Guanine Signal Research Articles

Electrochemical DNA nano-biosensor for the detection of genotoxins in water samples

In the present study, a disposable electrochemical DNA nano-biosensor is proposed for the rapid detection of genotoxic compounds and bio-analysis of water pollution. The DNA nano-biosensor is prepared by immobilizing DNA on Au nanoparticles and a self-assembled monolayer of cysteamine modified Au electrode. The assembly processes of cysteamine, Au nanoparticles and DNA were characterized by cyclic voltammetry (CV). The Au nanoparticles enhanced DNA immobilization resulting in an increased guanine signal. The interaction of the analyte with the immobilized DNA was measured through the variation of the electrochemical signal of guanine by square wave voltammetry (SWV). The biosensor was able to detect the known genotoxic compounds: 2-anthramine, acridine orange and 2-naphthylamine with detection limits of 2, 3 and 50 nmol/L, respectively. The biosensor was also used to test actual water samples to evaluate the contamination level. Additionally, the comparison of results from the classical genotoxicity bioassay has confirmed the applicability of the method for real samples.

Carbon nanotube-based label-free electrochemical biosensor for sensitive detection of miRNA-24

The recent findings concerning the function of microRNAs (miRNAs) and the relationship between miRNA levels with specific disease highlight the need for miRNA detection. In this work, multi-walled carbon nanotubes (MWCNTs), having shown great potential for biosensors, were used to develop a simple, label-free, and sensitive electrochemical biosensor for detection of miRNA-24 by monitoring the oxidation signal of guanine. The synthetic DNA probes, being complementary with miRNA-24, were immobilized onto the surface of MWCNT-modified glass carbon electrodes by covalent cross-linking. The probes were hybridized with different concentrations of miRNA-24. The formed hybrids on the electrode surface were evaluated by differential pulse voltammetry. The change of guanine oxidation signal was observed as a result of the hybridization between the probes and miRNA-24. Control experiments using the non-complementary miRNA-29 were performed to evaluate the selectivity. Numerous factors affecting probe immobilization, target hybridization, and nonspecific binding events were optimized. Under the optimal conditions, the proposed miRNA-24 biosensor exhibits good sensitivity (4.963μAcm−2decade−1), low detection limit (1pM), and good selectivity and reproducibility. The biosensor also has acceptable recovery for miRNA-24 detection in complex miRNA sample.

Use of Cationic Surfactants Film Carbon Paste Electrodes Modified with Multiwalled Carbon Nanotubes in Electrochemical Analysis of dsDNA

AbstractDirect electrochemistry of dsDNA based on the enhancement effect of cationic surfactants such as dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB) was achieved by using a carbon paste electrode modified with multiwalled carbon nanotubes (MWCNTs/CPE) as the basal electrode. The results indicated that the dsDNA molecules have been adsorbed quite strongly on the cationic surfactants’ film and very well developed peaks which were attributed to the oxidation of guanine residues on the dsDNA molecule structure were obtained from both electrodes. The electrochemical behavior of dsDNA at the surface of the modified electrodes was also evaluated. Based on the signal of guanine, under the optimal conditions, very low levels of dsDNA were detected following short accumulation times with detection limits of 0.650 mg L−1 and 0.119 mg L−1 for DTAB/MWCNTs/CPE and TTAB/MWCNTs/CPE, respectively.

Graphene and CdS nanocomposite: A facile interface for construction of DNA-based electrochemical biosensor and its application to the determination of phenformin

Graphene/cadmium sulphide (GR-CdS) nanocomposite was synthesized via a low temperature process in aqueous solution. The as-prepared nanocomposite was characterized by scanning electron microscopy, UV–visible spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The impedance analysis indicated that GR-CdS nanocomposite possessed outstanding electrochemical performance for facile electron transfer. When DNA was immobilized on GR-CdS (DNA/GR-CdS) modified electrode, the electrochemical oxidation of guanine and adenine in DNA residue bases was significantly promoted. Due to the interaction of DNA with phenformin, the voltammetric current of guanine or adenine on the DNA/GR-CdS electrode was decreased when phenformin was present in the electrolytic solution. Under optimized conditions, the signal of guanine on DNA/GR-CdS electrode decreased linearly with increasing the concentration of phenformin in the range of 1.0×10−6molL−1 to 1.0×10−3molL−1. The proposed DNA-based electrochemical biosensor was successfully applied to the determination of phenformin in real samples.

