Electrochemical Signal Of Methylene Blue Research Articles

Fascinating Immobilization-Free Electrochemical Immunosensing Strategy Based on the Cooperation of Buoyancy and Magnetism.

Rapid and accurate detection of biomolecules is of vital importance for the diagnosis of disease and for performing timely treatments. The point-of-care analysis of cancer biomarkers in the blood with low cost and easy processing is still challenging. Herein, an advanced and robust strategy, which integrates the buoyant recognition probe with the magnetic reporter probe in one solution, was first proposed for immobilization-free electrochemical immunosensing. The tumor marker of alpha fetoprotein (AFP) can be captured immune-buoyantly, and then a multifunctional magnetic reporter probe in pseudo-homogeneous solution was further captured to fulfill a sandwich-type immunoreaction. The residual magnetic reporter probe can be firmly and efficiently attracted on a magnetic glassy carbon electrode to fulfill the conversion of the target AFP amount into the residual magnetic electrochemical signal indicator. As a result, the electrochemical signal of methylene blue can accurately reflect the original level of target antigen AFP concentration. By integrating buoyancy-driven quasi-homogenous biorecognition with magnetism-mediated amplification and signal output, the proposed immobilization-free electrochemical immunosensing strategy displayed a wide range of linear response (100 fg mL-1 to 10 ng mL-1), low detection limit (14.52 fg mL-1), and good reproducibility, selectivity, and stability. The designed strategy manifests remarkable advantages including assay simplicity, rapidness, and high sensitivity owing to the in-solution instead of on-electrode biorecognition that could accelerate and improve the biorecognition efficiency. To the best of our knowledge, this is the first cooperation of buoyancy-driven biorecognition with magnetism-mediated signal output in bioanalysis, which would be attractive for rapid clinic biomedical application. Thus, this work provides a fresh perspective for convenient and favorable immobilization-free electrochemical biosensing of universal biomolecules.

An electrochemical aptasensor for detection of streptomycin based on signal amplification assisted by functionalized gold nanoparticles and hybridization chain reaction.

A ratiometric electrochemical aptasensor based on gold nanoparticles (AuNPs) functionalization and hybridization chain reaction (HCR) assisted signal amplification has been for thefirsttime designed for the detection of streptomycin (STR). The double-stranded DNA (dsDNA) formed by the hybridization of ferrocene (Fc)-labeled STR aptamer (Apt) and capture probe (CP) is first immobilized on the gold electrode (GE) surface via Au-S reaction. The specific binding of the target and Apt results in numerous Fc detachment from the sensing interface. Then, the remaining single-stranded CP is combined with AuNPs modified with initiator DNA (iDNA) by auxiliary DNA (aDNA). Among them, the iDNA triggers HCR between two hairpin probes (H1/H2), thus capturing a large number of methylene blue (MB) electrochemical probe, which generates a strong electrochemical signal of MB and a weak electrochemical signal of Fc. Signals are collected by square wave voltammetry (the potential window ranging from -0.5V to 0.6V, vs.Ag/AgCl ), and the oxidation peak currents at -0.200V (MB) and 0.416V (Fc) are recorded. The use of the ratiometric method has effectively improved the accuracy and reliability of the analysis. The successful application of AuNPs and HCR greatly improves the sensitivity of the sensor, and the detection limit is as low as 0.08pM. It can sensitively determine STR in the range 0.1pM to 10nM. In addition, the designed aptasensor has been successfully applied to the detection of STR in milk and honey samples.

Diazinon electrochemical biosensor mediated by aptamer and nanoscale porous carbon derived from ZIF-8

The development of high-performance sensors for the assay of organophosphate pesticides (OPs) is of significant importance due to their broad usage and harmful effects on mammals. In this study, we designed a simple platform based on aptamer immobilized in an engineered zeolitic imidazolate framework (ZIF) for accurate detection of diazinon (DZN) as a widely used pesticide. To do so, aptamer-functionalized ZIF was constructed by using nanoscale porous carbon ZIF (NPCZIF) as scaffolds to load signal dye, methylene blue (MB), and capped with an aptamer as a bio-gatekeeper via π-π interaction. In this sensor, surface-covering aptamers prevented the release of MB. Therefore, the electrochemical signal of MB in the absence of DZN was low. Upon the addition of DZN, the configuration of the aptamer showed a change, resulting in a large number of MB labels being released from the pores. Therefore, the signal of MB increased. The proposed platform was highly sensitive toward DZN with a detection limit as low as 7.8 fM. The validation of the aptasensor was also studied by analyzing DZN in different food and environmental samples with recovery rates of 95.6–102.6%, indicating the feasibility and reliability of aptasensor.

