Comparative study of different alcohol sensors based on Screen-Printed Carbon Electrodes.

Different very simple single-use alcohol enzyme sensors were developed using alcohol oxidase (AOX) from three different yeast, Hansenula sp., Pichia pastoris and Candida boidinii, and employing three different commercial mediator-based Screen-Printed Carbon Electrodes as transducers. The mediators tested, Prussian Blue, Ferrocyanide and Co-phthalocyanine were included into the ink of the working electrode. The procedure to obtain these sensors consists of the immobilization of the enzyme on the electrode surface by adsorption. For the immobilization, an AOX solution is deposited on the working electrode and left until dried (1h) at room temperature. The best results were obtained with the biosensor using Screen-Printed Co-phthalocyanine/Carbon Electrode and AOX from Hansenula sp. The reduced cobalt-phthalocyanine form is amperometrically detected at +0.4V (vs. Ag pseudo reference electrode). This sensor shows good sensitivity (1211 nA mM(-1)), high precision (2.1% RSD value for the slope value of the calibration plot) and wide linear response (0.05-1.00 mM) for ethanol determination. The sensor provides also accurate results for ethanol quantification in alcoholic drinks.

Amperometric fructose sensor based on ferrocyanide modified screen-printed carbon electrode.

The first fructose sensor using a commercial screen-printed ferrocyanide/carbon electrodes (SPFCE) is reported here. The ferrocyanide is included in the carbon ink of the commercial screen-printed carbon electrode. The immobilization of enzyme d-fructose dehydrogenase (FDH) was carried out in an easy way. An aliquot of 10µL FDH was deposited on the electrode surface and left there until dried (approximately 1h) at room temperature. The sensor, so constructed, shows a good sensitivity to fructose (1.25µA/mM) with a slope deviation of ±0.02µA/mM and a linear range comprised between 0.1 and 1mM of fructose, with a limit of detection of 0.05mM. These sensors show good intersensors reproducibility after a previous pretreatment and a high stability. Fructose was determined in real samples as honey, Cola, fruit juices (orange, tomato, apple and pineapple), red wine, red and white grapes, musts and liquor of peach with a good accuracy.

Simultaneous detection of free and total prostate specific antigen on a screen-printed electrochemical dual sensor.

Voltammetric enzyme dual sensors for simultaneous determination of free and total prostate specific antigen (fPSA and tPSA) are described. Alkaline Phosphatase (AP) and a mixture solution of 3-indoxyl phosphate and silver ions were used as the enzymatic label and substrate, respectively. 8A6 or 5G6 antibodies specific for free and total PSA, respectively, were immobilized on different screen-printed electrodes (SPEs)--screen-printed carbon electrodes, screen-printed gold electrodes and screen-printed carbon electrodes modified with nanogold--in order to be able to select one of the surfaces as the most adequate one to develop the dual sensor. Screen-printed carbon electrodes modified with nanogold were the SPEs with the best analytical characteristics and lead to the most repeatable bioelectrodes, so they were selected for the development of the dual sensor. On Dualsensor-nAu electrodes, 8A6 antibody was immobilized on one working electrode and 5G6 antibody was immobilized on the other one by deposition of a drop of solution of each antibody and left overnight at 4 degrees C. Biotinylated anti-PSA antibody and streptavidin-AP conjugate were used as detection reagents, giving rise, to our knowledge, to the first simultaneous electrochemical biosensor for free and total PSA. The PSA dual sensor was used to monitor PSA production from three different cultures of human androgen-sensitive prostate tumor cells.