Natural Rhein-grafted silane coatings for durable antibacterial and biocompatible PDMS

Polydimethylsiloxane (PDMS) is widely utilized in biomedical devices. However, its inherent hydrophobicity often leads to bacterial colonization, biofilm formation, and the limited durability of conventional surface modifications. Herein, we report a novel and stable surface modification strategy for covalently grafting Rhein, a bioactive compound derived from traditional Chinese medicine, onto PDMS using a tailored silane coupling agent (KH‑550‑Rhein). This covalent immobilization approach effectively suppresses hydrophobic recovery and ensures long‑term surface stability. The resultant PDMS-Rhein exhibited rapid, contact‑active antibacterial effects (> 92% reduction in S. aureus within 1.5 h; > 97% for E. coli within 4 h). Notably, the coating retains high antibacterial efficacy (> 96%) after 6 days of immersion in phosphate‑buffered saline (PBS) and demonstrates excellent reusability over multiple cycles. Moreover, PDMS-Rhein significantly reduced protein adsorption (by 67–82% for BSA, fibrinogen, and lysozyme), resists biofilm formation, and maintains good biocompatibility with hemolysis rates below 5% and fibroblast viability exceeding 80%. This innovative surface modification strategy, utilizing natural products, offers a reliable and translatable strategy for improving the safety and performance of implantable biomedical devices.