Triplex DNA logic gate based upon switching on/off their structure by Ag(+)/cysteine.

The formation of intramolecular triplex DNA can be regulated by Ag(+) and Cys (cysteine), which switch off/on the fluorescence of the oligonucleotides, 5'-TAMRA-TTC TCT TCC TCT TCC TTC TGA CGA CAG TTG ACT CTT CCT TCT CCT TCT CTT-BHQ-2-3' (Oligo 1) and 3'-GAA GGA AGA GGA AGA GAA-5' (Oligo 2). Based on this principle, sensors for Ag(+) and Cys are developed. The sensor for Ag(+) has a linear range of 2.5 nM-40 nM and a detection limit of 1.8 nM, whereas the sensor for Cys has a linear range of 10.0 nM-120.0 nM and a detection limit of 8.2 nM. Furthermore, the fluorescence is reversible with the alternate addition of Ag(+) and Cys. We constructed a DNA logic gate using Ag(+) and Cys as the input, and the fluorescence intensity as the output. The DNA logic gate is simple; moreover, it has a fast response and good reversibility.

Potential targets of diosgenin for the treatment of oral squamous cell carcinoma and their bioinformatics and transcriptional profiling analyses.

Diosgenin can inhibit the proliferation and cause apoptosis of various tumor cells, and its inhibitory effect on oral squamous cell carcinoma (OSCC) and its mechanism are still unclear. In this study, we predicted the targets of diosgenin for the treatment of OSCC through the database, then performed bioinformatics analysis of the targets, and further verified the effect of diosgenin on the activity of OSCC cell line HSC-3, the transcriptional profile of the targets and the molecular docking of the targets with diosgenin. The results revealed that there were 146 potential targets of diosgenin for OSCC treatment, which involved signaling pathways such as Ras, TNF, PI3K-AKT, HIF, NF-κB, and could regulate cellular activity through apoptosis, autophagy, proliferation and differentiation, inflammatory response, DNA repair, etc. Diosgenin significantly inhibited HSC-3 cell activity. The genes such as AKT1, MET1, SRC1, APP1, CCND1, MYC, PTGS2, AR, NFKB1, BIRC2, MDM2, BCL2L1, MMP2, may be important targets of its action, not only their expression was regulated by diosgenin but also their proteins had a high binding energy with diosgenin. These results suggest that diosgenin may have a therapeutic effect on OSCC through AKT1, MMP2 and other targets and multiple signaling pathways, which is of potential clinical value.

Sensitive detection of H2O2 and H2O2-related reactant with Ru(bipy)(2)(7,8-dimethyl-dipyridophenazine)2+ and oligodeoxyribonucleotide.

A sensor for H(2)O(2) and H(2)O(2)-related reactant was constructed with oligonucleotides and Ru(bipy)(2)dppx(2+) (bipy = 2,2'-bipyridine, dppx = 7,8-dimethyl-dipyridophenazine), which was performed by converting the H(2)O(2)-induced DNA cleavage into the change of luminescence. The 'DNA light switch' Ru(bipy)(2)dppx(2+) could emit strong luminescence in the presence of dsDNA. DNA cleavage occurred upon addition of H(2)O(2) due to the Fenton reaction, which resulted in the decrease of the luminescence of Ru(bipy)(2)dppx(2+). Therefore, the luminescence intensity depended on the concentration of H(2)O(2) and H(2)O(2)-related reactants, and the detection limits for H(2)O(2), uric acid and cholesterol were 0.20 µM, 0.46 µM and 1.25 µM, respectively. The recovery varied between 94.0% and 105.0% when the assay was applied to the determination of uric acid and cholesterol in biological samples, which demonstrated the good practicability of the assay.

Hybridization chain reaction and DNAzyme-based dual signal amplification strategy for sensitive fluorescent sensing of aflatoxin B1 by using the pivot of triplex DNA.

