In this work, an electrochemical impedance biosensor for high sensitive detection of Hg2+ was presented by coupling with Hg2+-induced activation of Mg2+-specific DNAzyme (Mg2+-DNAzyme) for target ...cycling and hybridization chain reaction (HCR) assembled DNA hydrogel for signal amplification. Firstly, we synthesized two different copolymer chains P1 and P2 by modifying hairpin DNA H3 and H4 with acrylamide polymer, respectively. Subsequently, Hg2+ was served as trigger to activate the Mg2+-DNAzyme for selectively cleavage ribonucleobase-modified substrate in the presence of Mg2+. The partial substrate strand could dissociate from DNAzyme structure, and hybridize with capture probe H1 to expose its concealed sequence for further hybridization. With the help of the exposed sequence, the HCR between hairpin DNA H3 and H4 in P1 and P2 was initiated, and assembled a layer of DNA cross-linked hydrogel on the electrode surface. The formed non-conductive DNA hydrogel film could greatly hinder the interfacial electronic transfer which provided a possibility for us to construct a high sensitive impedance biosensor for Hg2+ detection. Under the optimal conditions, the impedance biosensor showed an excellent sensitivity and selectivity toward Hg2+ in a concentration range of 0.1pM - 10nM with a detection limit of 0.042pM Moreover, the real sample analysis reveal that the proposed biosensor is capable of discriminating Hg2+ ions in reliable and quantitative manners, indicating this method has a promising potential for preliminary application in routine tests.
•Monitoring Hg2+ by utilizing DNA hydrogel as electrochemical signal amplification element.•Incorporating T-Hg2+-T into Mg2+-DNAzyme for target cycling amplification.•Analytical performance of the impedance biosensor is down to picomole level.•Displaying excellent applicability for evaluating Hg2+ in real samples.
In this work, we have demonstrated a novel electrochemical method based on target-induced cleavage of a specific peptide for sensitive analysis of prostate specific antigen (PSA) by using silver ...enhancement. First, multiwalled carbon nanotubes/poly(amidoamine) dendrimers (MWCNTs–PAMAM) nanohybrids were assembled on the electrode to bind the peptide. Subsequently, dithiobis(succinimidylpropionate) (DSP)@Au@SiO2 was prepared as a tracing tag and covalent bond with the peptides via the inherent interaction between DSP and the amino of peptide. In the presence of PSA, the peptide was specifically recognized and cleaved, resulting in the loss of the tracing tag in electrode surface. Thereafter, silver enhancement was performed on the left DSP@Au@SiO2 nanohybrids. The electrochemical stripping signal of the deposited silver was used to monitor this process. Under optimal conditions, the proposed biosensor achieved a wide line from 0.001 to 30 ng mL–1 with a detection limit of 0.7 pg mL–1. This work demonstrated the combination of the direct transduction of peptide cleavage events with the highly sensitive silver enhancement method, providing a promising effective strategy for PSA detection.
Herein, for the first time, we engineered click chemistry reaction to trigger a 3D DNA walking machine for ultrasensitive electrochemical detection of copper ion (Cu2+), which provided a convenient ...access to overcome the shortcomings of poor selectivity and limited amplification efficiency in traditional determination of Cu2+. Click chemistry reaction drove azido-S2 to bind with alkynyl-S1 for the formation of a walker probe on aminated magnetic polystyrene microsphere@gold nanoparticles (PSC@Au), which opened the hairpin-locked DNAzyme. In the presence of magnesium ion (Mg2+), the unlocked DNAzyme was activated to cleave the self-strand at the facing ribonucleotide site, accompanied by the release of product DNA (S3) and the walker probe. Therefore, the walker probe was able to open the adjacent hairpin-locked DNAzyme strand and then be released by DNAzyme cleavage along the PSC@Au-DNAzyme track. Eventually, the liberated single-strand S3 induced catalytic hairpin assembly (CHA) recycling, resulting in the capture of a large number of methylene blue-tagged hairpin DNA (MB-H2) on the sensor surface and significant electrochemical responses. By coupling click chemistry reaction with the dual-amplification strategy of the 3D DNA walking machine and CHA recycling, the proposed biosensor not only demonstrated high accuracy and selectivity for Cu2+ detection in real samples but also showed excellent performance for Cu2+ detection with a wide linear range of 1.0 pM to 500 nM and low detection limit of 0.33 pM. Moreover, this elaborated biosensor could be readily expanded to Mg2+ detection with a constant concentration of Cu2+, which paves a new way to apply the 3D DNA walking machine in various ion sensings.
