Assessment of silver ion disinfection in relation to microbial cell characteristics based on intrinsic quenching...

Silver ions (Ag⁺) are effective antimicrobial agents, but the quantitative role of microbial cell characteristics in governing Ag⁺ reactivity has remained unclear. This study aimed to quantitatively investigate how microbial cell characteristics influence their susceptibility to Ag⁺. Escherichia coli (Gram-negative), Micrococcus luteus (Gram-positive), Aspergillus brasiliensis (fungi), and Candida maltosa (yeast) were exposed to Ag⁺ dosing of 0.05-0.2 mg-Ag/L for 0-60 min. Then, the intrinsic quenching model was applied to the experimental results to quantify species-specific rate constant (k L min^-1 mg^-1), adsorption rate constant (β min^-1), and dilution coefficient (n dimensionless), linking cell features to observe the inactivation kinetics. Free-ion dosing achieved 99.8% disinfection of E. coli and ≥ 88.5% reduction of fungal species within 15 min at just 0.1 mg-Ag/L. E. coli exhibited the fastest Ag⁺ uptake and the highest inactivation rate (k₁₅ min^-1), followed by C. maltosa, A. brasiliensis, and M. luteus, reflecting increasing diffusion barriers. While the previous qualitative studies have clarified the basic mechanisms of Ag⁺ interaction with cells, we extended those insights to the quantitative assessment. By fitting the intrinsic quenching model to the experimental data, we derived species-specific parameters that translate cell characteristics into quantitative metrics, providing a practical basis for optimizing Ag⁺ dosing across microbes.