Antimicrobial and antibiotic-potentiating effect of calcium peroxide nanoparticles on oral bacterial biofilms

Bacterial biofilms represent a prominent biological barrier against physical and chemical attacks. Disturbing the anaerobic microenvironment within biofilms by co-delivery of oxygen appears as a promising strategy to enhance the activity of an antibiotic. Here, we report the effect of oxygen-producing calcium peroxide nanoparticles (CaO₂ NP) in combination with tobramycin sulfate (Tob). On Pseudomonas aeruginosa PAO1 biofilms in vitro, the additive effect of CaO₂ NP towards Tob activity enhanced biofilm eradication by 2 log compared to Tob alone. For natural biofilms grown in the oral cavity of human volunteers in situ, treatment by CaO₂ NP alone slightly increased the fraction of dead bacteria from 44% in various controls, including Tob alone, to 57%. However, the combination of CaO₂ NP with Tob further increased the fraction of dead bacteria to 69%. These data confirm the intrinsic antimicrobial and antibiotic-potentiating effect of CaO₂ NP also in a clinically relevant setting.