Chitin is a kind of natural macromolecule material which was first discovered in mushrooms and was widely found in the shells of crustaceans and arthropods, the cell walls of fungi (yeast and mold) and algae, and the mollusks. The original chitin in nature usually has an antiparallel molecular chain alignment forming nanofibers connected by inter‐ and intramolecular hydrogen bonds. These microfibers consist of nanofibers about 2‐5 nm in diameter, and about 300 nm long, embedded by protein matrices. Due to their unique dimensional, optical, mechanical, and other characteristics, the preparation of nano‐chitin materials is an important subject. It is possible to extract nano‐chitins from their sources with various methods, including acid hydrolysis, mechanical disintegration, TEMPO‐mediated oxidation, electrospinning, and others. In this article, the latest progress in recent years in the preparation and applications of nano‐chitin were reviewed. The morphology of the nano‐chitins obtained from the above methods was presented. The advantages and disadvantages of each method were analyzed. An overview of applications of nano‐chitins was discussed, including biomedicine, food applications, water treatment, green electronic materials, enzyme immobilization carriers, cotton textile materials, cosmetics, and others.

Collagen with a multi-hierarchical architecture exhibits powerful biological performance, thus being developed in biomedical applications as a processing building block. The isolated collagen after extraction from biological tissues can be processed into various forms such as fibrils, scaffolds, membranes, microspheres, hydrogels, and sponges for further use in specific applications. This review briefly discusses the multi-hierarchical structure, powerful biological performances, extraction, and processing approaches of collagen as a natural biomaterial. The processing of collagen including dissolution, self-assembly, cross-linking, and electrospinning, is discussed to show more feasibility for specific applications of collagen composite biomaterials. Further emphasis is directed towards the biomedical applications of drug and gene delivery, as well as tissue repair involving bone, cartilage, vascular, and corneal, along with wound healing. Additionally, there is a focus on the development of flexible sensors and electronic skins (e-skins). Furthermore, the potential challenges and perspectives for the development of collagen-based biomaterials are proposed. In short, collagen-based biomaterials are expected to facilitate sustainable development and the next generation of advanced biomaterial applications.Graphical Abstract