Preparation And Antibacterial Property And Biocompatibility Of Silver-coated PEEK Using Polydopamine-assisted Deposition Technique

Part I Preparation of silver-coated PEEK using polydopamine-assisted deposition techniqueObjective: Dopamine(DA) can self-polymerize into polydopamine(PDA) under weak alkaline aqueous conditions, which spontaneously deposits a thin adherent coating onto PEEK(polyetheretherketone). PDA can be a reductant because of the catechol structure, so, [Ag(NH3)2]+ ions in aqueous solution can be reduced to silver nano particles(Ag NPs) by PDA, and deposited onto the surface of PEEK to get the silver modified PEEK( PEEK-PDA-Ag). Method: The polished PEEK were treated with Plasma to get –OH modified surface. At same time, dopamine aqueous solution(2 mg m L-1) was prepared by dissolving dopamine into the Tris–HCl buffer(10 m M; p H=8.5). Then the plasma treated PEEK was immersed into the dopamine solution, and kept shaking at room temperature for 24 hours to get the PDA modified PEEK, which was immersed into [Ag(NH3)2]+ ion aqueous solutions( 0.02 mol/L), and shook for 0.5 h to get the silver modified PEEK( PEEK-PDA-Ag). The surface morphologies and microstructure of the coatings were observed by scanning electron microscopy(SEM). The elemental composition and distribution of the coatings were measured by energy-dispersive X-ray spectrometry(EDS). Also the surface hydrophilicity was observed by Contact Angle measuring instrument and the releasing amount of silver ion. Result: The color of the sample has changed obviously after the deposition of silver. It is obviously to observe that there were some particles on the surface of PEEK-PDA-Ag with the diameter at about 90 nm. N element was found on the surface of both two samples(PEEK-PDA and PEEK-PDA-Ag), and Ag element was found only on the surface of PEEK-PDA-Ag, and the wt% of Ag element was 5.83. The contact angle test showed that the hydrophilicity of PEEK-PDA-Ag changed after the deposition of silver. Meanwhile, the coating can release the silver ion into the surrounding solution. Conclusion: Silver coating with uniform size can be prepared by using the self polymerization of dopamine and the reduction of poly dopamine on the PEEK surface. At the same time, the coating can release silver ion into the surrounding solution for a long time.Part II Antibacterial property of polydopamine-assisted surface deposition of silver-coated PEEKObjective: To explore the antibacterial property of PDA-assisted surface immobilization of nano silver on PEEK against Staphylococcus aureus. Method: Staphylococcus aureus was inoculated with the material culture for 24 hours, and inhibitory effect were observed by colony counts. Also, the inhibition zone was observed and measured by vernier caliper after 24 hours of culture. In addition, Staphylococcus aureus were inoculated on the surface of each specimen to observed bacterial proliferation by the application of scanning electron microscopy(SEM). Result: These results from inhibition of surface suggested that: after 24 hours of culture, the PEEK-PDA-Ag group showed a significant inhibitory effect when compared with PEEK group(P?0.05). Meanwhile, the PEEK-PDA group also showed a perfect inhibitory effect in a certain extent(P?0.05) We also found the inhibition zone around the PEEK-PDA-Ag material compared with the other two groups, the diameter of the inhibition zone is 8.8 mm. After 24 hours of culture, the number of bacteria on the surface of PEEK-PDA-Ag group was significantly less than that of the other two groups, under the scanning electron microscope(P?0.05). Conclusion: PEEK-PDA-Ag material has obvious antibacterial effect on Staphylococcus aureus, the antibacterial rate can reach 99.84%, and PEEK-PDA material also has certain antibacterial effect. Meanwhile, the inhibition zone was observed around the PEEK-PDA-Ag group.Part III Biocompatibility and immune regulation of polydopamine-assisted surface deposition of silver-coated PEEKObjective: To explore the biocompatibility and i immune regulation of polydopamine-assisted surface deposition of silver-coated PEEK by MC3T3-E1 and RAW264.7. Method: MC3T3-E1 cells were cultured on PEEK-PDA-Ag, PEEK and PEEK-PDA respectively. Cell spreading was detected by scanning electron microscopy(SEM). After 1, 3and 5 days of cultivation respectively, the proliferation was detected by Cell Counting Kit(CCK8). RAW264.7 were seeded on the PEEK-PDA-Ag and PEEK-PDA materials respectively, and tissue culture plate as control, to investigate the expression of anti-inflammatory factors such as IL-4, IL-10, TGF-?, and also the pro-inflammatory factors such as IL-1?, IL-6, TNF-?. Result: The SEM indicated that MC3T3-E1 cell spread well on the PEEK-PDA-Ag, however the cells were more slender under the influence of silver. Also we found that MC3T3-E1 cell can proliferate on the surface of the PEEK-PDA-Ag. The result of CCK-8 showed that at 3 and 5 days, the proliferation of MC3T3-E1 was obviously increased, not only on the surface of control groups( PEEK-PDA and PEEK), but also on the PEEK-PDA-Ag. However, the cell proliferation in PEEK-PDA-Ag group was slightly weaker than that in control groups, but not show a significant cytotoxicity(P?0.05). The result of the expression of inflammatory cytokines showed that, after the cultivation of RAW264.7 macrophages on the surface of the PEEK-PDA-Ag and PEEK-PDA, in the anti-inflammatory factors, compared with the control group, the expression of IL-4 gene in PEEK-PDA-Ag group is significantly reduced(P < 0.05), the expression of IL-10 and TGF-? gene was also decreased, but not significantly. In the anti-inflammatory factor, the expression of IL-1 in PEEK-PDA-Ag group was significantly increased(P < 0.05), but there was no significant difference in the expression of IL-6 and TNF-?. Conclusion: The MC3T3-E1 showed a good adhesion and proliferation on the surface of PEEK-PDA-Ag, and no serious toxicity. The expression of inflammatory cytokines was detected by co-culture with mouse macrophage RAW264.7, showed that PEEK-PDA-Ag material has no anti-inflammatory effect, but also slightly to promote inflammation.