An amperometric biosensor for nitrite was prepared by immobilizing cytochrome c (Cyt c) on a gold electrode that was modified with Nafion and a Cu-Mg-Al layered double hydroxide (Cu-LDH). The Cu-LDH was characterized by Fourier transform infrared spectroscopy and powder X-ray diffraction. The UV-visible spectrum suggests that Cyt c retains its native conformation in the modified film. The direct electrochemical investigation indicated that the composite film represents a good platform for the immobilization of Cyt c as well as an excellent promoter for the electron transfer between Cyt c and the gold electrode. Moreover, the biosensor showed a remarkable bioelectrocatalytic activity for the oxidation of nitrite with a linear range from 0.75 to 123 μM. The detection limit is 2 × 10 −7 M (S/ N = 3). The biosensor was successfully applied to the determination of nitrite in food samples.
Lin Fuxing,Yang Jie,Muhammad Umair,Sun Jing,Huang Zhenghua,Li Wei,Lv Fengxia,Lu Zhaoxin
Bacillomycin D can inhibit the growth of Aspergillus ochraceus in food samples. In addition, it can induce apoptosis in and inhibit the proliferation of cancer cells, although the details of this mechanism are unknown. In this study, we separated bacillomycin D-C14, D-C15, D-C16
monomers from the Bacillus subtilis strain fmbJ. The bacillomycin D monomers containing longer fatty acid chains better induced apoptosis in Bgc-823, Sgc-7901, and Hgc-27 gastric cancer cells. The Bgc-823 cell line was the most sensitive. Acridine orange-ethidium bromide staining indicated
that bacillomycin D-C16-induced Bgc-823 cell death by triggering apoptosis, characterized by membrane blebbing, cellular shrinkage, and DNA fragmentation. Flow cytometric analysis showed a bacillomycin D-C16 dose-dependent trigger of Bgc-823 apoptosis. Bacillomycin D-C16-induced the mitochondrial
pathway, as indicated by a reduced Bcl-2/Bax expression ratio, enhanced cytochrome C release, and higher levels of cleaved caspase-3. Furthermore, bacillomycin D-C16 effectively repressed phosphorylation of the serine–threonine protein kinase Akt at Ser-473 and increased the levels of
the FoxO3a protein. The combination of the PI3K/Akt-inhibitor BEZ235 with bacillomycin D-C16 enhanced the apoptosis of Bgc-823 cells. Together, these findings indicated that bacillomycin D-C16 induces apoptosis through the PI3K/Akt and FoxO3a signaling pathways.
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