An impedance spectroscopy method for the detection and evaluation of Babesia bovis antibodies in cattle

An immunosensor method for diagnosis of Babesia bovis in cattle based on impedance measurement is presented in this study. The method probes the interaction between antibodies present in serum of B. bovis infected cattle and a recombinant version of the C-terminal portion of RAP-1 obtained from the Portuguese B. bovis Santarém strain (rRAP-1/CT-STR). Following immobilization of rRAP-1/CT-STR on gold electrodes through the formation of a self-assembled layer, the alteration of the interface properties was traced by electrochemical impedance spectroscopy (EIS). The changes of the impedimetric properties of the deposited rRAP-1/CT-STR B. bovis protein layer, interaction with different concentrations of anti-rRAP-1/CT-STR antibodies, and the association constants of the immunoreactive molecules involved, were obtained using EIS. The results were compared with an enzyme-linked immunosorbent assay using the same antigen, and immunofluorescence. The results confirmed the potential for further developing of an immunosensor-based method for the detection and characterization of antibodies against B. bovis in cattle. In addition, such method would provide the advantage of determining the association constant between antibody–antigen interactions without the use of labelling molecules.