Construction Of Novel Bio-inspired Antibacterial Coating

Nosocomial infection,which was mainly caused by microbes adhering to medical devices,has been a serious threat to human health.However,traditional antibacterial coatings,generally based on cationic polymers,antibiotics or heavy metal,are limited in real application because of the missing biocompatibility,instability and especially the tendency to promote bacterial drug-resistance.Therefore,it is of great need to explore novel antibacterial coatings.From the point view of nature,lots of enlightenment could be sought.For instance,most amphibians and fishes have effective defensive weapons against microbes by secreting a thin slime layer containing antimicrobial peptides(AMPs)to reduce proliferation of pathogenic bacterium on their skin.Such kind of dynamic slime layer is desirable for bacterial coating design.On the other hand,polydopamine(PDA),which was found from foot protein of marine mussel,provide huge convenience for surface modification.What's more,the photothermal property of PDA reinvest antibacterial coating with novel approach.Given the wide range of sources and natural biocompatibility of those biomolecule,antibacterial coatings based on such compounds would have special advantages in application.Inspired by the above phenomena,we build up two kinds of novel antibacterial coatings:1 A dynamic spongy film for immobilizing AMPs was built up through layer-by-layer technique with polyethylenimine(PEI)and PAA poly(acrylic acid)as the assembly unit,providing a potential platform to fabricate bactericidal coating based on AMPs.Because of the special property of weak polyelectrolyte,the(PEI/PAA)film could switch from thin,solid film into spongy,full of micropores film after acidic solution treatment(pH=2.9).The microporous structure could be conserved after freeze-drying.Consequently,the loading and integration of hydrophobic AMPs such as gramicidin A(GA)into the(PEI/PAA)film were achieved via simple wicking action rapidly(<5 s)with GA solution and subsequent humidity treatment for 8 h,respectively,with the GA density in the coating could be as high as?0.22mg cm-2.Antibacterial assays demonstrated that(PEI/PAA)-GA coating was able to kill not only common S.aureus but also drug-resistant bacteria MRS A with killing efficiency higher than 90%.What,s more,(PEI/PAA)-GA coating could eliminate a 50 ?m Wide scratch in 2 h with 100%relative humidity treatment,indicating the self-healing capability of this coating.2 The photothermal antibacterial ability of PDA coating was tested.At first,PDA coatings on various substrates were fabricated through simple dip-coating of objects in an alkaline aqueous solution of dopamine.The thickness of PDA could be well controlled through adjusting the polymerization time.A wide range of light absorbance(from 400 nm to 900 nm)of PDA coating was observed.When irradiated by 808 nm wavelength laser,PDA coatings on different substrates presented increased temperature in various degrees,from 20 ? to 50 ??demonstrating the efficient photothermal conversion property of PDA.Furthermore,the linear relationship between temperature and thickness of PDA coating was determined.Every nanometer of PDA contributes to the rising about 0.8 ? of the coating temperature.Antibacterial assays showed the PDA coating was able to kill not only bacteria(S.aureus and E.coli)but also fungus(C,albicans)with its photothermal function,realizing a broad-spectrum antibacterial effect without any traditional bactericidal drugs.What,s more,it was convenient to fabricate PDA coating on common catheters(PVC and SR catheter)with bactericidal ability remained(killing efficiency>95%),confirming the potential value of PDA coating in the field of antibacterial coatings for biomaterial.