Synthesis of Chitosan-Coated Silver Nanoparticle Bioconjugates and Their Antimicrobial Activity against Multidrug-Resistant Bacteria

Surbhi Shinde,Annarita Falanga,Gianluigi Franci,Luigi Rosati,Marilena Galdiero,Marina Prisco,Carla Zannella,Massimiliano Galdiero,Veronica Folliero,Avinash Mali,Anna De Filippis,Annalisa Chianese

doi:10.3390/app11199340

Abstract

The increase in multidrug-resistant bacteria represents a true challenge in the pharmaceutical and biomedical fields. For this reason, research on the development of new potential antibacterial strategies is essential. Here, we describe the development of a green system for the synthesis of silver nanoparticles (AgNPs) bioconjugated with chitosan. We optimized a Prunus cerasus leaf extract as a source of silver and its conversion to chitosan–silver bioconjugates (CH-AgNPs). The AgNPs and CH-AgNPs were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), and zeta potential measurement (Z-potential). The cytotoxic activity of AgNPs and CH-AgNPs was assessed on Vero cells using the 3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) cell proliferation assay. The antibacterial activity of AgNPs and CH-AgNPs synthesized using the green system was determined using the broth microdilution method. We evaluated the antimicrobial activity against standard ATCC and clinically isolated multisensitive (MS) and multidrug-resistant bacteria (MDR) Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), Klebsiella pneumonia (K. pneumoniae), and Staphylococcus aureus (S. aureus), using minimum inhibitory concentration (MIC) assays and the broth dilution method. The results of the antibacterial studies demonstrate that the silver chitosan bioconjugates were able to inhibit the growth of MDR strains more effectively than silver nanoparticles alone, with reduced cellular toxicity. These nanoparticles were stable in solution and had wide-spectrum antibacterial activity. The synthesis of silver and silver chitosan bioconjugates from Prunus cerasus leaf extracts may therefore serve as a simple, ecofriendly, noncytotoxic, economical, reliable, and safe method to produce antimicrobial compounds with low cytotoxicity.

Highlights

The synthesis of AgNPs and CH-AgNPs were confirmed via ultraviolet–visible spectroscopy (UV–Vis) spectroscopy analysis
The simple and rational exploitation of a green synthesis procedure was used to produce biogenic silver nanoparticles and silver nanoparticles conjugated with chitosan
On the basis of obtained results, the combination of chitosan with AgNPs against Grampositive and Gram-negative bacteria offers a valuable contribution to nanomedicine

Summary

Introduction

Antibiotics have been given in high doses due to increasing drug resistance, and the resulting toxicity has focused the attention on the need to develop and define innovative and effective antimicrobial treatments [3,4]. Silver nanoparticles are studied for their excellent antimicrobial properties, which are due to silver ions inhibiting bacterial DNA replication and damaging cytoplasmic membrane, which causes cell death after a decrease in ATP levels [6]. These observations suggest that nanoparticles can be effective against both Gram-positive and Gram-negative bacteria. There are many advantages of using silver nanoparticles (AgNPs) as antimicrobial agents: they have high antibacterial activity based on multiple mechanisms of action and can help in overcoming the resistance of microorganisms to conventional antibiotics [7]

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