Recent progress on synthesis, property and application of modified chitosan: An overview

Abstract

Because of the unique chemical structure, chitosan and its derivatives have been paid close extensive attention as the potential bio-functional material. This review presents recent synthesis of modified chitosan via N-substitution, O-substitution, free radical graft copolymerization and other modification methods and properties of the modified chitosan. The applications of the modified chitosan in metal ions adsorption, dye removal and pharmaceutical fields are illustrated as well. The rapid development in the modification of chitosan describes broad perspectives of the modified chitosan.

Introduction

Chitosan is a linear polysaccharide which consists of d-glucosamine and N-acetyl-d-glucosamine and can be obtained by de-acetylation of chitin which is the second abundant and widely distributed natural polymer [1], [2], [3]. The chemical structure of chitosan [4] is shown in Scheme 1. It has been proved that chitosan has many prominent biological properties like biodegradability [5], [6], [7], biocompatibility [8], [9], non-toxicity [10], [11] and antibacterial activity [12], [13]. What’ s more, chitosan can act as natural electrolyte due to protonation of amino groups of chitosan in acidic medium [14]. However, the incomplete N-deacetylation of chitosan can greatly influence its properties, such as solubility, and significantly limit its utilization [15]. Fortunately, the existence of chemically active hydroxyl and amino groups results in easy modification of chitosan to improve its intrinsic properties or to give some new properties. Functional groups are introduced to chitosan backbone by grafting. The application prospects of chitosan can be expanded by grafting various functional groups [16]. The main modification methods of chitosan include but not limit to N-substitution, O-substitution and free radical graft copolymerization.

Chitosan and its derivatives have been paid close extensive attention as potential bio-functional materials and widely applied in various fields [17], [18], [19], [20], [21]. Metal ions and dyes widely exist in industrial effluents which are often discharged into environment and harmful to human beings. As a natural electrolyte, chitosan can be modified to acts as a potential material for metal ion adsorption [22], [23], [24] and dye removal [25], [26], [27]. Most of the chitosan based bio-sorbents show excellent adsorption capacity for specific metal ion or dye after modification [28]. The modified chitosan can also be applied in pharmaceutical fields due to its biocompatibility and non-toxicity [29], [30], [31]. The potential antibacterial and antioxygenic properties make modified chitosan one of the most promising candidate for cancer therapy [32], [33], [34].

This review highlights recent synthesis of modified chitosan via N-substitution, O-substitution, free radical graft copolymerization and other modification methods and properties of the modified chitosan. The applications of the modified chitosan in metal ions adsorption, dye removal and pharmaceutical fields are illustrated as well.