Multivalent and synergistic chitosan oligosaccharide-Ag nanocomposites for therapy of bacterial infection

Lin Mei,Zhenlong Xu,Chunlei Lin,Lijun Zhang,Shuyan Jiao,Yanmei Shi,Pengxu Li

doi:10.1038/s41598-020-67139-7

Abstract

Chitosan oligosaccharide functionalized silver nanoparticles with synergistic bacterial activity were constructed as a multivalent inhibitor of bacteria. Placing the chitosan oligosaccharide on silver nanoparticles can dramatically enhance the adsorption to the bacterial membrane via multivalent binding. The multicomponent nanostructures can cooperate synergistically against gram-positive and gram-negative bacteria. The antibacterial activity was increased via orthogonal array design to optimize the synthesis condition. The synergistic bacterial activity was confirmed by fractional inhibitory concentration and zone of inhibition test. Through studies of antimicrobial action mechanism, it was found that the nanocomposites interacted with the bacteria by binding to Mg2+ ions of the bacterial surface. Then, the nanocomposites disrupted bacterial membrane by increasing the permeability of the outer membrane, resulting in leakage of cytoplasm. This strategy of chitosan oligosaccharide modification can increase the antibacterial activity of silver nanoparticles and accelerate wound healing at the same time. The nanomaterial without cytotoxicity has promising applications in bacteria-infected wound healing therapy.

Highlights

Chitosan oligosaccharide functionalized silver nanoparticles with synergistic bacterial activity were constructed as a multivalent inhibitor of bacteria
The Minimal inhibitory concentrations (MIC) values against S. aureus and E. coli were determined to evaluate the antibacterial activity of the nine synthesized AgNPs-Chitosan oligosaccharide (COS) and the results were shown in Tab. 1
The results showed that the fractional inhibitory concentration (FIC) indices were 0.34 and 0.29 against S. aureus and E. coli, respectively, indicating that COS binding to the AgNPs can obtain synergistic antimicrobial effect

Summary

Introduction

Chitosan oligosaccharide functionalized silver nanoparticles with synergistic bacterial activity were constructed as a multivalent inhibitor of bacteria. Through studies of antimicrobial action mechanism, it was found that the nanocomposites interacted with the bacteria by binding to Mg2+ ions of the bacterial surface. The nanocomposites disrupted bacterial membrane by increasing the permeability of the outer membrane, resulting in leakage of cytoplasm This strategy of chitosan oligosaccharide modification can increase the antibacterial activity of silver nanoparticles and accelerate wound healing at the same time. AgNPs can contact with bacterial cell membranes, penetrate into the cytoplasm, and inactivate essential respiratory enzymes and proteins, leading to bacterial death[7,8] These antibacterial action of AgNPs is often dependent on high concentration since their physical collision with bacterial surface is random[9]. We further explore the biocompatibility toward RAW 264.7 cells and the treatment of bacteria-induced wound infection

Methods

Results

Conclusion