Label-free Electrochemical DNA Research Articles

Investigating the Impact of Blocking Monolayer Architecture on the Performance of Electrochemical DNA Biosensors in Microfluidic Channels

An electrochemical nucleic acid biosensor typically involves the immobilization of DNA strands onto a surface, which serves as a recognition element for specific DNA or RNA target molecules.1-3 DNA strands can be single-stranded or double-stranded, and their immobilization onto a surface is crucial for sensing applications. This allows the formation of monolayers which is often used to prevent nonspecific adsorption of interfering molecules onto the surface. This layer acts as a barrier, allowing only specific interactions with the DNA target molecules or analytes of interest. Traditionally, redox mediators such as ferrocyanide/ ferricyanide that undergo reversible oxidation-reduction reactions are often used to detect hybridization of DNA targets with immobilized complementary DNA probes. Under these conditions, the heterogeneous charge transfer rate of redox mediators at the electrode surface is often a key factor taken into account to interpret the sensitivity and efficiency of the biosensor.3-5 In this work, with a set of experiments carried out by hydrodynamic voltammetry and impedance spectroscopy at channel microelectrodes, we propose a new approach supported by numerical modeling to highlight the influence of the mass transport of redox mediators on the response of DNA biosensors. Contrary to what is commonly accepted in the literature, we showed that the presence of DNA monolayers acting as blocking monolayers does not affect the charge transfer rate of redox mediators, regardless of the electrode accessibility (surface coverage). We demonstrated that under flow conditions, the current response of the biosensors was controlled by the mass transport rather than the charge transfer rate of redox mediators. This phenomenon was attributed to the nonlinear effects of diffusion-convection of the redox mediators at the remaining active sites, thereby affecting the overall kinetics of the transduction signal. These experiments, coupled with numerical calculations, allowed us to compare the performance of DNA biosensors obtained with different blocking monolayers and to evaluate the average size of the active sites. In this model, they were assumed to be small compared to the electrode size.This study constitutes an important advance in the field of sensors or biosensors, in the broad sense, as it points out the influence of parameters controlling mass transport and therefore the performance of electrochemical DNA biosensors, such as the density of DNA monolayers, the composition of the blocking agents, and size of holes (active sites). REFERENCES 1 Slinker, J. D.; Muren, N. B.; Gorodetsky, A. A.; Barton, J. K. Multiplexed DNA-Modified Electrodes. J Am Chem Soc 2010, 132 (8). 2 Horny, M. C.; Lazerges, M.; Siaugue, J. M.; Pallandre, A.; Rose, D.; Bedioui, F.; Deslouis, C.; Haghiri-Gosnet, A. M.; Gamby, J. Electrochemical DNA Biosensors Based on Long-Range Electron Transfer: Investigating the Efficiency of a Fluidic Channel Microelectrode Compared to an Ultramicroelectrode in a Two-Electrode Setup. Lab Chip 2016, 16 (22). 3 Zambry, N. S.; Awang, M. S.; Beh, K. K.; Hamzah, H. H.; Bustami, Y.; Obande, G. A.; Khalid, M. F.; Ozsoz, M.; Manaf, A. A.; Aziah, I. A Label-Free Electrochemical DNA Biosensor Used a Printed Circuit Board Gold Electrode (PCBGE) to Detect SARS-CoV-2 without Amplification. Lab Chip 2023, 23 (6). 4 Tersch, C.; Lisdat, F. Label-Free Detection of Protein-DNA Interactions Using Electrochemical Impedance Spectroscopy. Electrochim Acta 2011, 56 (22). 5 Cardoso, A. R.; Moreira, F. T. C.; Fernandes, R.; Sales, M. G. F. Novel and Simple Electrochemical Biosensor Monitoring Attomolar Levels of MiRNA-155 in Breast Cancer. Biosens Bioelectron 2016, 80.

