Rapid biofilm disruption by ionic buffers enables calcium phosphate cement functionalization

Abstract

Antimicrobial resistance and biofilm-associated infections continue to undermine standard antibiotic therapies, prompting the need for physicochemical adjuvant strategies. In this study, we evaluated the antibiofilm and antimicrobial activity of 7 biological buffer systems including citrate, acetate, sodium phosphate, potassium phosphate, borate, carbonate, and Tris-buffered saline against methicillin-susceptible and methicillin-resistant Staphylococcus aureus (MSSA and MRSA). Using a range of biofilm, metabolic, and cytotoxicity assays coupled with bioluminescence imaging, we demonstrate that low-concentration (20 mM) buffers significantly disrupted metabolic activity and biofilm structure within minutes of exposure as indicated by rapid functional perturbations observed via bioluminescence and without cytotoxicity in human dermal fibroblasts. Among the tested solutions, citrate emerged as the most potent antibiofilm agent (>50% reduction), while acetate, borate, and phosphate systems also demonstrated significant antibiofilm activity (25–50% reduction). MRSA exhibited reduced sensitivity to buffer treatment, consistent with known stress-response adaptations. Biofilm reduction >50% was recapitulated in three functionalized brushite cement formulations prepared with selected buffer systems, supporting the feasibility of incorporating chemically active ionic additives into calcium phosphate biomaterials. These findings highlight the potential of ionic systems as non-antibiotic antimicrobial agents and therapeutic adjuvants. Strategic integration into biomaterial design or wound irrigation strategies carries significant promise as a non-antibiotic strategy to combat infection.

Statement of significance

Biofilm-associated infections remain difficult to treat because bacteria in biofilms are far less responsive to antibiotics. This study shows that several simple biological buffer systems, especially citrate, can rapidly disrupt Staphylococcus aureus biofilms at low concentrations without harming human dermal fibroblasts. Beyond identifying these ionic solutions as non-antibiotic antibiofilm agents, the work also shows that their activity can be translated to calcium phosphate cements, creating biomaterials with infection-modulating properties. This is significant because it introduces a simple and scalable strategy to design antimicrobial biomaterials without relying on conventional antibiotics, metallic agents, or toxic additives, which is of broad interest to researchers developing safer materials for infection control and regenerative medicine.