Colloidal particle based electrodeposition coatings on NiTi alloy: Reduced releasing of nickel ions and improved biocompatibility

Photo-crosslinking copolymer Poly (2-Hydroxyethyl methacrylate-co-2-(Dimethylamino) ethyl methacrylate-co-7-hydroxy-4-methylcoumarin methacrylate) (PHDC)) was first synthesized by free radical polymerization of 7-hydroxy-4-methylcoumarin methacrylate (CA), 2-Hydroxyethyl methacrylate (HEMA) and 2-(Dimethylamino)ethyl methacrylate (DMA). Then, the copolymers were self-assembled into colloidal particles and immobilized on the NiTi alloy by a simple one-step electrophoretic deposition. After irradiation, a photo-crosslinked coating was obtained. The structure and morphology were characterized by OCA and SEM. The copolymer coatings could significantly decrease the release of nickel ions into the environment and reduce cytotoxicity inducing by nickel ions according to immersion experiment. Meanwhile, the coatings have good cytocompatibility. This work provides a simpler polymer coating method to inhibit the release of toxic ions by inducing ion adsorption with certain molecular structures, which have potential for biomedical applications such as artificial bone and bone fixation device.