Here we have developed a "signal-on" peptide cleavage-based assay to directly transduce the peptide cleavage events into electrochemical signals via the host-guest interaction between ferrocene (Fc) ...and β-cyclodextrin (β-CD) for prostate specific antigen (PSA) detection.
We presented a novel dual-DNAzyme feedback amplification (DDFA) strategy for Pb2+ detection based on a micropipette tip-based miniaturized homogeneous electrochemical device. The DDFA system involves ...two rolling circle amplification (RCA) processes in which two circular DNA templates (C1 and C2) have been designed with a Pb2+-DNAzyme sequence (8–17 DNAzyme, anti-GR-5 DNAzyme) and an antisense sequence of G-quadruplex. And a linear DNA (L-DNA), which consists of a primer sequence and a Pb2+-DNAzyme substrate sequence, could hybridize with C1 and C2 to form two DNA complexes. In presence of Pb2+, the Pb2+-DNAzyme exhibited excellent cleavage specificity toward the substrate sequence in L-DNA, leaving primer sequence to trigger two paths of RCA process and finally resulting in massive long nanosolo DNA strands with reduplicated G-quadruplex sequences. And then, methylene blue (MB) could selectively intercalate into G-quadruplex to reduce the free MB concentration in the solution. Thereafter, a carbon fiber microelectrode-based miniaturized electrochemical device was constructed to record the decrease of electrochemical signal due to the much lower diffusion rate of MB/G-quadruplex complex than that of free MB. Therefore, the concentration of Pb2+ could be correctively and sensitively determined in a homogeneous solution by combining DDFA with miniaturized electrochemical device. This protocol not only exhibited high selectivity and sensitivity toward Pb2+ with a detection limit of 0.048 pM, but also reduced sample volume to 10 µL. In addition, this sensing system has been successfully applied to Pb2+ detection in Yangtze River with desirable quantitative manners, which matched well with the atomic absorption spectrometry (AAS).
•Integrating dual Pb2+-DNAzyme into one RCA-mediated feedback amplification for Pb2+ detection.•Presenting a facile and efficient method for carbon fiber microelectrode fabrication.•Reducing analyte sample volume down to microliter level.•Analytical performance of the sensing system is down to picomole level.•Displaying excellent applicability for evaluating Pb2+ in real samples.
Traditionally, genomic DNA detection is relay on a rigorous DNA amplification process, which always accompanied with complicated gel electrophoresis or expensive fluorescence detection methods. In ...this work, we have translated genomic DNA detection into adenosine triphosphate (ATP) test based on a split aptamer-based electrochemical sandwich assay. The key characteristic of our method are list as follows: first, nucleic acid amplification of the target gene was performed by the use of a loop mediated isothermal amplification (LAMP) process. The pyrophosphate (PPi), which released as the byproduct during the LAMP reaction, were further converted into ATP in the presence of adenosine 5′-phosphosulfate (APS) and ATP sulfurylase. Thereafter, the converted ATP was detected by constructing an electrochemical sandwich aptasensor. With such design, the conversion from the difficult detecting target (genomic DNA) into a convenient measured object (ATP) has been achieved. This proposed strategy was highly sensitive for Nosema bombycis genomic DNA PTP1 detection with a detection limit as low as 0.47 fg/μL and a linear range from 0.001pg/μL to 50ng/μL. And we supposed that this novel target conversion electroanalytical strategy established a universal approach for quantitative analysis of any other kinds of nucleic acid in assistance of nucleic acid polymerization reaction.
•Genomic DNA has been translated into ATP test by using PPi generated during LAMP.•The split aptamer-based electrochemical sandwich assay shows good performances.•The Au@Fe3O4 nanocomposites were employed as enhancer to improve the sensitivity.
