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Time-resolved toxicity study reveals the dynamic interactions between uncoated silver nanoparticles and bacteria
Feng Dong1, Nurul Fitriah Mohd Zaidi1, Eugenia Valsami-Jones2
1a School of Biosciences , Institute of Microbiology and Infection, University of Birmingham , Birmingham , UK.
The toxicity of silver nanoparticles (AgNPs) primarily stems from dissolved silver ions (Ag+), not the nanoparticles themselves. This study clarifies AgNP effects by examining dissolution and bacterial response over time at low cell densities.
Area of Science:
- Environmental Science
- Nanotechnology
- Microbiology
Background:
- Distinguishing the toxic effects of silver ions (Ag+) from silver nanoparticles (AgNPs) is challenging.
- AgNPs can change during toxicity testing, complicating results.
- Previous studies noted reduced AgNP toxicity at higher cell densities.
Purpose of the Study:
- To investigate the influence of silver nanoparticle (AgNP) dissolution over time on bacterial viability.
- To differentiate the roles of dissolved Ag+ and nanoparticulate Ag in AgNP toxicity.
- To conduct high-resolution, low-cell-density experiments to avoid artifacts.
Main Methods:
- Synthesized uncapped AgNPs to prevent surface coating interference.
- Studied AgNP dissolution kinetics in Davis minimal medium (DMM) at varying concentrations.
- Measured bacterial viable counts at high time resolution and low cell density.
Main Results:
- AgNP aggregation decreased at lower concentrations in DMM.
- AgNPs dissolved more slowly in DMM than in water.
- Bacterial toxicity was dominated by dissolved Ag+, with AgNPs acting as a sustained Ag+ reservoir.
Conclusions:
- The toxicity of AgNPs is primarily driven by the release of Ag+ ions.
- Controlled, low-density, high-resolution studies reveal distinct roles for ionic and nano silver in bacterial death.
- AgNPs maintain silver stress by continuously releasing Ag+.
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