Study On Surface Modification And Its Biological Properties Of 316L Stainless Steel

316LSS stainless steel（316LSS） is widely used in the medical field of orthopedic implant, dental implant and coronary stents due to its good biocompatibility, mechanical properties and corrosion resistance. However, it still has some disadvantages, such as bio-inert and non-antibacterial properties. It is general recognize that infection is unavoidable after transplantation, which would result in failure of surgery. Therefore, the surface of 316 LSS needs to be modified to improve its biological properties. Nano pit arrays could be prepared by anodization method on 316 LSS. It can take advantage of this special nano-structure（nano pit arrays） to load bioactivity materials to improve the biological properties of 316 LSS. Hence, it is reasonable to assume that preparing nano-Se/316 LSS could acquire antibacterial properties by introducing nano-Se into nano pit arrays. Many studies show that silicon-containing materials possess bioactivity, which can rapidly induce the bone-like apatite formation. Therefore, it is reasonable to assume that preparing nano-SiO₂/316 LSS could get bioactivities by introducing nano-SiO₂ into nano pit arrays.Firstly, nano pit arrays were prepared on 316 LSS by anodization method. Secondly, nano-Se was introduced into nano pit arrays. Then we studied the antibacterial property and cell compatibility of nano- Se/316 LSS. Thirdly, we introduced nano SiO₂ on the nano pit arrays and studied its bone-like apatite formation ability. Finally, a dual-nanostructures was constructed on the 316 LSS surface by the two-step-method（anodic oxidation method combined with hydrochloric acid etching）, then modified with PTES. Then we studied the antibacterial property of these samples. The conclusions are as follows:Nano pit arrays were prepared by anodic method. XPS showed that, the main chemical composition of nano pit arrays was Fe2O3 and Cr2O3 after anodization. FESEM analysis indicated that nano pit arrays（30V and 40V） were arranged in order on the surface of 316 LSS. A hexagonal arrangement of nano pit on 316 LSS surface was distributed evenly. Diameters of nano pit were about 49±6nm and 62±8nm, respectively. When the anodic voltage is further increased（50V, 60 V and 70V）, the arrangement of nano pit began to destroy.Nano-Se/316 LSS were prepared by redox template method. The EDS and XPS results show that the specimen contains Se element and its chemical valence is zero. FESEM results show that nano-Se was well distributed into the surface of the nano pit arrays. Diameter of nano-Se was uniformity, and was about 58±10nm. The diameter of nano-Se on 316 LSS surface was concident with those of nano pit arrays anodized at 40 V. The results of antibacterial activities show that the inhibition rates of nano-Se/316 LSS to E.coli and S.aureus were 89%±1% and 90%±1% after 24 h incubation. With the increase of the incubation time（48h, 72h）, the inhibition rate were decreased. In addition, the cellular compatibility experiment shows that: the OD value of HUVEC on nano-pit arrays and nano-Se/316 LSS was significant higher than that blank control and had a significant difference with blank control（p<0.01）, after 1, 3 and 7days of culture.Nano-SiO₂/316 LSS was prepared by sol-gel template method. FESEM analysis indicated that SiO₂ nanoparticles could be uniformly filled in the nano-pit array on 316 LSS surface, which its arrangement was ordered. XRD results show that SiO₂ formed on 316 LSS was amorphous. In vitro SBF experiments revealed that nano-SiO₂/316 LSS dramatically enhanced the apatite-forming ability after 14 d soaking.Dual-nano-structures on 316 LSS were constructed by a two-step-method（anodic oxidation combined with hydrochloric acid etching） and then modified with PTES. FESEM results show that nano-enmbossments were formed in the nano pit. FTIR results show that PTES has been chemisorbed to the surface of 316 LSS. The contact angle of 316 LSS was improved from 76°±3° to 106°±4°. Antibacterial experiment results show that the inhibition rates of PTES/316 LSS to E.coli and S.aureus were 20%±6%and 17%±6%, after 24 h of incubation respectively.In summary, these studies demonstrated that nano-Se/316 LSS and nano-SiO₂/316 LSS samples possess admirable antibacterial activity and good apatite-forming ability, respectively. The hydrophobic surface of PTES/316 LSS also inhibits the growth of E.coli and S.aureus. Thoes modifications of 316 LSS are expected to provide experimental and theoretical evidences for the study of functionalization surface of biomaterials.