A disposable strip biosensor for the visual detection of Hg(2+) in aqueous solution has been constructed on the basis of Hg(2+)-triggered toehold binding and exonuclease III (Exo III)-assisted signal amplification. Thymine-thymine (T-T) mismatches in the toehold domains can serve as specific recognition elements for Hg(2+) binding with the help of T-Hg(2+)-T base pairs to initiate toehold-mediated strand displacement reaction. Exo III-catalyzed target recycling strategy is introduced to improve the sensitivity. Using gold nanoparticles as a tracer, the output signals can be directly observed by the naked eye. The assay is ultrasensitive, enabling the visual detection of trace amounts of Hg(2+) as low as 1 pM without instrumentation. This sensing system also displays remarkable specificity to Hg(2+) against other possible competing ions. This sensor is robust and can be applied to the reliable monitoring of spiked Hg(2+) in environmental water samples with good recovery and accuracy. With the advantages of cost-effectiveness, simplicity, portability, and convenience, the disposable strip biosensor will be a promising candidate for point-of-use monitoring of Hg(2+) in environmental and biological samples.

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Concatenated logic circuits operating as a biocomputing keypad-lock security system with an automatic reset function have been successfully constructed on the basis of toehold-mediated strand displacement and three-way-DNA-junction architecture. In comparison with previously reported keypad locks, the distinctive advantage of the proposed security system is that it can be reset and cycled spontaneously a large number of times without an external stimulus, thus making practical applications possible. By the use of a split-G-quadruplex DNAzyme as the signal reporter, the output of the keypad lock can be recognized readily by the naked eye. The "lock" is opened only when the inputs are introduced in an exact order. This requirement provides defense against illegal invasion to protect information at the molecular scale.

Abundant biomass is well accepted as a carbon-rich, sustainable, and renewable precursor for three-dimensional carbon materials, offering us a plethora of possibilities for energy conversion and storage as well as environmental treatments.

An enzyme-free biosensor for the amplified detection of aflatoxin B1 has been constructed based on a catalytic DNA circuit. Three biotinylated hairpin DNA probes (H1, H2, and H3) were designed as the assembly components to construct the sensing system (triplex H1-H2-H3 product). Cascaded signal amplification capability was obtained through toehold-mediated strand displacement reactions to open the hairpins and recycle the trigger DNA. By the use of streptavidin-functionalized gold nanoparticles as the signal indicators, the colorimetric readout can be observed by the naked eye. In the presence of a target, the individual nanoparticles (red) aggregate into a cross-linked network of nanoparticles (blue) via biotin-streptavidin coupling. The colorimetric assay is ultrasensitive, enabling the visual detection of trace levels of aflatoxin B1 (AFB1) as low as 10 pM without instrumentation. The calculated limit of detection (LOD) is 2 pM in terms of 3 times standard deviation over the blank response. The sensor is robust and works even when challenged with complex sample matrices such as rice samples. Our sensing platform is simple and convenient in operation, requiring only the mixing of several solutions at room temperature to achieve visible and intuitive results, and holds great promise for the point-of-use monitoring of AFB1 in environmental and food samples.

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Artesunate (ARS) induced significant reactive oxygen species (ROS) generation in HepG2, HeLa, and A549 lines. However, ARS induced ROS-dependent apoptosis in HeLa and A549 cell lines but ROS-independent apoptosis in HepG2 cells. A total of 200 μM hydrogen peroxide (H 2 O 2) significantly induced cytotoxicity in HeLa cells, while H 2 O 2 up to 300 μM did not induce cytotoxicity in HepG2 cells, further demonstrating the strong resistance of HepG2 cells to ROS. HeLa cells had much higher basic total glutathione (T-GSH) level than HepG2 cells, while the ratio of basic reduced glutathione (GSH)/oxidized glutathione (GSSG) in HepG2 cells was nearly twice than that in HeLa and A549 cells. Inhibition of glutathione markedly enhanced H 2 O 2-or ARS-induced cytotoxicity in HeLa and A549 cell lines but modestly enhanced the cytotoxicity of H 2 O 2 and even did not affect the cytotoxicity of ARS in HepG2 cells. Moreover, addition of GSH remarkably prevented H 2 O 2-or ARS-induced cytotoxicity in HeLa and A549 cell lines, further indicating the involvement of GSH in scavenging ROS in the two cell lines. HepG2 cells exhibited higher catalase activity than HeLa cells, and inhibiting catalase activity by using 3-aminotriazole (3-AT, a specific inhibition of catalase) or catalase siRNA remarkably reduced the resistance of HepG2 cells to ROS, demonstrating the key roles of catalase for the strong resistance of HepG2 cells to ROS. Collectively, catalase activity instead of glutathione level dominates the resistance of cells to ROS.

No abstract