Chitin and chitosan nanofibers: preparation and chemical modifications.

Shinsuke Ifuku

doi:10.3390/molecules191118367

Abstract

Chitin nanofibers are prepared from the exoskeletons of crabs and prawns, squid pens and mushrooms by a simple mechanical treatment after a series of purification steps. The nanofibers have fine nanofiber networks with a uniform width of approximately 10 nm. The method used for chitin-nanofiber isolation is also successfully applied to the cell walls of mushrooms. Commercial chitin and chitosan powders are also easily converted into nanofibers by mechanical treatment, since these powders consist of nanofiber aggregates. Grinders and high-pressure waterjet systems are effective for disintegrating chitin into nanofibers. Acidic conditions are the key factor to facilitate mechanical fibrillation. Surface modification is an effective way to change the surface property and to endow nanofiber surface with other properties. Several modifications to the chitin NF surface are achieved, including acetylation, deacetylation, phthaloylation, naphthaloylation, maleylation, chlorination, TEMPO-mediated oxidation, and graft polymerization. Those derivatives and their properties are characterized.

Highlights

A nanofiber (NF) is generally defined as a fiber of less than 100 nm diameter and an aspect ratio of more than 100 [1,2]
Chitin NFs were prepared from crab shells by a disintegration process [2]
The method of preparing chitin NF from crab shell is applicable to a variety of prawn shells, since prawn shell is made up of a hierarchical organized structure

Summary

Introduction

A nanofiber (NF) is generally defined as a fiber of less than 100 nm diameter and an aspect ratio of more than 100 [1,2]. Nature produces a variety of bio-NFs, such as collagen triple helix fibers, fibroin fibrils, and keratin fibrils. These NFs basically form a complex hierarchical organization. Chitin is produced in Nature at a rate of 1010 to 1011 tons per year, most chitin is thrown away as commercial waste [8] This is obviously due to the low workability of the biopolymer, since commercially available chitin powder is not soluble in any solvent but precipitates immediately. Since crab and prawn shells have a complex hierarchical structure consisting of NFs [9], we expected that chitin NFs could be prepared by mechanical disintegration. The author reviews the preparation of chitin NFs and chemical modifications to endow them with certain properties

Preparation of Chitin Nanofibers

Chemical Modifications of Chitin Nanofibers

Conclusions