Label-free electrochemical biosensor with magnetic self-assembly constructed via PNA-DNA hybridization process on α-Fe2O3/Fe3O4 nanosheets for APOE ε4 genes ultrasensitive detection

A label-free electrochemical DNA detection strategy based on self-assembled α-Fe2O3/Fe3O4 nanosheets with PNA-DNA hybridization process was developed for ultrasensitive detection of APOE ε4 gene, one of the most robust genetic risks for Alzheimer’s Disease (AD). In this work, magnetic α-Fe2O3/Fe3O4 heterogeneous nanosheets were prepared by hydrothermal-calcined reduction method and loaded with Au nanoparticles (AuNPs) on their surfaces. The magnetic α-Fe2O3/Fe3O4@Au nanocomposites significantly enhanced the electrochemical response as a signal amplification matrix and were able to bind to the magnetic glassy carbon electrode (MGCE) surface by magnetic self-assembly. Moreover, owing to the high specificity and stable binding capacity of PNA with respect to the target DNA, the biosensor not only enabled accurate (the limit of detection was estimated to be 0.147 pM) and rapid detection of the APOE ε4 gene, but also exhibited excellent specificity, stability and regeneration capability. Additional, the satisfactory recoveries were also obtained in real samples of human serum, ranging from 92.83 % to 106.22 % with relative standard deviation (RSD) between 0.25 % and 1.85 %. The results possessed important reference value for exploring the application of DNA biosensor technology in the diagnosis of APOE gene mutation.

Label-free, background-free detection of nucleic acid with immobilization-free heterogeneous biosensor and one-pot hybridization chain reaction amplification

Although immobilization-free and label-free electrochemical DNA (E-DNA) biosensors have engaged tremendous interest due to their superior properties, such as easy operation, time-saving and cost-saving, most of them are fabricated in homogeneous modes and usually produce high background current. In the present work, we proposed a new immobilization-free and label-free heterogeneous E-DNA assay based on a dual-blocker-aided multibranched hybridization chain reaction (HCR) for one-pot nucleic acid detection with zero background. The target nucleic acid triggers the HCR involving cascaded hybridization between two metastable hairpins, resulting in the generation of HCR products with multibranched arms, which can be captured onto the electrode via π-π stacking interactions between multibranched arms and reduced graphene oxide (rGO). Prior to the incubation process with an electrode, two blockers are designed to prohibit the nonspecific absorption of unreacted hairpin probes. Thus, an immobilization-free and label-free heterogeneous electrochemical assay for one-pot nucleic acid detection with zero background is readily realized. This strategy also presents additional merits of simplicity and cheap cost, since probe immobilization, signal tag labeling, and multiple incubation processes are avoided. Therefore, the as-proposed effective and versatile biosensor has great potential to be applied in nucleic acid-related practical biosensing.

Development of label-free electrochemical OMP-DNA probe biosensor as a highly sensitive system to detect of citrus huanglongbing

The fabrication of the first label-free electrochemical DNA probe biosensor for highly sensitive detection of Candidatus Liberibacter asiaticus (CLas), as the causal agent of citrus huanglongbing disease, is conducted here. An OMP probe was designed based on the hybridization with its target-specific sequence in the outer membrane protein (OMP) gene of CLas. The characterization of the steps of biosensor fabrication and hybridization process between the immobilized OMP-DNA probe and the target ssDNA oligonucleotides (OMP-complementary and three mismatches OMP or OMP-mutation) was monitored using cyclic voltammetry and electrochemical impedance spectroscopy based on increasing or decreasing in the electron transfer in [Fe (CN)6]3−/4− on the modified gold electrode surface. The biosensor sensitivity indicated that the peak currents were linear over ranges from 20 to 100 nM for OMP-complementary with the detection limit of 0.026 nM (S/N = 3). The absence of any cross-interference with other biological DNA sequences confirmed a high selectivity of fabricated biosensor. Likewise, it showed good specificity in discriminating the mutation oligonucleotides from complementary target DNAs. The functional performance of optimized biosensor was achieved via the hybridization of OMP-DNA probe with extracted DNA from citrus plant infected with CLas. Therefore, fabricated biosensor indicates promise for sensitivity and early detection of citrus huanglongbing disease.

