Search

Abstract: Single-stranded deoxyribonucleic acid (ssDNA)-wrapped single-walled carbon nanotubes (SWNTs) were modified on the surface of glassy carbon electrode (GCE) by covalent modification technique. Field emission scanning electron microscope (FE-SEM), X-ray photoelectron spectrum (XPS), electrochemical impedance spectroscopy (EIS), and cyclic voltammetric (CV) were used to characterize the properties of this modified electrode. The results showed that SWNTs–ssDNA composites were successfully immobilized onto the surface of GCE. Moreover, this modified electrode exhibited high stability, largely active areas, and efficiently electrocatalytic activities. It had been used for the analysis of various biomolecules, such as dopamine (DA), uric acid (UA), and ascorbic acid (AA), and the results were satisfactory. [Copyright &y& Elsevier]

The development of a simple and effective method for the highly sensitive and selective discrimination of proteins is a subject of enormous interest. Herein, we report the construction of a novel fluorescence detection method based on a perylene probe for the highly efficient discrimination of multiple proteins. Single-stranded DNA (ssDNA) could induce aggregation of the perylene probe which caused quenching of probe fluorescence. After the addition of a protein, the protein could interact with the ssDNA-probe assembly complex with "turn-on" or further "turn-off" fluorescence response. A sensor array was designed based on the above phenomena which could realize the successful discrimination of proteins with 100% accuracy of cross validation. Nine representative proteins were successfully recognized. Moreover, it was observed that a protein could induce characteristic effect on the DNA-probe assembly with varying pH of assay buffer. Thus, different proteins showed unique fluorescence response towards assay buffers having different pH values. The assay buffer pH was then utilized as a sensing channel. Based on Linear Discriminant Analysis (LDA) nine proteins were successfully discriminated at the nanomolar concentration with 100% accuracy of cross validation. Furthermore, the sensor array also demonstrated differentiation of the nine proteins regardless of their concentration. The developed sensor array could also detect the proteins with great precision in human urine sample at a quite low concentration, which suggests its practical applicability for analysis of biological fluids. Fluorescence sensor array based on DNA induced PeryProbe self-assembly. Image 1 • A fluorescence sensor array is developed for the discrimination of proteins. • Negatively charged ssDNA induced self-assembly of the perylene probe. • The array was based on the different interactions between the protein and the ssDNA-PeryProbe assembly complex. • The array could discriminate proteins regardless of their concentration. • The array was applied to discriminate proteins in human urine samples. [ABSTRACT FROM AUTHOR]

The cancer diagnosis with single level of biomarkers suffers from limitation of insufficient accuracy. Hence, developing sensitive, rapid and adaptative analytical strategies for double-level biomarkers are essential for improving the accuracy of clinical cancer diagnosis at early stage. Herein, a DNA biosensor was established based on the catalytic hairpin assembly-mediated Y-junction nicking enzyme assisted signal amplification (CHA-YNEASA) circuits, where the two circuits were concatenated by molecular beacon (MB). In absence of target, both the CHA and YNEASA circuits were effectively hindered because of MB's outstanding ability to control signal background. In presence of target, the initiated CHA circuits made enzyme recognition sequences in close proximity to the assisted sequences to open MB, leading to further trigger the YNEASA circuits. Due to the unique design of dual signal amplification strategies, CHA-YNEASA circuits significantly shorten the reaction time, and improve signal-to-background ratio as well as facilitate the analysis process. It was demonstrated that a high sensitivity with limit of detection (LOD) of 0.9 pM for p53 gene detection was obtained just within 23 min by the proposed DNA biosensor. Moreover, mismatched p53 gene at nucleic acid level was effectively discriminated and strong anti-interference capability was achieved. Noticeably, the DNA biosensor was adaptative for designing a cytosensor at cell level using hairpin DNA, containing MUC1 aptamer and initiation strand of CHA-YNEASA circuits, as switch based on modularity principle. The cytosensor is able to measure MUC1 positive breast cancer cells (MCF-7) with the LOD as low as 100 cells/mL. Excellent specificity for MUC1 negative cells, and good anti-interference capability in 10% fetal bovine serum (FBS) were observed by the cytosensor. Therefore, the proposed DNA biosensor is a sensitive, rapid, adaptative platform for detection of double-level biomarkers, offering novel strategy applied for clinical cancer diagnosis. Image 1 1. DNA biosensor was developed based on catalytic hairpin assembly-mediated Y-junction nicking enzyme assisted signal amplification. 2. The DNA biosensor shows high efficiency of reaction leading to rapid analysis just in one-step. 3. High sensitivity, strong selectivity and anti-interference were achieved for p53 gene and cancer cell detection. 4. The DNA biosensor is adaptative for the detection of multilevel biomarkers using modularity principle. [ABSTRACT FROM AUTHOR]