Search

We fabricated a ratiometric electrochemical strategy for the ultrasensitive analysis of telomerase activity. The hairpin DNA probe labeled with methylene blue (MB) tags at its 5' termini is firstly immobilized on the gold electrode. It then hybridizes with the telomerase substrate primer labeled with ferrocene (Fc) tags. With the telomerase‐catalyzed reaction, a repeating sequence of (TTAGGG)n is generated, which is able to trigger the conformational transduction of the hairpin DNA probe. Consequently, MB tags are released from the electrode surface and the oxidation peak current (IMB) decreases. Meanwhile, the Fc signal remains stable and the peak current (IFc) can be used as the internal control, which improves the signal stability. This smart design allows reliable target recognition and the obtained results assure excellent analytical performances. IMB/IFc is found to be linearly related with logarithmic telomerase concentration with a quite low limit of detection (0.02 cells/μL). This proposed ratiometric method may emerge as a powerful practical tool for the analysis of telomerase activity, which may also be developed as a versatile tool for other nucleic acid assays. [ABSTRACT FROM AUTHOR]

miRNAs are novel diagnostic and prognostic biomarkers for a diversity of diseases like cancers. In this study, an ultrasensitive electrochemical biosensor for miRNA evaluation is fabricated. A methylene blue (MB) labeled DNA probe is firstly modified on a gold electrode. By employing target induced strand displacement amplification and subsequent DNAzyme cleavage cycles, a large number of MB molecules are released. The decreased oxidation peak current could be used to reveal the miRNA concentration. Based on the two efficient signal amplifications, this method shows ultrahigh sensitivity. Its feasibility for the analysis of miRNA in cell lysates is also demonstrated. Therefore, the method shows attractive potential for promising applications in early diagnosis of certain diseases. [ABSTRACT FROM AUTHOR]

Abstract: The molecular level DNA logic gates assisted by nanomaterials hold great promise for disease diagnosis applications. However, designing convenient and sensitive logic gates for molecular diagnostics still remains challenging. In this work, a DNA logic gate platform for miRNA inputs analysis based on the observation of localized surface plasmon resonance variation of gold nanoparticles (AuNPs) is fabricated. As a demonstration, two biomarkers to differentiate indolent and aggressive forms of prostate cancer, miR‐200c and miR‐605, are selected as examples of logical inputs. In addition, five DNA probes are designed according to strand displacement reaction and hybridization chain reaction which are required for DNA logical operation. Since target miRNA inputs are able to trigger DNA structural transformations, which are further used to precisely regulate salt‐induced AuNPs aggregation, miRNA inputs information can be converted to the information of AuNPs states as outputs. This developed system performs amplified detection of low‐abundant target miRNAs without the requirement of any enzymes. In addition, single base‐pair mismatched miRNAs can be effectively differentiated. High‐order logic gates can also be developed with further modifications. Therefore, the DNA AND logic gate is successfully constructed with flexible operations, which has potential in biochemical study and disease diagnosis. [ABSTRACT FROM AUTHOR]

Hybridization chain reaction (HCR) is a simple isothermal enzyme-free process with the advantages of high simplicity and versatility. Generally, initiator single-stranded DNA is amplified to form long double-stranded DNA based on a chain reaction, during which recognition and hybridization events between a pair of complementary DNA sequences occur in succession. Repeating units of HCR product can be further utilized as templates for the assembly of various nanospecies, generating complicated DNA superstructures. Therefore, HCR is regarded as an attractive technique for DNA nanotechnology, biosensing, bioimaging and biomedicine. Particularly, HCR has been utilized to develop promising biosensors for the detection of various small molecules, nucleic acids, proteins and cells. In this review, we provide a comprehensive overview of HCR directed DNA superstructures assembly for biosensing applications. We hope this review will offer readers general concept of HCR and stimulate interest, new ideas, and discoveries in the fascinating field. [ABSTRACT FROM AUTHOR]

MiRNAs are riveting RNA molecules due to their close relevance to the regulation of gene expression and certain physiological or pathological processes. Rapid and sensitive methods for miRNA assay are essential for biological researches and clinical diagnosis of many diseases. In this work, gold nanoparticles (AuNPs) have been modified with adamantane derivatives and then Dwith NA probes for colorimetric detection of miRNA. Target miRNA induces a change in DNA conformation and initiates strand displacement amplification, eventually leading to massive aggregations of AuNPs. By comparing the UV-vis absorption spectra, miRNA concentration can be determined. This developed method can detect miRNA as low as 3.7 × 10−15 m with remarkable specificity. Moreover, it is successfully used to inspect the expression of miRNA in biological samples. Therefore, adamantane derivatives functionalized AuNPs are demonstrated to offer a novel platform for biosensing and the miRNA sensing strategy may find a broad spectrum of practical applications. [ABSTRACT FROM AUTHOR]

