Robust anti-infective multilayer coatings with rapid self-healing property.

Surface coatings are extensively applied on biomedical devices to provide protection against biofouling and infections. However, most surface coatings prevent both bacteria and cells interactions with the biomaterials, limiting their uses as implants. Furthermore, damage to the surface such as scratches and abrasions can happen during transport and clinical usage, resulting in the loss of antibacterial property. In this work, we introduce an efficient method to fabricate stable anti-infective and self-healable multilayer coatings on stainless steel surface via a three-step procedue. Firstly, modified polyethyleneimine (PEI) and poly(acrylic acid) (PAA), both contain pendant furan groups, were deposited on the surface using Layer-by-Layer (LbL) self-assembly technique. Secondly, the polymer layers were cross-linked, via Diels-Alder cycloaddition, using a bismaleimide poly(ethylene glycol) linker, to enhance the stability of the coatings. Thirdly, the Diels-Alder adduct was utilised in the thiol-ene click reaction for post-modification of the coatings, which allowed for the grafting of antimicrobial poly(hexamethylene biguanide) (PHMB) and ε-poly(lysine) (EPL). The resultant multilayer coatings not only exhibited rapid self-healing property, with complete scratch closure within 30 min, but also demonstrated effective antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). In addition, biofouling of bovine serum albumin was found to be inhibited on the coated surfaces. Furthermore, these coatings showed no toxicity effect towards seeded osteoblastic cells (MC3T3-E1) and evidence of anti-inflamatory activity when tested against macrophage cell line U-937. Our coating method thus represents an effective strategy for the anti-infective protection of biomedical-devices having direct contact with tissues.