Potential contribution of ELISA and LFI assays to assessment of the oxidative stress condition based on 8-oxodG biomarker.

Immunoassays have been extensively applied in the medical diagnostic field. Enzyme-Linked Immunosorbent Assay (ELISA) and Lateral Flow Immunochemical Assay (LFIA) are methods that have been well established to analysis of clinical substances such as protein, hormones, drugs, identification of antibodies and in the quantification of antigen. Over the past years, the application of these methods has been extended to assess the clinical oxidative stress condition based on monitoring of the 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) biomarker levels. The present manuscript provides an overview of the current immunoassays based on ELISA and LFIA technologies applied for a quantitative analysis of the 8-oxodG. The discussion focuses on the principles of development, improvement and analytical performance of these assays. The relationship of the molecule 8-oxodG as a clinical biomarker of the assessment of the oxidative stress condition is also discussed. Commercially available products to 8-oxodG analysis are also presented.

Correlation between antioxidant activity and total phenolic content with physicochemical parameters of blended extracts of Camellia sinensis / Correlação da atividade antioxidante e teor de fenos totais com parâmetros físico-químicos de extratos mistos de Camellia sinensis

This paper evaluated the total antioxidant activity (TAA) and the correlation with parameters such as total phenols (FT), total acidity, pH, redox potential (ORP) and conductivity (EC), of commercial teas of Camellia sinensis, single or blended with other plants. The extracts tested were: Camellia sinensis fermented and unfermented, Camellia sinensis with Citrus limonium, Camellia sinensis with Mentha piperita, Camellia sinensis with Prunus persica, Camellia sinensis with Citrus sinensis. All extracts showed high percentages of TAA and were not significantly different by Tukey's test. The correlation matrices indicated that except for the extract of Camellia sinensis with Prunus persica, all the other extracts had statistically significant correlations. Strong correlations were found between TAA and FT, and between pH and FT. The extract of Camellia sinensis with Mentha piperita presented the highest correlation between TAA and FT. The same compounds that influence the pH and ORP may also influence the EC, for almost all teas. For the fermented and unfermented extracts of Camellia sinensis all parameters had been strongly correlated (r 0.7).

Este trabalho apresenta os resultados da avaliação da atividade antioxidante total (AAT) e a correlação com parâmetros como teor de fenóis totais (FT), acidez titulável, pH, potencial redox (ORP) e condutividade elétrica (CE), de chás comerciais puros e mistos de Camellia sinensis. Os extratos testados foram Camellia sinensis fermentado e não-fermentado, Camellia sinensis com Citrus limonium, Camellia sinensis com Mentha piperita, Camellia sinensis com Prunus pérsica e Camellia sinensis com Citrus sinensis. Todos os extratos mostraram altos valores percentuais de AAT e não diferiram estatisticamente entre si, pelo Teste de Tukey. As matrizes de correlação obtidas mostraram que, com exceção do extrato de Camellia sinensis com Prunus persica, todos os demais extratos apresentaram correlações estatisticamente significantes. Foram observadas fortes correlações entre a AAT e FT e entre o pH e FT. O extrato de Camellia sinensis com Mentha piperita foi o que apresentou a melhor correlação entre AAT e FT. Os mesmos compostos que influenciam o pH e o ORP também podem influenciar o parâmetro de CE para quase todos os chás. Para os extratos de Camellia sinensis fermentado e não-fermentado todos os parâmetros apresentaram fortes correlações entre si (r 0,7).

Biosensors for antioxidant evaluation in biological systems.

The prevention of oxidative reactions in a biological medium as well as the role of reactive oxygen species (ROS) in chronic degenerative diseases are questions that continue to be investigated. Electrochemical biosensors have shown attractive features to evaluate the oxidative stress condition at a level comparable to chromatographic and spectroscopic techniques. The biosensors developed so far are based on direct analysis of specific indicators such as biomarkers of oxidative stress on the monitoring of reactive oxygen species the free radicals in cells or tissues, aiming to obtain a correlation between the index obtained from these indicators with the oxidative stress levels in cells. In this review we will provide an overview of the development of electrochemical biosensors to evaluate the content of antioxidants and reactive oxygen species in physiological systems. Some discussion regarding the analysis of antioxidant capacity at the single cell level is also presented.

Simple and sensitive electroanalytical method for the determination of ascorbic acid in urine samples using measurements in an aqueous cationic micellar medium.

An electroanalytical study for the amperometric determination of ascorbic acid (AA) in a human urine sample at a bare glassy carbon electrode using the CPC (cetylpyridinium chloride) surfactant is described. Under the optimized conditions of E(pa), I(pa), CPC concentration and pH, the oxidation peak potential of the AA shifts towards a less positive potential, and the peak current increase in a significant way in the presence of the surfactant. Under the best conditions, the method provided a linear calibration curve to AA in a 0.1 mol L(-1) phosphate buffer solution (pH 7.0) in the concentration range from 5.0 x 10(-7) up to 4.3 x 10(-4) mol L(-1), with a detection limit of 2.0 x 10(-7) mol L(-1) and a high correlation coefficient (r = 0.9996). The recovery test presented values of 98 - 105%, suggesting a great potential of the proposed method for AA determination in complex samples, such as urine.

Investigations of the antioxidant properties of plant extracts using a DNA-electrochemical biosensor.

In this work, the results of a method based on an electrochemical biosensor to detect DNA damage in vitro for the evaluation of the antioxidant properties of plant extracts are reported. The biosensor consisted of a dsDNA immobilized on a screen-printed electrode surface (SPE). DNA damage was promoted by the generation of the *OH radicals via Fenton-type reaction. The interaction of the radical species with immobilised DNA in the absence and presence of antioxidants was evaluated by means of changes in the guanine oxidation peak obtained by square wave voltammetry. The results demonstrated that the DNA-based biosensor is suitable as a rapid screening test for the evaluation of antioxidant properties of samples.