Guanine Oxidation Peak Current Research Articles

Evaluation of antioxidant performance of economic crops by electrochemical sensors using guanine as a probe

The evaluation of antioxidant performance in economic crops is of significant importance due to their potential health benefits and increasing demand for functional foods. In this study, we developed an electrochemical sensor based on guanine binding technology to assess the antioxidant capacity of common economic crops, including tomatoes, blueberries, spinach, grapes, and oranges. The guanine oxidation peak current, measured using square wave voltammetry on a composite film-modified electrode (RGO/G/GCE), served as an indicator of antioxidant activity. Statistical analysis, including one-way analysis of variance (ANOVA) and post-hoc tests, revealed significant differences (p < 0.05) in the guanine oxidation peak currents among the tested crops, highlighting variations in their antioxidant activities. Blueberries exhibited the highest guanine oxidation peak current, indicating the strongest antioxidant capacity, followed by spinach and grapes with significant antioxidant activity. Tomatoes and oranges displayed relatively lower antioxidant capacity. The working/linear range for the electrochemical sensor was determined to be 0.5–4.0 mg/L of ascorbic acid (AA), and the limit of detection (LOD) was calculated as 0.35 mg/L. The proposed electrochemical sensor provides a rapid, sensitive, and cost-effective approach for assessing antioxidant capacity, offering potential applications in quality control, nutraceutical analysis, and functional food development.

Development of a new electrochemical DNA biosensor based on Eu3+−doped NiO for determination of amsacrine as an anti-cancer drug: Electrochemical, spectroscopic and docking studies

The present research reported a new electrochemical biosensor based on ds-DNA/Eu3+ doped NiO/CPE to detect amsacrine. Therefore, UV–Vis spectrophotometry, docking, and differential pulse voltammetry (DPV) have been used to study the interactions between amsacrine and dsDNA. Then, experimental parameters affected DNA immobilization and interactions between amsacrine and ds-DNA have been optimized. Afterwards, guanine oxidation peak current of ds-DNA has been chosen as a signal to analyze amsacrine in a concentration ranging between 0.1 and 100.0 μM and finally, limit of detection (LOD) of 0.05 μM has been calculated at optimal condition. Ultimately, it was found that the suggested biosensor is able to determine amsacrine in human serum and urine samples successfully.

Electrochemical antioxidant screening and evaluation based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE)

AbstractIn this study, an electrochemical biosensor based on guanine and chitosan immobilized MoS2 nanosheet modified glassy carbon electrode (guanine/CS/MoS2/GCE) was developed and employed for antioxidant screening and antioxidant capacity evaluation. The oxidation peak current of guanine was improved and nearly tripled after modifications of chitosan and MoS2 nanosheet. The immobilized guanine could be damaged by hydroxyl radicals generated in Fenton solution. However, in the presence of antioxidants, the guanine was protected and the oxidation peak current of guanine increased. This process mimics the mechanism of antioxidant protection in human body. The factors affecting preparation of sensor and detection of antioxidant capacity were optimized. At the optimum conditions, the guanine/CS/MoS2/GCE showed wide linear range, low detection limit, satisfactory reproducibility and stability for detection. Ascorbic acid was used as a model antioxidant to evaluate the antioxidant capacity. A good linearity was observed with a correlation coefficient of 0.9959 in the concentrations between 0.5 and 4.0 mg L-1. The antioxidant capacities of three flavonoids were also tested and the rank of antioxidant capacities was ascorbic acid (51.84%), quercetin (45.82%), fisetin (34.39%) and catechin (16.99%). Due to the rapid measurement and low cost, this sensor could provide an available sensing platform for antioxidant screening and evaluation.

