Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Direct extraction of silk nanofibers (SNs) from natural silk fibers was developed via a low-intensity ultrasonic-assisted sulfuric acid hydrolysis process. The effects of sulfuric acid (H₂SO₄) amount, hydrolysis time and temperature were investigated. SNs with a length and width of 306 ± 107 nm and 4–18 nm, respectively, were obtained with a yield of 64.54%. Furthermore, unlike for the silk nanofibers formed from a regeneration process, the original crystal structure of the silk was maintained. The aqueous dispersion of SNs was steady for at least 30 days at pH 3 and 7–10 with no aggregation. Furthermore, the as-prepared SNs were amphoteric due to the intrinsic characteristics of the protein that endow them with the ability to mix well with either positively or negatively charged polymers, possibly contributing to the field of high-tech silk materials in the future.