Development of a facile electrochemical sensor based on GCE modified with one-step prepared PNMA-CeO2-fMWCNTs composite for simultaneous detection of UA and 5-FU.

In this study, a poly(N-methyl aniline)-cerium oxide-functionalized MWCNTs (PNMA-CeO2-fMWCNTs) composite was synthesized in a one-step preparation technique. As a highly efficient modifier, the composite was used to modify the glassy carbon electrode surface for simultaneous detection of uric acid (UA) and 5-fluorouracil (5-FU). Morphological characterization of the GCE/PNMA-CeO2-fMWCNTs was studied using scanning electron microscopy. Structural characterization of the composite was performed using X-ray diffraction and Fourier-transformed infrared spectroscopy. Electron transfer properties of the prepared electrodes were carried out with electrochemical impedance spectroscopy and cyclic voltammetry. The linear working range for UA and 5-FU was found to be 0.25-50 µM and 0.5-750 µM, respectively. The limit of detection values for UA and 5-FU were 0.04 µM and 0.19 µM, respectively. The effects of various interfering substances on the electrochemical response of UA and 5-FU were investigated. The GCE/PNMA-CeO2-fMWCNTs sensor has excellent stability, reproducibility, anti-interference ability, and reproducibility. To demonstrate the practical application of the sensing platform, fetal bovine serum was selected and tested in the spiked samples, and satisfactory results were obtained. The prepared composite proved to be a promising platform for simple, rapid, and simultaneous analysis of UA and 5-FU.

Interaction of prednisone with dsDNA at silver nanoparticles/poly(glyoxal-bis(2-hydroxyanil))/dsDNA modified electrode and its analytical application.

This paper reports the fabrication of an electrochemical DNA biosensor for the electrochemical determination of prednisone (PRD), which is a synthetic corticosteroid. For this purpose, silver nanoparticles (AgNPs) and a new polymer film poly(glyoxal-bis(2-hydroxyanil)) (P(GBHA)) were electrochemically deposited on a glassy carbon electrode (GCE), respectively. Then, an electrochemical DNA biosensor was prepared onto this electrode surface (GCE/AgNPs/P(GBHA)) by the immobilization of dsDNA using a chronoamperometry method. The proposed electrode was characterized by FESEM, XPS, and cyclic voltammetry (CV). The interaction between the PRD and dsDNA immobilized on the GCE/AgNPs/P(GBHA) electrode was investigated via a differential pulse voltammetry (DPV) method and UV-Vis spectrophotometry. The experimental factors affecting the interaction between the PRD concentration and dsDNA were optimized. The fabricated biosensor showed a wide linear response in a PRD concentration range of 1.0-50.0 µg mL-1 depending on both the adenine and guanine base signals. The detection limit based on the guanine and adenine signals was 0.3 µg mL-1 and 0.25 µg mL-1, respectively. The sensor exhibited excellent anti-interferential ability, good stability and reproducibility and was satisfactorily employed for the electrochemical assay of PRD in serum samples. The new DNA biosensor can be utilized for the sensitive, accurate and rapid analysis of PRD.

Electrochemical DNA biosensor based on poly(2,6-pyridinedicarboxylic acid) modified glassy carbon electrode for the determination of anticancer drug gemcitabine.

In this study, a simple methodology was used to develop a new electrochemical DNA biosensor based on poly(2,6-pyridinedicarboxylic acid) (P(PDCA)) modified glassy carbon electrode (GCE). This modified electrode was used to monitor for the electrochemical interaction between the dsDNA and gemcitabine (GEM) for the first time. A decrease in oxidation signals of guanine after the interaction of the dsDNA with the GEM was used as an indicator for the selective determination of the GEM via differential pulse voltammetry (DPV). The guanine oxidation peak currents were linearly proportional to the concentrations of the GEM in the range of 1-30mgL(‒1). Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.276mgL(‒1) and 0.922mgL(‒1), respectively. The reproducibility, repeatability, and applicability of the analysis to pharmaceutical dosage forms and human serum samples were also examined. In addition to DPV method, UV-vis and viscosity measurements were utilized to propose the interaction mechanism between the GEM and the dsDNA. The novel DNA biosensor could serve for sensitive, accurate and rapid determination of the GEM.

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 0.5 mol L(-1) acetate buffer (pH 4.8) containing 0.02 mol L(-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 1.0-50 mg L(-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.

Electrochemical glucose biosensor based on nickel oxide nanoparticle-modified carbon paste electrode.

In the present work, we designed an amperometric glucose biosensor based on nickel oxide nanoparticles (NiONPs)-modified carbon paste electrode. The biosensor was prepared by incorporation of glucose oxidase and NiONPs into a carbon paste matrix. It showed good analytical performances such as high sensitivity (367 µA mmolL(-1)) and a wide linear response from 1.9×10(-3) mmolL(-1) to 15.0 mmolL(-1) with a limit of detection (0.11 µmolL(-1)). The biosensor was used for the determination of glucose in human serum samples. The results illustrate that NiONPs have enormous potential in the construction of biosensor for determination of glucose.

Amperometric carbon paste enzyme electrodes with Fe(3)O(4) nanoparticles and 1,4-benzoquinone for glucose determination.

Two new amperometric carbon paste enzyme electrodes including Fe(3)O(4) nanoparticles with and without 1,4-benzoquinone were developed for glucose determination. Electron transfer properties of unmodified and Fe(3)O(4) nanoparticles and/or 1,4-benzoquinone modified carbon paste electrodes were investigated in 0.1 M KCl support electrolyte containing Fe(CN)6(3-/4-) as redox probe by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. Fe(3)O(4) nanoparticles increased electron transfer at solution/electrode interface. The parameters affecting the analytical performance of the enzyme electrode have been investigated in detail and optimized for Fe(3)O(4) nanoparticle modified enzyme electrode (Fe(3)O(4)-CPEE). Fe(3)O(4) nanoparticles and 1,4-benzoquinone modified enzyme electrode (BQ-Fe(3)O(4)-CPEE) exhibited linear response from 1.9 × 10(-7) M to 3.7 × 10(-6) M, from 7.2 × 10(-6) M to 1.5 × 10(-4) M and from 1.3 × 10(-3) M to 1.2 × 10(-2) M with an excellent detection limit of 1.9 × 10(-8) M. BQ-Fe(3)O(4)-CPEE was used for determination of glucose in serum samples and results were in good agreement with those obtained by spectrophotometric method.