Quantitative Biodetection of Anticancer Drug Rituxan with DNA Biosensor Modified PAMAM Dendrimer/Reduced Graphene Oxide Nanocomposite

AbstractPAMAM dendrimer/reduced graphene oxide nanocomposite modified pencil graphite electrode (PAMAM/RGO/PGE) was used to fabricate an electrochemical DNA biosensor for determination of Rituxan (RTX) at low concentrations, for the first time. The fabricated biosensor was characterized with FE‐SEM, EIS, and CV techniques. The ds‐DNA/PAMAM/RGO/PGE was used as a working electrode to study the interaction between the RTX and salmon sperm ds‐DNA by DPV technique. Because of the interaction between the drug and DNA leads to a decrease in the guanine oxidation peak current, it was used as an indicator for the determination of the RTX. Under the optimized experimental conditions, a wide linear relationship between RTX concentration and guanine signal was obtained within the range of 7.0 to 60.0 μmol L−1 and 60.0 to 300.0 μmol L−1 with a low detection limit (0.56 μmol L−1). To clarify the interaction mechanism between the RTX and the ds‐DNA, DPV and UV‐Vis measurements were used. The reproducibility, stability, and performance of the constructed biosensor was examined by quantitative measuring RTX in pharmaceutical and human serum samples with good precision (RSD; 2.0–6.0 %) and acceptable recoveries (100.04–101.95 %).

A sensitive electrochemical DNA biosensor for antineoplastic drug 5-fluorouracil based on glassy carbon electrode modified with poly(bromocresol purple)

This paper describes an electrochemical sensor for the first time based on poly(bromocresol purple) (P(BCP)) developed to observe the interaction between 5-fluorouracil (5-FU) and fish sperm double strand DNA (dsDNA). The P(BCP) film was electrosynthesized by cyclic voltammetry method on the glassy carbon electrode (GCE). The dsDNA was electrochemically immobilized on the surface of P(BCP) modified GCE and the DNA biosensor was prepared. The interaction mechanism of dsDNA with 5-FU was investigated by differential pulse voltammetry using this biosensor. A decrease in the guanine oxidation peak current of the biosensor was observed after the interaction of dsDNA and 5-FU in 0.5molL−1 acetate buffer (pH 4.8) containing 0.02molL−1 NaCl. The accumulation time and dsDNA concentration were optimized to obtain the best peak current response. Under optimum conditions, the linear response on the guanine signal decreasing curve was observed in the 5-FU concentration range of 1.0–50mgL−1. The interaction mechanism between dsDNA and 5-FU was further investigated by UV–vis spectroscopy and viscometer. The results reveal that intercalation is the primary mode of interaction between 5-FU and dsDNA.

Simultaneous determination of guanine and adenine on CuO shuttle-like nanocrystals/poly(neutral red) film on glassy carbon electrode

CuO shuttle-like nanocrystals on a poly(neutral red) glassy carbon electrode (nano-CuO/PNR/GCE) has been fabricated and used to simultaneously detect guanine and adenine. The sample is characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). It has been shown that the oxidation peak current of guanine and adenine could be greatly enhanced with the nano-CuO/PNR/GCE. Under optimal conditions, the anodic peak current of differential pulse voltammetry is proportional to the concentration of the guanine and adenine in the range of 0.05 to 3.0 μM. The corresponding detection limits are 1.6 × 10−2 μM for guanine and 2.3 × 10−2 μM for adenine (S/N = 3). The nano-CuO/PNR/GCE exhibits good storage stability and reproducibility for practical application. It could be applied to simultaneously determination of guanine and adenine for the samples with good anti-interference ability.

An electrochemical sensor based on polyaniline for monitoring hydroquinone and its damage on DNA

A dsDNA/PANI/CTS/GCE biosensor was constructed by using the biocompatible chitosan (CTS) and the polyaniline (PANI) with excellent electric catalytic properties and large specific surface areas. The electrochemical behavior of hydroquinone on biosensor and its DNA-damaging mechanisms were investigated. Results showed that the redox peak current was remarkably increased after glassy carbon electrode (GCE) was modified by PANI/CTS. The dsDNA damage by hydroquinone was concentration dependent, and increased along with the increase of hydroquinone oxidation peak current and the reduction of dsDNA guanine oxidation peak current. The linear detection range of hydroquinone with dsDNA/PANI/CTS/GCE was 1.25×10−6–3.2×10−4M, and the detection limit was 9.65×10−7M. It was confirmed by the UV method that applying dsDNA/PANI/CTS/GCE to monitor hydroquinone was accurate and reliable. In addition, it could be deduced that the mode of interaction between the hydroquinone and dsDNA was intercalation. The electrochemical oxidation of hydroquinone on the dsDNA/PANI/CTS/GCE electrode was an adsorption-controlled irreversible and a two-electron two-proton transfer process.

