Electrochemical DNA Sensor Research Articles

Development of a sandwich-type electrochemical DNA sensor based on CeO2/AuPt nanoprobes for highly sensitive detection of hepatitis B virus DNA.

To provide accurate diagnostic evidence for early hepatitis B virus (HBV) infection-related diseases, this study targeted HBV DNA as an analyte, where a sandwich-type electrochemical DNA sensor based on gold nanoparticles/reduced graphene oxide (Au NPs/ERGO) and cerium oxide/gold-platinum nanoparticles (CeO2/AuPt NPs) was constructed. Au NPs/ERGO composite nanomaterials were first synthesized on the surface of a glass carbon electrode using electrochemical co-reduction, which significantly improved the specific surface area and electrical conductivity of the electrode. Further specific hybridization of target HBV-DNA was performed by combining capture probe DNA (S1-DNA) bound to AuNPs/ERGO with CeO2/AuPt modified signal probe DNA (S2-DNA). Leveraging the excellent H2O2 catalytic activity of the CeO2/AuPt nanocomposite, the constructed sandwich-type electrochemical DNA sensor was used to detect HBV DNA. By optimizing the detection conditions, the sensor showed a good linear response in the range of 1fmol/L to 1nmol/L, with a detection limit as low as 0.36fmol/L. The sensor had good specificity, repeatability, and stability. Further, spiked recovery experiments of actual serum samples showed recoveries ranging from 98.7% to 102.7%, and the relative standard deviations were all lower than 4.77%. This study provides a new method for the detection of HBV DNA with potential clinical applications.

Electrochemical Detection of DNA in Agriculture Using Lamp-Based Amplification

The variety and complexity of genetically modified organisms (GMOs) are increasing, which makes their detection harder than ever before. This impacts the traceability, safety, and monitoring of food. Current research indicates that GM crop technology may pose risks to human health and the environment. The aim of this study is the development of a LAMP-based GMO electrochemical detection device. LAMP amplification of P-35S, P-FMV, and T-NOS regions (three elements that are most often present in genetically modified plants as part of the transgenic construct) is done using gBlocks, synthetic dsDNA fragments that have an identical DNA sequence to that of the targeted part of a transgenic construct.Using single-stranded DNA probes containing methylene blue as a redox probe, the electrochemical DNA sensor detects LAMP products that are complementary to the target DNA. The probes were attached to the gold electrodes functionalized by gold nanoparticles, and 2D nanomaterials (MoS2, Mxenes, and reduced graphene oxide). The electrochemical methods, such as alternating current voltammetry, square wave voltammetry, and differential pulse voltammetry were employed in testing the electrochemical detection response of the DNA probes immobilized on 2D nanomaterials.The research has shown that the obtained DNA detection signal depends significantly on the methods (and setup parameters) used in electrochemical detection, and the nanomaterials used on electrodes. The electrochemical detection resulted in a signal decrease consequential to the conformational changes of the DNA probes upon attachment of the target DNA. The methylene blue molecules attached at the top of the DNA probes get higher resistance in the electron transfer to the electrode materials, which makes the target DNA detection quantitatively and qualitatively visible. These results are promising for the development of a device that will enable a specific, sensitive, fast, cost-effective, and precise in-field detection system for the routine detection of GMOs.**Acknowledgments:*This project is supported by The Science Fund of the Republic of Serbia DEVELOPMENT Program - Green program of cooperation between science and industry - LABOUR project (grant agreement No. 6710), and The Ministry of Science, Technological Development and Innovation of the Republic of Serbia (451-03-66/2024-03/200358).*This work is supported through the ANTARES project that has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement SGA-CSA. No. 739570 under FPA No. 664387. https://doi.org/10.3030/739570 Figure 1

Electrochemical DNA Sensor Based on Poly(proflavine) Deposited from Natural Deep Eutectic Solvents for DNA Damage Detection and Antioxidant Influence Assessment