Electrochemical study of dsDNA on carbon nanotubes paste electrodes applying cyclic and differential pulse voltammetry

Abstract Abstract Carbon nanotubes paste electrodes (CNTPEs) in combination with adsorptive transfer stripping voltammetry are shown to be very suitable for the determination of calf thymus double-stranded DNA (dsDNA). The performance of three types of multi-walled carbon nanotubes paste electrodes (MWCNTPEs) is investigated. The effects of surface pre-treatment and accumulation conditions on the adsorption and electrooxidation of the dsDNA at MWCNTPEs are also described. The results indicate that the electroactivity inherent to carbon nanotubes/paste electrodes allows a large enhancement of the guanine oxidation signal compared to that obtained at the conventional carbon paste electrodes (CPEs). Moreover, the extent of the enhancement dependents on the type of MWCNTs incorporated into the paste. Based on the signal of guanine, under optimal conditions, very low levels of dsDNA can be detected following short accumulation times for all three types of MWCNTPEs (MWCNTPE1, MWCNTPE2, MWCNTPE3), with detection limits of 2.64 mg L−1, 2.02 mg L−1 and 1.46 mg L−1, respectively. Additionally, the dsDNA isolated from rat liver tissues is determined by use of the previously mentioned MWCNTPEs. Graphical abstract

DNA-functionalized electrochemical biosensor for detection of vitamin B1 using electrochemically treated multiwalled carbon nanotube paste electrode by voltammetric methods

A simple methodology was used to develop a novel electrochemical biosensor for the determination of vitamin B1. The interaction of vitamin B1 with DNA based on the decreasing of the oxidation signal of guanine and adenine bases was studied electrochemically with a pretreated multiwalled carbon nanotube paste electrode (PMWCNTPE) using differential pulse voltammetry. The decrease in the intensity of the guanine and adenine oxidation signals after interaction with vitamin B1 was used as an indicator signals for the sensitive determination of vitamin B1. Under the optimum conditions, a linear dependence of the guanine and adenine oxidation signals was observed for the vitamin B1 concentration in the range of 1.0–80 μg mL −1 with a detection limit of 0.44 μg mL −1 at ds-DNA modified PMWCNTPE. The reproducibility and applicability of the analysis to serum, plasma and urine sample were also investigated. Vitamin B1 was also determined on a pretreated multiwalled carbon nanotube paste electrode by means of adsorptive stripping differential pulse voltammetry. The peak current was linearly dependent on Vitamin B1 concentration over the range of 0.0025–0.80 μg mL −1 , with a detection limit of 1.1 ng mL −1 Vitamin B1. Both ds-DNA-modified MWCNPTE and PMWCNTPE were applied to analyze Vitamin B1 in real samples.

Graphene oxide integrated sensor for electrochemical monitoring of mitomycin C–DNA interaction

We present a graphene oxide (GO) integrated disposable electrochemical sensor for the enhanced detection of nucleic acids and the sensitive monitoring of the surface-confined interactions between the anticancer drug mitomycin C (MC) and DNA. Interfacial interactions between immobilized calf thymus double-stranded (dsDNA) and anticancer drug MC were investigated using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) techniques. Based on three repetitive voltammetric measurements of 120 μg mL(-1) DNA immobilized on GO-modified electrodes, the RSD % (n = 3) was calculated as 10.47% and the detection limit (DL) for dsDNA was found to be 9.06 μg mL(-1). EIS studies revealed that the binding of the drug MC to dsDNA leads to a gradual decrease of its negative charge. As a consequence of this interaction, the negative redox species were allowed to approach the electrode, and thus increase the charge transfer kinetics. On the other hand, DPV studies exploited the decrease of the guanine signal due to drug binding as the basis for specifically probing the biointeraction process between MC and dsDNA.

