Photografted Dual-Network Zwitterionic Hydrogel Coatings for Biomaterials

Abstract

Reduction of foreign body response and fibrotic capsule formation with implanted biomaterials can significantly improve the lifetime and function of medical devices, including those that deliver electrical stimulation such as cochlear implants. Zwitterionic hydrogels resist biofouling but may lack the mechanical strength and stability necessary for long-term applications. In this study, we have developed durable and robust antifouling dual-network zwitterionic coatings covalently bonded to poly(dimethylsiloxane) (PDMS). These dual-network hydrogels are formed using photografting and photopolymerization of a primary network, followed by swelling and photopolymerization of a secondary monomer system, thereby enhancing the strength and durability of the coating. For example, the material stiffness increases slightly with lightly to moderately crosslinked secondary networks, while higher coating strength results from a highly crosslinked secondary network. The introduction of a secondary network also enables control of swelling and ultimate thickness with up to threefold reductions in swelling for hydrogels with lower crosslink density. As with single-network hydrogels, dual-network coatings demonstrate high flexibility and a low coefficient of friction. Additionally, dual-network hydrogel coatings reduce fibroblast adhesion compared to PDMS in vitro with large decreases in fibrotic capsule thickness in vivo. These results illustrate the potential of dual-network coatings as an effective strategy for improving the long-term performance of implanted biomaterials by reducing biofouling and controlling material properties of the photografted hydrogel.