Gelatin Thin Coatings Covalently Cross-Linked and Grafted on Model Plane Substrates and Surgical Implant Fibers

We present a facile and precise approach for designing biopolymer thin coatings grafted on solid substrates, which could have potential applications in biotechnology and biomedicine. For example, in implant surgery, biogel coatings can prevent damage to biological tissues, reducing friction during implantation by swelling and lubrication. Biogel coatings are required to be interfacially and thermally stable during implantation, while their bioresorbability is valuable after implantation. Moreover, biogel coatings can store drugs and opportunely deliver them in the implant zone. In this Article, we report the preparation and properties of biopolymer thin coatings based on gelatins. The gelatin thin coatings are covalently cross-linked and grafted onto solid substrates to ensure good interfacial and thermal stability. They were obtained using a cross-linking and grafting (CLAG) strategy, which consists of simultaneously cross-linking and surface grafting gelatin chains through peptide bonds. The CLAG strategy was used on different substrates such as model plane silicon substrates and silicone microfibers serving as cochlear implants. The thickness of thin coatings was shown to vary over a wide range from nanometers to micrometers with a change in the coating parameters or by stacking gelatin hydrogel multilayers. Physical chemistry properties, such as the swelling of hydrogel coatings and their biodegradation, were finely characterized. The gelatin thin coatings were also shown to be a promising platform to encapsulate and release drugs such as dexamethasone, an anti-inflammatory agent.