Electrochemical DNA sensors for DNA damage detection based on electroactive polymer poly(proflavine) (PPFL) that was synthesized at screen-printed carbon electrodes (SPCEs) from phosphate buffer (PB) and two natural deep eutectic solvents (NADESs) consisting of citric or malonic acids, D-glucose, and a certain amount of water (NADES1 and NADES2) were developed. Poly(proflavine) coatings obtained from the presented media (PPFLPB, PPFLNADES1, and PPFLNADES2) were electrochemically polymerized via the multiple cycling of the potential or potentiostatic accumulation and used for the discrimination of thermal and oxidative DNA damage. The electrochemical characteristics of the poly(proflavine) coatings and their morphology were assessed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). The working conditions for calf thymus DNA implementation and DNA damage detection were estimated for all types of poly(proflavine) coatings. The voltammetric approach made it possible to distinguish native and chemically oxidized DNA while the impedimetric approach allowed for the successful recognition of native, thermally denatured, and chemically oxidized DNA through changes in the charge transfer resistance. The influence of different concentrations of conventional antioxidants and pharmaceutical preparations on oxidative DNA damage was characterized.

Highlighting the impact of blocking monolayers on DNA electrochemical sensors. Theoretical and experimental investigations under flow conditions

A model is proposed to account for the influence of electrode surface modifications in electrochemical DNA sensors operating under flow conditions. With blocking self-assembled monolayers of double-stranded DNA, the performance of the electrochemical transduction signal in the presence of a redox mediator is generally attributed to the rate of long-range electron transfer or to the screening effects of the monolayers due to negatively charged DNA. The originality of this model is here to only consider the influence of non-linear mass transport at the free-remaining sites. The model was tested for the detection of microRNAs (21 nucleotides) by implementing microchannel electrodes in the presence of an equimolar mixture of Fe(CN)63− / Fe(CN)64-. Two operating conditions leading to distinct monolayer structures were investigated using Pt and Au electrodes. The model successfully simulated the voltammograms confirming the apparent decrease in the signal transduction kinetics due to altered mass transport. These results were supported by measurements in electrochemical impedance spectroscopy.

Electrochemical sensor based on Y-shaped DNA by “one-pot” method for mercury detection

A DNA electrochemical sensor based on Y-shaped DNA probes was successfully designed for Hg2+ detection. The sensor was modified with carbon self-doping graphite-like carbon nitride (C-g-C3N4) and electrodeposited gold nanoparticles (EAu) to enhance conductivity and enrich the binding sites for DNA. DNA probe (S1) binded on the modified electrode via –SH, forming a stable Y-shaped DNA double helix structure with probe S2 and probe S3 anchoring on gold nanoparticles (nanoAu) in the presence of Hg2+ solution. The Y-shaped DNA duplex, with its tight and nondeformable rigid structure, created well-defined stereoscopic reaction areas and efficiently captures Hg2+ due to its structural differences, thereby improving the signal response. Moreover, larger amounts of methyleneblue (MB) could be loaded to provide adequate electrochemical response signal. The proposed sensor possessing signal amplification ability displayed a linear relationship between the square wave voltammetry (SWV) peak currents. Under the optimal conditions, Hg2+ could be detected in the range from 5000.0 to 5.0 nM with a detection limit of 8.5 pM. The sensor was also tested with tap water, river and medical wastewater samples. It showed the good recovery and accuracy and represented a promising method for Hg2+ detection.

An Electrochemical DNA Sensor for Doxorubicin Based on Graphene Oxide, Electropolymerized Azure A, and Methylene Green Composites

An Electrochemical DNA Sensor for Doxorubicin Based on Graphene Oxide, Electropolymerized Azure A, and Methylene Green Composites

Deep eutectic solvent-assisted synthesis of gold nanoflowers supported on glassy carbon electrode for DNA sensor application

Gold nanoflowers (AuNF) were synthesized on a glassy carbon electrode via a one-step, eco-friendly protocol in deep eutectic solvent (DES) of choline choloride and urea, called reline, for label-free detection of DNA hybridization. DES is eco-friendly, low-cost, biocompatible, and nontoxic, and it can be used as an electrolyte to synthesize nanomaterials by using the electrochemical method. In this protocol, highly branched and stable AuNFs were obtained without using any surfactants for DNA sensor application. The electrochemical performance of the AuNF-modified electrode was studied by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimal conditions, the AuNF-based DNA biosensor exhibited a sensitivity of 294.9 Ω nM−1cm−2 and 218 μA nM−1cm−2 and a limit of detection (LOD) of 10−9 M. The remarkable sensitivity and low LOD could be attributed to the good conductivity of AuNFs for accelerating electron transfer, resulting in obvious signal amplification. The DNA biosensor showed good reproducibility (RSD <3.65 %) and acceptable stability and selectivity. Its excellent performance in DNA detection suggested that the proposed electrochemical DNA sensor has great application potential in clinical diagnosis.

