A simple electrochemical lectin-probe for in situ homogeneous cytosensing and facile evaluation of cell surface glycan

This work constructed a novel electrochemical lectin-probe, ferrocene–concanavalin A (Fc-ConA), for in situ monitoring of cell surface glycan by incorporating the specific recognition ability of lectin to glycan and favorable electrochemical property of ferrocenyl group. The covalent conjugation of ConA with ferrocenyl group was achieved by a carbodiimide coupling reaction and proved with UV–vis absorption spectroscopy and infrared spectroscopy. Cyclic voltammetric behavior of Fc-ConA at glassy carbon electrode demonstrated a reversible diffusion-controlled process. A facile homogeneous cytosensing strategy was then developed using Fc-ConA probe for detection of K562 cells. The suspending cells specifically captured Fc-ConA via membrane mannosyl groups and decreased the concentration of free Fc-ConA, producing a response correlative with cell number and the content of cell surface glycan. A wide linear response to cells ranging from 1 × 104 to 1 × 107 cells mL−1 with a calculated detection limit of 3000 cells mL−1 was obtained. The lectin-probe could be conveniently used to in situ evaluate cell surface glycan. The average number of mannose moieties on single living K562 cell was detected to be 3.0 × 1010, while this value increased by 81% on drug-treated cells. These results agreed with those from flow cytometric detection. This strategy presented a promising platform for homogeneous sensitive cytosensing and facile monitoring of carbohydrate expression on living cells in response to drugs.