Mannosyl electrochemical impedance cytosensor for label-free MDA-MB-231 cancer cell detection

A label-free and ultrasensitive electrochemical impedance cytosensor was developed to specifically detect the breast cancer cells MDA-MB-231 via the interaction between the mannosyl glassy carbon electrode (GCE) and the overexpressed mannose receptors on the target cell surface. The mannosyl GCE was prepared through electrografting of the amino-functionalized mannose derivatives on GCE surface in which a covalent bond was formed between carbon of the electrode and the amino group of the mannose derivative. The fluorescent microscopy indicated that the electrode is specific for MDA-MB-231 cells, with good biocompatibility for viable captured cells. The derivative with a shorter alkyl linker, mannose-C₂NH₂, showed a better sensitivity than that with a longer linker, mannose-C₆NH₂. GCE modified with amino-functionalized galactose derivative, galactose-C₂NH₂, shows no function to the detection of MDA-MB-231 cells. The specific interaction between the mannosyl GCE and Con A (a mannose-binding lectin) or MDA-MB-231 breast cancer cells with overexpressed mannose receptors was determined through the change of peak separation in the cyclic voltammogram or the change of charge transfer resistance in the electrochemical impedance spectra (Nyquist plot) in the electrolytes containing a reversible redox couple [Fe(CN)₆]^3-/[Fe(CN)₆]^4-. The charge transfer resistance in the Nyquist plots linearly depended on the concentration of MDA-MB-231 cells (1.0 × 10-1.0 × 10⁵ cells mL^-1, with 10 cells mL^-1 being the lower detection limit). Introducing 0.1% polyethylene glycol-200 (PEG-200) was able to prevent the interference caused by 1.0 × 10³ HEK-293T cells mL^-1, a non-cancer cell line (control).