Lysozyme-coated silver nanoparticles for differentiating bacterial strains on the basis of antibacterial activity

Sumaira Ashraf,Hussnain Ahmed Janjua,Irshad Hussain,Mariyam Asghar Chatha,Wardah Ejaz

doi:10.1186/1556-276x-9-565

Abstract

Lysozyme, an antibacterial enzyme, was used as a stabilizing ligand for the synthesis of fairly uniform silver nanoparticles adopting various strategies. The synthesized particles were characterized using UV-visible spectroscopy, FTIR, dynamic light scattering (DLS), and TEM to observe their morphology and surface chemistry. The silver nanoparticles were evaluated for their antimicrobial activity against several bacterial species and various bacterial strains within the same species. The cationic silver nanoparticles were found to be more effective against Pseudomonas aeruginosa 3 compared to other bacterial species/strains investigated. Some of the bacterial strains of the same species showed variable antibacterial activity. The difference in antimicrobial activity of these particles has led to the conclusion that antimicrobial products formed from silver nanoparticles may not be equally effective against all the bacteria. This difference in the antibacterial activity of silver nanoparticles for different bacterial strains from the same species may be due to the genome islands that are acquired through horizontal gene transfer (HGT). These genome islands are expected to possess some genes that may encode enzymes to resist the antimicrobial activity of silver nanoparticles. These silver nanoparticles may thus also be used to differentiate some bacterial strains within the same species due to variable silver resistance of these variants, which may not possible by simple biochemical tests.

Highlights

Nanomaterials composed of metal nanoparticles are attracting significant attention because of their enormous applications in photonics [1], electronics [2], optoelectronics [3], catalysis [4,5], sensing [6], antimicrobial products [7,8], pharmaceuticals [9], and therapeutics [10,11]
We have tested the effect of silver nanoparticles on several bacterial species and observed that their antimicrobial activity is variable for different strains even from the same species
This variable resistance for silver nanoparticles from strains of the same bacterial species can be correlated to silver-resistant genes that may have acquired through horizontal gene transfer (HGT)

Summary

Introduction

Nanomaterials composed of metal nanoparticles are attracting significant attention because of their enormous applications in photonics [1], electronics [2], optoelectronics [3], catalysis [4,5], sensing [6], antimicrobial products [7,8], pharmaceuticals [9], and therapeutics [10,11]. Several protocols have been reported for the synthesis of silver nanoparticles, such as borohydride reduction [18], acrylate/citrate reduction [19,20,21,22], microwave irradiation [23,24,25,26], photoreduction [27], polyol process [28,29], plant extracts and vegetable oils [30,31,32,33,34,35], vitamins [36], amino acids [24], polymers and proteins [37,38,39] These silver nanoparticles exhibit varying degrees of antimicrobial activity depending on their size, shape, and surface chemistry. A few other proteins such as casein [38] and bovine serum albumin have been reported to produce gold/silver nanoparticles/clusters [42,43,44,45,46] for different applications

Methods

Results

Conclusion