Development of electrochemical CA 125 immunosensor

In this study, a new immunosensor was developed for the electrochemical determination of cancer antigen 125 (CA 125) that is a cancer biomarker and its application was performed on human blood serum samples. In this work, firstly the screen printed carbon electrodes (SPCE) were modified with reduced graphene oxide (RGO), then the electrode surface was coated with poly(thionine) by applying the electropolymerization technique, and finally, gold nanoparticles (AuNP) were created by electrodeposition on the surface. Electrochemical characterizations of the SPCE/RGO/PTH/AuNP electrode were performed using cyclic voltammetry (CV), differential pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) methods. Immobilization of Anti-CA 125 to the surface of SPCE/RGO/PTH/AuNP electrodes were carried out by covalent binding method using 3-mercaptopropionic acid (3-MPA) and 1-ethyl-3-(3-dimethylamino-propyl) carbodiimide/N-hydroxy succinimide (EDC/NHS). The optimum working parameters of the prepared CA 125 immunosensor were determined by DPV and EIS methods. The optimum Anti-CA 125 concentration, incubation time of Anti-CA 125 and incubation time of CA 125 were found to be 66.66 µg/mL, 45 min and 30 min, respectively. The analytical characterization of electrochemical CA 125 immunosensors were performed under the optimum working parameters. It was calculated that the linear ranges were 1-100 pg.mL-1 by EIS, DPV and SWV methods, limit of detections (LOD) were 0.0012 ng.mL-1, 1.61 ng.mL-1 and 1.68 ng.mL-1, respectively. The repeatability of the CA 125 immunosensor was tested for 50 ng.mL-1 CA 125 concentration and relative standard deviation (R.S.D.) values were calculated as 3.34% (n = 10), 2.03% (n = 10) and 1.48% (n = 10) for EIS, DPV and SWV methods, respectively. The operation stability of the developed CA 125 immunosensor was examined by voltammetric methods for 60 days, and the storage stability for 12 weeks. The selectivity of the CA 125 immunosensor was tested by performing CA 125 analysis in the presence of 9 different antigen mixes and it was found that the antigen mixture made a 4.97% interference. The prepared CA 125 immunosensors were used for the analysis of different concentrations of CA 125 added to the human blood serum samples in a known amount and over 95% recoveries were obtained.