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Magnesium alloys are used as bone implants because of their good biocompatibility and degradability. However, due to the rapid and uneven degradation, its clinical application is limited. To improve the corrosion resistance of medical magnesium alloys, a novel technique of semisolid powder molding was used to prepare Mg-6Zn alloy, and then microarc oxidation (MAO) was firstly applied to modify the surface. In this study, the effects of different current densities (4, 6, 8 A/dm2) and microarc oxidation time (8, 14, 20 min) on the phase composition, thickness, density, microstructure, roughness, and corrosion resistance of MAO film were systematically studied, and then the optimized parameters were obtained. Finally, the optimized coating's biocompatibility (cytotoxicity, cell adhesion, hemolysis, osteogenic differentiation) was evaluated. The results show that the MAO film mainly comprises α-Mg, MgO, and Mg2SiO4. The film's roughness, microhardness, and thickness increase with the current density and oxidation time. The lowest electrochemical corrosion rate of the coating is (2.3 ± 0.5 × 10–4 mm/year under the parameter of 6 A/dm2-20 min, which decreases by about 3 orders of magnitude compared with naked Mg-6Zn (0.32 ± 0.06 mm/year). The optimized microarc oxidation parameter is 6 A/dm2-20 min, with a thickness of 18 ± 1.45 μm, and microhardness of 339.6 ± 9.09 HV (increases by 165.3%). Additionally, the cytotoxicity and hemolysis rate of naked and coated Mg-6Zn were reduced, but the cell viability and adhesion as well as the differentiation of osteoblast cells of coated Mg-6Zn were improved, exhibiting better biocompatibility. Therefore, semisolid powder molding can be used to prepare medical Mg alloys with high performance, and MAO improves corrosion resistance greatly. [ABSTRACT FROM AUTHOR]

Tumor growth is an angiogenesis-dependent process and accompanied by the formation of hypoxic areas. Tumstatin is a tumor-specific angiogenesis inhibitor that suppresses the proliferation and induces the apoptosis of tumorous vascular endothelial cells. VNP20009, an attenuated Salmonella typhimurium strain, preferentially accumulates in the hypoxic areas of solid tumors. In this study, a novel Salmonella-mediated targeted expression system of tumstatin (VNP-Tum5) was developed under the control of the hypoxia-induced J23100 promoter to obtain anti-tumor efficacy in mice. Treatment with VNP-Tum5 effectively suppressed tumor growth and prolonged survival in the mouse model of B16F10 melanoma. VNP-Tum5 exhibited a higher efficacy in inhibiting the proliferation and inducing the necrosis and apoptosis of B16F10 cells in vitro and in vivo compared with VNP (control). VNP-Tum5 significantly inhibited the proliferation and migration of mouse umbilical vascular endothelial cells to impede angiogenesis. VNP-Tum5 downregulated the expression of anti-vascular endothelial growth factor A, platelet endothelial cell adhesion molecule-1, phosphorylated phosphoinositide 3 kinase, and phosphorylated protein kinase B and upregulated the expression of cleaved-caspase 3 in tumor tissues. This study is the first to use tumstatin-transformed VNP20009 as a tumor-targeted system for treatment of melanoma by combining anti-tumor and anti-angiogenic effects. [ABSTRACT FROM AUTHOR]

3′-Phosphoadenosine-5′-phosphosulfate (PAPS) is the obligate cosubstrate and source of the sulfonate group in the chemoenzymatic synthesis of heparin, a clinically used anticoagulant drug. Previously, we have developed a method to synthesize PAPS with Escherichia coli crude extracts, which include three overexpressed enzymes and a fourth unidentified protein. The unknown protein degrades adenosine diphosphate (ADP), the by-product of PAPS synthesis reaction. To further understand and control the process of in vitro enzymatic PAPS synthesis, we decide to identify the fourth protein and develop a defined method to synthesize PAPS using purified enzymes. Here, we show that the purified Nudix hydrolase NudJ degrades ADP at high efficiency and serves as the fourth enzyme in PAPS synthesis. Under the defined condition of PAPS synthesis, all of the 10-mM ADP is hydrolyzed to form adenosine monophosphate (AMP) in a 15-min reaction. ADP is a better substrate for NudJ than adenosine triphosphate (ATP). Most importantly, the purified NudJ does not cleave the product PAPS. The removal of ADP makes the PAPS peak more separable from other components in the chromatographic purification process. This developed enzymatic approach of PAPS production will contribute to the chemoenzymatic synthesis of heparin. [ABSTRACT FROM AUTHOR]