Measurement of Neuropeptide Y By Square Wave Voltammetry Using Aptamer-Modified Platinum Microelectrodes and Methylene Blue

In comparison to other methods of detection, electrochemistry offers a number of major advantages that make it the superior choice. One of these advantages is the capacity to monitor a wide variety of molecules, as opposed to just those that oxidize or deplete, by modifying the electrodes' surface areas and changing the material that makes up the electrodes in order to provide selectivity toward the biomolecule that is of interest. For more than three decades, the method known as Fast Scan Cyclic Voltammetry (FSCV) has been regarded as the method of choice for assessing neurotransmitters in animal models both in vitro and in vivo. It is important to create a unique method for measuring neuropeptides and other biomolecules in order to make use of long-term implants that have been approved by the FDA, such as electrodes used in deep brain stimulation (DBS). This research focuses on the use of electrochemical methods to biological applications, such as Square Wave Voltammetry (SWV) and Cyclic Voltammetry (CV). These methods allow researchers to detect biomolecules with a greater degree of accuracy. We investigated a variety of electrical devices for monitoring and detecting neuropeptide Y (NPY) using SWV and CV. For the purpose of NPY detection, we made use of platinum microelectrodes in conjunction with SWV and CV. Research on neurotransmission makes frequent use of microelectrodes because of their small size, electrochemical characteristics, and compatibility with quick electrochemical processes. Due to the precision and specificity offered by electrochemical techniques, we were required to develop a real-time technique in order to quantify biomolecules that were transported into the artificial cerebrospinal fluid (aCSF). This technique included the use of CV and SWV, both of which are examples of techniques that fall under the real-time category. The idea behind using aptamer-modified microelectrodes with methylene blue (MB) as a redox probe for the detection of NPY by SWV and CV is that the oxidizing potentials recorded by SWV may be utilized to evaluate the probe. This is the logic behind the use of these aptamer-modified microelectrodes. In order to conduct the test, an aCSF with a pH of 7.4 was used. It was essential to investigate SWV in space and time at NPY adsorption potentials and watch as MB was oxidized. For the purpose of studying SWV using platinum microelectrodes, we analyzed NPY with an aptamer that has been modified with MB. As a result of the fact that we were able to see a stable signal of MB throughout the characterizations, we have come to the conclusion that the strategy that we are utilizing for the modification of the aptamer is an effective one. In addition to this, we were successful in measuring NPY in a range of concentrations through the MB signal observed in the SWV. During the measurement of NPY we were able to see a decrease in current seen in the electrochemical signal of MB as we augmented the concentration of the neuropeptide. This enabled us to do a calibration curve that will be utilized for further measurements.

Ratiometric electrochemical biosensor based on silver nanoparticles coupled with walker amplification for sensitive detection of microRNA

A novel ratiometric electrochemical biosensor for sensitive detection of microRNA was developed by using walker amplification technique. Ag nanoparticles (NPs) and methylene blue (MB) were used as signal probe and as reference, respectively. Firstly, the present target (miR-155) hybridized with DNA2 to release walker (DNA1), and then the walker hybridized with DNA3 to form activated DNA enzyme, inducing cycling shearing of DNA3 in the presence of Mn2+, thus a large number of product chains (S1) were produced. Then, S1 opened hairpin DNA (HP1) labeled with MB on the electrode, initiating enzyme-assisted cyclic clipping to generate abundant capture DNA. Thus numerous signal probes (DNA HP2-Ag NPs) were linked for electrochemical detection of target. As the electrochemical signal of MB at capture DNA was constant, so it was used as internal reference. Thus the signal ratio of Ag NPs to MB was used for detection, which can greatly reduce the background. The relation between the IAg/IMB and the concentration of target was 10−13-10−6 M, showing wide linear detection range. The biosensor displayed simple design, excellent sensitivity and high specificity for microRNA, showing enormous application prospect in bioanalysis and disease diagnosis fields.

Ratiometric Antifouling Electrochemical Biosensors Based on Multifunctional Peptides and MXene Loaded with Au Nanoparticles and Methylene Blue.

