In the present study, an eco-friendly solid surface fluorescence immunosensor was fabricated for the ultra-selective and sensitive determination of CA 19-9 antigen based on polydopamine (PDA) molecular imprinted polymer (MIP) as an antibody substitution and Ni nanoclusters (Ni NCs) as the fluorescent signal probe. Here, the uniform MIP film for CA 19-9 antigen was established by electropolymerization of DA and target antigen on the surface of ITO electrode. When the imprinted cavities were occupied by CA 19-9 antigen and Ni NCs-Ab, respectively, the fluorescence emission of Ni NCs on the MIP-modified electrode surface was increased. Actually, MIP has been used in immunoassays as antibody substitute. Under optimized experimental conditions, taking advantage of both MIP-FL assays, the proposed immunosensor demonstrated a good analytical performance for the CA 19-9 antigen detection in an excellent linear range from 1 pg mL-1 to 48 ng mL-1 with detection limit of 0.13 pg mL-1 (S/N = 3). The application of the proposed MIP-FL immunosensor for detection of CA 19-9 antigen in human serum samples was evaluated, and the obtained results were found to be in acceptable agreement with those obtained with an ELISA assay as standard method. The developed fluorescence immunosensor demonstrated high specificity and can provide a simple, sensitive and reliable approach for the ultra-trace detection of other tumor markers in clinical monitoring.
