Nanopore Arrays And Three-dimensional Graphene Fabricated On 316 L Stainless Steel Surface And Its Biocompatibility Evaluations

As the advantages of good mechanical property,strong corrosion resistance,and low cost,316L stainless steel is recognized as a kind of metal biomaterial which hold immense potential applications in medical field.However,the low biocompatibility of 316L stainless steel and the Cr and Ni in it can arouse cytotoxicity under biological condition.These drawbacks listed above limited its application in medical fields.Herein,we fabricated self-organized nanopore arrays on 316L stainless steel surface and reduced the atom concentrations of Cr and Ni significantly on the surface oxide layer of 316L stainless steel via a two-step anodic method to improve its biocompatibility.In addition,the two-dimensional(2D)graphene is prone to aggregation or restacking due to intersheet van der Waals attractions,resulting in the loss of its unique properties.3D graphene configurations exhibit an amplified surface area and an interconnected graphene framework,thus offering novel opportunitiesand have been intensively investigated due to their novel properties.But few reports have been intentionally carried out to understand the biological influences of 3D graphene materials so far.Thus,we presented an evaluation of the in vitro cytotoxicity of 3D graphene sheets fabricated on the template of aligned nanopore arrays(NPAs)on 316L stainless steel surface.1.We report a two-step anodic method to fabricate self-organised nanopore arrays on 316L stainless steel surface.As a result,the dimension of the nanopores depends linearly on the anodization time and was controlled by the applied voltage and current density in a certain range.At the premise of no appreciable expansion in the mean pore size after the second step in contrast to the initial pores,the depth of nanopores could reach seven times of the previous depth.The analysis of XPS spectrum performed on the nanostructure,no metallic Fe,Cr,and Ni peaks were detected on the surface after the second anodization.2.Herein,we fabricated the 3D graphene from polydopamine on the stainless steel nanoporous surface and evaluated its cytotoxicity in vitro.The prepared 3D graphene sheets with a thickness of ~20 nm displayed a nanoporous architecture that can be readily tuned by the NPAs template to control the morphology of the 3D configuration.The in vitro toxicity of the nanoporous 3D graphene sheets with pore sizes of ~50 nm and ~240 nm was evaluated by using NIH-3T3 fibroblast.The NPAs structure exhibits enhanced properties in cell attachment,spreading,proliferation,and the assembling of focal adhesions and actin filament associated proteins.Morpholgy-dependent cytotoxicity aroused by the 3D graphene configuration should be attributed to the engulfment of the carbon nanospheres embedded in the 3D configuration and the lack of both focal adhesions and actin filament associated proteins assembling at the nanoscale.