Immobilization-free and label-free electrochemical DNA biosensing based on target-stimulated release of redox reporter and its catalytic redox recycling

Herein, we demonstrate a simple, homogenous and label-free electrochemical biosensing system for sensitive nucleic acid detection based on target-responsive porous materials and nuclease-triggered target recycling amplification. The Fe(CN)63− reporter was firstly sealed into the pores of Fe3O4 nanoparticles by probe DNA. Target DNA recognition triggered the controllable release of Fe(CN)63− for the redox reaction with the electron mediator of methylene blue enriched in the dodecanethiol assembled electrode and thereby generating electrochemical signal. The exonuclease III (Exo III)-assisted target recycling and the catalytic redox recycling between Fe(CN)63− and methylene blue contributed for the enhanced signal response toward target recognition. The low detection limit toward target was obtained as 478 fM and 1.6 pM, respectively, by square wave voltammetry and cyclic voltammetry methods. It also possessed a well-discrimination ability toward mismatched strands and high tolerance to complex sample matrix. The coupling of bio-gated porous nanoparticles, nuclease-assisted target amplification and catalytic redox recycling afforded the sensing system with well-controllable signal responses, sensitive and selective DNA detection, and good stability, reusability and reproducibility. It thus opens a new avenue toward the development of simple but sensitive electrochemical biosensing platform.

A portable label-free electrochemical DNA biosensor for rapid detection of Salmonella Typhi.

A highly accurate, rapid, portable, and robust platform for detecting Salmonella enterica serovar Typhi (S. Typhi) is crucial for early-stage diagnosis of typhoid to avert and control the outbreaks of this pathogen, which threaten global public health. This study presents a proof-of-concept for our developed label-free electrochemical DNA biosensor system for S. Typhi detection, which employs a printed circuit board gold electrode (PCBGE), integrated with a portable potentiostat reader. Initially, the functionalized DNA biosensor and target detection were characterized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) methods using a benchtop potentiostat. Interestingly, the newly developed DNA biosensor can identify target single-stranded DNA concentrations ranging from 10 nM to 20 μM, achieving a detection limit of 7.6 nM within a brief 5 minute timeframe. Under optimal detection conditions, the DNA biosensor exhibits remarkable selectivity, capable of distinguishing a single mismatch base pair from the target single-stranded DNA sequence. We then evaluated the feasibility of the developed DNA biosensor system as a diagnostic tool by detecting S. Typhi in 50 clinical samples using a portable potentiostat reader based on the DPV technique. Remarkably, the developed biosensor can distinctly distinguish between positive and negative samples, indicating that the miniaturised DNA biosensor system is practical for detecting S. Typhi in real biological samples. The developed DNA biosensor device in this work proves to be a promising point-of-care (POC) device for Salmonella detection due to its swift detection time, uncomplicated design, and streamlined workflow detection system.

A label-free electrochemical biosensor for the detection of alpha-thalassemia 1 (SEA deletion) carriers using screen-printed carbon electrodes

A label-free electrochemical DNA biosensor based on electrochemical impedance spectroscopy (EIS) biosensor has been extensively developed for diagnosing human genetic diseases. However, its application has been limited to simulated target DNA. The aim of this study was to develop an EIS biosensor that can identify carriers of alpha (α)-thalassemia 1 with Southeast Asia (SEA) deletion. The biosensor was coupled with screen-printed carbon electrodes (SPCEs) and Hoechst 33,258 dye. To determine the optimal conditions and cutoff criteria, we evaluated forty samples with known DNA genotypes. Our findings suggested that the cutoff value for identifying α-thalassemia 1 (SEA deletion) carriers was more than 26.84 kΩ of negative imaginary impedance (-Z″) and 48.83 kΩ of charge transfer resistance (Rct). The sensitivity of the developed EIS biosensor was comparable to that of conventional gel electrophoresis, with no cross-reactivity observed in α-thalassemia 1 (THAI deletion), α-thalassemia 2 (3.7 deletion), α-thalassemia 2 (4.2 deletion), and beta (β)-thalassemia carriers. The diagnostic potential of the developed EIS biosensor was evaluated using 81 clinical blood samples, demonstrating 100% sensitivity, 88.2% specificity, 83.3% positive predictive value (PPV), 100% negative predictive value (NPV) and 92.6% accuracy for Rct measurement. The developed EIS biosensor presents an attractive screening method for the detecting α-thalassemia 1 (SEA deletion) carriers due to its simplicity, cost-effectiveness, and 45-fold reduction in turnaround time compared to conventional gel electrophoresis. Consequently, the identification of α-thalassemia 1 (SEA deletion) carrier through this approach represents the most effective strategy for the management and prevention of the most severe form of thalassemia.