Label-free and ultrasensitive electrochemical detection of nucleic acids based on an exonuclease III-assisted target recycling amplification strategy using a heated gold disk electrode.

The present work demonstrates a label-free, rapid and ultrasensitive electrochemical sensor for specific DNA detection with an exonuclease III (Exo III)-assisted target recycling amplification strategy and elevated electrode temperature at a heated gold disk electrode (HAuDE). The proposed electrochemical DNA (E-DNA) sensor was designed such that in the presence of the target DNA, the electrode self-assembled capture probe hybridizes with the target DNA to form a duplex structure, which triggers Exo III to specifically recognize this structure and selectively digest the capture probe, while the released target DNA underwent recycling to hybridize with a new capture probe, leading to the gradual digestion of a large amount of capture probes. It was found that during the digestion period, the activity of Exo III could be significantly improved by elevating electrode temperature, thus promoting the digestion reaction and improving the sensitivity for target DNA detection. Furthermore, an electrochemical indicator ([Ru(NH3)6]3+) was electrostatically bound to the capture probe, leading to a significant square wave voltammetry (SWV) response, which directly related to the amount and length of the capture probes remaining in the electrode and provided a quantitative measure for target DNA detection. The proposed strategy realized the highly sensitive detection of the target DNA with a detection limit of 26 aM (S/N = 3) at an electrode temperature of 40 °C during the digestion period, which was about two magnitudes lower than that at 24 °C.

Facile construction of nanocubic Mn3[Fe(CN)6]2@Pt based electrochemical DNA sensors for ultrafast precise determination of SARS-CoV-2

Owing to the high mortality and strong infection ability of COVID-19, the early rapid diagnosis is essential to reduce the risk of severe symptoms and the loss of lung function. In clinic, the commonly used detection methods, including the computed tomography (CT) and reverse transcription-polymerase chain reaction (RT-PCR), are often time-consuming with bulky instruments, which normally require more than one hour to report the results. To shorten the analytical period for testing the COVID-19 virus (SARS-CoV-2), we proposed an ultrafast and ultrasensitive DNA sensors to achieve an accurate determination of the DNA sequence by the RNA reverse transcription (rtDNA) of the SARS-CoV-2. A nanocubic architecture of the MnFe@Pt crystals was constructed to integrate both electrocatalysis and conductivity to greatly improve the biosensing performance. After the immobilization of a specific capture and report DNA on above nanocomposite, the rtDNA can be rapidly caught to the DNA sensor to form a double-helix structure, thus generating the current signal change. Within only 10 min, the as-prepared DNA sensors exhibited ultralow detection limit (1 × 10−20 M) and wide linear detection range, together with an outstanding selectivity among various interfering substances.

Nanofilm-enhanced electrochemical DNA sensing: a breakthrough for yellow rust detection in wheat

This study showcases the development of a genosensor utilizing a nanoscale NiO thin film. The genosensor is constructed on a glass substrate coated with tin-doped indium oxide (ITO) and is designed for the specific detection of DNA sequences associated with Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat yellow rust. The detection process relies on the utilization of methylene blue (MB) as an electrochemical indicator, with NiO acting as the matrix and the electrochemical measurement system serving as the transducer. Various single-stranded DNA oligonucleotide sequences related to Pst pathogenesis are employed as probes to enable sensing. The electrochemical response of the nanoscale bioelectrode is characterized and studied using two distinct electrochemical techniques, cyclic voltammetry (CV) and differential pulse voltammetry (DPV), in conjunction with a potentiostat. The detection ranges spans from 40 pg μl−1 to 115 ng μl−1, demonstrating a linear correlation with exceptional precision. The absence of DNA-based biosensors for the detection of Puccinia striiformis f. sp. tritici (Pst) has prompted the need for a new method to address the limitations associated with previously reported technologies. Although surface plasmon resonance (SPR) immunoassays have been reported for Pst detection, the development of DNA-based biosensors specifically tailored for Pst detection remains unexplored. Introducing a novel method aims to overcome the challenges and shortcomings of existing techniques, providing a new approach to detect and combat the devastating effects of Pst on wheat crops. By leveraging the advantages of DNA-based biosensors, such as their sensitive and precise detection capabilities, this new method seeks to enhance the accuracy and efficiency of Pst detection, ultimately contributing to the development of effective strategies for disease management and crop protection. The developed nanoscale electrochemical DNA sensor offers outstanding sensitivity, extended shelf life, and reliable recovery, effectively minimizing the likelihood of obtaining erroneous results. A significant highlight of this study is the first-time utilization of conserved sequences associated with pathogenesis in selected Pst strains for the development of a nanoscale genosensor.

