Bactericidal Effects of Silver Nanoparticles on Lactobacilli and the Underlying Mechanism

Abstract

While the antibacterial properties of silver nanoparticles (AgNPs) have been demonstrated across a spectrum of bacterial pathogens, the effects of AgNPs on the beneficial bacteria are less clear. To address this issue, we compared the antibacterial activity of AgNPs against two beneficial lactobacilli ( Lactobacillus delbrueckii subsp. bulgaricus and Lactobacillus casei) and two common opportunistic pathogens ( Escherichia coli and Staphylococcus aureus). Our results demonstrate that those lactobacilli are highly susceptible to AgNPs, while the opportunistic pathogens are not. Acidic environment caused by the lactobacilli is associated with the bactericidal effects of AgNPs. Our mechanistic study suggests that the acidic growth environment of lactobacilli promotes AgNP dissolution and hydroxyl radical (•OH) overproduction. Furthermore, increases in silver ions (Ag) and •OH deplete the glutathione pool inside the cell, which is associated with the increase in cellular reactive oxygen species (ROS). High levels of ROS may further induce DNA damage and lead to cell death. When E. coli and S. aureus are placed in a similar acidic environment, they also become more susceptible to AgNPs. This study provides a mechanistic description of a pH-Ag-•OH bactericidal pathway and will contribute to the responsible development of products containing AgNPs.

Generation of Vanadium Oxide Quantum Dots with Distinct Fluorescence and Antibacterial Activity via a Room‐Temperature Agitation Strategy

“…The leakage of their cytoplasm content from both cells was indicative of the damage of the outer cell walls and inner membrane for both bacteria (red arrow pointed in Figure m and 3p). Thus it can be concluded that the as‐prepared VO x QDs had a direct killing effect on bacteria, which should be attributed to the trace toxic vanadium ions release on the surface of VO x QDs, the overproduction of hydroxyl radical (•OH) and the oxidation of halides X − (such aschloride (Cl − ) orbromide (Br − ) ions) to the corresponding hypohalous acids (HOX) ,. It was reported that VO x nanomaterials possess excellent catalytic performance, such as peroxidase activity, which plays a key role in the bacteriostasis of VO x through the generation of .…”

A convenient detection system consisting of efficient Au@PtRu nanozymes and alcohol oxidase for highly sensitive alcohol biosensing

“…To verify the peroxidase-like property of the Au@PtRu nanorods, we followed the intermediates of the reaction, specically cOH. [36][37][38] The formation of cOH was monitored with terephthalic acid (TA), a typical uorescent probe for the detection of cOH. In the presence of H 2 O 2 , the Au@Pt and Au@PtRu nanorods catalyzed the uorescence of TAOH, indicating the formation of cOH (Fig.…”

Nanoparticles for the Treatment of Oral Biofilms: Current State, Mechanisms, Influencing Factors, and Prospects

“…Some studies have shown that nanoparticles affect the bacteria in biofilms via the same mechanisms by which they affect planktonic bacteria. These include physical damage to bacteria from the sharp edges of nanoparticles ( Figure ), ion release, production of reactive oxygen species (ROS) leading to oxidative stress, nanoparticle‐mediated enzyme‐like catalytic activity, and DNA damage ( Figure ). At the same time, many experts have pointed out that the aforementioned mechanisms cannot explain the complex interactions between nanoparticles and biofilms, and any proposed mechanism should take into account the formation and structure of the oral biofilm.…”

“…The acidic growth environment (pH as low as 4.5) of L. bulgaricus and L. casei enhances AgNP dissolution and OH production, which results in bacteria death. Reproduced with permission . Copyright 2018, American Chemical Society.…”