Hyperstable and Fibril-Forming Collagen-Mimetic Peptides in Shortest Triple Helices: Empowering the Capping by π-systems.

Developing collagen-mimetic peptides (CMPs) with short triple helices and fibril-forming ability remains challenging. Herein, we stabilized short CMPs (3-6 GPO repeats) by attaching extended aromatic π-system─fluorenyl groups at the N-terminus and tyrosine at the C-terminus. These modifications promoted triple helix folding through π-π interactions, acting as a "glue" to stabilize the structure and facilitate fibrillation. A single fluorenyl cap required 5 GPO repeats for helix formation, while double fluorenyl capping reduced this to 4 repeats. Notably, at pH 5.5, triple helices formed with only 3 GPO repeats. The double-capped CMPs exhibited hyperstability (T_m = 76 °C) and formed fibrillar networks at physiological pH. Biophysical and computational studies confirmed the role of π-π and CH-π interactions, along with hydrogen bonding, in stabilization. The minimalistic CMPs supported cell viability, demonstrating their potential for biomedical applications. This strategy offers a method to design highly stable, short CMPs that form robust fibrillar networks.