Photochemical Synthesis of Silver Hydrosol Stabilized by Carbonate Ions and Study of Its Bactericidal Impact on Escherichia coli: Direct and Indirect Effects.

Vadim Ershov,Evgeny Abkhalimov,Vladimir Sorokin,Boris Ershov,Natalia Tarasova,Alexey Safonov

doi:10.3390/ijms23020949

Abstract

The great attention paid to silver nanoparticles is largely related to their antibacterial and antiviral effects and their possible use as efficient biocidal agents. Silver nanoparticles are being widely introduced into various areas of life, including industry, medicine, and agriculture. This leads to their spreading and entering the environment, which generates the potential risk of toxic effect on humans and other biological organisms. Proposed paper describes the preparation of silver hydrosols containing spherical metal nanoparticles by photochemical reduction of Ag+ ions with oxalate ions. In deaerated solutions, this gives ~10 nm particles, while in aerated solutions, ~20 nm particles with inclusion of the oxide Ag2O are obtained. Nanoparticles inhibit the bacterium Escherichia coli and suppress the cell growth at concentrations of ~1 × 10−6–1 × 10−4 mol L−1. Silver particles cause the loss of pili and deformation and destruction of cell membranes. A mechanism of antibacterial action was proposed, taking into account indirect suppressing action of Ag+ ions released upon the oxidative metal dissolution and direct (contact) action of nanoparticles on bacterial cells, resulting in a change in the shape and destruction of the bacteria.

Highlights

The synthesis and applications of nanosized metal particles is currently one of the most rapidly developing fields of nanotechnologies [1–6]
The average size of NPs obtained in the absence of air calculated from transmission electron microscope (TEM) data were 10.1 ± 2.8 nm (Figure 1c), while the size of NPs formed in the presence of air oxygen was 22.3 ± 4.2 nm (Figure 1d)
The size of the silver colloid, including the stabilizing electrical double layer (EDL), was measured by DLS and amounted to 12.3 ± 2.5 nm for NPs obtained in the absence of air (Figure 1e) and 24.1 ± 4.0 nm for particles obtained in air (Figure 1f)

Summary

Introduction

The synthesis and applications of nanosized metal particles is currently one of the most rapidly developing fields of nanotechnologies [1–6]. They have a large surface area to volume ratio, which endows them with unique properties and accounts for high efficiency of their action. Silver nanoparticles are known to exhibit relatively high biocidal and fungicidal activities [10–12]; one of numerous applications of silver nanoparticles is medicine. In view of the increase in the bacterial resistance to the existing antibiotic drugs, the search for alternative agents for fast and efficient combating of pathogenic microbial strains is highly relevant. In this respect, a promising approach is functionalization of silver nanoparticle surface, which enhances their biocidal activity [13–15]

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