This work developed an enzyme-free fluorescent aptasensor for sensitive aflatoxin B1 (AFB1) detection based on a dual signal amplification strategy of hybridization chain reaction (HCR) and Zn2+-dependent DNAzyme. In the presence of AFB1, the aptamer specifically binds to the target, releasing the blocking DNA, which can initiate HCR between hairpin probes H1 and H2. With the addition of the substrate strand (Zn-Sub) and enzyme strand (Zn-Enz) of DNAzyme, HCR product can hybridize with Zn-Sub and Zn-Enz to form triplex DNA and Y-shaped structure together, which further activates the DNAzyme to cleave Zn-Sub. Then, two separated fragments of Zn-Sub respectively hybridize with the fluorescent probe and quencher probe, which results in a dramatic increase in the fluorescence intensity. The proposed aptasensor shows high sensitivity and selectivity for AFB1 detection with a detection limit of 0.22 nmol/L in a linear range of 0.4-16 nmol/L. Moreover, the fluorescent aptasensor exhibits acceptable applicability for detecting AFB1 in oil samples with satisfactory recoveries of 92.2-107.8%. Results are also in agreement with those of the ELISA method, indicating that the fluorescent sensing strategy has great potential applications in food safety control.

1,3-Bis(2-nitro-phen-oxy)propan-2-ol.

In the title compound, C(15)H(14)N(2)O(7), the planes of the two benzene rings form a dihedral angle of 33.16 (17)°. In the crystal, inter-molecular hydrogen bonds involveing the OH group and nitro O atoms link the mol-ecules into chains propagating along the a axis.

Electrochemical molecular beacon biosensor for sequence-specific recognition of double-stranded DNA.

Direct recognition of double-stranded DNA (dsDNA) was crucial to disease diagnosis and gene therapy, because DNA in its natural state is double stranded. Here, a novel sensor for the sequence-specific recognition of dsDNA was developed based on the structure change of ferrocene (Fc) redox probe modified molecular beacon (MB). For constructing such a sensor, gold nanoparticles (AuNPs) were initially electrochemical-deposited onto glass carbon electrode (GCE) surface to immobilize thiolated MB in their folded states with Au-S bond. Hybridization of MB with target dsDNA induced the formation of parallel triplex DNA and opened the stem-loop structure of it, which resulted in the redox probe (Fc) away from the electrode and triggered the decrease of current signals. Under optimal conditions, dsDNA detection could be realized in the range from 350 pM to 25 nM, with a detection limit of 275 pM. Moreover, the proposed method has good sequence-specificity for target dsDNA compared with single base pair mismatch and two base pairs mismatches.

Sequence-specific recognition of double-stranded DNA with molecular beacon with the aid of Ag(+) under neutral pH environment.

A sensitive fluorescent sensor for sequence-specific recognition of dsDNA was established with a molecular beacon (MB) based upon the formation of parallel triplex DNA in the presence of Ag(+) under neutral pH environment.

Colorimetric detection of cholesterol with G-quadruplex-based DNAzymes and ABTS2-.

A novel colorimetric method for detection of cholesterol was developed with hemin-G-quadruplex DNAzyme by transducing oxidation of cholesterol into the color change of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS(2-)). Oligonucleotide 5'-GTGGGTAGGGCGGGTTGG-3' (Oligo-1) formed G-quadruplex structure in the presence of K(+), it acted as a horseradish peroxidase (HRP) mimicking DNAzyme when binding hemin and catalyzed the oxidation of colorless ABTS(2-) to green ABTS(·-) by H(2)O(2), which was produced by the reaction of cholesterol and oxygen that catalyzed by cholesterol oxidase. Therefore, the oxidation of cholesterol could be transduced into the color change of ABTS(2-) by combining these two reactions. Under the optimum conditions, the absorbance was proportional to the concentration of cholesterol over the range of 1.0-30 µM, with a linear regression equation of A=0.362+0.0256C (C: µM, R=0.998) and a detection limit of 0.10 µM (3σ/slope). Moreover, the practicability of the assay in the detection of cholesterol in human serum was studied as well.