Prolonged Release of <scp>IL</scp> ‐10 From Enzyme‐Mediated Poly‐ <scp>l</scp> ‐(Tyrosine‐ <i>co</i> ‐Phenylalanine) Nanocrystals Enhances Stability and Modulates Inflammatory Responses

Protease-catalyzed synthesis of a peptide composed of l-tyrosine and l-phenylalanine (2.2:1 M ratio) was achieved in a natural deep eutectic solvent (NADES) medium and subsequently employed to encapsulate the anti-inflammatory cytokine interleukin-10 (IL-10). IL-10 was loaded into enzyme-mediated peptide nanocrystals at doses of 200 and 400 ng, achieving stable nanocomposite formulations. Release studies were conducted in phosphate-buffered saline (PBS, pH 7.4) at 37°C under gentle agitation, revealing a sustained release profile extending up to 30-31 days, with an initial release of approximately 16% within the first 5 days and near-complete release between Days 10 and 25, depending on loading. Encapsulation effectively protected IL-10 from rapid degradation observed for the free cytokine under identical conditions, resulting in markedly enhanced stability. The nanocrystals were further integrated into porcine gelatin-hyaluronic acid (Ge:HA) and microbial poly(hydroxybutyrate-co-valerate) (PHBV) matrices, where IL-10 release was further modulated, reaching up to ~80% release from Ge:HA and ~100% from PHBV-based systems over 31 days. Cytotoxicity assays using primary human dermal fibroblasts confirmed excellent biocompatibility of all formulations. Moreover, studies in PMA-activated THP-1 macrophage-like cells demonstrated reduced intracellular reactive oxygen species (ROS) and suppression of the pro-inflammatory cytokine IL-6, highlighting the combined protective and immunomodulatory effects of IL-10 encapsulation. The presence of tyrosine residues within the nanocarrier further suggests intrinsic antioxidant contributions. Overall, these results support enzyme-mediated peptide nanocrystals as an effective platform for the stabilization and prolonged release of IL-10, with strong potential for treating inflammation-related skin conditions.