Electrochemical DNA Sensor for Valrubicin Detection Based on Poly(Azure C) Films Deposited from Deep Eutectic Solvent.

A novel electrochemical DNA sensor was developed for the detection of the anthracycline drug, valrubicin, on the base of poly(Azure C) electropolymerized from the deep eutectic solvent reline and covered with adsorbed DNA from calf thymus. Biosensor assembling was performed by multiple scanning of the potential in one drop (100 µL) of the dye dissolved in reline and placed on the surface of a screen-printed carbon electrode. Stabilization of the coating was achieved by its polarization in the phosphate buffer. The electrochemical characteristics of the electron transfer were determined and compared with a similar coating obtained from phosphate buffer. The use of deep eutectic solvent made it possible to increase the monomer concentration and avoid using organic solvents on the stage of electrode modification. After the contact of the DNA sensor with valrubicin, two signals related to the intrinsic redox activity of the coating and the drug redox conversion were found on voltammogram. Their synchronous changes with the analyte concentration increased the reliability of the detection. In the square-wave mode, the DNA sensor made it possible to determine from 3 µM to 1 mM (limit of detection, 1 µM) in optimal conditions. The DNA sensor was successfully tested in the voltammetric determination of valrubicin in spiked artificial urine, Ringer-Locke solution mimicking plasma electrolytes and biological samples (urine and saliva) with a recovery of 90-110%. After further testing on clinical samples, it can find application in the pharmacokinetics studies and screening of new drugs' interaction with DNA.

Introducing common oxazine fluorophores as new redox labels for electrochemical DNA sensors

The electrochemical properties of three oxazine fluorophores, ATTO655, ATTO680 and ATTO700 have been investigated at gold electrodes. They display a reversible or quasi-reversible voltammetric behaviour involving either a 2e−, 2H+ or a 2e−, 1H+ redox process depending on the pH, at a formal potential located in the stability range of thiolate self-assembled monolayers (E°' ≈ −0.33 V vs. Ag|AgCl|3M KCl at pH 7.2). The performance of ATTO655 as redox label for electrochemical nucleic acid sensing was evaluated in a typical E-DNA configuration. The redox label has no detrimental impact on the folding of DNA, as shown with the i-motif forming sequence investigated here. An electron transfer rate constant around 40 s−1 was determined, which is comparable to the values reported for the popular methylene blue label. Hybridisation experiments show a significant signal variation between ssDNA and dsDNA, though it is emphasised that the sign and amplitude of the variation are highly dependent on the electrochemical parameters such as the frequency in square wave voltammetry.

Electrochemical DNA Sensor Designed Using the Pencil Graphite Electrode to Detect Listeria monocytogenes.

In the present work, a novel electrochemical DNA sensor was designed to detect L. monocytogenes. Two different gene fragments were selected for the sensor design. One is a 702bp long fragment of the hlyA gene, encoding the synthesis of listeriolysin O toxin, which is unique only to pathogenic strains of L. monocytogenes and is essential for pathogenicity. The other is a 209bp long fragment of the 16S RNA gene found in all species of the Listeria genus. As the working electrode, the pencil graphite electrode was modified in various ways (activated or covered with polypyrrole), and six different combinations were constituted using three types of the modified working electrode and two different gene fragments. The developed system is based on differential pulse voltammetric transduction of guanine oxidation after hybridization between the selected gene fragment (38µg/mL) and the selected fragment-specific inosine-modified probe (1.8 µmol/L) immobilized on a pencil graphite electrode surface. The comparison of all combinations demonstrates that the best results are obtained with the combination formed from a polypyrrole-coated pencil graphite electrode (prepared at 2 scans) and 702bp fragment of the hlyA gene. The analysis time is less than 1 hour, and the necessary DNA concentrations for the analysis have been determined as 8.2 × 10-11M DNA and 2.7 × 10-10M DNA respectively, for the hlyA gene and 16S RNA gene.