A novel electrochemical DNA biosensor based on poly-(5-amino-2-mercapto-1,3,4-thiadiazole) modified glassy carbon electrode for the determination of nitrofurantoin

In this study, poly(5-amino-2-mercapto-1,3,4-thiadiazole) (PAMT) modified glassy carbon electrode (GCE) was fabricated and this electrode was used for the electrochemical monitoring of interaction between the dsDNA and nitrofurantoin (NFT) for the first time. Electrochemical behavior of PAMT modified GCE (GCE/PAMT) was investigated by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and compared with those of the bare GCE. The GCE/PAMT/dsDNA electrode was prepared by adsorption of dsDNA upon the PAMT deposited the GCE and the binding of NFT with dsDNA was investigated via differential pulse voltammetry (DPV) method. The decrease in the guanine oxidation peak current at +0.82V was used as an indicator for the interaction in 0.5molL−1 acetate buffer (pH 4.8) containing 0.02molL−1 NaCl. Under the optimal conditions, the guanine oxidation peak currents were linearly proportional to the concentrations of NFT in the range of 2–25mgL−1 and detection limit was found to be 0.65mgL−1. Furthermore, the reproducibility, repeatability, stability and applicability of the analysis to pharmaceutical dosage forms in human serum samples were also examined. These results showed that this DNA biosensor could be used for the sensitive, accurate and precise determination of NFT–dsDNA interaction.

Electrochemical Study of the Interaction Between the Antibacterial Drug Gemifloxacin and dsDNA Using Pencil Graphite Electrode

Gemifloxacin (GMF) is a broad-spectrum quinolone antibacterial agent used in the treatment of acute bacterial exacerbation of chronic bronchitis and mild-to-moderate pneumonia. The investigation of the GMF - double-stranded DNA (dsDNA) interaction using an electrochemical DNA-biosensor, showed for the first time clear evidence of interaction with dsDNA. The interaction between GMF and dsDNA onto pencil graphite electrode (PGE) was assessed at pH 4.80 acetate buffer using differential pulse voltammetry (DPV). The interaction mechanism was disclosed with the decrease of the guanine oxidation peak current. The changes in the experimental parameters such as the accumulation time and the concentration of GMF were studied. Linearity of the guanine oxidation signals was obtained in response to the range of 0.5 – 8.0 μg/mL GMF. Detection and quantification limits in the range of μg/mL were determined. Keywords: Biosensor, dsDNA, Voltammetry, Guanine, Gemifloxacin.

Study of interactions between DNA and aflatoxin B1 using electrochemical and fluorescence methods

In this study, a carbon paste electrode modified with N-butylpyridinium hexafluorophosphate (BPPF6) ionic liquid and DNA was introduced as an electrochemical biosensor to study the interaction between DNA and aflatoxin B1 molecules. For this purpose, variations in oxidation peak current of guanine in various concentrations of aflatoxin B1 were measured by using the differential pulse voltammetry (DPV) method. According to this study, the binding constant of DNA–aflatoxin B1 was found to be 3.5×106M−1. This modified electrode was also used for determination of low concentrations of aflatoxin B1 by using differential pulse voltammetry. A linear dynamic range from 8.00×10−8 to 5.91×10−7M and a limit of detection of 2.00×10−8M resulted from DPV measurements. To confirm our results, a fluorescence study was also performed. It resulted in a binding constant of 2.8×106M−1, which is in good agreement with that obtained from electrochemical study.

A novel sensitive electrochemical DNA biosensor for assaying of anticancer drug leuprolide and its adsorptive stripping voltammetric determination

The anticancer drug, leuprolide (LPR) bound to double-stranded fish sperm DNA (dsDNA) which was immobilized onto the surface of an anodically activated pencil graphite electrode (PGE), was employed for designing a sensitive biosensor. The interaction of leuprolide (LPR) with double-stranded DNA (dsDNA) immobilized onto pencil graphite electrode (PGE) have been studied by electrochemical methods. The mechanism of the interaction was investigated and confirmed by differential pulse voltammetry using two different interaction methods; at the PGE surface and in the solution phase. The decrease in the guanine oxidation peak current was used as an indicator for the interaction in acetate buffer at pH 4.80. The response was optimized with respect to accumulation time, potential, drug concentration, and reproducibility for both interaction methods. The linear response was obtained in the range of 0.20–6.00 ppm LPR concentration with a detection limit of 0.06 ppm on DNA modified PGE and between 0.20 and 1.00 ppm concentration range with detection limit of 0.04 ppm for interaction in solution phase method. LPR showed an irreversible oxidation behavior at all investigated pH values on a bare PGE. Differential pulse adsorptive stripping (AdSDPV) voltammetric method was developed for the determination of LPR. Under these conditions, the current showed a linear dependence with concentration within a range of 0.005–0.20 ppm with a detection limit of 0.0014 ppm. Each determination method was fully validated and applied for the analysis of LPR in its pharmaceutical dosage form.

