Nonenzymatic Amperometric Aptamer Cytosensor for Ultrasensitive Detection of Circulating Tumor Cells and Dynamic...

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 Fe₃O₄@SiO₂ nanoparticles (Fe₃O₄@SiO₂-NH₂ 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 (H₂O₂). 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 × 10⁶ 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.