A novel sensitive DNA–biosensor for detection of a carcinogen, Sudan II, using electrochemically treated pencil graphite electrode by voltammetric methods

A simple and inexpensive methodology was used to develop a novel electrochemical sensor for the determination of Sudan II. The interaction of Sudan II with salmon sperm ds-DNA on the surface of salmon sperm ds-DNA-modified pencil graphite electrode (PGE) and in solution phase was studied, using differential pulse voltammetry. The difference between adenine and guanine signals of the ds-DNA after and before interaction with Sudan II was directly proportional to Sudan II concentration, which used for quantitative inspections. Using PGE, a linear calibration curve (R2=0.9958) was observed with 0.5–6.0μgmL−1 Sudan II. Furthermore, the LOD of 0.4μgmL−1 and linear range between 0.5 and 4.0μgmL−1 were achieved in solution phase. In the second part, Sudan II was determined on a pretreated pencil graphite electrode by means of adsorptive stripping differential pulse voltammetry. The peak current was linearly dependent on Sudan II concentration over the range of 0.0015–0.30μgmL−1, with a detection limit of 0.00007μgmL−1 Sudan II. Both ds-DNA-modified PGE and PPGE were applied to analyze Sudan II in real samples.

DNA-functionalized biosensor for riboflavin based electrochemical interaction on pretreated pencil graphite electrode

The interaction of riboflavin with salmon sperm double-stranded DNA based on the decreasing of the oxidation signal of guanine and adenine bases was studied electrochemically with a pencil graphite electrode (PGE) using differential pulse voltammetry. The decrease in the intensity of the guanine and adenine oxidation signals after interaction with riboflavin was used as an indicator signals for the sensitive determination of riboflavin. Under the optimum conditions, a linear dependence of the guanine and adenine oxidation signals was observed for the riboflavin concentration in the range of 0.5–70μgmL−1 with a detection limit of 0.34μgmL−1 at ds-DNA modified PGE. The reproducibility and applicability of the analysis to pharmaceutical dosage forms and urine sample were also investigated. These results showed that this DNA biosensor could be used for the sensitive, rapid, simple and cost effective detection and determination of riboflavin-ds-DNA interaction. Pretreated pencil graphite electrode (PPGE) was also used for the determination of riboflavin by differential pulse adsorptive stripping voltammetry. With PPGE, a linear relationship was obtained for riboflavin over the concentration range of 0.003–0.88μgmL−1 with differential pulse adsorptive stripping voltammetric signal and with a detection limit of 0.076ngmL−1. Both determination methods were fully validated and applied for the analysis of riboflavin.

Electrochemical detection of DNA damage induced by acrylamide and its metabolite at the graphene-ionic liquid-Nafion modified pyrolytic graphite electrode

A new electrochemical biosensor for directly detecting DNA damage induced by acrylamide (AA) and its metabolite was presented in this work. The graphene-ionic liquid-Nafion modified pyrolytic graphite electrode (PGE) was prepared, and then horseradish peroxidase (HRP) and natural double-stranded DNA were alternately assembled on the modified electrode by the layer-by-layer method. The PGE/graphene-ionic liquid-Nafion and the construction of the (HRP/DNA) n film were characterized by electrochemical impedance spectroscopy. With the guanine signal in DNA as an indicator, the damage of DNA was detected by differential pulse voltammetry after PGE/graphene-ionic liquid-Nafion/(HRP/DNA) n was incubated in AA solution or AA + H 2O 2 solution at 37 °C. This method provides a new model to mimic and directly detect DNA damage induced by chemical pollutants and their metabolites in vitro. The results indicated that, in the presence of H 2O 2, HRP was activated and catalyzed the transformation of AA to glycidamide, which could form DNA adducts and induce more serious damage of DNA than AA. In order to further verify these results, UV–vis spectrophotometry was also used to investigate DNA damage induced by AA and its metabolites in solution and the similar results were obtained.

Early stage of nucleic acid electrochemistry. Detection of DNA damage in X-ray-irradiated rats

First papers on electroactivity of DNA and RNA were published more then 50 years ago. For about 8 years oscillographic polarography at controlled a.c. (OP, proposed by J. Heyrovský already in 1941) was the method of choice for DNA analysis. Since approximately 1954 Robert Kalvoda developed OP for wide application in various fields. It is shown that already before 1960 it was possible to detect damage to DNA in X-ray-irradiated rats by means of OP. DNA samples from irradiated animals produced significantly larger OP anodic guanine signal indicating changes in the DNA structure. At present, radiation-induced strand breaks and damage to bases in DNA can be electrochemically detected at high sensitivity.