Distinguishing Tumor Cells via Analyzing Intracellular Telomerase Activity

Two strategies to identify tumor cells were developed in this research via analyzing the activity of telomerase inside the cells, which is regarded as the mark enzyme of tumors. The lysate of cells was used to assay directly. In the electrochemical assay, the substrate of telomerase was incubated with the lysate, followed by PCR amplification of the elongated products. Then the oxidation peak current of guanine that existed in the hydrolyte of PCR products was used as a target to identify tumor cells. In the spectral assay, the lysate of cells was used to catalyze the elongation of the substrate of telomerase modified on the surface of gold nanoparticles. Due to the formation of G-quadruple structures after elongation and subsequent aggregation of gold nanoparticles, the changes in UV-visible spectra can also be utilized to identify tumor cells.

Electrochemical DNA nano-biosensor for the study of spermidine–DNA interaction

An electrochemical DNA nano-biosensor is prepared by immobilization of double stranded DNA (dsDNA) onto a mixed self-assembled monolayer (SAM) composed of azide- and hydroxyl-terminated thiols. The SAMs- and dsDNA-modified gold electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The interaction of spermidine with DNA was studied by differential pulse voltammetry at the DNA-modified electrode. The decrease in the guanine oxidation peak current was used to study the interaction. The binding constant (K), obtained by differential pulse voltammetry, was 1.85×105M−1. A linear dependence of the guanine peak currents was observed in the range of 1.6–70.4μM spermidine, with a detection limit of 0.72μM and r=0.994 by using differential pulse voltammetry.

Electrochemical studies of DNA immobilization onto the azide-terminated monolayers and its interaction with taxol

A surface modification procedure for the creation of self-assembled monolayers (SAMs) that can be used as a scaffold for double-stranded DNA (dsDNA) incorporation onto the gold surfaces is described. The SAMs of an azidohexane thiol derivative were prepared on the Au electrode and then used for the immobilization of dsDNA. The electrochemical characteristics of dsDNA onto the SAM-modified gold electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy, and the surface concentration of dsDNA onto the SAMs surface was estimated. The interaction of dsDNA with the anticancer drug, taxol (paclitaxel), was also studied on the surface of DNA/SAM/Au electrode. The observed decrease in the guanine oxidation peak current was used to monitor the interaction of taxol with DNA. The resulting Langmuir isotherm for taxol binding to DNA at the modified electrode was used to evaluate the binding constant of taxol–DNA. The results obtained supported the groove binding interaction of taxol with DNA. The modified electrode was used as a sensitive sensor for quantification of taxol in human serum sample.

Electrochemical behavior and detection of guanine using a sodium montmorillonite-modified carbon paste electrode

Herein, a sodium montmorillonite-modified carbon paste electrode is described for the electrochemical determination of guanine. Guanine yields a well-defined and very sensitive oxidation peak at the sodium montmorillonite-modified carbon paste electrode. Compared with the unmodified carbon paste electrode, the modified electrode facilitates the electron transfer of guanine, since it notably increases the oxidation peak current and lowers the oxidation overpotential of guanine. Based on this, a simple sensitive reliable electrochemical method is proposed for the detection of guanine after all the experimental parameters, such as solution pH value, sodium montmorillonite content in the carbon paste electrode, accumulation potential, and time, are optimized. Under the optimized conditions, the oxidation peak current of guanine varies linearly with its concentration in the range 5.0×10−8 to 2.0×10−5 M and the detection limit (signal-to-noise=3) is 2.0×10−8 M after 4-min accumulation. This method is successfully demonstrated with urine samples.