A universal strategy for the construction of ratiometric antifouling electrochemical biosensors was developed based on multifunctional peptides and 2D nanomaterial MXene loaded with gold nanoparticles (AuNPs) and methylene blue (MB). The nanocomposite of MXene loaded with AuNPs and MB (MXene-Au-MB) exhibited excellent conductivity, where the AuNPs were able to capture biomolecules containing sulfhydryl terminus, and the MB molecules were used to generate electrochemical signal. The MXene-Au-MB was fixed on the electrode surface by Nafion, and the anchored peptide captured the electrochemical signal probe carboxyl-modified ferrocene (Fc) to construct an electrochemical biosensor. The multifunctional peptide containing the anchoring, antifouling, and recognizing sequences endowed the sensing surface not only the assaying function but also the capability to resist nonspecific adsorption from complex samples. In the biosensing system, with the increase in the target concentration, the electrochemical signal of MB remained constant, whereas the electrochemical signal of Fc gradually decreased, and the ratiometric detection strategy greatly improved the accuracy of the biosensor. In the presence of a model target prostate-specific antigen (PSA), the recognizing sequence was recognized and cleaved, and the ratiometric signal of Fc and MB indicated the concentration of PSA accurately and sensitively, with a detection range from 5 pg/mL to 10 ng/mL and a limit of detection of 0.83 pg/mL. Electrochemical biosensors based on the MXene-Au-MB and multifunctional peptides possessed high selectivity, accuracy, and sensitivity even in real complex biological samples because of the excellent antifouling ability of the peptide. More importantly, the assaying of other targets can be easily realized with a similar biosensing strategy by changing the recognition sequence of the multifunctional peptide, and the detection of thrombin (TB) has also been achieved in this work.

A label-free electrochemical biosensor based on magnetic biocomposites with DNAzyme and hybridization chain reaction dual signal amplification for the determination of Pb2.

A highly sensitive and selective electrochemical biosensor for Pb2+ with a dual-amplification strategy is proposed. The first amplification step was realized by the cycle of Pb2+ and 8-17 DNAzyme (S2), and the hybridization chain reaction (HCR) triggered by S1 further amplified the electrochemical signal. Fe3O4@Au NPs, as a multifunctional magnetic carrier, is not only manifested in the construction of a magnetically controlled electrochemical response interface, but also has significant contribution in the purifying system, reducing interference, increasing the specific surface area, and the DNA loading. The magnetic nanocomposites were characterized by TEM as spheres with particle size of around 39nm. When there was no Pb2+, long double-strand DNA (dsDNA) is formed on the surface of Fe3O4@Au NPs by the S1-triggered HCR; in the presence of Pb2+, S2 is activated and S1 on the surface of magnetic biocomposites (Fe3O4@Au NPs-S1) is continuously cleaved with the cycle of Pb2+ and S2, leading to a significant decrease of methylene blue (MB) absorbed on dsDNA. Such reverse dual-signal amplification strategy effectively increased the current difference and improved the sensitivity of the proposed sensor. The electrochemical signal of MB was obtained by differential pulse voltammetry (DPV) with preconcentration, showing a linear response toward Pb2+ ranging from 50pM to 1μM with a detection limit of 15pM. The proposed method has feasible applications in detecting other heavy metal ions based on other metal-dependent DNAzyme. Graphical Abstract.

One-step triggered branched DNA nanostrucuture for ultra-sensitive electrochemical detection of microRNA

A one-step triggered branched DNA nanostrucuture strategy was proposed for ultra-sensitive detection of microRNA (miRNA) based on two levels of hybridization chain reaction (HCR). The branched DNA nanostrucuture was produced through two HCR amplification procedures initiated by the target miRNA. After insertion of methylene blue (MB) into the base pairs, the concentration of miRNA can be obtained with a linear relationship from 10 fM to 50 pM by detecting the electrochemical signal of MB. The sensitivity for miRNA was significantly improved by HCR amplification, and the limit of detection was 2 fM. The proposed electrochemical biosensing strategy provides good reliability and ultra-high sensitivity as well as a satisfactory result for human serum sample. In addition, the one-step strategy greatly simplifies the operation step and reduce the systematic error, showing potential for real sample detection.

