Lectin-based electrochemical biosensor constructed by functionalized carbon nanotubes for the competitive assay of glycan expression on living cancer cells

In this paper, we report a novel lectin-based electrochemical biosensor constructed by functionalized multiwalled carbon nanotubes (CNTs) for a competitive assay of glycan expression on living cells. The biosensor was fabricated by adsorbing poly(diallyldimethylammonium chloride) (PDDA)-functionalized CNTs (PDCNTs) onto a glassy carbon working electrode (GCE), followed by adsorbing glutathione (GSH)-protected gold nanoparticles (AuNPs). The resulting GCE/PDCNT/Au–GSH offers an effective platform for concanavalin A (Con A, a lectin) immobilization with high stability and bioactivity. A thiol-derivatized carbohydrate (thiomannosyl dimer) was synthesized to construct {CNT/thionine/Au–S–mannose} biocomposites, which exploit CNTs as carriers to load enormous amounts of thionine for generating an electrochemical signal and AuNPs for anchoring the thiomannosyl dimer. These two applications of the functionalized CNTs as a biosensing platform and biocomposites play important roles in signal enhancement for glycan detection. Using a competitive assay, the electrochemical biosensor shows good analytical performance with high sensitivity, selectivity and a rapid response for the analysis of mannose on human lung cancer cells as a model glycan. This proposed strategy possesses promising application for the assay of other glycans on living cancer cells with the selection of more lectins with the biosensor development.