Ultrasensitive Fluorescence Detection and Accurate Colocalization Visualization of Dual-miRNAs in Cancer Cells Based on the Conjugated Chain Reaction of Multifunctional Pentagon DNA Nanostructures.

Herein, a multifunctional pentagon DNA nanostructure (MPDN) was assembled by the hybridization of a circular DNA scaffold containing five different fragments with five diverse DNA oligonucleotides for simultaneous sensitive detection and accurate colocalization imaging of dual-miRNAs in cancer cells. Exactly, the MPDN could specifically and efficiently internalize into folate (FA) receptor-overexpressed cells via specific binding of FA and the FA receptor to distinguish cancer cells from normal cells and transform trace amounts of targets miRNA-21 and miRNA-155 into substantial FAM and Cy5-labeled DNA polymers as the signal probe to generate two remarkable fluorescence emissions, realizing simultaneously sensitive detection of dual-miRNAs. Impressively, compared with traditional small fragment DNA probes with high fluidity, the DNA copolymers with extremely low diffusivity kept it in the originally generated position to achieve the colocalization imaging of dual-miRNAs more accurately for revealing the spatial expression information of dual-miRNAs in tissues and cells. This strategy provided programmable tool to simultaneously detect and accurately colocate dual-miRNAs for understanding normal physiology and the tumor mechanism.

Cosensitization Strategy with Cascade Energy Level Arrangement for Ultrasensitive Photoelectrochemical Protein Detection.

Here, a photoelectrochemical (PEC) biosensor was established by a cosensitization strategy with cascade energy level arrangement for ultrasensitive detection of prostate-specific antigen (PSA). The proposed cosensitization strategy was based on the well-matched energy level arrangement of four kinds of organic photoactive materials, in which poly{4,8-bis[5-(2-ethylhexyl)thiophen-2-yl]benzo[1,2- b:4,5- b']dithiophene-2,6-diyl- alt-3-fluoro-2-[(2-ethylhexyl)-carbonyl]thieno[3,4- b]thiophene-4,6-diyl} (PTB7-Th) was used as the photoactive material and perylenetetracarboxyl diimide (PDI), fullerene (nano-C60), and polyaniline (PANI) were employed as the sensitizers. The resulting PTB7-Th/PDI/nano-C60/PANI cascade cosensitization structure with narrow energy level gradient (<0.54 eV) could effectively improve electron transfer capability, obviously raise light energy utilization and significantly enhance photoelectric conversion efficiency, leading to dramatically enhanced photocurrent response. Using PSA as a target model, the proposed PEC biosensor exhibited high sensitivity and excellent stability with a wide detection range from 1 fg/mL to 0.1 ng/mL and a detection limit of 0.43 fg/mL. Moreover, the proposed PEC biosensor provides a cascade cosensitization strategy that could significantly improve PEC performances and open up a promising platform to establish high selectivity, stability, and ultrasensitive analytical techniques.

Overoxidized polyimidazole/graphene oxide copolymer modified electrode for the simultaneous determination of ascorbic acid, dopamine, uric acid, guanine and adenine.

In the present work, a novel strategy based on overoxidized polyimidazole (PImox) and graphene oxide (GO) copolymer modified electrode was proposed for the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA), guanine (G) and adenine (A). The copolymer was characterized by the scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effects between PImox and GO, the proposed electrode exhibited excellent electrochemical catalytic activities and high selectivity and sensitivity toward the oxidation of AA, DA, UA, G and A. The peak separations between AA and DA, AA and UA, UA and G, and G and A were 140 mV, 200 mV, 380 mV and 300 mV, respectively. The linear response ranges for AA, DA, UA, G and A were 75-2275 µM, 12-278 µM, 3.6-249.6 µM, 3.3-103.3 µM and 9.6-215 µM, respectively, and corresponding detection limits were 18 µM, 0.63 µM, 0.59 µM, 0.48 µM and 1.28 µM.

Detection of organophosphorus pesticides using potentiometric enzymatic membrane biosensor based on methylcellulose immobilization.

In this research, a new potentiometric enzymatic membrane biosensor for the detection of organophosphorus pesticides (OPs) was constructed. The basic element of this biosensor was a pH electrode modified with an immobilized acetylcholinesterase layer formed by entrapment with methylcellulose, N,N-dimethylformamide, and bovine serum albumin. The response characteristics of the biosensor were measured and discussed. It was shown that there is a good linear relationship between the inhibition rate and the negative logarithm of OPs concentration in the range from 10(-7) to 10(-5) mol/L, with the detection limits of 10(-7) mol/L for the five pesticides. Moreover, the biosensor could resist the disturbances of below 10(-6) mol/L of Cu(2+) and Pb(2+), and below 10(-5) mol/L of Cd(2+). In addition, the measurement results obtained by the biosensor method were in good agreement with those obtained by the gas chromatography method. This method was successfully applied to detect OPs that remained in the potted lettuce.