Amperometric immunosensor of Brucella abortus CE-protein antigen shows post-zone phenomena

Brucella abortus is an intracellular pathogen of zoonotic nature and causes brucellosis in humans, means it can be transferred from cattle to a human and remains pathogenic. In this study, attempts were made for detection of B. abortus cell envelop protein (CE-protein) antigen by using amperometric immunosensors. Screen printed electrodes were characterized electrochemically with 1-naphthol and used in sandwich enzyme linked immunosorbent assay system to detect CE protein antigen. Linear range was found in the range of 1.56 μg/mL to100 μg/mL with a regression equation of I (nA) = 43.12 + 1.235 (antigen (μg/mL)) (R2 = 0.991). Relative standard deviation was found 5.5%. At high concentrations post-zone like phenomenon was observed. At very low concentrations the response was higher compared to that of at higher concentrations. However, no false results were observed. The detection limit was found to be 0.1 μg/mL. By conventional plate ELISA it is possible to detect 50 μg/mL only. Experiments were conducted using suspected human patient serum samples and results were compared with ELISA and RBPT test. The immunosensor was found to be highly sensitive compared to ELISA and RBPT. In order to confirm that whether these results obtained from electrochemical technique (amperometric technique) was true positive or false positive, we further diluted the patient serum samples and then tested. We found that even after dilution of patient serum samples results obtained were same as before dilution of patient serum samples. Hence, it is concluded that electrochemical technique does not give false result. Thus electrochemical immunosensors can be used for diagnosis of brucellosis in patient serum sample. Shelf life of immunosensor was found 18 days.