Triplex DNA Helix Sensor Based on Reduced Graphene Oxide and Electrodeposited Gold Nanoparticles for Sensitive Lead(II) Detection.

A triplex DNA electrochemical sensor based on reduced graphene oxide (rGO) and electrodeposited gold nanoparticles (EAu) was simply fabricated for Pb2+ detection. The glass carbon electrode (GCE) sequentially electrodeposited with rGO and EAu was further modified with a triplex DNA helix that consisted of a guanine (G)-rich circle and a stem of triplex helix based on T-A•T base triplets. With the existence of Pb2+, the DNA configuration which was formed via the Watson-Crick and Hoogsteen base pairings was split and transformed into a G-quadruplex. An adequate electrochemical response signal was provided by the signal indicator methylene blue (MB). The proposed sensor demonstrated a linear relationship between the differential pulse voltammetry (DPV) peak currents and the logarithm of Pb2+ concentrations from 0.01 to 100.00 μM with a detection limit of 0.36 nM. The proposed sensor was also tested with tap water, river and medical wastewater samples with qualified recovery and accuracy and represented a promising method for Pb2+ detection.

Precise Differentiation of Wobble-Type Allele via Ratiometric Design of a Ligase Chain Reaction-Based Electrochemical Biosensor for CYP2C19*2 Genotyping of Clinical Samples.

Due to the comparable stability between the perfect-base pair and the wobble-base pair, a precise differentiation of the wobble-type allele has remained a challenge, often leading to false results. Herein, we proposed a ligase chain reaction (LCR)-based ratiometric electrochemical DNA sensor, namely, R-eLCR, for a precise typing of the wobble-type allele, in which the traditionally recognized "negative" signal of wobble-base pair-mediated amplification was fully utilized as a "positive" one and a ratiometric readout mode was employed to ameliorated the underlying potential external influence and improved its detection accuracy in the typing of the wobble-type allele. The results showed that the ratio between current of methylene blue (IMB) and current of ferrocene (IFc) was partitioned in three regions and three types of wobble-type allele were thus precisely differentiated (AA homozygote: IMB/IFc > 2; GG homozygote: IMB/IFc < 1; GA heterozygote: 1 < IMB/IFc < 2); the proposed R-eLCR successfully discriminated the three types of CYP2C19*2 allele in nine cases of human whole blood samples, which was consistent with those of the sequencing method. These results evidence that the proposed R-eLCR can serve as an accurate and robust alternative for the identification of wobble-type allele, which lays a solid foundation and holds great potential for precision medicine.

Voltammetric Sensor for Doxorubicin Determination Based on Self-Assembled DNA-Polyphenothiazine Composite.

A novel voltammetric sensor based on a self-assembled composite formed by native DNA and electropolymerized N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine has been developed and applied for sensitive determination of doxorubicin, an anthracycline drug applied for cancer therapy. For this purpose, a monomeric phenothiazine derivative has been deposited on the glassy carbon electrode from the 0.4 M H2SO4-acetone mixture (1:1 v/v) by multiple potential cycling. The DNA aliquot was either on the electrode modified with electropolymerized film or added to the reaction medium prior to electropolymerization. The DNA entrapment and its influence on the redox behavior of the underlying layer were studied by scanning electron microscopy and electrochemical impedance spectroscopy. The DNA-doxorubicin interactions affected the charge distribution in the surface layer and, hence, altered the redox equilibrium of the polyphenothiazine coating. The voltametric signal was successfully applied for the determination of doxorubicin in the concentration range from 10 pM to 0.2 mM (limit of detection 5 pM). The DNA sensor was tested on spiked artificial plasma samples and two commercial medications (recovery of 90-95%). After further testing on real clinical samples, the electrochemical DNA sensor developed can find application in monitoring drug release and screening new antitumor drugs able to intercalate DNA.

Multi-Walled Carbon Nanotube Array Modified Electrode with 3D Sensing Interface as Electrochemical DNA Biosensor for Multidrug-Resistant Gene Detection.

