Preparation, Surface Modification And Preliminary Evaluation Of Two Kinds Of Medical Implants

The medical implant materials have good biocompatibility,but after being implanted in the body,some negative biological reactions will happen,such as inflammation,fibrous encapsulation and biofilm formation attributed to bacterial adhesion.To address these issues,polydimethylsiloxane?PDMS?and titanium alloy were used as research objects,and surface modification and drug loading were used to improve their application performance.PDMS is often used as a silicone carrier material to immobilize the platinum electrode of the cochear implant.Inflammation and fibrosis caused by inserting cochlear implants into the inner ear are of great concern in the clinic.To address these issues,we studied new cochlear implant electrode analogs,PDMS filaments loaded with anti-inflammation/fibrosis dexamethasone?Dex?and coated with hyaluronic acid?HA?as a surface modifier.The PDMS filaments were prepared by incorporating Dex into PDMS that contained different amounts of poloxamer 188?P188?as a drug release enhancer.HA coatings were performed to prevent protein adsorption by treating the surfaces of the PDMS filaments with O₂ plasma,3-aminopropyltriethoxysilane and HA in sequence.The prepared PDMS filaments were investigated by attenuated total reflection Fourier transform infrared spectroscopy,contact angle measurement and atomic force microscopy.Their protein adsorption and drug release behaviors were examined as well.L929 mouse fibroblast cells were used to evaluate the anti-cell adhesion/proliferation effects of the PDMS filaments.The results showed that the prepared PDMS filaments had the expected structure,good surface properties and excellent anti-fibroblast cell proliferation effects.The HA coatings provided filament surfaces that were more hydrophilic,smoother and more protein-repelling.Dex release was significantly facilitated by adding P188and slightly slowed down by the HA coatings.The PDMS filaments that contained 5%Dex and 5%P188 and that were coated with HA showed a significant decrease in the fibroblast cell number by approximately 51%,with obviously reduced cell adhesion on the surfaces.Secondly,in order to inhibit biofilm formation on the surfaces of titanium alloy attributed to bacterial adhesion,two kinds of surface modified titanium alloy were prepared by immobilizing dicarboxylic polyethylene glycol?HOOC-PEG-COOH?and phosphorylcholine glyceraldehyde?PCGA?on the surfaces of titanium alloy.In this study,the pristine titanium alloy substrates were immersed in a dopamine/hexamethylenediamine?DA/HD?solution to get polyopamine/hexamethylenediamine?PDA/HD?coatings immobilized on the surfaces by self-polymerization of DA.PCGA was synthesized by oxidizing L-Alpha-Glycerophosphorylcholine?GPC?.Then,the PDA/HD coating was used as an intermediate layer to immobilize HOOC-PEG-COOH and PCGA on the surface of titanium alloy substrate,respectively,to prepare Ti-PEG and Ti-PCGA.The synthesized PCGA was analyzed by NMR spectroscopy and the prepared titanium alloy substrates were investigated by Fourier transformation infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?.Furthermore,the surface hydrophilicity of pristine titanium alloy substrate and modified substrates was measured by contact angle measurement.Finally,different titanium alloy substrates were co-cultivated with Staphylococcus aureus?S.aureus?to investigate bacterial adhesion behaviors on the surfaces.¹H-NMR spectrum showed that the PCGA was synthesized successfully.FTIR and XPS spectra indicated that Ti-PEG and Ti-PCGA had the expected structure and elemental composition.The contact angle measurement results showed that the surface hydrophilicity of Ti-PEG and Ti-PCGA was higher than that of pristine titanium alloy substrate.Antibacterial assay with S.aureus showed that the Ti-PEG and Ti-PCGA substrates significantly reduced bacterial adhesion on surfaces.