An electrochemical glycan biosensor based on a thionine-bridged multiwalled carbon nanotube/gold nanoparticle composite-modified electrode

Glycans that attached to glycoproteins on cell surfaces are known to be functionally important and they have potential diagnostic values. The development of effective methods to analyze glycan expression on living cell surface is desirable for understanding their functions in disease progression and providing a powerful tool for early diagnosis. In this paper, thionine-bridged multiwalled carbon nanotube/gold nanoparticle (MWCNT/Th/AuNP) as a mediator/nanomaterial composite was synthesized to develop an electrochemical biosensor for glycan assay on living cancer cells. The MWCNT/Th/AuNP composite was fabricated by binding AuNPs to the surface of Th-coated MWCNTs, in which thionine acted as a linker to enable the negatively charged AuNPs to bind to the anionic MWCNT surface. When compared with conventional nanomaterial-based electrochemical biosensors, the MWCNT/Th/AuNP-modified electrode contained thionine as an electron mediator and simplified the electrochemical process based on enzymatic catalysis for signal amplification. Under a sandwich-type assay format, the MWCNT/Th/AuNP-based biosensor facilitated highly sensitive and specific detection of mannose on human liver and prostate cancer cells and offered great promise for the analysis of other glycans on living cells by utilizing a greater variety of lectins.