New toxicity mechanism of silver nanoparticles: promoting apoptosis and inhibiting proliferation.

Huijing Bao,Dianjun Wei,Zhaoyang Li,Xue Li,Yunde Liu,Xiaoxu Yu,Chen Xu,Ying-Jan Wang

doi:10.1371/journal.pone.0122535

Abstract

Silver nanoparticles are increasingly recognized for their utility in biological applications, especially antibacterial effects. Herein, we confirmed the antibacterial effect of silver nanoparticles on Escherichia coli using the conventional optical density (OD) and colony-forming units (CFU) method and used flow cytometry (FC), TEM and BrdU ELISA to investigate the mechanisms of this effect. From the results, we conclude that AgNPs can simultaneously induce apoptosis and inhibit new DNA synthesis in the cells in a positive concentration-dependent manner. This study presents the first induction of apoptosis in these bacteria by AgNPs in this field. Our findings may provide a new strategy for the use of silver nanoparticles in antibacterial applications.

Highlights

Silver is used as a strong inhibitor for a broad spectrum of antimicrobial activities, such as those of bacteria, fungi, and viruses
We demonstrate the antibacterial mechanism of AgNPs in terms of inducing bacterial apoptosis
No evidence was available for the relationship between the optical density and actual growth (CFU) for the bacterial throughout the growth period

Summary

Introduction

Silver is used as a strong inhibitor for a broad spectrum of antimicrobial activities, such as those of bacteria, fungi, and viruses. Nanometer-sized silver particles (AgNPs) have long been known to have an antibacterial effect. AgNPs are generally smaller than 100 nm, containing 20–15,000 silver atoms, and exhibit unusual physical, chemical and biological properties[3]. Due to their strong antibacterial activities, the use of AgNPs and their composites has been suggested for preventing bacterial infection in surgery[4], in the coatings of medical devices[5,6] or even as a water disinfectant or room spray[3]. It has been discovered that silver can bind to the DNA, increasing the PLOS ONE | DOI:10.1371/journal.pone.0122535 March 30, 2015

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