A sensitive electrochemical aptasensor based on MB-anchored GO for the rapid detection of Cronobacter sakazakii

Cronobacter sakazakii (C. sakazakii) can cause extremely high mortality diseases especially in infants, so it is necessary to rapidly and specifically detect C. sakazakii in powdered infant formula (PIF). In this work, the amplification strategy of methylene blue (MB)-anchored graphene oxide (GO) was used to develop an electrochemical aptasensor for detecting C. sakazakii easily and quickly. In the absence of C. sakazakii, GO would be bound to the aptamer of C. sakazakii by π-π interaction, and then adsorbed MB through electrostatic adherence; thus, the electrochemical signal of MB amplified. While in the presence of C. sakazakii, the bacteria would be specifically combined with the aptamer, and hindered the electrostatic adsorption of GO and MB to the aptamer, resulting in the decreasing electrochemical signal of MB. The fabricated electrochemical aptasensor showed a wide linear range from 2 × 101 to 2 × 106 CFU mL−1 of the bacteria concentration, and its limit of detection reached 7 CFU mL−1 (S/N = 3). In addition, the applicability of the aptasensor in PIF for the analysis of C. sakazakii was successfully demonstrated. This aptasensor would provide a new method for the detection of C. sakazakii but also a novel sensing platform for the rapid detection of pathogen bacteria.

A new sensing strategy based on thymine bases–Hg2+–methylene blue coordination on the electrospun PES–QDs platform for detection of Hg2+ in fruit juice samples

A novel label-free and highly sensitive electrochemical aptasensor for highly sensitive mercury ion detection has been successfully fabricated in fruit juice samples using of electrospun nanofibers polyethersulfone and quantum dots (NFs–QDs) at the surface of carbon paste electrode (CPE). In addition to the T bases used in the designed aptasensor which can be strong and specific binding to the Hg2+, the methylene blue (MB) also can interact specifically with the Hg2+ (T–Hg2+–MB), as well as interact with the guanine bases in the DNA aptamer as an receiver site for interaction. According to this, the proposed sensor has more receiver sites for interaction with the Hg2+. Here, the electrochemical signal of MB was employed for Hg2+ measurements which this signal was amplified by NFs–QDs nanocomposites. The Apt–MB binding event easily investigated by the peak current variations in Apt–MB1–Hg2+–MB2/NFs–QDs/CPE through cyclic voltammetry, differential pulse voltammetry (DPV) measurement. Also, this study was evaluated with electrochemical impedance spectroscopy. Under optimized conditions, the constructed aptasensor illustrated a wide linear range using the DPVs, from 0.1 to 150 nM and an excellent low detection limit of 0.02 nM. The quality of carefully choosing, an excellent stability and specificity sensitivity of the designed aptasensor were accredited by spiked juice samples as real sample. Moreover, the aptasensor exhibits the good reproducibility as well as has high selectivity to other cations. The recoveries of the Hg2+ assay of the fruit juice samples were obtained satisfactorily which can use for measurement of Hg2+ in the laboratory.

Cationic Dye Modified Sawdust as Electrode Modifier for Electrochemical Detection of Anions

AbstractBecause of its chemical properties, sawdust displays poor anionic exchange capacity. Here we demonstrate that sawdust modification with methylene blue (MB) dye represents an interesting and facile alternative to render this natural biomaterial capable to accumulate anionic species. MB adsorption onto sawdust was monitored by cyclic voltammetry and experimental parameters carefully optimized. Under the ideal experimental conditions (composition of accumulation and desorption solution, accumulation and desorption time and the nature of the electrolytic solution), the adsorbed MB showed poor mobility, which results in the absence of the characteristic electrochemical signal of MB. The ability of the material to accumulate anionic species was thus evaluated using Fe(CN)63− as a model anions. The slow Fe(CN)63−/4− system recorded onto the electrode modified by pristine sawdust (P/SFE) become fast and reversible after immobilization of MB onto P/SFE (MB/SFE). Electrochemical impedance spectroscopy confirms this result through the spectacular decrease of charge transfer resistance after MB adsorption (from 83 kΩ on P/SFE to 637 Ω on MB/SFE). MB/SFE was applied to the electroanalysis of nitrites and a sensitivity of 7.4 μA mM−1 was obtained. Although this sensitivity was less important compared to that obtained on glassy carbon electrode (9.4 μA mM−1), the dye modified electrode displays by far the best reproducibility even at higher nitrite concentration.

