Study On The Surface Functionalization Of Medical Titanium Alloy And Its Antibacterial And Antifouling Properties

Bacterial contamination is a very serious problem in the biomedical field.For instance,the occurrence of bacterial colonization after implant insertion into the patients may cause severe infections at the implantation site,which ultimately requires antibiotic treatment.Also,the persistence of serious bacterial infections cause implant failure,requires surgery and re-implantation,and even more severe cases leads to death.Implant infections are not only prolonging the duration of hospital stay,also increases the financial burden on the patients consequences with both physiological and psychological stresses.Commercial titanium and its alloys have excellent mechanical,corrosion resistance,and biocompatibility,and are often used in the preparation of permanent implants.However,the titanium-based implants have no inherent antibacterial activity,which may lead to bacterial contamination and subsequent implant infections.Therefore,it is of great scientific significance to introduce appropriate surface coatings in order to inhibit the adhesion and growth of bacterial pathogens.The outcome can provide a potential solution to the implant infection problem of titanium-based implants.This thesis focuses on the surface modification of titanium-based materials,and uses biomimetic technology inspired by Mytilus edulis foot protein 5(Mefp-5)and tea stains to introduce functional coatings on the surface of medical titanium plates.Firstly,the dual antibacterial surface containing Ag NPs and catechol-modified chitosan were fabricated.Inspired by the super adhesive properties of Mytilus edulis foot protein,the water-soluble catechol-containing chitosan(CACS)was synthesized through esterification reaction,which can be anchored on the surface of titanium sheet by CACS self-polymerization and surface attachment of catechol groups.The remaining catechol groups on the surface of titanium sheet can reduce the Ag~+ions in situ,and the resulting AgNPs/CACS-coated Ti surfaces were obtained.Furth 1H NMR,X-ray photoelectron spectroscopy(XPS),and energy dispersive spectrometer(EDS)were used to characterize their chemical compositions.The inhibition of bacterial attachment and bacterial biofilm formation was evaluated by inhibition zone test,spread plate method,live/dead bacterial staining assay.The cytotoxicity of the surface of the modified titanium sheets were measured against L929 mouse cells by the MTT method.The overall results showed that in weakly alkaline environment,CACS can effectively modify the surface of titanium sheet.The Ag NPs/CACS-coated Ti surfaces posses good antibacterial properties and can effectively prevent the surface adhesion of bacterial cells.In addition,The Ag NPs/CACS-coated Ti surfaces exhibited only negligible level of cytotoxicity to L929 mouse fibroblast cells.Secondly,inspired by the attachment of tea stains on any surface,primary amine moieties were introduced on the gallic acid groups in tannic acid(TA)by the Williamson ether synthesis and Boc removal reaction to obtain amine-containing TA derivatives(TAA).Through the self-polymerization and TA's surface adhesion ability,TAA can form colorless and uniform coatings on the surface of various materials.The surface roughness,thickness,and elemental composition of TAA coatings on silicon(Si)sheets were characterized by atomic force microscopy(AFM),ellipsometry and XPS analyses.Biotin-PEG-NHS and mPEG-NHS were further grafted onto TAA coatings by the NHS coupling reaction.Moreover,the non-specific and specific adsorption properties of proteins on mPEG and Biotin-PEG modified surfaces were studied by Surface plasmon resonance(SPR).Ag NPs were introduced on TAA coatings via in situ reduction and its ability to inhibit bacterial adhesion and biofilm formation was evaluated.The results showed that the mPEG brush grafted on the TAA coating holds the ability to inhibit the non-specific adsorption of bovine serum albumin(BSA)and fibrinogen from human plasma(FBG),while the biotin probe on the TAA coating promotes the specific binding of avidin and inhibits the binding of BSA and FBG.On the other hand,the surface of titanium sheet co-deposited with TAA and Ag NPs effectively inhibits the adhesion of E.coli and S.aureus and hindering the formation of S.aureus biofilm.