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.