The Optimization of a Label-Free Electrochemical DNA Biosensor for Detection of Sus scrofa mtDNA as Food Adulterations

Fast, sensitive, and easy-to-use methods for detecting DNA related to food adulteration, health, religious, and commercial purposes are evolving. In this research, a label-free electrochemical DNA biosensor method was developed for the detection of pork in processed meat samples. Gold electrodeposited screen-printed carbon electrodes (SPCEs) were used and characterized using SEM and cyclic voltammetry. A biotinylated probe DNA sequence of the Cyt b S. scrofa gene mtDNA used as a sensing element containing guanine substituted by inosine bases. The detection of probe-target DNA hybridization on the streptavidin-modified gold SPCE surface was carried out by the peak guanine oxidation of the target using differential pulse voltammetry (DPV). The optimum experimental conditions of data processing using the Box–Behnken design were obtained after 90 min of streptavidin incubation time, at the DNA probe concentration of 1.0 µg/mL, and after 5 min of probe-target DNA hybridization. The detection limit was 0.135 µg/mL, with a linearity range of 0.5–1.5 µg/mL. The resulting current response indicated that this detection method was selective against 5% pork DNA in a mixture of meat samples. This electrochemical biosensor method can be developed into a portable point-of-care detection method for the presence of pork or food adulterations.

Dual targets-induced specific hemin/G-quadruplex assemblies for label-free electrochemical detection capable of distinguishing Salmonella and its common serotype in food samples

Efficient detection of pathogenic bacteria is paramount for ensuring food safety and safeguarding public health. Herein, we developed a label-free and signal-on dual-target recognition electrochemical DNA sensing platform based on the conformational formation of split G-quadruplex. This platform focused on achieving sensitive and low-cost detection of Salmonella and its most human-infecting S. typhimurium serotype. In simple terms, the dual-target recognition probe (DTR-6P) was ingeniously designed for the loop sequence on the loop-mediated isothermal amplification (LAMP) amplicons. It could recognize two different genes and release their corresponding G-rich sequences. The exfoliated G-rich sequences could be captured by the capture probes on the electrode, and then the bimolecular G-quadruplex or the tetramolecular G-quadruplex would be formed to capture hemin, thereby enabling dual-signal reporting. The minimum detection amount of target genes can be as low as 2 copies/μL. Encouragingly, the real food samples contaminated by Salmonella and the S. typhimurium serotype can be readily identified. The sensing platform with ingenious design paves a new way for label-free, multi-target simultaneous detection, whose advantage of rapidity, sensitivity, cost-effectiveness, and specificity also lay a solid foundation for practical applications.

Label-free electrochemical DNA biosensing of MR TV 29 18s ribosomal RNA gene of Trichomonas vaginalis by signalization of non-spherical gold nanoparticles

Label-free electrochemical DNA biosensing of MR TV 29 18s ribosomal RNA gene of Trichomonas vaginalis by signalization of non-spherical gold nanoparticles

A novel spin-based label-free electrochemical dna hybridization biosensor and its applications for dengue virus detection

In this study, we have rationally constructed a spin-based label-free DNA hybridization sensor employing the spin-polarized electrons as a tool of detection. Recent research, that takes into account chiral-induced spin selectivity, has demonstrated colossal spin filtering by DNA at room temperature. Traditional DNA hybridization sensors use electronic(charge) current to probe the hybridization of double-strand (ds)-DNA. The benefit of the chiral-induced spin selectivity (CISS)-based DNA sensor lies in the direct probe of hybridization through its symmetry present in the secondary structure of ds-DNA. To this end, a self-assembled monolayer of DNA was prepared on Au-coated Ni devices and hybridization phenomena were investigated using differential pulse voltammetry. The accuracy of the CISS-based hybridization sensor was tested using additional complementary techniques such as cyclic voltammetry, electrochemical impedance spectroscopy, FTIR, and XPS, and the same method was successfully employed to detect the Dengue virus as well. With a limit of detection of up to 0.12 picomolar (pM), the results are reliable and repeatable. The current approach opens up new possibilities for developing spin-based point-of-care devices in the future.

