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. (C) 2009 Elsevier B.V. All rights reserved.