Bactericidal activity of novel calcium-based core-shell particles and its mechanism of action

The global rise in antimicrobial resistance (AMR) poses a significant challenge to infection control efforts worldwide. This growing threat highlights the critical need for innovative technologies with advanced antimicrobial properties to improve infection prevention and control strategies. To address this challenge, we developed a novel core–shell \(\:{Ca\left(OH\right)}_{2}\)–\(\:{CaCO}_{3}\) (CSCC) particle exhibiting antibacterial properties against both gram-positive and gram-negative bacteria. Through confocal microscopy imaging and the developed in vitro microbiology protocol, we identified the bacteria-killing mechanism, wherein the bacteria adhere to the \(\:{CaCO}_{3}\) shell and are subsequently killed, by the membrane disruption and aggregation mechanisms of the \(\:{Ca\left(OH\right)}_{2}\) core. The minimum Bactericidal content of CSCC, \(\:{CaCO}_{3}\) and \(\:{Ca\left(OH\right)}_{2}\) was measured using a combination of broth dilution and spot-plating methods. The results indicate that 2.5 mg/mL CSCC kills both gram-positive and gram-negative bacteria, whereas 2.5 mg/mL and 5 mg/mL of \(\:{Ca\left(OH\right)}_{2}\) killed gram-negative and gram-positive bacteria, respectively. No antimicrobial properties were observed for \(\:{CaCO}_{3}\). We believe the mechanism of binding and killing bacteria may offer a prominent solution to the global challenge of antimicrobial resistance. Accelerated aging tests confirmed that the CSCC particles retained full antibacterial activity against E. coli equivalent to 100 years of natural aging.