A target induced recycling amplification method for the detection of cellular microRNA is reported based on strand displacement polymerization and nicking endonuclease mediated cleavage. Moreover, by utilizing silver nanoparticle-based solidstate Ag/AgCl reaction, ultrahigh sensitivity is achieved with powerful discriminating towards the identification of target microRNA. The limit of detection is as low as 70 am. This method also allows the detection of cellular microRNA by lysing cells, thus making it a powerful tool for microRNA expression profiling and disease diagnosis. [ABSTRACT FROM AUTHOR]

This review provides a comprehensive overview of current research involving the use of enzymatic tools for nucleic acids in the fabrication of signal amplification for biosensors. The enzymes include polymerases, nucleases, helicases, and ligases. They have the capability to mimic biological signal transduction or amplification processes, which can be applied in nucleic-acid assays by smart designs. Since most of the enzymatic tools have highly efficient catalytic effects, the sensitivity of the assays can be guaranteed. Moreover, DNA can be used as a promising material for nanobiotechnology, and the nanostructures of DNA can be engineered to recognize a variety of molecules. Thus, such enzymatic tools can be largely used for biosensing. Enzymatic tools for nucleic acids may have great practical utility in cutting-edge analytical methods and protocols. [ABSTRACT FROM AUTHOR]

As described by Peng Miao, Yuguo Tang, and co‐workers in article number 1600405, adamantane derivatives functionalized gold nanoparticles act as a novel platform for colorimetric biosensing. By further modification with designed DNA probes, strand displacement amplification, triggered by target miRNA, is achieved, leading to massive aggregation of gold nanoparticles. The approach shows promise for amplified detection of miRNA in biological samples. [ABSTRACT FROM AUTHOR]

In this work, a novel strategy to fabricate a highly sensitive and selective biosensor for the detection of Ag+ is proposed. Two DNA probes are designed and modified on a gold electrode surface by gold-sulfur chemistry and hybridization. In the presence of Ag+, cytosine-Ag+-cytosine composite forms and facilitates the ligation event on the electrode surface, which can block the release of electrochemical signals labeled on one of the two DNA probes during denaturation process. Ag+ can be sensitively detected with the detection limit of 0.1 nM, which is much lower than the toxicity level defined by U.S. Environmental Protection Agency. This biosensor can easily distinguish Ag+ from other interfering ions and the performances in real water samples are also satisfactory. Moreover, the two DNA probes are designed to contain the recognition sequences of a nicking endonuclease, and the ligated DNA can thus be cleaved at the original site. Therefore, the electrode can be regenerated, which allows the biosensor to be reused for additional tests. [ABSTRACT FROM AUTHOR]

Abstract Synthetic artificial DNA probes are excellent architectural scaffolds which can be assembled into various nanostructures for further applications. A DNA walker is usually designed in response to certain external stimuli, and can significantly enhance the obtained signals. Herein, we have developed a novel DNA walker biosensor for the detection of target DNA with enzymatic recycling cleavage. By using the target DNA as a driving force, a DNA star trigon nanostructure is formed on the electrode surface, which can be recognized by a nicking endonuclease. The DNA walker is then activated to move around for the cleavage reactions on the electrode. The resulting DNA biosensor shows excellent analytical performance with a low limit of detection of 1 fM. Good selectivity and practical utility are also demonstrated. This approach has many other advantages such as ease of use, low cost, mild conditions, and may hold great potential for a range of applications in the future. Graphical abstract Unlabelled Image Highlights • A DNA walker biosensor is designed for DNA assay by measuring square wave voltammetry responses. • Signal amplification is achieved by coupling star trigon structure and enzymatic cycles. • The limit of detection is as low as 1 fM. • The DNA walking strategy may encourage the development of novel DNA nanomachines. [ABSTRACT FROM AUTHOR]

Accurate and sensitive analysis of biomarkers is a promising way to provide comprehensive physio-pathological information that is significant for early diagnosis of certain diseases. miRNA is a type of noncoding small RNAs which are involved in the regulation of a number of cellular processes. It has been regarded as an important tumor biomarker. Herein, we have constructed a three-dimensional DNA layer on electrode interface and achieved ladder hybridization chain reaction strategy for the enrichment of electrochemical signals. In addition, duplex-specific nuclease catalyzed amplification is previously performed on magnetic nanocomposites, which further improves the sensitivity for the detection of target miRNA initiator. This approach shows great molecular recognition efficiency as well as cascade signal amplification. The analytical performances are superior. In addition, the identification of cancer cell types according to target biomarker information is achieved and the testing results in clinical serum samples further demonstrate its great potential utility for diagnosis. • Fe3O4@AuNPs are prepared for magnetic separation and enzymatic catalyzed amplification. • Ladder hybridization chain reaction monolayer is designed to enrich electrochemical signal reporters. • An ultrasensitive electrochemical biosensor is developed with triangular prism structured DNA as recognition layer. [ABSTRACT FROM AUTHOR]