Fabrication And Properties Of AgNPs-Loaded Polyelectrolyte Multilayers On Pure Titanium Surface

Objective:On alkali-heat treated Ti substrates,AgNPs-loaded chitosan-heparin polyelectrolyte multilayers(PEMs)via layer-by-layer self-assembly(LbL)were fabricated.And its physicochemical characteristics,cytocompatibility and antibacterial properties were investigated,in order to find new surface stucture of dental implant neck with adherence of gum collagenous fiber and antibiotic activity.Materials and methods:1.CS as stabilizing and reducing agents,AgNPs were synthesized by hydrothermal method and characterized by UV-VIS-NIR spectrophotometer and TEM.2.The physicochemical characteristics of CS/AgNPs-Heparin PEMs on the alkali-treated Ti surface were assessed by means of AFM,FESEM,SEM-EDX,XPS,XRD and contact angle measurements.3.HGFs were cultured on polished(Ti),hot alkali-treated(Ti-OH)and PEMs modified(Ti-PEMs)Ti surfaces to evaluate the cytocompatibility of AgNPs-loaded PEMs by cell count,Cell Counting Kit-8,SEM and immunofluorescence technique,respectively.4.The sustained-release concentration of Ag~+was detected by ICP-AES.To estimate antibacterial effect of AgNPs-loaded PEMs,S.aureus,E.coli and P.gingivalis,which is one main pathogen of peri-implantitis,were selected.Its antibacterial efficiency against S.aureus and E.coli were evaluated by dilution plate counting method.And the antibacterial efficiency of PEMs against P.gingivalis were performed by agar disk diffusion method and SEM observation.Results:1.The result of UV-VIS-NIR indicated that specific absorption peak of chitosan-AgNPs solution appeared at around 420 nm,which manifested the formation of AgNPs.The TEM image showed that AgNPs were globose with the diameter of 10~20 nm.2.The presence of Ag~0 and S elements by XPS and SEM-EDX confirmed the success in fabricating CS/AgNPs-Heparin PEMs on the alkali-treated Ti substrate.The FESEM and AFM images showed surface appearance of each sample.The surface roughness of Ti,Ti-OH and Ti-PEMs by AFM was 46.625±2.325 nm,92.875±18.505 nm,59.827±13.257 nm separately.The result of contact angle measurement revealed that alkali treatment and PEMs helped to significantly improve the surface hydrophilicity and surface free energy.3.The initial adhesion,proliferation and spreading of HGFs were promoted on Ti-PEMs,which displayed good cytocompatibility.4.PEMs provided continuous and slow Ag+release for 28 days by ICP-AES analysis.In Ti-PEMs group,the quantity of S.aureus and E.coli reduced obviously and antibacterial rate could be up to 85%on the seventh day.Furthermore,the results of agar disk diffusion and SEM observation of P.gingivalis at 1 and 4 d showed that the amount of bacteria had signifcantly decreased and SEM images also displayed the bacteria fractured on Ti-PEMs surface.The results confirmed that PEMs modified Ti possessed strong antimicrobial activity.Conclusions:AgNPs-loaded PEMs were immobilized via LbL on alkali-heat treated Ti substrates.Ti-PEMs exhibited no cytotoxic effects,promoted cell adhesion and proliferation and also possessed significant antimicrobial activity to provide a new idea and method for soft tissue-implant biologic seal and anti-infection of dental implant neck.