Preparation, Characterization and Antibacterial Properties of Silver-Chitosan Nanocomposites Using Different Molecular Weight Grades of Chitosan

K Ghajar,P Shalchian,P Khazaeli,S Honary

doi:10.4314/tjpr.v10i1.66543

Abstract

Purpose : To study the effect of chitosan molecular weight on the physicochemical and antibacterial properties of silver-chitosan nanoparticles. Methods : A series of silver-chitosan nanoparticles of different sizes were produced using various molecular weight (MW) grades of chitosan by an aqueous chemical reduction method. The nanoparticles were characterized by ultraviolet-visible absorption spectroscopy (UV-Vis), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic light scattering (DLS) and laser Doppler electrophoresis (LDE). The antibacterial properties of the nanoparticles were also evaluated by agar diffusion method. Results : The size of the silver-chitosan nanoparticles, ranging from 21.9 to 175.3 nm, was influenced by chitosan MW as well as by other process conditions. Although, the nanoparticles were not stable in liquid form, they however showed good stability in the solid state due to their low zeta potential. SEM images indicate that the nanoparticles were spherical. The antibacterial activity of the nanoparticles against Staphylococcus aureus increased with decrease in particle size owing to increase in surface area. The smallest particle size (21.9 nm) was obtained by using high chitosan MW at 4 °C and a stirring speed of 800 rpm. Conclusion : Chitosan is an effective agent for the preparation of silver nanoparticles. The size of the nanoparticles can be modulated by varying both chitosan MW and process conditions such as temperature and stirring speed.

Highlights

The antibacterial effects of silver (Ag) salts have been known for over 2000 years, but they have only been in common use as an antimicrobial since the 19th century [1]
It indicates that the size of silver nanoparticles depends on various process factors including chitosan molecular weight (MW), temperature, zeta potential and stirring rate
The smallest size (21.9 nm) was achieved for F18 when high MW chitosan was used at 4 °C and 800 rev/min

Summary

Introduction

The antibacterial effects of silver (Ag) salts have been known for over 2000 years, but they have only been in common use as an antimicrobial since the 19th century [1]. Ag is currently used to control bacterial growth in a variety of applications, including dental work, catheters, and burn wounds [1]. Silver nitrate solution causes argyria (staining of the skin) and a burning sensation on application. Ag ions and Ag-based compounds are highly toxic to microorganisms. They show strong biocidal activity against as many as 12 species of bacteria including E. coli [2]. Other forms of silver are available which do not have the disadvantages of earlier solutions

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