A novel signal amplification strategy for label-free electrochemical DNA sensor based on the interaction between α-cyclodextrin and ferrocenyl indicator

The synthesized ferrocene appended naphthalimide derivative (FND) exhibited great binding ability toward dsDNA, while its usage as the electrochemical hybridization indicator was restricted by the poor water solubility. Herein, a simple and effective signal amplification strategy for FND based label-free DNA biosensors was developed based on the interaction between FND and cyclodextrin. α-Cyclodextrin (α-CD), β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) were helpful to amplify the signal of the DNA biosensor, while the signal amplification effect of α-CD was better than that of β-CD and γ-CD. Under the optimum conditions, there was a 3-fold increase in the sensitivity of the DNA biosensor after the addition of α-CD. The interaction between FND and α-/β-/γ-CD was investigated by differential pulse voltammetry and fluorescence experiment. Experimental results showed that α-CD not only minimized the impact on the electrochemical activity of FND but also improved the dispersity of FND in aqueous solution. That was why the proposed biosensor showed higher sensitivity in the presence of α-CD. This strategy was universal for other ferrocenyl indicators with similar structures as used in this work.

A label-free electrochemical DNA biosensor used a printed circuit board gold electrode (PCBGE) to detect SARS-CoV-2 without amplification.

The emergence of coronavirus disease 2019 (COVID-19) motivates continuous efforts to develop robust and accurate diagnostic tests to detect severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Detection of viral nucleic acids provides the highest sensitivity and selectivity for diagnosing early and asymptomatic infection because the human immune system may not be active at this stage. Therefore, this work aims to develop a label-free electrochemical DNA biosensor for SARS-CoV-2 detection using a printed circuit board-based gold substrate (PCBGE). The developed sensor used the nucleocapsid phosphoprotein (N) gene as a biomarker. The DNA sensor-based PCBGE was fabricated by self-assembling a thiolated single-stranded DNA (ssDNA) probe onto an Au surface, which performed as the working electrode (WE). The Au surface was then treated with 6-mercapto-1-hexanol (MCH) before detecting the target N gene to produce a well-oriented arrangement of the immobilized ssDNA chains. The successful fabrication of the biosensor was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and atomic force microscopy (AFM). The DNA biosensor performances were evaluated using a synthetic SARS-CoV-2 genome and 20 clinical RNA samples from healthy and infected individuals through EIS. The developed DNA biosensor can detect as low as 1 copy per μL of the N gene within 5 minutes with a LOD of 0.50 μM. Interestingly, the proposed DNA sensor could distinguish the expression of SARS-CoV-2 RNA in a patient diagnosed with COVID-19 without any amplification technique. We believe that the proposed DNA sensor platform is a promising point-of-care (POC) device for COVID-19 viral infection since it offers a rapid detection time with a simple design and workflow detection system, as well as an affordable diagnostic assay.

Label free electrochemical DNA biosensor for COVID-19 diagnosis

The COVID-19 pandemic has significantly increased the development of the development of point-of-care (POC) diagnostic tools because they can serve as useful tools for detecting and controlling spread of the disease. Most current methods require sophisticated laboratory instruments and specialists to provide reliable, cost-effective, specific, and sensitive POC testing for COVID-19 diagnosis. Here, a smartphone-assisted Sensit Smart potentiostat (PalmSens) was integrated with a paper-based electrochemical sensor to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A disposable paper-based device was fabricated, and the working electrode directly modified with a pyrrolidinyl peptide nucleic acid (acpcPNA) as the biological recognition element to capture the target complementary DNA (cDNA). In the presence of the target cDNA, hybridization with acpcPNA probe blocks the redox conversion of a redox reporter, leading to a decrease in electrochemical response correlating to SARS-CoV-2 concentration. Under optimal conditions, a linear range from 0.1 to 200 nM and a detection limit of 1.0 pM were obtained. The PNA-based electrochemical paper-based analytical device (PNA-based ePAD) offers high specificity toward SARS-CoV-2 N gene because of the highly selective PNA-DNA binding. The developed sensor was used for amplification-free SARS-CoV-2 detection in 10 nasopharyngeal swab samples (7 SARS-CoV-2 positive and 3 SARS-CoV-2 negative), giving a 100% agreement result with RT-PCR.

