Hierarchical Assemblies of Collagen-Mimetic Peptides: From a Fundamental Understanding to Developing Biomaterials.

Collagen is the most abundant protein in animals and crucial for maintaining the structural and functional integrity of the extracellular matrix. Its primary structure consists of ∼300 repeats of the Xaa-Yaa-Gly triplet, where Xaa and Yaa are often proline (Pro) and 4-()-hydroxyproline (Hyp) residues, respectively. Collagen is fundamentally a right-handed triple helix that undergoes self-association, forming complex supramolecular structures in the body. Despite extensive study, the detailed mechanisms behind its higher-order assembly remain unclear due to challenges in its purification and the extensive post-translational modifications that it undergoes. To better understand the molecular aspects of collagen's complex structure, researchers developed collagen-mimetic peptides (CMPs)─short peptides composed of 7-17 Xaa-Yaa-Gly triplets─easily synthesized in the laboratory. Over the years, research on CMPs has provided significant insights into the formation and stability of the collagen triple helix. However, creating multihierarchical self-assembled structures beyond the triple helix remains challenging. Recently, various strategies such as covalent linkages, salt-bridge interactions, incorporation of hydrophobic groups, metal-coordinated assembly, and coassembly with foreign partners have been employed to design higher-order CMP assemblies. These innovations have led to the creation of fibers, 2D sheets, wires, and spherical micelles. This progress has paved the way for the rational design of novel peptide-based biomaterials, which may offer advantages over animal-derived collagen, including the absence of potential allergens and contaminants. This review highlights recent advancements in CMP assembly design, discussing the principles, challenges, and prospects of these biomaterials in clinical applications.