Self-Assembled Hydrogels Developed from THPA-γ⁴-Phe-γ⁴-Phe-OH Loaded with Icariin Promote Chronic Diabetic Wound...

Peptide hydrogels are extensively used in biomedical applications due to their excellent biocompatibility and distinctive benefits stemming from their amino acid-derived architectures and functionalities. The exploration of hydrogels developed from peptide conjugates and natural products as potential biomaterials for chronic diabetic wound healing remains limited. Herein, we synthesized and characterized γ-dipeptide conjugates with piperic acid (PA) and tetrahydropiperic acid (THPA) containing γ⁴-Phe residues, PA-γ⁴-Phe-γ⁴-Phe-OH (P1), and THPA-γ⁴-Phe-γ⁴-Phe-OH (P2). Our findings showed that conjugate P2 exhibits a distinct hydrogel morphology in DMSO and H₂O (1:1), as characterized by IR spectroscopy, circular dichroism (CD), and scanning electron microscopy (SEM). The P2 hydrogel exhibited higher proteolytic stability and lower cytotoxicity. Furthermore, the 1.0% (w/v) Icariin-loaded P2 hydrogel exhibited an encapsulation efficiency of 81.1%, which increased slightly to 82.66% at 1.5% (w/v), indicating that 1.0% (w/v) is the optimal drug-loading concentration for the P2 hydrogel network. The cumulative Icariin release profile showed an initial burst release of 89.0% at 12 h, followed by a gradual increase to 92.9% at 24 h. This sustained release behavior is likely attributed to the dense nanofibrous network and strong intermolecular interactions within the P2 hydrogel. The Icariin-loaded P2 hydrogel was further evaluated for diabetic wound-healing activity in-vitro and in-vivo. In-vitro scratch assays demonstrated enhanced fibroblast migration and proliferation, while in-vivo studies in a diabetic mouse model showed accelerated wound healing efficacy. Notably, it regulated inflammatory signals by downregulating pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) and upregulating the anti-inflammatory cytokine IL-10, thus promoting a shift to a regenerative microenvironment. Histological analysis further confirmed the improved tissue architecture, indicating efficient progression through the healing phases.