Label free flexible electrochemical DNA biosensor for selective detection of Shigella flexneri in real food samples

An effective tool for early-stage selective detection of the foodborne bacterial pathogen Shigella flexneri (S. flexneri) is essential for diagnosing infectious diseases and controlling outbreaks. Here, a label-free electrochemical DNA biosensor for monitoring S. flexneri is developed. To fabricate the biosensor, detection probe (capture probe) is immobilized on the surface of poly melamine (P-Mel) and poly glutamic acid (PGA), and disuccinimidyl suberate (DSS) functionalized flexible indium tin oxide (ITO) electrode. Anthraquinone-2-sulfonic acid monohydrate sodium salt (AQMS) is used as a signal indicator for the detection of S. flexneri. The proposed DNA biosensor exhibits a wide dynamic range with concentration of the targets ranging from 1 × 10−6 to 1 × 10−21 molL−1 with a limit of detection (LOD) of 7.4 × 10−22 molL−1 in the complementary linear target of S. flexneri, and a detection range of 8 × 1010–80 cells/ml with a LOD of 10 cells/ml in real S. flexneri sample. The proposed flexible biosensor provides high specificity for the detection of S. flexneri compared to other target signals such as discrete base mismatches and different bacterial species. The developed biosensor displayed excellent recoveries in detecting S. flexneri in spiked food samples. Therefore, the proposed biosensor can serve as a model methodology for the detection of other pathogens in a broad span of industries.

A label-free electrochemical impedimetric DNA biosensor for genetically modified soybean detection based on gold carbon dots.

A label-free electrochemical impedimetric biosensor was constructed based on gold carbon dots (GCDs) modified screen-printed carbon electrode for the detection of genetic modified (GM) soybean. The structure and property of GCDs were investigated. The GCDs can directly bind to single-stranded DNA probes through Au-thiol interaction and boost electric conductivity for the DNA sensor construction. The quantification of target DNA was monitored by the change of electron-transfer resistance (Ret) upon the DNA hybridization on sensor surface. Under the optimal conditions, the Ret response (vs. Ag reference electrode) increased with the logarithm of target DNA concentrations in a wide linear range of 1.0 × 10-7 - 1.0 × 10-13M with a detection limit of 3.1 × 10-14M (S/N = 3). It was also demonstrated that the proposed DNA sensor possessed high specificity for discriminating target DNA from mismatched sequences. Moreover, the developed biosensor was applied to detect SHZD32-1 in actual samples, and the results showed a good consistency with those obtained from the gel electrophoresis method. Compared with the previous reports for DNA detection, the label-free biosensor showed a comparatively simple platform due to elimination of complicated DNA labeling. Therefore, the proposed method showed great potential to be an alternative device for simple, sensitive, specific, and portable DNA sensor.

A novel and ultrasensitive label-free electrochemical DNA biosensor for Trichomonas vaginalis detection based on a nanostructured film of poly(ortho-aminophenol)

