DNA Nanosieve-Based Regenerative Electrochemical Biosensor Utilizing Nucleic Acid Flexibility for Accurate Allele Typing in Clinical Samples.

Herein, an interface-based DNA nanosieve that has the ability to differentiate ssDNA from dsDNA has been demonstrated for the first time. The DNA nanosieve could be readily built through thiol-DNA's self-assembly on the gold electrode surface, and its cavity size was tunable by varying the concentration of thiol-DNAs. Electrochemical chronocoulometry using [Ru(NH3)6]3+ as redox revealed that the average probe-to-probe separation in the 1 µM thiol-DNA-modified gold electrode was 10.6 ± 0.3 nm so that the rigid dsDNA with a length of ∼17 nm could not permeate the nanosieve, whereas the randomly coiled ssDNA could enter it due to its high flexibility, which has been demonstrated by square wave voltammetry and methylene blue labels through an upside-down hybridization format. After combining the transiently binding characteristic of a short DNA duplex and introducing a regenerative probe (the counterpart of ssDNA), a highly reproducible nanosieve-based E-DNA model was obtained with a relative standard deviation (RSD) as low as 2.7% over seven cycles. Finally, we built a regenerative nanosieve-based E-DNA sensor using a ligation cycle reaction as an ssDNA amplification strategy and realized one-sensor-based continuous measurement to multiple clinical samples with excellent allele-typing performance. This work holds great potential in low-cost and high-throughput analysis between biosensors and biochips and also opens up a new avenue in nucleic acid flexibility-based DNA materials for future applications in DNA origami and molecular logic gates.

Ultrasensitive Detection of RNA with Single-Base Resolution by Coupling Electrochemical Sensing Strategy with Chimeric DNA Probe-Aided Ligase Chain Reaction.

Accurate and sensitive detection of single-base mutations in RNAs is of great value in basic studies of life science and medical diagnostics. However, the current available RNA detection methods are challenged by heterogeneous clinical samples in which trace RNA mutants usually existed in a large pool of normal wild sequences. Thus, there is still great need for developing the highly sensitive and highly specific methods in detecting single-base mutations of RNAs in heterogeneous clinical samples. In the present study, a new chimeric DNA probe-aided ligase chain reaction-based electrochemical method (cmDNA-eLCR) was developed for RNA mutation detection through the BSA-based carrier platform and the horseradish peroxidase-hydrogen peroxide-tetramethylbenzidine (HRP-H2O2-TMB) system. The denaturing polyacrylamide gel electrophoresis and a fluorophore-labeled probe was ingeniously designed to demonstrate the advantage of cmDNA in ligation to normal DNA templated by RNA with the catalysis of T4 RNA ligase 2 as well as its higher selectivity than DNA ligase system. Finally, the proposed cmDNA-eLCR, compared with the traditional eLCR, showed excellent performance in discriminating single base-mismatched sequences, where the signal response for mismatched targets at a high concentration could overlap completely with that for the blank control. Besides, this cmDNA-eLCR assay had a wide linear range crossing six orders of magnitude from 1.0 × 10-15 to1.0 × 10-10 M with a limit of detection as low as 0.6 fM. Furthermore, this assay was applied to detect RNA in real sample with a satisfactory result, thereby demonstrating its great potential in diagnosis of RNA-related diseases.

KISS1 methylation and expression as predictors of disease progression in colorectal cancer patients.

AIM: To examine the effect of aberrant methylation of the KISS1 promoter on the development of colorectal cancer (CRC) and to investigate reversing aberrant methylation of the KISS1 promoter as a potential therapeutic target. METHODS: KISS1 promoter methylation, mRNA expression and protein expression were detected by methylation-specific polymerase chain reaction (PCR), real-time quantitative PCR and Western blotting, respectively, in 126 CRC tissues and 142 normal colorectal tissues. Human CRC cells with KISS1 promoter hypermethylation and poor KISS1 expression were treated in vitro with 5-aza-2'-deoxycytidine (5-Aza-CdR). After treatment, KISS1 promoter methylation, KISS1 mRNA and protein expression and cell migration and invasion were evaluated. RESULTS: Hypermethylation of KISS1 occurred frequently in CRC samples (83.1%, 105/126), but was infrequent in normal colorectal tissues (6.34%, 9/142). Moreover, KISS1 methylation was associated with tumor differentiation, the depth of invasion, lymph node metastasis and distant metastasis (P < 0.001). KISS1 methylation was also associated with low KISS1 expression (P < 0.001). Furthermore, we observed re-expression of the KISS1 gene and decreased cell migration after 5-Aza-CdR treatment in a CRC cell line. CONCLUSION: These data suggest that KISS1 is down-regulated in cancer tissues via promoter hypermethylation and therefore may represent a candidate target for treating metastatic CRC.

[Protective effects of melatonin on cultural human retinal pigment epithelial cells against oxidative damage in vitro].

OBJECTIVE: To investigate the protective effects of melatonin on the retinal pigment epithelium (RPE) against oxidative damage induced by hydrogen dioxide (H2O2) and its mechanism. METHODS: The RPE cells were seeded and divided into normal control group, oxidative damage group and the treatment group (treated with melatonin at the concentration of 1 x 10(-7) mol/L, 1 x 10(-6) mol/L, 1 x 10(-5) mol/L and 1 x 10(-4) mol/L). The model of oxidative damage on the RPE cells was established by culturing the RPE cells with H2O2 at the concentration of 600 micromol/L for 1 hour in vitro. The cell viability of RPE cells was detected by the methyl thiazolyl tetrazolium (MTT) method. The degree of oxidative damage was evaluated by detecting the superoxide dismutase (SOD) and maleic dialdehyde (MDA). Apoptosis was detected qualitatively using the DNA Ladders electrophoretic method, and quantitatively using the Annexin V-FITC/PI double staining flow cytometry. RESULTS: Compared with normal control group, the oxidative damage group had low cell viability, low SOD and high MDA contents, and high apoptosis rate (t = 2.25, 39.50, 68.42; P < 0.05). Compared with oxidative damage group, the treatment group had high cell viability, high SOD and low MDA contents, and low apoptosis rate (P < 0.05). CONCLUSIONS: Melatonin has a protective effect on the RPE against oxidative damage induced by H2O2. The mechanism may involve in reinforcing the cell viability, strengthening the activity of antioxidase, and reducing the apoptosis.