Cancer immunosensor based on apo and holo transferrin binding

An electrochemical immunosensor was developed for the determination of apo-Tf (non-iron-bound) and holo-Tf (iron-bound) using polyclonal antibody transferrin (anti-Tf) immobilized at an electrode surface as a biorecognition platform. The monitoring was based on the anti-Tf binding with both Tf forms which allows the detection of cancer cells due to the constant iron cycle and the overexpression of anti-Tf on the cancer cell surface. The immunosensor characterization was performed using electrochemical impedance spectroscopy (EIS), which evalnnt'sl the impedimetric biorecognition of the antigens-antibody by the use of K4Fe(CN)(6) redox group. The immunosensor was able to detect both forms of Tf in terms of charge transfer resistance (R-ct). Analytical curves showed a limit of detection of 0.049 and 0.053 ng mL(-1) for apo-Tf and holo-Tf respectively. The immunosensor was applied to the detection of the two cancer cells A549 (lung carcinoma) and MCF-7 (breast carcinoma) and compared with BHIC570, a healthy cell line. The impedimetric response of healthy cells differs significantly firm that of the cancerous cells, as revealed by a Dunnett's test in 95% confidence level-ca. 10(2) cells mL(-1)-indicating the feasibility of the immunosensor to discriminate both types of cells. The indirect detection of anti-Tf based on apo-Tf and holo-Tf binding can be considered an advanced approach for cancer recognition.