Preliminary Experimental Research For The Preparation And Antibacterial Property Of Cationic Polymerization Nano Film On The Surface Of Medical Titanium Alloys

ObjectiveThanks to their low elastic modulus,excellent corrosion resistance,and superior biocompatibility,Titanium and its alloys have been widely exploited in orthopedic implants in recent years.Nevertheless,implant-related infection is a disastrous complication of modern orthopaedic surgery that often poses a significant health risk to patients because of the implant materials are the carriers for bacterial growth when fulfill their functions of cure.Bacteria can form biofilms after attachment,which act as a barrier to against the host immune response or antibiotics.Several studies have found polycations can be absorbed to the surface of bacteria,penetrate the bacterial cell membrane and destroy surface structure of cell.This study aims to utilize low temperature plasma polymerization technique and layer-by-layer self-assembly technique to achieve multilayer cationic polymerization nano films on the surface of titanium alloy,and explore its surface characterization,antimicrobial properties and cell toxicity in vitro.Method1.The preparation of cationic polymerization nano films on titanium surfaceAmino was introduced and a layer of polymer cation membrane was obtained after the polymerization of allylamine monomer in the surface of titanium alloy with low temperature plasma polymerization technique.Then the substrate was mo dified by Layer-by-layer technique to obtain a nano-layered coating using poly(sod ium4-styrenesulfonate)(PSS)and poly(allylamine hydrochloride)(PAH)as polyelec trolytes.Respectively,the assembly time was 5,10,15.2.Surface characterization study of cationic polymerization nano films on substrateThe surface topography of control group,sample processed by Plasma and samples with 5,10,15 times of layer-by-layer self-assembly were observed with scanning electron microscope(SEM).Energy Dispersive Spectroscopy and X-ray photoelectron spectroscopy was used to analyze the surface elements composition.Atomic Force Microscope was used to know the surface roughness.We also measure the contact angle.3.antibacterial experiment and cell toxicity experiment in vitroThe antibacterial activity of the samples was performed by bacteria counting using Escherichia coli(E.coli,CGMCC 1.2463)and Staphylococcus aureus(S.aureus,CGMCC 1.2465)with dipping patch method.The cell toxicity was measured using a commercially available CCK-8 assay.Results1.Surface characterization study of cationic polymerization nano films on substrateAccording to the results of SEM,EDS,XPS,AFM and water contact angle,allylamine monomer induced polymerization and deposited in the surface of sample successfully treated with Plasma method,and N element was also introduced.SEM observed the diffused distribution of spherical particles,while AFM showed rough surface of three-dimensional topography.The thickness of polycation film was 7nm.Water contact angle reduced from 101±3°to 23±7°in contrast with control group and hydrophilic was greatly increased.With the increase of number of LBL self-assembly,homogeneous and orderly polyelectrolytes of PSS and PAH were observed in the surface of samples.The distribution of polycation groups are regular.The thickness of films were increased with the number of LBL self-assembly,and after 15 self-assembly,the thickness was 76 nm.S element appeared when PSS began to assemble and content has a linear growth with the increase of the number of assembly.Water contact angles of 5,10,15 times of LBL self-assembly were 79±5°,88±5°,90±3°.2.antibacterial experiment and cell toxicity experiment in vitroThe bacteriostatic ratio of Staphylococcus aureus of control group,sample processedby Plasma and samples with 5,10,15 times of layer-by-layer self-assembly were 0%,57.72%,64.22%,77.68%,70.99% respectively.While the bacteriostatic ratio of Escherichia col were 0.00%,76.08%,68.26%,89.13%,95.22%.The difference of five samples has statistical siganificance(P<0.001).The difference of cell growth inhibition rate of MC3T3-E1 in five samples has statistical siganificance(P<0.05).The cell toxicity assessment level was between 0 and 1 with a slight cytotoxicity.Conclusion1.Regular,orderly and homogeneous polycation nano films could be achieved by low temperature plasma polymerization technique and layer-by-layer self-assembly technique in the surface of titanium alloy.2.Polycations deposited on the surface of titanium alloy by low temperature plasma polymerization technique and layer-by-layer self-assembly technique have excellent antibacterial activity against Staphylococcus aureus and Escherichia col.With the increase of thickness of polication films,its antibacterial ability increases.3.Polycations achieved by low temperature plasma polymerization technique and layer-by-layer self-assembly technique in the surface of titanium alloy will not affect osteoblast adhesion and growth.4.It can provide theory guidance for further animal studies.