Nonenzymatic Amperometric Aptamer Cytosensor for Ultrasensitive Detection of Circulating Tumor Cells and Dynamic Evaluation of Cell Surface N-Glycan Expression

[Image: see text] Dynamic assessment of glycan expression on the cell surface and accurate determination of circulating tumor cells are increasingly imperative for cancer diagnosis and therapeutics. Herein, a unique and versatile nonenzymatic sandwich-structured electrochemical cytosensor was developed. The cytosensor was constructed based on a cell-specific aptamer, the lectin-functionalized porous core–shell palladium gold nanoparticles (Pd@Au NPs). To establish the cytosensor, amine-modified-SYL3C aptamer was first attached to the surface of aminated Fe(3)O(4)@SiO(2) nanoparticles (Fe(3)O(4)@SiO(2)–NH(2) NPs) through cross-linked reaction via glutaraldehyde. Besides, in terms of noncovalent assembly of concanavalin A on Pd@Au NPs, a lectin-functionalized nanoprobe was established. This nanoprobe had the capabilities of both the specific carbohydrate recognition and the current signal amplification in view of the Pd@Au NPs as the electrocatalyst for the reduction of hydrogen peroxide (H(2)O(2)). Herein, we used MCF-7 cells as a model target, and the constructed cytosensor showed a low detection limit (down to three cells), a wide linear detection ranging from 100 to 1 × 10(6) cells mL(–1). The established method sensitively realized the detection of the amount of cell and exact evaluation of glycan expression on cell surface, demonstrating great application prospects.