic Biomechanics, Technische Universiteit Eindhoven, Eindhoven, Netherlands

Introduction: Prosthetic joint infections (PJI) affect 1-3% of prosthetic joint replacements, frequently linked to biofilm formation on implant surfaces. PJIs account for 13.0-31.3% of all revision surgeries. As treatment is not always successful, prevention remains critical. Currently, silver based antimicrobial coatings are justified in select high-risk arthroplasty cases, restricted to metal surfaces. An antibacterial silver multilayer coating (SML) has been developed for implant materials: titanium alloy (Ti) and cobalt-chromium-molybdenum alloy (CoCr), often used in hip or knee prostheses. The SML coating is intended for revision implants, often required due to infection related implant failure. This study investigates antibacterial performance of the SML coating across different surfaces and implant materials, using multiple bacterial strains not previously investigated to this extent. Methods: Antibacterial efficacy of the SML coating was assessed by quantifying colony forming units (CFU) reduction on Ti6Al4V and Co28Cr6M discs with three different surfaces (polished and two grades of corundum blasted (CB)). In vitro standardized testing followed ISO 22196, JIS Z-2801, and ASTM E-2180 standards using American Type Culture Collection (ATCC) strains Pseudomonas aeruginosa ATCC15442, Staphylococcus aureus ATCC6538p, Staphylococcus epidermidis ATCC35984, Pseudomonas aeruginosa ATCC15442, and Escherichia coli ATCC8739. Two groups were tested: non-SML-coated samples and SML-coated samples. After 24 hours incubation in viscous nutrient broth at 37oC, viable bacteria were quantified per disc after sonication in neutralizing broth and CFU enumeration. Results: Across all materials and strains, the SML coating achieved >99.2% and >0.9-4.0 CFU log10 reduction in viable bacteria compared to non-SML-coated controls. Material-dependent effects were observed for each of the bacterial species analyzed. S. aureus and E. coli exhibited more CFUs on Ti than on CoCr. The CoCr CB surface yielded the lowest level of bacterial growth for P. aeruginosa ATCC15442, whereas S. epidermidis colonized the Ti CB surface more extensively. Discussion and conclusion: These findings demonstrate a thorough and broad-spectrum antibacterial activity of the SML coating across diverse implant materials and surface textures. Future studies will focus on testing clinical PJI isolates in both in vitro and in vivo models to further evaluate translational potential of the SML coating for prevention of bacterial colonization in joint arthroplasty.