Traditionally, amplified DNA detection in a loop-mediated isothermal amplification (LAMP) was carried out in a complicated gel electrophoresis or with expensive fluorescence-based methods. Here, ...instead of direct detection that relies on amplified DNA, the indirect detection based on tracing phosphate ions (Pi) generated during LAMP by using an electrochemical method has been proposed for sensitive nucleic acid detection. Pyrophosphate (PPi) as the byproduct of nucleic acid polymerization reaction in LAMP was hydrolyzed into Pi by the preaddition of thermostable inorganic pyrophosphatase (PPase). Thus, the total amount of Pi in the LAMP-amplified sample was proportional to the amount of starting DNA templates. The obtained Pi could then react with acidic molybdate to form the molybdophosphate precipitates on the electrode surface, which serve as redox mediators to give a readily measurable electrochemical signal. The practicality of this strategy has been further demonstrated by employing it for sensitive and accurate quantification of Nosema bombycis genomic DNA PTP1. The electrochemical method allowed the quantitative analysis for target genomic DNA with a detection limit of 17 fg/μL. Thus, we suppose that the novel method proposed in this work with superior sensitivity and specificity, as well as the simple feature, can be easily established for quantitative analysis of many other kinds of nucleic acids in the assistance of LAMP.
In this work, iron-based metal organic frameworks (Fe-MOF) are used as a self-sacrifice beacon to produce Prussian blue (PB). Then, a dual-mode electrochemical-colorimetric biosensing platform for ...kanamycin (KAN) detection is established considering the prominent redox activity and blue color of PB. CoFe2O4 magnetic nanobeads (CoFe2O4 MBs) are employed for immobilization and separation of the signal beacon in the complex matrix, and the combination between CoFe2O4 MBs and magnetic electrodes simplifies the electrochemical testing process. The linear range of the electrochemical mode is 0.1 nM–1.0 μM with a detection limit of 39 pM, and that of the colorimetric mode is 10 nM–2.0 μM with a detection limit of 3.6 nM. Furthermore, the dual-mode strategy shows satisfactory specificity and enhanced applicability for KAN detection in real samples. Compared with known dual-mode determination methods, the proposed design employs the same reaction to produce two signal output modes, thus eliminating the effect of different reactive pathways on the outcome and in turn promoting greater accuracy.
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•A dual-mode sensing strategy was established for the determination of kanamycin.•Fe-MOF are used to produce prussian blue with excellent redox activity and blue color.•Magnet-driven operations facilitated separation and immobilization of signal beacon.•Zn2+-dependent DNAzyme induced target cyclic strategies achieved signal amplification.•This dual-mode avoids the influence of diverse reactive modes and promotes the accuracy.
In this work, a highly sensitive impedimetric biosensor was developed for mercuric ion (Hg2+) detection. The biosensor design was based on Hg2+-triggered exonuclease III (Exo III) cleavage for target ...recycling and DNAzyme-mediated catalytic for precipitation polymerization. Hg2+ induced thymine-thymine (T-T) mismatches were used to trigger the Exo III-catalyzed target recycling and produce free single-stranded DNA (defined as M). The outputted M then assisted the in formation of a DNA network on electrode surface to efficiently immobilize the porphyrin manganese (MnTmPyP). The formed MnTMPyP-double-stranded DNA (MnTmPyP-dsDNA) complex exhibited peroxidase-like activity capable of catalyzing a 3,3-diaminobenzidine (DAB) oxidation reaction, which produced an insoluble precipitate on the electrode surface. This reaction significantly enhanced the resistance signal for the quantitative determination of Hg2+. Under optimal conditions, the impedimetric biosensor exhibited a wide dynamic working range of 0.005 nM–100 nM with a detection limit of 1.47 pM. This platform also demonstrated good reproducibility and selectivity, offering a promising avenue for the detection of other molecules.
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•T-Hg2+-T mismatches and Exo III are adopted for target converting and recycling.•MnTMPyP-dsDNA peroxidase-like DNAzyme is used for precipitation polymerization.•Biosensor shows good performances and is applied to Hg2+ detection in real samples.
Created by Shuting Liang, the cover image shows electricity‐generating insoles that are composed of silicone holes filled with liquid metal. The movement of the human foot generates electricity. With ...a friction area of 18.75 cm 2 , a maximum output voltage of 221 mV is obtained. LM‐TENG could be used in various fields to convert human mechanical energy into electricity and continue to provide clean energy for wearable electronic devices. DOI: 10.1002/app.55092 image