Drug resistance in cancer is associated with overexpression of the multidrug resistance (MDR1) gene, leading to the failure of cancer chemotherapy treatment. Therefore, the establishment of an effective method for the detection of the MDR1 gene is extremely crucial in cancer clinical therapy. Here, we report a novel DNA biosensor based on an aligned multi-walled carbon nanotube (MWCNT) array modified electrode with 3D nanostructure for the determination of the MDR1 gene. The microstructure of the modified electrode was observed by an atomic force microscope (AFM), which demonstrated that the electrode interface was arranged in orderly needle-shaped protrusion arrays. The electrochemical properties of the biosensor were characterized by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Chronocoulometry (CC) was used for the quantitative detection of the MDR1 gene. Taking advantage of the good conductivity and large electrode area of the MWCNT arrays, this electrochemical DNA sensor achieved a dynamic range from 1.0 × 10-12 M to 1.0 × 10-8 M with a minimal detection limit of 6.4 × 10-13 M. In addition, this proposed DNA biosensor exhibited high sensitivity, selectivity, and stability, which may be useful for the trace analysis of the MDR1 gene in complex samples.

Electrochemical DNA Sensor for adh 1 Gene Sequence from Corn Endogenous with Carbon Microsphere Modified Electrode

Electrochemical DNA Sensor for adh 1 Gene Sequence from Corn Endogenous with Carbon Microsphere Modified Electrode

A graphitic nano-onion/molybdenum disulfide nanosheet composite as a platform for HPV-associated cancer-detecting DNA biosensors

An electrochemical DNA sensor that can detect human papillomavirus (HPV)-16 and HPV-18 for the early diagnosis of cervical cancer was developed by using a graphitic nano-onion/molybdenum disulfide (MoS2) nanosheet composite. The electrode surface for probing DNA chemisorption was prepared via chemical conjugation between acyl bonds on the surfaces of functionalized nanoonions and the amine groups on functionalized MoS2 nanosheets. The cyclic voltammetry profile of an 1:1 nanoonion/MoS2 nanosheet composite electrode had an improved rectangular shape compared to that of an MoS2 nanosheet elecrode, thereby indicating the amorphous nature of the nano-onions with sp2 distancing curved carbon layers that provide enhanced electronic conductivity, compared to MoS2 nanosheet only. The nanoonion/MoS2 sensor for the DNA detection of HPV-16 and HPV-18, respectively, was measured at high sensitivity through differential pulse voltammetry (DPV) in the presence of methylene blue (MB) as a redox indicator. The DPV current peak was lowered after probe DNA chemisorption and target DNA hybridization because the hybridized DNA induced less effective MB electrostatic intercalation due to it being double-stranded, resulting in a lower oxidation peak. The nanoonion/MoS2 nanosheet composite electrodes attained higher current peaks than the MoS2 nanosheet electrode, thereby indicating a greater change in the differential peak probably because the nanoonions enhanced conductive electron transfer. Notably, both of the target DNAs produced from HPV-18 and HPV-16 Siha and Hela cancer cell lines were effectively detected with high specificity. The conductivity of MoS2 improved by complexation with nano-onions provides a suitable platform for electrochemical biosensors for the early diagnosis of many ailments in humans.Graphical

Electrochemical DNA-Sensor Based on Macrocyclic Dendrimers with Terminal Amino Groups and Carbon Nanomaterials.

The assembling of thiacalix[4]arene-based dendrimers in cone, partial cone, and 1,3-alternate configuration on the surface of a glassy carbon electrode coated with carbon black or multiwalled carbon nanotubes has been characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Native and damaged DNA were electrostatically accumulated on the modifier layer. The influence of the charge of the redox indicator and of the macrocycle/DNA ratio was quantified and the roles of the electrostatic interactions and of the diffusional transfer of the redox indicator to the electrode interface indicator access were established. The developed DNA sensors were tested on discrimination of native, thermally denatured, and chemically damaged DNA and on the determination of doxorubicin as the model intercalator. The limit of detection of doxorubicin established for the biosensor based on multi-walled carbon nanotubes was equal to 1.0 pM with recovery from spiked human serum of 105-120%. After further optimization of the assembling directed towards the stabilization of the signal, the developed DNA sensors can find application in the preliminary screening of antitumor drugs and thermal damage of DNA. They can also be applied for testing potential drug/DNA nanocontainers as future delivery systems.