Wear Resistance and Non-Magnetic Layer Formation on 316L Implant Material with Plasma Nitriding

In this study, the applicability of plasma nitriding treatment in the production of non-magnetic and corrosion resistant layer on 316L stainless steel implant material was investigated. 316L stainless steel substrates were plasma nitrided at temperatures of 350 ℃, 375 ℃, 400 ℃, 425 ℃ and 450 ℃ for 2 h in a gas mixture of 50% N2-50% H2, respectively. It was determined that the treatment temperature is the most important factor on the properties of the corrosion resistant layer of 316L stainless steel. The results show that s-phase formed at the temperatures under 400 ℃, and at the temperatures above 400 ℃, instead of s-phase, CrN and y＇-Fe4N phases were observed in the modified layer. The electrical resistivity and surface roughness of the modified layer increase with treatment temperature. Under 400 ℃ the corrosion resistance increased with the temperature, above 400 ℃ it decreased with the increase in treatment temperature. It was analyzed that the electrical resistivity and the soft （ideal） ferro- magnetic properties of 316L stainless steel increased with treatment temperature during nitriding treatment. Also, plasma ni- triding at low temperatures provided magnetic behavior close to the ideal untreated 316L stainless steel.

Synthesis of Fe-doped carbon hybrid composed of CNT/flake-like carbon for catalyzing oxygen reduction

Carbon-based materials with tunable properties have emerged as promising candidates to replace Pt-based catalysts for accelerating oxygen reduction reaction(ORR)in fuel cells or metal-air batteries.In this work,we constructed a carbon hybrid which consists of one-dimensional(1D)carbon nanotubes and flake-like carbons by pyrolysis of leaf-like metal-organic frameworks.The optimal hybrid electrocatalyst of Fe_(7%)-L-CNT-900 possesses the desired features for ORR,including active Fe species,high degree of graphitization,large specific surface area,and hierarchical porous structures.Consequently,Fe_(7%)-L-CNT900 performs a high electrocatalytic activity for ORR with a half-wave potential of 0.88 V,which is comparable to that of Pt/C(20 wt.%).This strategy provides an insight into the investigation of highly efficient and low-cost composite electrocatalyst for oxygen reduction reaction.

Electrically controlled mRNA delivery using a polypyrrolegraphene oxide hybrid film to promote osteogenic differentiation of human mesenchymal stem cells

Direct messenger ribonucleic acid(mRNA)delivery to target cells or tissues has revolutionized the field of biotechnology.However,the applicability of regenerative medicine is limited by the technical difficulties of various mRNA-loaded nanocarriers.Herein,we report a new conductive hybrid film that could guide osteogenic differentiation of human adipose-derived mesenchymal stem cells(hADMSCs)via electrically controlled mRNA delivery.To find optimal electrical conductivity and mRNAloading capacity,the polypyrrole-graphene oxide(PPy-GO)hybrid film was electropolymerized on indium tin oxide substrates.We found that the fluorescein sodium salt,a molecule partially mimicking the physical and chemical properties of mRNAs,can be effectively absorbed and released by electrical stimulation(ES).The hADMSCs cultivated on the PPy-GO hybrid film loaded with pre-osteogenic mRNAs showed the highest osteogenic differentiation under electrical stimulation.This platform can load various types of RNAs thus highly promising as a new nucleic acid delivery tool for the development of stem cell-based therapeutics.