Preparation and characterization of ascorbic acid-mediated chitosan–copper oxide nanocomposite for anti-microbial, sporicidal and biofilm-inhibitory activity

Introduction

Green synthesis of metal and metal oxide nanoparticles has attracted much attention than other nanoparticles synthesis methods such as microwave assist [1], phase transfer [2], electrochemical [3], sol–gel method and photochemical methods [4]. Green synthesis of metal and metal oxide nanoparticles using plants, microorganisms and bio-compounds is environmental friendly without using toxic compounds and involves simple preparation methods [5].

Nowadays, anti-microbial-resistant pathogens have been increasing with great frequency. Traditional medicine and some of the therapeutic drugs could not control the infections from microbial pathogens [6]. In recent years, metal oxide nanoparticles have gained attention for treating and preventing microbial pathogens. Among the metal oxide nanoparticles, copper oxide nanoparticle (CuO) capped with biologically active molecules such as carbohydrates, vitamins and proteins are the new hope as nanoparticle agents to treat microbial pathogens [7].

The importance of polymers such as chitosan and chitin on metal oxide nanoparticles has attracted attention in the pharmaceutical and biological field [8]. Chitosan is a linear polysaccharide composed of randomly distributed β-(1 → 4)-linked d-glucosamine and N-acetyl-d-glucosamine (Fig. 1) with a number of commercial and biomedical uses [9]. Recently, chitosan-coated polypropylene films exhibited important antibacterial activity [10]. As chitosan is in a solid form, only organisms in direct contact with the active sites of chitosan are inhibited. The CuO nanoparticles enhance the diffusivity of chitosan, so that it can be used as an effective anti-microbial agent [11]. The anti-microbial activity of chitosan may be enhanced with incorporation of CuO into chitosan as nanocomposite. In the present study, we prepared chitosan-coated copper oxide nanocomposites using ascorbic acid as a bio-template for the first time. Here, we have demonstrated the preparation, physical characterization of Chi–CuO nanocomposites and its anti-microbial activity against bacterial and fungal pathogens, sporicidal and biofilm inhibition activity.

[See PDF for image]

Fig. 1

Structure of chitosan biopolymer molecule

Materials and methods

Materials

Copper sulfate (CuSO₄·₅H₂O), ascorbic acid and acetic acid were purchased from Himedia Laboratories, Mumbai, India. Chitosan (medium molecular weight with 90% deacetylation) was obtained from Sigma-Aldrich. All other chemicals and reagents were of analytical grade.

Preparation of Chi–CuO nanocomposites

About 0.2 g chitosan in 10 mL of 0.04% acetic acid was mixed with 90 mL of copper sulfate solution (10 mM) containing 1%...