A label-free electrochemical aptasensor based on magnetic biocomposites with Pb2+-dependent DNAzyme for the detection of thrombin

Herein, a novel magnetic biocomposite (Fe3O4@Au-S1/S2) was applied to analyze thrombin. The Fe3O4@Au-S1/S2 consisted of Fe3O4@Au nanoparticles (Fe3O4@Au NPs) as carriers for magnetic separation and magnetic field-induced self-assembly, thiolated complementary strand (S1) anchored based on Au-S bond and thrombin binding aptamer (S2) as a recognition element. As a redox indicator, methylene blue (MB) can be adsorbed to DNA anchored on the surface of Fe3O4@Au NPs by electro-static interaction. In the absence of thrombin, MB were adsorbed on double-stranded DNA (S1/S2) which anchored on Fe3O4@Au NPs and a high electrochemical signal of MB was recorded by Differential pulse voltammetry. Conversely, the complementary strand (S1) exposed after thrombin competitively bonded with aptamer. The introduction of Pb2+-dependent DNAzyme (S3) split S1 at specific rA site, resulting in the significantly decreased adsorption capacity of MB. Thus, the thrombin detection could be recorded by monitoring the electrochemical signal reduction of MB through incubation of thrombin with S3. This method exhibited a high sensitivity toward thrombin with a broad linear range from 5 pmol L−1 to 5 nmol L−1 and a limit of detection of 1.8 pmol L−1.

A simple and universal electrochemical assay for sensitive detection of DNA methylation, methyltransferase activity and screening of inhibitors

Many studies have confirmed that DNA methylation is highly correlated with the occurrence and development of various diseases including cancers. In this work, we developed a simple, sensitive, selective, and universal electrochemical biosensor for detection of DNA methylation and assay of DNA methyltransferase (MTase) activity using M.SssI MTase as an example. The thiolated single-stranded DNA S1 was self-assembled on the surface of gold nanoparticles deposition modified glassy carbon electrode via AuS bonding, then hybridization between the DNA S1 and its complementary DNA S2 formed a double-stranded target sequence for both M.SssI MTase and restriction endonuclease HpaII. HpaII could not cleave the target sequence after it was methylated by M.SssI MTase, while the sequence without methylation could be cleaved. Here, we used methylene blue (MB) as electrochemical indicator. The electrochemical signal of MB increased linearly with increasing M.SssI MTase concentration from 0.5 to 25 U/mL and from 25 to 400 U/mL with a detection limit of 0.04 U/mL. Moreover, screening of M.SssI MTase inhibitors 5-azacytidine (5-Aza) and 5-Aza-2′-deoxycytidine (5-Aza-dC) were successfully investigated using the fabricated electrochemical biosensor and showed that the two classic drugs could both inhibit the M.SssI MTase activity with the IC50 of 2.8 μM and 0.37 μM, respectively, indicating potential application in discovery of new anticancer drugs.

Boronic acid functionalized magnetic composites with sandwich-like nanostructures as a novel matrix for PDGF detection

In this paper, we present a novel multifunctional magnetic composite with sandwich-like nanostructure, which is composed of a yolk-egg-like magnetic silica core and a continuous polydopamine(PDA)-Au coating. Firstly, yolk-egg-like magnetic composite(SiO2@Fe3O4@PDA) was prepared by a combined high temperature decomposition method with mussel chemistry. Then, Au nanoparticles(NPs) were in-situ generated on the surface of the SiO2@Fe3O4@PDA by reaction between the PDA shell and HAuCl4, forming a multilayer sandwich-like nanostructure. Benefiting from the good affinity of the PDA shell and Au NPs with thiol group, the 4-mercaptophenylboronic acid was successfully assembled on the surface of Au NPs and PDA layer. The hybrid magnetic composite functionalized with boronic acid was used as affinity probes to selectively capture PDGF from solution. Meanwhile, methylene blue(MB)-doped silica NPs (SiO2-MB) were prepared to immobilize aptamer. In the presence of PDGF, the aptamer labeled SiO2-MB (SiO2-MB-aptamer) specifically bound with the PDGF protein. By monitoring the change of the electrochemical signal of MB, we were able to detect the binding events between the aptamer and PDGF in homogeneous solutions. The sensor was highly selective and sensitive with a detection limit of 0.22 fM for PDGF. The developed method showed wide potential applications in protein monitoring and cancer diagnosis.

