A Sensitive Electrochemical Immunosensor for the Determination of ProstateSpecific Antigen

Clinical analysis of a cancer biomarker leads to early cancer diagnosis which in turn, is followed by increase the chances of successful treatment [1]. Prostate specific antigen (PSA) has beendemonstrated to be the most validated serum marker for prostate and breast cancers [2,3]. Blood PSA concentrations above 4 ng/ml are often related to prostate cancer [4]. So, sensitive andaccurate quantification of PSA is critical to early detection of prostate cancer, increase the expectancy of complete patient recovery and monitor for disease recurrence after treatment [5]. Herein, an electrochemical immunosensor for the quantification of PSA is presented. For the preparation of the sensor, at first streptavidin was covalently immobilized on the surface of a nanoTiO2-modified carbon paste electrode using glutaraldehyde as crosslinking agent. Then anti-PSA antibody functionalized with biotin was linked to the electrode surface after specific interaction between streptavidin and biotin. After sandwich-type immunoreaction, thionine-conjugated polycolonal antibody was bound to PSA and the reduction current of the thionine was recorded with differential pulse voltammetry. This electrochemical signal was directly correlated to the concentration of PSA. All experimental parameters affecting the sensor response including those involved in the construction of the sensor and in the electrochemical transduction, were optimized.The immunosensor exhibited a linear concentration range of 0.10-100 ng/ml under the optimized conditions. The proposed sensor was successfully applied to the determination of PSA in health and cancerous human serum samples. In addition, the designed immunosensor minimized the issue of nonspecific protein adsorption using streptavidin-biotin specific interaction.

Keywords:

Prostate cancer antigen , Immunosensor , HRP , Electrochemistry