Scrambled RGD Hexameric Peptide Hydrogel Supports Efficient Self-Assembly and Cell Activity

The amino acid sequence is crucial in controlling peptide-based hydrogel formation, whereby changing the position of a single amino acid can significantly alter the gel's properties. Herein, we report the gelation kinetics and cell viability of scrFmoc-GFFRDG (where we have scrambled the RGD-based gel hexapeptide; Fmoc-GFFRGD). The scrambled sequence showed improved gelation properties compared to the original Fmoc-GFFRGD sequence, with scrFmoc-GFFRDG forming a gel in under 10 min, significantly faster than the 2-h gelation time, and at a concentration eight times lower than the original Fmoc-GFFRGD sequence. We also examined the combination of the two gelators in a ratio of 1:1, final concentration of 0.4% (w/v). Interestingly, the stiffness of the hybrid hydrogel was ∼3 kPa, whereas individually, neither gelator at the same concentration exceeded 0.5 kPa. The cell-adhesion motif RGD improves the ability of the peptides to promote attachment of cells due to integrin recognition. However, when fibroblasts were cultured on the hydrogels, scrFmoc-GFFRDG yielded a higher level of α-SMA expression in cells than those cultured on Fmoc-GFFRGD, suggesting a microenvironment conducive to myofibroblast transitions. This study provides a new outlook on how a well-known scrambled peptide motif (RDG) can fine-tune hydrogel assembly and cell culture applications.