Reaching Increased Hydrogel Stability In Vivo through β-Hairpin Peptide-Based Hydrogels

Peptide-based hydrogels are increasingly used in pharmaceutical and biomedical applications due to their versatility and biocompatibility. β-Hairpin design enhances β-strand alignment and fine-tunes hydrogel physicochemical properties. In this study, we investigate the design of β-hairpin hydrogelators from two P1-based (H-FQFQFK-NH₂) hexamer strands linked by a d-Pro-l-Pro β-turn. The fluorinated proline surrogate CF₃-ΨPro was evaluated for hairpin stabilization and gel properties. Hydrogels were characterized for physicochemical, mechanical, and structural properties, and selected hydrogels were screened in in vitro drug release experiments. Based on these data, in vivo hydrogel stability experiments were conducted on hairpin structures P3 (H-FQFQFKpPFQFQFK-NH₂) and its fluorinated analogue P17 (H-FQFQFKp(l-CF₃-ΨPro)FQFQFK-NH₂), via subcutaneous injection in mice. P3 and P17 demonstrated enhanced hydrogel lifespan with 70% and 45% of the hydrogel remaining at the injection site after 11 days, respectively, versus 10% for P1 after 7 days. These findings highlight the advantage of β-hairpin peptide hydrogels for prolonged drug delivery.