# Silver Nanoclusters Decrease Bacterial Resistance to Heavy Metals and Antibiotics

## TL;DR

Silver nanoclusters reduce bacteria's resistance to heavy metals and antibiotics, potentially aiding in combating drug-resistant infections.

## Contribution

Demonstrates that silver nanoclusters can inhibit bacterial resistance to heavy metals and antibiotics.

## Key findings

- AgNCs decreased resistance to copper (II), cadmium (II), erythromycin, and levofloxacin in bacteria.
- A dose-dependent effect of AgNCs on bacterial resistance was observed.
- AgNCs showed no significant growth inhibition at low concentrations used in the study.

## Abstract

Nanomaterials are widely used in biomedical research as drug and antibody carriers, and some nanomaterials have been shown to exhibit antimicrobial activity. Previously, silver nanoclusters (AgNCs) were predicted to interact with the bacterial TolC protein, which is involved in the development of multidrug resistance in pathogens. In this study, glutathione-coated AgNCs were synthesized and characterized. Their toxicological properties were studied in a microplate assay against five bacterial strains, both as single components and in mixtures with heavy metal salts and antibiotics. The resulting AgNCs had a diameter of 2.2 ± 0.5 nm, with excitation and emission maxima of λ = 490 nm and λ = 638 nm, respectively. No significant growth inhibition was observed at the concentrations used in resistance modulation assays (≤2.5 µg/mL Ag), except for transient effects at very high concentrations. A decrease in bacterial resistance to copper (II) and cadmium (II) cations and the antibiotics erythromycin and levofloxacin was observed upon the addition of AgNCs containing 2.5 μg/mL silver to the nutrient medium. A dose-dependent effect of AgNCs on bacterial resistance to toxicants was established. Thus, nanoclusters can be considered as inhibitors of bacterial resistance to heavy metals and antibiotics, which may be useful in studying bacterial adaptation mechanisms and developing technologies for overcoming multidrug resistance in bacteria.