Trichomoniasis, as a major public health concern, is the world’s most common sexually transmissible disease. This infection is caused by a protozoan parasite called Trichomonas vaginalis (TV) that can lead to reproductive and genital area problems. Accordingly, it is of great significance to expand new methods for increasing the sensitivity of TV detection. In this study, a novel label-free electrochemical DNA biosensor for TV quantitation was constructed based on an electropolymerized poly(ortho-aminophenol) thin film simultaneously acting as a transducer as well as a redox indicator. The redox-active polymeric film was utilized to covalent immobilization of a specific thiolated DNA probe. The hybridization process was then monitored by differential pulse voltammetry. The proposed biosensor detected a synthetic TV target sequence with a calibration sensitivity of − 0.0113 µA (log (concentration/mol L−1))−1, a linear concentration range of 1.0 × 10−20 to 1.0 × 10−12 mol L−1, and a detection limit of 3.9 × 10−21 mol L−1. It also showed an ability to differentiate between the complementary sequence and the base-mismatched and non-complementary sequences with a nice selectivity. Moreover, the designed biosensor was able to detect the TV genome with a calibration sensitivity of − 0.0774 µA (log (concentration/ng µL−1))−1, a linear range of 0.55–64 ng mL−1 and a detection limit of 1.0 pg µL−1.

Platinum nanoparticles loaded carbon black: reduced graphene oxide hybrid platforms for label-free electrochemical DNA and oxidative DNA damage sensing

• Rapid and effective synthesis of platinum nanoparticles on the carbon black:reduced graphene oxide hybrids were achieved. • Facile and efficient electrode modification was performed with the hybrids. • Characterization of the surfaces proved homogeneous and robust distribution of the structures. • Sensitive fsDNA detection was accomplished with a low detection limit. • DNA damage and protection monitoring were carried out successfully. Carbon black-based hybrid materials have attracted great attention in the design of electrochemical sensors due to their consistent electroanalytical properties. With this in mind, for the first time, we present the preparation of platinum nanoparticles loaded carbon black:reduced graphene oxide (PtNPs/CB:rGO) hybrid platforms for label-free electrochemical DNA and DNA damage sensing. Synthesis of different hybrids was performed via microwave-assisted reduction method for the impregnation of platinum nanoparticles efficiently. These materials were characterized with X-ray diffraction analysis (XRD), Raman spectroscopy, transmission emission spectroscopy (TEM) and subsequently they were used for pencil graphite electrode modification in order to improve the characteristics of the surface. Modified electrodes were firstly applied for fish sperm DNA (fsDNA) analysis. The effect of different ratios (wt.:wt. %) of CB and rGO was investigated and it was shown that the hybrid material with 50:50 ratio had better sensitivity with a low detection limit of 0.14 mg L −1 and a good linearity to fsDNA between 1 and 200 mg L −1 (n = 3) based on guanine (G) oxidation by using differential pulse voltammetry (DPV). In order to expand this comparison, PtNPs/CB and PtNPs/rGO modified electrodes were also incorporated. Furthermore, the electroanalytical response of the hybrid material modified electrode was investigated based on the oxidation of thymine (T). Later on, oxidative DNA damage detection in the presence of Cu(II)/H 2 O 2 reagents and protection studies in the presence of ascorbic acid were performed successfully by using electrochemical impedance spectroscopy (EIS). The study pointed out the remarkable reproducibility and sensitivity of the CB-based modification for nanoparticle decoration.

Label-based and label-free electrochemical DNA biosensors for the detection of viruses: A review

Label-based and label-free electrochemical DNA biosensors for the detection of viruses: A review

Highly sensitive and label-free electrochemical biosensor based on gold nanostructures for studying the interaction of prostate cancer gene sequence with epirubicin anti-cancer drug

A label-free electrochemical DNA hybridization biosensor was developed based on gold nanocubes (AuNCs) modified graphite screen-printed electrodes (GSPEs) for investigating the epirubicin (EPI) interaction with the short sequence DNA of prostate cancer gene. The electrochemical behavior of the genosensor was assessed in different steps of construction using cyclic voltammetry and electrochemical impedance spectroscopy methods. The changes in the biosensor responses versus the DNA interactions with the various concentrations of EPI were monitored by the differential pulse voltammetry method. The reduction peak current of EPI linearly increased with the increasing concentration of EPI. Under optimal conditions, two linear ranges were obtained from 0.04 to 0.80 μM and 0.8 to 20.0 μM, respectively with a limit of detection 0.01 μM. The prepared biosensor exhibited a proper selectivity toward the target drugs. The applicability of the sensor was demonstrated by the explored of epirubicin in a human blood serum sample. In addition, the prepared biosensor was used as a reproducible and stable device for EPI determination.