Determination of 5-aminosalicylic acid in pharmaceutical formulations by square wave voltammetry at pencil graphite electrodes

An analytical method for the determination of the anti-inflammatory drug 5-aminosalicylic acid (5-ASA) in pharmaceutical formulations using square wave voltammetry at pencil graphite electrodes was developed. After the optimization of the experimental conditions, calibration curves were obtained in the linear concentration range from 9.78 × 10-7 to 7.25 × 10-5 mol L-1 resulting in a limit of detection of 2.12 ± 0.05 x 10-8 mol L-1. Statistical tests showed that the concentrations of 5-ASA in commercial tablets and enemas obtained with the proposed voltammetric method agreed with HPLC values at a 95% confidence level.CNPqFAPES

Spectrophotometric Evaluation of the Behavior of Disperse Red 1 Dye in Aqueous Media and its Interaction with Calf Thymus ds-DNA

UV-Vis spectrophotometry was used to measure the solubility of disperse red 1 (DR1) dye in aqueous solutions, using different solvents and dispersants. The dye was quantified in water samples, and its interaction with calf thymus ds-DNA was investigated. The results showed that the commercial dispersant Fongranal (R) FB was suitable for the preparation of aqueous DR1 solutions. For the determination of DR1 in purified water, the limit of detection was 2.47 x 10(-6) mol L-1, and the limit of quantification was 8.22 x 10(-6) mol L-1. Percentage recoveries of 91.2 and 103% were obtained for DR1 concentrations of 3.00 x 10(-6) and 40.0 x 10(-6) mol L-1, respectively. The recoveries achieved for DR1 present in tap and river water were in the range 85.9-113%. The interaction of DR1 with calf thymus DNA was accompanied by hypochromic and hyperchromic effects, which were related to conformational changes and damage to the DNA double helix.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Detection of DNA nucleotides on pretreated boron doped diamond electrodes

The individual detection and equimolar mixture of DNA nucleotides guanosine monophosphate (GMP), adenosine monophosphate (AMP), thymidine (TMP) and cytidine (CMP) 5'-monophosphate using square wave voltammetry was performed on boron doped diamond (BDD) electrodes cathodically (Red-DDB) and anodically (Oxi-DDB) pretreated. The oxidation of individual DNA nucleotides was more sensitive on Oxi-BDD electrode. In a simultaneous detection of nucleotides, the responses of GMP, AMP, TMP and CMP were very adequate on both treated electrodes. Particularly, more sensitive and separate peaks for TMP and CMP on Oxi-BDD and Red-BDD electrodes, respectively, were observed after deconvolution procedure. The detection of nucleotides in aqueous solutions will certainly contribute for genotoxic evaluation of substances and hybridization reactions by immobilizing ss or ds-DNA on BDD surface

Diagnostic tests for hepatitis C: Recent trends in electrochemical immunosensor and genosensor analysis

Hepatitis C is a liver disease that is transmitted through contact with the blood of an infected person. An estimated 150 million individuals worldwide have been chronically infected with the hepatitis C virus (hcv). Hepatitis C shows significant genetic variation in the global population, due to the high rate of viral RNA mutation. There are six variants of the virus (HCV genotypes 1, 2, 3, 4, 5, and 6), with 15 recorded subtypes that vary in prevalence across different regions of the world. A variety of devices are used to diagnose hepatitis C, including HCV antibody test, HCV viral load test, HCV genotype test and liver biopsy. Rapid, inexpensive, sensitive, and robust analytical devices are therefore essential for effective diagnosis and monitoring of disease treatment. This review provides an overview of current electrochemical immunosensor and genosensor technologies employed in HCV detection. There are a limited number of publications showing electrochemical biosensors being used for the detection of hcv. Due to their simplicity, specificity, and reliability, electrochemical biosensor devices have potential clinical applications in several viral infections. (C) 2014 Baishideng Publishing Group Inc. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Electrochemical reduction of disperse orange 1 textile dye at a boron-doped diamond electrode

Electrochemical reduction of the azo dye disperse orange 1 (DO1) was performed by square wave and cyclic voltammetry using a boron-doped diamond electrode. The dissolution of DO1 was evaluated by monitoring the UV-Vis spectra of the solutions, and best results were obtained using aqueous solutions containing 5 % Fongranal FB dispersant. Three irreversible peaks were obtained for the electrochemical reduction of DO1, while the dispersant showed one irreversible peak. The overall electrodic process was mainly diffusion controlled. A mechanism is proposed for the reduction of the dye.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Optimization of an amperometric biosensor for the detection of hepatitis C virus using fractional factorial designs

Fractional factorial design and factorial with center point design were applied to the development of an amperometric biosensor for the detection of the hepatitis C virus. Biomolecules were immobilized by adsorption on graphite electrodes modified with siloxane-poly(propyleneoxide) hybrid matrix prepared using the sol-gel method. Several parameters were optimized, such as the streptavidin concentration at 0.01 mg mL(-1) and 1.0% bovine serum albumin, the incubation time of the electrodes in the complementary DNA solution for 30 minutes and a 1: 1500 dilution of the avidin-peroxidase conjugate, among others. The application of chemometric studies has been efficient, since the best conditions have been established with a restricted number of experiments, indicating the influence of different factors on the system

Fully disposable microfluidic electrochemical device for detection of estrogen receptor alpha breast cancer biomarker

A novel fully disposable microfluidic electrochemical array device (?FED) was developed and successfully applied for detection of the biomarker estrogen receptor alpha (ER?). The ?FED was constructed using low-cost materials and an inexpensive home cutter printer enabled the manufacture of dozens of ?FEDs in less than 2h, at a cost of less than US$ 0.20 in material per device. The ?FED incorporates counter and reference electrodes and eight carbon-based working electrodes, which were modified with DNA sequences known as estrogen response elements (DNA-ERE), where ER? binds specifically. Paramagnetic particles heavily decorated with anti-ER? antibody and horseradish peroxidase (MP-Ab-HRP) were used to efficiently capture ER? from the sample solution. The ER?-MP-Ab-HRP bioconjugate formed was injected into the ?FED and incubated with the DNA-ERE-modified electrodes, followed by amperometric detection with application of -0.2V vs. Ag|AgCl while a mixture of H2O2 and hydroquinone was injected into the microfluidic device. An ultralow limit of detection of 10.0 fg mL(-1) was obtained with the proposed method. The performance of the assay, in terms of sensitivity and reproducibility, was studied using undiluted calf serum, and excellent recoveries in the range of 94.7-108% were achieved for the detection of ER? in MCF-7 cell lysate. The ?FED system can be easily constructed and applied for multiplex biomarker detection, making the device an excellent cost-effective alternative for cancer diagnosis, especially in developing countries