Crack Formation and Control in an AlCoCrFeNi High Entropy Alloy Fabricated by Selective Laser Melting.

The equiatomic AlCoCrFeNi high entropy alloy (HEA) is prone to cracking during the additive manufacturing process due to the high cooling rates observed, which limits its application to a large extent. In this study, the selective laser melting (SLM) technique was adopted to fabricate the alloy and the mechanism of crack formation was revealed. Most importantly, a new design strategy was proposed to suppress the generation of cracks, and the optimization of the preparation process was also studied in detail. It is found that the interlaminar crack is related to the heat input at the edge of the specimen, and the internal cracks are formed by solidification cracks. Alloys without interlaminar crack can be prepared by means of combination of the side inclination angle and the process parameters. Side inclination angle optimization provides a possibility for the preparation of crack-free AlCoCrFeNi HEA by SLM.

Protection of HeLa cells against ROS stress by CuZnSOD mimic system.

A new copper zinc complex (CZpbi), [(bipyridinyl)2Cu-µ-pbi-Zn(pbi)](ClO4)2, pbi = 2-(2-pyridyl)-benzimidazole, was synthesized to mimic copper zinc superoxide dismutase (CuZnSOD). CZpbi was then encapsulated onto a dye (fluorescein isothiocyanate, FITC) functionalized mesoporous silica nanoparticles (MSN) where MSN serves as a nanofactory platform for delivering the catalytic action of the center copper complex. We examined the inhibition of oxidative damage of HeLa cells in the presence of paraquat (PQ, 1,1'-dimethyl-4,4'-bipyridylium dichloride, an oxidative stressor). We further studied the cell viability and cell cycle process under the influence of paraquat stress in the presence of the SOD-mimic FITC-MSN-CZpbi material by flow cytometry and western blot test. We found the nano-sized FITC-MSN is an excellent nano-carrier for delivering the mimic SOD complexes to HeLa cells. Here the reactants are already inside the cell and the result is a promotion of cell function. We present the methodology of encapsulating bio-inspired SOD-mimic in FITC-MSN to achieve a better drug delivery vehicle and catalytic (detoxification) activity. The potency and the stability of SOD-mimic FITC-MSN-CZpbi may provide a new avenue in the future development of artificial antioxidant enzymes.