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

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⁺. <i>Escherichia coli</i> (Gram-negative), <i>Micrococcus luteus</i> (Gram-positive), <i>Aspergillus brasiliensis</i> (fungi), and <i>Candida maltosa</i> (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 (<i>k</i> L min^-1 mg^-1), adsorption rate constant (<i>β</i> min^-1), and dilution coefficient (<i>n</i> dimensionless), linking cell features to observe the inactivation kinetics. Free-ion dosing achieved 99.8% disinfection of <i>E. coli</i> and ≥ 88.5% reduction of fungal species within 15 min at just 0.1 mg-Ag/L. <i>E. coli</i> exhibited the fastest Ag⁺ uptake and the highest inactivation rate (<i>k</i>₁₅ min^-1), followed by <i>C. maltosa</i>, <i>A. brasiliensis</i>, and <i>M. luteus</i>, 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.