In Vitro Assessment of the Biocompatibility and Antimicrobial Activity of S53p4 Bioactive Glass Micron Powder Against Biofilm Formation

Introduction & Aim The challenging properties of biofilm-associated infections and the rise of multidrug-resistant- bacteria are prompting the exploration of alternative treatment options for the prevention of prosthetic joint infection (PJI). This study investigates the efficacy of S53P4 bioactive glass (BAG) micro powder to eradicate biofilm. Methods The Minimum Inhibitory Concentration (MIC) of S53P4 BAG micron powder (particle size <25 µm) was determined using a broth microdilution assay[1] against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). Biofilm growth inhibition and immature (24h) biofilm disintegration were assessed using S. aureus cultured on ultra-high-molecular-weight polyethylene (UHMWPE) disks exposed to a S53P4 BAG powder concentration of 635.62 mg/mL for 24 hours and 5 days. Analysis was performed via colony-forming unit (CFU) counting and scanning electron microscopy (SEM). Biocompatibility was evaluated in vitro according to ISO 10993-5 using L929 fibroblasts, with viability and metabolic activity assessed by WST-1 and LDH assays, respectively. Results The MIC of BAG micron powder was evaluated for E. coli and S. aureus. Experimental replicates identified a consistent MIC of 166.67 mg/mL for both strains. Pilot biofilm studies (n=2) demonstrated that co-incubation with 635.62 mg/mL of S53P4 powder achieved a 5-log reduction in bacterial growth. This concentration effectively inhibited biofilm formation and disintegrated immature biofilms after 24 hours, with these antimicrobial effects sustained for up to 5 days. Scanning electron microscopy (SEM) imaging corroborated these quantitative findings. However, cytotoxicity assays revealed a significant reduction in cell viability, below 30%, at all tested concentrations of 50 mg/mL and above. Conclusions S53P4 BAG micron powder exhibits potent, long-lasting antimicrobial activity and effective biofilm eradication capabilities in vitro, supporting its potential as an adjunctive therapy for PJIs. The observed cytotoxicity in static in vitro models stresses the necessity for future dose-optimization and the development of dynamic experimental designs that more accurately reflect in vivo flow conditions to further validate clinical safety. Acknowledgements This publication is part of the project DARTBAC (with project number NWA.1292.19.354) of the research programme NWA-ORC, which is (partly) financed by the Dutch Research Council (NWO).