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)-O-center dot 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. (c) 2005 Elsevier B.V. All rights reserved.2171374138

Disposable electrochemical enzyme-amplified genosensor for Salmonella bacteria detection

This paper describes the use of oligonucleotide modified screen-printed carbon electrodes for the enzyme-amplified sensing of DNA sequences that identify the Salmonella bacteria. The capture probe was immobilized onto screen-printed carbon electrodes using the adsorption method. Hybridization reaction was detected through the sandwich format, based on the coupling of biotin-streptavidin interaction using a streptavidin conjugated to alkaline phosphatase. The enzyme catalyzed the conversion of electroinactive ?-naphthyl phosphate to ?-naphthol; this product is electroactive and has been detected by differential pulse voltammetry. The electrochemical genoassay allowed specific detection of the polymerase chain reaction (PCR) amplified targets, even diluting the sample of interest about 50-fold. Copyright © Taylor & Francis, Inc

SnO2 nanowire bio-transistor for electrical DNA sensing

An innovative JFET bio-transistor, based on a metal oxide (MOX) nanowire bundle, was developed in order to electrically detect biological binding. The working principle of this device relies on modulation of a MOX space charge region (SCR), acting as the channel of a field effect transistor, instead of an enriched/depleted Si channel like in chem.-FETs. The feasibility was at first demonstrated by the development of a bio-sensor made of an SnO2 thin film derivatized with oligodeoxyribonucleotide-probes. We implemented a protocol to immobilize single strands of nucleic acid over SnO2 and developed a system for electrical sensing of hybridization in liquid solution. The same protocol was then applied on a SnO2 nanowire bundle, synthesized by thermal evaporation of oxide powders under controlled conditions with the presence of Pt catalyst. The results obtained on a group of nanowires suggest the possibility - now under development - to produce nano-bio-transistors based on single nanowires of metal oxides

New label free CA125 detection based on gold nanostructured screen-printed electrode

This paper describes the optimisation and the analytical performances of a label-free impedimetric immunosensor for the detection of tumour marker CA125 based on gold nanoparticles modified screen-printed graphite electrode. Experimental conditions of each step for the developed immunosensor were studied and optimised. The immunosensor response varied linearly (r(2)=0.996) with antigen concentration between 0 and 100 U/mL. The estimated detection limit was 6.7 U/mL. The electrochemical immunosensor allowed unambiguous identification of CA125, while no significant non-specific signal was detected in the case of all negative controls. The analytical usefulness of the impedimetric immunosensor was finally demonstrated analysing serum samples. (C) 2012 Elsevier B.V. All rights reserved