Thioketal-Mediated Silk Fibroin Nanoparticles with Reactive Oxygen Species-Triggered Structural Disintegration for Site-Specific Anti-Inflammatory Therapy

Silk fibroin (SF), a biocompatible natural macromolecule with self-assembly ability, has emerged as a promising drug delivery carrier. However, native SF lacks smart responsiveness. In this study, we introduced thioketal (TK) into SF to engineer an SF-based macromolecular network and further developed a reactive oxygen species (ROS)-responsive nanoparticle (NP) for site-specific drug release in ROS-rich microenvironments. An orthogonal experimental design was employed to obtain the optimal preparation formulation for SF/TK NPs, yielding spherical NPs with a mean diameter below 300 nm. Epigallocatechin gallate (EGCG) was selected as a model agent, and SF/TK@EGCG NPs with a mean diameter of 269.9 nm were prepared via solution self-assembly. The NPs exhibited pronounced ROS-triggered structural disintegration and accelerated EGCG release in 10 mM H 2 O 2, with the cumulative release rate reaching approximately 49% within 24 h. All NPs were noncytotoxic and nonhemolytic, and they can be efficiently internalized by RAW 264.7 macrophages. Notably, the SF/TK@EGCG NPs demonstrated site-specific anti-inflammatory efficacy both in vitro and in vivo . The SF/TK@EGCG NPs significantly suppressed the upregulation of the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α) expression in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. In the treatment of LPS-induced inflammatory liver injury, the SF/TK@EGCG NPs significantly reduced the serum levels of alanine aminotransferase and aspartate aminotransferase and effectively suppressed the upregulation of TNF-α and cleaved caspase-3 expression, compared with the SF@EGCG and free EGCG groups. These findings indicate that the ROS-responsive SF/TK@EGCG NPs represented an effective and biocompatible nanocarriers for site-specific anti-inflammatory therapy.