Bioorthogonally Active Silk Fibroin Patch Facilitate Immunomodulatory Prodrug Activation for Tissue Repair

Current silk fibroin (SF)-based tissue repair patches often exhibit limited immunomodulatory efficacy, exacerbating inflammatory responses and compromising functional tissue integration. To address this limitation, we developed a bioorthogonal prodrug activation strategy within an SF patch via tetrazine functionalization (SF-Tz). This platform enables the spatiotemporally controlled release of trans-cyclooctene (TCO)-caged dexamethasone (TCO-Dex) via inverse electron-demand Diels-Alder reactions. The SF-Tz platform was engineered through optimized carboxylation and tetrazine conjugation protocols, achieving high grafting density of tetrazine while preserving the native SF's mechanical strength. In vitro analyses demonstrated efficient TCO-Dex activation (78.0% within 24 h), accompanied by significant suppression of pro-inflammatory cytokines (TNF-α: 76.0% reduction; IL-6: 95.0% reduction) and increase in anti-inflammatory IL-10 secretion (239.7% increase). Macrophage polarization assays demonstrated a 21.2% suppression of CD86+ M1 macrophages and a 13.8% promotion of CD206+ M2 macrophage, confirming their anti-inflammatory efficacy through phenotypic reprogramming. In a rat abdominal wall defect model, the SF-Tz patch mediated local release of Dex achieved marked reductions in inflammation, accelerated collagen deposition, and successful defect closure within 28 days. Notably, systemic toxicity markers remained within physiological ranges, validating the biocompatibility of this approach. This bioorthogonal strategy uniquely combines SF's inherent biocompatibility with programmable immunomodulation, establishing a translational platform for treating chronic wounds and complex tissue defects requiring precise inflammatory control.