Different DNA Immobilization Strategies for the Interaction of Anticancer Drug Irinotecan with DNA Based on Electrochemical DNA Biosensors

The interaction of anticancer drug irinotecan (CPT-11) which is the inhibitor of the Topoisomerase I enzyme, with fish sperm double stranded deoxyribonucleic acid (dsDNA) and synthetic short oligonucleotides were studied electrochemically based on the oxidation signals of guanine and CPT-11 by using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) at pencil graphite electrode (PGE). In this work, three types of methods such as adsorption, covalent attachment and electrostatic binding were used for the immobilization of DNA onto the PGE surface. It is found that an effective modification method for DNA on the electrode surface is very important because it shows an effect on the drug and DNA interaction. As a result of the interaction, the electrochemical signal of guanine and CPT-11 greatly decreased. Experimental parameters, such as the effect of buffer solution on the interaction between CPT-11 and DNA, the concentration of CPT-11/DNA, the immobilization time of DNA and the accumulation time of CPT-11 were studied in DPV; in addition, the interaction of CPT-11 with oligonucleotides was evaluated for use as a hybridization indicator in CV and DPV. The detection limit and the reproducibility were also determined.

The Comparison of Electrochemical Assay and Agarose Gel Electrophoresis for the Determination of DNA Damage Induced by Kainic Acid

AbstractA possible DNA damage after interaction of kainic acid (KA) with calf thymus double stranded DNA and genomic DNA was herein determined in in vitro and in vivo conditions using; electrochemical assay and agarose gel electrophoresis. The changes in guanine signal were detected as an indicator of DNA damage in genomic DNA samples isolated from 1 or 10 mg/kg KA‐treated animals. The decreased levels of guanine signal were found as 29% and 33% by 1 and 10 mg/kg KA treatment when compared to controls, respectively. The results of gel electrophoresis confirmed DNA damage obtained in identical samples by electrochemical method.

Direct DNA Hybridization on the Single‐Walled Carbon Nanotubes Modified Sensors Detected by Voltammetry and Electrochemical Impedance Spectroscopy

AbstractCarboxylic acid functionalized single‐walled carbon nanotubes modified graphite sensors (SWCNT‐PGEs) were developed for electrochemical monitoring of direct DNA hybridization related to specific sequence of Hepatitis B virus, which substantially enhance the electrochemical transduction resulting from guanine oxidation signal comparison to bare PGEs. The performance characteristics of DNA hybridization on disposable CNT‐PGE were explored measuring the guanine signal in terms of optimum analytical conditions; probe and target concentration, hybridization time, and selectivity. The voltammetric results were also complemented with electrochemical impedance spectroscopy (EIS), that was used to characterize the successful construction of carbon nanotubes modification onto the surface of PGEs.

Differential Pulse Voltammetric Detection of Hepatitis C Virus 1a Oligonucleotide Chain by a Label‐Free Electrochemical DNA Hybridization Biosensor Using Consensus Sequence of Hepatitis C Virus 1a Probe on the Pencil Graphite Electrode

AbstractThe short sequence related to hepatitis C virus (HCV1) is detected by a label‐free DNA hybridization biosensor. The sensor relies on the immobilization of a 20‐mer oligonucleotide containing 2 guanine and 11 cytosine bases denoted PHCV1 as probe on the pencil graphite electrode (PGE). The hybridization event was monitored by differential pulse voltammetry (DPV) using the guanine signal. The selectivity of the biosensor was studied using some noncomplementary oligonucleotides. Diagnostic performance of the biosensor is described and the detection limit was found to be 6.5 nM.

Voltammetric studies on the HIV-1 inhibitory drug Efavirenz: The interaction between dsDNA and drug using electrochemical DNA biosensor and adsorptive stripping voltammetric determination on disposable pencil graphite electrode

The interaction of Efavirenz (EFV) with fish sperm dsDNA immobilized onto pencil graphite electrode (PGE) has been studied by using differential pulse voltammetric technique using an electrochemical DNA biosensor. The guanine signal was lower with (double stranded-DNA) dsDNA-treated PGE than the untreated electrode after the interaction with EFV occurred. The changes in the experimental parameters such as the accumulation time and the concentration of EFV were also studied. All necessary parameters such as sensitivity, selectivity, accuracy and precision were calculated. In addition, the detection and determination limits, reproducibility and applicability of the analysis to pharmaceutical dosage forms were also investigated. These results showed that this DNA biosensor could be used for the sensitive, rapid simple and cost effective detection and determination of EFV–dsDNA interaction. The linearity was between 2 and 24ppm of EFV concentration on guanine signal decreasing curve.EFV showed an irreversible oxidation behavior at all investigated pH values. This oxidation step was adsorption controlled on PGE. Hence, differential pulse adsorptive stripping (AdsDPV) voltammetric method was developed for the determination of EFV. Accumulation time and potential were optimized. Under these conditions, the current showed a linear dependence with concentration in the range between 0.018 and 2.56ppm. Both determination methods were fully validated and applied for the analysis of EFV pharmaceutical dosage form.

