Design and implementation of electrochemical cytosensor for evaluation of cell surface carbohydrate and glycoprotein

A new strategy for assessing cell surface carbohydrates and P-glycoprotein (P-gp) expression status and quantifying the cell numbers with an electrochemical immunoassay was designed. In order to construct the base of the cytosensor, a novel 3-D architecture was initially fabricated by combining nitrogen-doped carbon nanotubes, thionine, and gold nanoparticles via a simple layer-by-layer method. The formed architecture provided an effective matrix for concanavalin A (Con A) binding and made the immobilized Con A hold high stability and bioactivity. On the basis of the specific recognition of cell surface mannosyl groups to Con A, the Con A/3-D architecture interface showed a predominant capability for cell capture. With another coupled signal amplification based on a enzymatic catalytic reaction of HRP toward the oxidation of thionine by the H₂O₂, which was induced by two-step immunoreactions, the proposed cytosensor showed an excellent analytical performance for the detection of HeLa cells ranging from 8.0 × 10 ² to 2.0 × 10⁷ cells mL^-1 with a limit of detection of 500 cells mL^-1. Moreover, with the use of preblocking procedures, the mannosyl groups and P-gp on single HeLa cell could be further detected to be (4 ± 2) × 10¹⁰ molecules of mannose moieties and 8.47 × 10⁶ molecules of P-gp. This strategy offers great promise for sensitive detection of cancer cells and cell surface receptors and thus may help improve cancer diagnosis and treatment.