An exonuclease-assisted amplification electrochemical aptasensor of thrombin coupling “signal on/off” strategy

In this work, a dual-signaling electrochemical aptasensor based on exonuclease-catalyzed target recycling was developed for thrombin detection. The proposed aptasensor coupled “signal-on” and “signal-off” strategies. As to the construction of the aptasensor, ferrocene (Fc) labeled thrombin binding aptamer (TBA) could perfectly hybridize with the methylene blue (MB) modified thiolated capture DNA to form double-stranded structure, hence emerged two different electrochemical signals. In the presence of thrombin, TBA could form a G-quadruplex structure with thrombin, leading to the dissociation of TBA from the duplex DNA and capture DNA formed hairpin structure. Exonuclease could selectively digest single-stranded TBA in G-quadruplex structure and released thrombin to realize target recycling. As a consequence, the electrochemical signal of MB enhanced significantly, which realized “signal on” strategy, meanwhile, the deoxidization peak current of Fc decreased distinctly, which realized “signal off” strategy. The employment of exonuclease and superposition of two signals significantly improved the sensitivity of the aptasensor. In this way, an aptasensor with high sensitivity, good stability and selectivity for quantitative detection of thrombin was constructed, which exhibited a good linear range from 5pM to 50nM with a detection limit of 0.9pM (defined as S/N=3). In addition, this design strategy could be applied to the detection of other proteins and small molecules.

A 3D origami electrochemical immunodevice based on a Au@Pd alloy nanoparticle-paper electrode for the detection of carcinoembryonic antigen.

Herein, a novel 3D microfluidic paper-based electrochemical (EC) immunodevice (μ-PEI) for sensitive detection of carcinoembryonic antigen (CEA) was developed. Au@Pt core-shell nanoparticles (NPs), with high conductivity, large surface area, and synergistic electronic effects, were not only used as carriers of secondary antibodies, methylene blue (MB) redox probes and glucose oxidase but also catalyzed the EC reaction of MB, thus amplifying the EC signal of MB in the presence of glucose. In addition, using a novel Au@Pd alloy NP modified porous paper working electrode as the biosensor platform could not only enhance the surface area to immobilize antibodies but also catalyze the reduction of hydrogen peroxide, which further amplified the detection response. On the basis of the considerably amplified EC signal and the sandwich-type format, the EC immunosensor has a sensitive response to CEA in a linear range of 1.0 pg mL-1-100 ng mL-1 with a detection limit of 0.4 pg mL-1. Additionally, this 3D μ-PEI showed satisfactory reproducibility, selectivity and stability.

Electrochemical biosensing method for the detection of DNA methylation and assay of the methyltransferase activity

In this article, we presented an electrochemical method for detection of DNA methylation and assay of DNA methyltransferase (MTase) activity using methylene blue (MB) as electrochemical indicator. After the DNA hybrid was methylated by T.aqI MTase, it could not be cleaved by HincII endonuclease. On the contrary, the double DNA without methylation could be cleaved, which would decrease the amount of intercalated MB. Thus, the DNA methylation status and MTase activity could be determinated based on the voltammetric signal change of MB. The methylation site could be found based on this method. The electrochemical signal of MB increased linearly with increasing T.aqI MTase concentration from 0.1 to 100U/mL. Moreover, the inhibition investigation demonstrated that fisetin could inhibit the T.aqI MTase activity with the IC50 value of 280μM. Therefore, the screening of the inhibitors of MTase could be accomplished using the novel method.

Semi-real time electrochemical monitoring for influenza virus RNA by reverse transcription loop-mediated isothermal amplification using a USB powered portable potentiostat

In this paper, the semi-real time electrochemical monitoring method using a screen-printed electrode, which employs reverse transcription loop-mediated isothermal amplification (RT-LAMP) for influenza virus RNA, is presented. The amplified DNA combined with methylene blue (MB), which was used as an electroactive DNA intercalator, and the electrochemical signal was monitored using square wave voltammetry in the presence of RT-LAMP reagent components. MB molecules binding to amplified DNA caused the reduction of the peak current due to the slow diffusion of MB-amplified DNA complex to the electrode surface. We successfully monitored the amplification process of DNA on the basis of RT-LAMP by measuring and analyzing the electrochemical signal of MB with only one screen-printed electrode that connected with a USB powered portable potentiostat. The peak height of the current was related to the extent of amplification of DNA and the amount of input RNA. Since laborious probe immobilization is not required and both the amplification and the monitoring are possible in a single tube, our method does not suffer from potential cross-contamination. Furthermore, our method provides a new rote for the development of electrochemical hand held biosensors.