Abstract
Prostatic-specific antigen is considered as the best marker for prostate cancer. Due to the importance of PSA for diagnostic purposes it is not surprising that there are tested and optimized various methods for its determination.
In spite of such intensive research in the field of electrochemical detection of some by-products connected with concentration of PSA, electrochemical behaviour of PSA has not been studied yet. The aim of this study was to investigate electrochemical catalytic signals of PSA using differential pulse voltammetry Brdicka reaction.
The catalytic signals were studied using adsorptive transfer stripping technique as well as directly in the electrochemical cell. Nevertheless, we primarily tested detection of PSA by standard immunoanalysis and by gel and capillary chip electrophoresis to investigate behaviour of this protein in electric field.
Both electrophoretic methods showed that the most intensive band of PSA was determined at 37 kDa under reducing conditions and at 26 kDa under non-reducing. Band at 37 kDa corresponds to a reduced, and at 26 kDa to non-reduced PSA.
Studying of basic electrochemical behaviour of PSA was primarily carried out using standard electrochemical cell and HMDE as a working electrode. Co(NH 3) 6Cl 3 (1mM) was used as a supporting electrolyte.
Temperature of the electrolyte was maintained at 4 °C. The effects of accumulation time andconcentration of Co(NH 3) 6Cl3 as a key component of supporting electrolyte were studied.
Time of accumulation of 240 s and 1.00mM Co(NH 3) 6Cl 3 were found the optimal for detection of PSA in electrochemical cell. Further, we used adsorptive transfer stripping technique coupled with differential pulse voltammetry Brdicka reaction for detection of PSA.
Two temperatures of adsorption as 4 °C and 20 °C and several times of adsorption as 40, 60, 80, 120, 180, 240, 360 and 420 s were tested. Under the optimized conditions (4 °C temperature of adsorption and 240 s time of adsorption) calibration curve with the following equation y = 36.865x - 11.949, R2 = 0.9911 within the concentration interval from 1 to 1,500pg/ml was measured.
Detection limit of PSA expressed as 3S/N was estimated down to 1 fg of PSA in 0.5μl.