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

Dually crosslinked graphene oxide reinforced alginate/polyvinyl alcohol (PVA) double network (DN) hydrogels were prepared via a facile freeze/thaw method followed by soaking in a Ca²⁺ solution. The morphology and structure of the hydrogels were systematically examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The effects of pH, dosage of hydrogel, adsorption time, and temperature on the adsorptive property of DN hydrogels towards methylene blue (MB) were also studied. Results indicated that the hydrogels exhibited typical 3D porous structures and had an efficient adsorption effect towards MB due to strong interactions between DN hydrogels and MB molecules. The adsorption isotherm was found to coincide with the Langmuir model with a monolayer adsorption. The highest adsorption capacity of DN hydrogels for MB was examined as 480.76 mg·g⁻¹.

A pioneering way is demonstrated to synthesize Co₃O₄ catalysts with abundant edge dislocation defects, which exhibit excellent OER catalytic performance.