Ultrasensitive quantitative detection of circulating tumor cells (CTCs) and the profile of glycan expression are active and rapidly advancing fields in cancer research. This work designed a dual-potential ratiometric electrochemiluminescence (ECL) system for highly sensitive detection of CTCs and simultaneous evaluation of glycan expression on cell surface. Two kinds of ECL nanoemitters, carbon nitride nanosheets and luminol-reduced gold nanoparticles as cathodic and anodic nanoemitters respectively, were prepared to successfully achieve the dual-potential ratiometric ECL The carbon nitride nanosheets were decorated with gold nanoparticles to conjugate aptamer for specific capture of CTCs, and the anodic nanoemitters were functionalized with lectin for specific recognition of surface glycans. Using MCF-7 CTCs as model target, the proposed ratiometric ECL sensor exhibited excellent analytical performance with a wide linear detection range and a detection limit down to 2 cells. This method could be further used for profiling the variation of glycans such as N-acetylglucosamine, N-acetylneuraminic acid and mannose on cell surface upon treatment. The proposed strategy realized highly sensitive determination of cell concentration, and accurate analysis of glycan expression on cell surface, showing promising application. (C) 2016 Elsevier B.V. All rights reserved.