No abstract

In this work, a facile approach was successfully developed for in situ catalyzing Au nanoparticles loaded on Fe3O4@SiO2 magnetic nanospheres via Sn(2+) linkage and reduction. After the Fe3O4@SiO2 MNPs were first prepared via a sol-gel process, only one step was needed to synthesize the Fe3O4@SiO2-Au magnetic nanocomposites (Fe3O4@SiO2-Au MNCs), so that both the synthesis step and the reaction cost were remarkably decreased. Significantly, the as-synthesized Fe3O4@SiO2-Au MNCs showed high performance in the catalytic reduction of 4-nitrophenol to 4-aminophenol and could be reused for several cycles with convenient magnetic separability. This approach provided a useful platform based on Fe3O4@SiO2 MNPs for the fabrication of Au or other noble metal magnetic nanocatalysts, which would be very useful in various catalytic reductions.

In this paper, we first discovered that Co3O4 nanoparticles (NPs) possess intrinsic oxidase-like activity and can catalytically oxidize peroxidase substrates, such as 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 3,3',5,5'-tetramethylbenzidine (TMB), to form colored products, in the absence of exogenously added H2O2. The presence of sulfite inhibited the TMB-O2-Co3O4 NPs reaction system and caused a change in color of the reaction system. On the basis of this phenomenon, a colormetric approach to detect sulfite was established with a good linear relationship ranging from 0.2×10(-6) to 1.6×10(-5) M and a detection limit of 5.3×10(-8) M. The method was used to detect sulfite in foods. Good recoveries ranging from 93.8% to 100.5% were obtained. Furthermore, the mechanism was studied and results showed that the oxidase-like activity of the Co3O4 NPs was not from •OH or O2•- radical generated. It may probably originate from their ability to transfer an electron between the peroxidase substrate and oxygen absorbed on the surface of the Co3O4 NPs.

Diallyl disulfide (DADS) has been shown to have multi-targeted antitumor activities. We have previously discovered that it has a repressive effect on LIM kinase-1 (LIMK1) expression in gastric cancer MGC803 cells. This suggests that DADS may inhibit epithelial-mesenchymal transition (EMT) by downregulating LIMK1, resulting in the inhibition of invasion and growth in gastric cancer. In this study, we reveal that LIMK1 expression is correlated with tumor differentiation, invasion depth, clinical stage, lymph node metastasis, and poor prognosis. DADS downregulated the Rac1-Pak1/Rock1-LIMK1 pathway in MGC803 cells, as shown by decreased p-LIMK1 and p-cofilin1 levels, and suppressed cell migration and invasion. Knockdown and overexpression experiments performed in vitro demonstrated that downregulating LIMK1 with DADS resulted in restrained EMT that was coupled with decreased matrix metalloproteinase-9 (MMP-9) and increased tissue inhibitor of metalloproteinase-3 (TIMP-3) expression. In in vitro and in vivo experiments, the DADS-induced suppression of cell proliferation was enhanced and antagonized by the knockdown and overexpression of LIMK1, respectively. Similar results were observed for DADS-induced changes in the expression of vimentin, CD34, Ki-67, and E-cadherin in xenografted tumors. These results indicate that downregulation of LIMK1 by DADS could explain the inhibition of EMT, invasion and proliferation in gastric cancer cells.