Long-Term Hydrophilic, Anti-Clotting, and Anti-Fibrotic Dynamic Covalent Silicone-Based Biomaterials

Abstract: 

While polydimethylsiloxane (PDMS) has been widely applied in biomedical devices and implants, its interfacial hydrophobicity and poor blood compatibility limit its long-term effectiveness. Existing approaches to enhance the surface hydrophilicity and reduce the interfacial biological responses of PDMS implants often result in a gradual loss of hydrophilicity due to the chemical instability of the coating and/or the hydrophobic recovery of the low surface energy silicone. Herein, dynamic covalent crosslinking of a Schiff base-crosslinked silicone elastomer (PDMSS) with an anti-fouling hydrazide-functionalized poly(oligoethylene glycol methacrylate) (OEGMA-Hzd) or zwitterionic sulfobetaine (DMAPS-Hzd) polymer is demonstrated to improve the long-term hydrophilicity and anti-fouling properties of PDMS. Dip coating PDMSS into a hydrazide-functionalized polymer solution significantly improved both the interfacial and bulk properties of the material, increasing its tensile and compressive strength while preventing hydrophobic recovery over at least 100 days, significantly longer than most reported approaches. Blood-contacting studies show the material resists clotting, while subcutaneous implants indicate a significant reduction in immune cell density at the tissue-implant interface as well as a decrease in capsule thickness and collagen deposition compared to PDMSS and Sylgard PDMS. This dynamic covalent crosslinking approach can thus address a key barrier to the fabrication of tissue-compatible and long-term hydrophilic PDMS-based biomedical implants.