Electrofluorochromic Imaging Analysis of Glycan Expression on Living Single Cell with Bipolar Electrode Arrays

The in situ glycan profiling of a single tumor cell plays an important role in personalized cancer treatment. Herein, an integrated microfluidic system was designed for living single-cell trapping and real-time monitoring of galactosyl expression on the surface, combining closed bipolar electrode (BPE) arrays and electrofluorochromic (EFC) imaging. Galactosyl groups on human liver cancer HepG2 cells were used as the model analysts, galactose oxidase (GAO) could selectively oxidize hydroxyl sites of galactosyl groups on the cell surface to aldehydes, and then biotin hydrazide (BH) was used to label the aldehydes by aniline-catalyzed hydrazone ligation. With the biotin-avidin system, nanoprobes were finally introduced to the galactosyl groups on the cell surface with avidin as a bridge, which was prepared by simultaneously assembling ferrocene-DNA (Fc-DNA) and biotin-DNA (Bio-DNA) on gold nanoparticles (AuNPs) due to their large surface area and excellent electrical conductivity. After a labeled single cell was captured in the anodic microchannel, the Fc groups attached on the cell surface were oxidized under suitable potential, and the nonfluorescent resazurin on the cathode was correspondingly reduced to produce highly fluorescent resorufin, collected by fluorescence confocal microscope. The combination of EFC imaging and BPE realized monitoring galactosyl group expression of 5.0 × 108 molecules per cell. Furthermore, the proposed platform had the ability to distinguish a single cancer cell from a normal cell according to the expression level of galactosyl groups and to dynamically monitor the galactosyl group variation on the cell surface, providing a simple and accessible method for the single-cell analysis.