Preparation of nanochitin using deep eutectic solvents

Abstract

Chitin is an abundant and renewable non-wood biopolymer. Nanochitin is formed by the assembly of chitin molecules, which has the advantages of large tensile strength, high specific surface area, and biodegradability, so it has been widely used. However, the traditional methods of preparing nanochitin have many drawbacks. As the new generation of green solvents, deep eutectic solvents (DESs) have been successfully applied in the fields of chitin dissolution, extraction, and nanochitin preparation. In this review, the relevant knowledge of chitin, nanochitin, and DESs was first introduced. Then, the application status of DESs in the fields of chitin was summarized, with a focus on the preparation of nanochitin using DESs. In conclusion, this review provided a comprehensive analysis of the published literature and proposed insights and development trends in the field of preparation of nanochitin using DESs, aiming to provide guidance and assistance for future researchers.

Keywords: Materials chemistry.

Graphical abstract

Figure 1

Structure and polymorphic configuration of chitin (A) and ball-and-stick model of dGlcNAc monomer (B). The schematic view of the alignment of the molecular chains in chitin (C). Schematic diagrams of the molecular chain orientations in the polymorphic configuration of different types of chitins (D–F). Nanofiber packaging diagram and molecular chain packaging diagram in chitin (G and H). Copyright 2021 Elsevier Ltd.

Figure 2

α-chitin The multiscale structure of α-chitin in nature. Copyright 2022 Wiley.

Figure 3

Overview of the methods for preparing ChNFs (A) and ChNCs (B). ChNFs containing crystalline and disordered structures are produced by mechanical treatment (a₁) or mechanical treatment assisted by chemical modification (a₂) and biological processing (a₃). Copyright 2022 American Chemical Society.

Figure 4

ChNCs at the interface The photo of O/W HIPPE gel containing 96% internal phase (hexadecane) by using the stability of ChNCs at the oil/water interface (A). Copyright 2014 American Chemical Society. The ChNFs/CMC films prepared by using extracted ChNFs as the enhancer exhibit excellent mechanical and antibacterial properties (B). Copyright 2016 American Chemical Society. Transmission electron microscopy and atomic force microscopy images of ChNFs (c₁). Schematic illustration of the formation of nanochitin hydrogels and cryogels via ice templating and cross-linking (c₂). The photographs of cylindrical nanochitin hydrogels (c₃). The photographs of cylindrical nanochitin cryogels (c₄). Copyright 2019 American Chemical Society.

Figure 5

General formula and classification of DESs (A) Common HBAs and HBDs are used for the preparation of DESs (B). Copyright 2021 Springer.

Figure 6

Extraction of chitin Schematic depiction for the extraction of chitin from lobster shell by DESs (A). Copyright 2017 Elsevier Ltd. Schematic depiction for the extraction of chitin from shrimp shell by DESs (B). Copyright 2018 American Chemical Society. Schematic diagram of extracting chitin from crayfish shell waste by DESs (C). Copyright 2021 American Chemical Society.

Figure 7

ChNFs prepared by ChCl/thiourea DES Schematic illustration and TEM photo of ChNFs prepared by choline chloride/thiourea DES (A). Copyright 2014 Elsevier. Schematic illustration and SEM photo of ChNCs prepared by choline chloride/p-toluenesulfonic acid DES (B). Copyright 2019 Elsevier.

Figure 8

ChNFs prepared by ChCl/ZnCl₂ DES Schematic illustration and AFM photo of ChNCs prepared by choline chloride/ZnCl₂ DES (A). Copyright 2019 Elsevier. Schematic illustration of ChNCs prepared by betaine hydrochloride/ferric chloride hexahydrate DES (B). Copyright 2020 MDPI.

Figure 9

ChNFs prepared by ChCl/OA DES Schematic illustration and AFM photo of ChNCs prepared by choline chloride/organic acids DESs (A). Copyright 2020 Elsevier. Schematic illustration and TEM photo of ChNCs prepared by choline chloride/malic acid DES (B). Copyright 2022 Royal Society of Chemistry.