Label-free electrochemical aptasensor for the detection of lysozyme

This work reports the advantages of a label free electrochemical aptasensor for the detection of lysozyme. The biorecognition platform was obtained by the adsorption of the aptamer on the surface of a carbon paste electrode (CPE) previously blocked with mouse immunoglobulin under controlled-potential conditions. The recognition event was detected from the decrease in the guanine and adenine electro-oxidation signals produced as a consequence of the molecular interaction between the aptamer and lysozyme. The biosensing platform demonstrated to be highly selective even in the presence of large excess (9-fold) of bovine serum albumin, cytochrome C and myoglobin. The reproducibility for 10 repetitive determinations of 10.0 mg L −1 lysozyme solution was 5.1% and 6.8% for guanine and adenine electro-oxidation signals, respectively. The detection limits of the aptasensor were 36.0 nmol L −1 (if considering guanine signal) and 18.0 nmol L −1 (if taking adenine oxidation current). This new sensing approach represents an interesting and promising alternative for the electrochemical quantification of lysozyme.

PCR-free electrochemical assay of telomerase activity

In this paper, we report a non-PCR-based electrochemical assay that can detect telomerase activity. Telomerase from HeLa cells may induce telomerization of thiolated primers immobilized on a gold electrode surface. With the telomerization reaction, more and more guanine-rich telomeric repeats are formed, so the electrochemical oxidation signal of guanine at about 1.00 V, which is utilized to indicate the elongated guanine-rich telomeric repeats tethered to the primers, will be increased. This assay method can detect the telomerase activity originated from 3000 HeLa cells and thus holds promise as a simple and sensitive approach in clinical diagnosis of cancer.

Design of Electrochemical Biosensor Systems for the Detection of Specific DNA Sequences in PCR-Amplified Nucleic Acids Related to the Catechol-O-methyltransferase Val108/158Met Polymorphism Based on Intrinsic Guanine Signal

Psychiatric disorders are common and complex diseases that show polygenic and multifactorial heredity. A single nucleotide polymorphism (Val108/158Met) in the catechol-O-methyl transferase (COMT) gene is related to many psychiatric disorders such as schizophrenia, alcoholism, bipolar disorder, and obsessive-compulsive disorder. Schizophrenia is a complex disorder and a single nucleotide polymorphism (Val108/158Met) at the COMT gene is related to schizophrenia susceptibility. A novel hybridization-based disposable electrochemical DNA biosensor for the detection of a common functional polymorphism in the COMT gene from polymerase chain reaction (PCR) amplicons has been described without using an external label. This developed technology combined with a disposable carbon graphite electrode and differential pulse voltammetry was performed by using short synthetic oligonucleotides and PCR amplicons in length 203 bp to measure the change of guanine oxidation signal obtained at approximately +1.0 V after DNA hybridization between probe and target (synthetic target or denatured PCR samples). COMT-specific oligonucleotides were immobilized onto the carbon surface with a simple adsorption method in two different modes: (a) Guanine-containing targets were attached or (b) inosine-substituted probes were attached onto an electrode. By controlling the surface coverage of the target DNA, the hybridization event between the probes and their synthetic targets or specific PCR products was optimized. The wild-type or polymorphic allele-specific probes/targets were also interacted with an equal amount of noncomplementary and one-base mismatch-containing DNAs in order to measure the sensor selectivity. The decrease or appearance in the intrinsic guanine signal simplified the detection procedure and shortened the assay time because protocol eliminates the label-binding step. The nonspecific binding effects were minimized by using sodium dodecyl sulfate with different washing methods. The Val108/158Met COMT genotype detection were performed with real samples containing wild-type (healthy controls), polymorphic (mutant type), and heterozygous PCR products. The detection limit (S/N = 3) of the biosensor was 2.44 pmol of target sequence in the 30-muL samples. Analytical performance of the sensor is described, along with future prospects.

Ultrasensitive label-free aptamer-based electronic detection.

Ultrasensitive label-free aptamer-based electronic detection.