Rapid and sensitive detection of cell surface N-glycans in live cancer cells using a novel acid-activated...

Glycans on the surface of cells play critical roles in various biological processes, including cell communication, the immune response, infection, development, and differentiation. The presence of glycans is closely related to cancer growth and metastasis. This study presents a biosensor based on an acid-activated nanoplatform for glycan detection on live cancer cells. Using human breast cancer cells (MCF-7 cells) and N-glycans as the target, concanavalin A (ConA)-modified magnetic nanoparticles (ConA-Cu(II)-MNPs) serve as the loading interface. Specifically, the nanoprobe consists of ConA with active N-glycan binding sites, glucose, and 5(6)-carboxytetramethylrhodamine (TAMRA) conjugated to pH-sensitive PDPA polymeric micelles, and these elements are used to prepare the acid-activated biosensor. In this strategy, the magnetic nanoparticle interface increases the loading capacity of ConA, and the active mannose binding sites allow ConA to capture the target cells. Therefore, the presence of glycans on the cell surface is reflected by the number of cells captured on the interface. Upon the addition of the specific nanoprobe to the captured cells at pH < 6.0, TAMRA is released from the micelles, generating a fluorescence signal. Additionally, the ConA on the nanoprobe specifically recognizes MCF-7 cells. The increase in the number of target cells captured on the ConA-Cu(II)-MNP interface leads to the loading of more TAMRA nanoprobes, and subsequently, a stronger fluorescence signal. The nanoprobe exhibits a substantial response to MCF-7 cells, detecting them at concentrations as low as 10 cells/mL. This biosensor can also selectively monitor changes in mannose levels on the cell surface after treatment with an N-glycan inhibitor. Using A549 and MRC-5 cells as models, the developed strategy demonstrates a low detection limit (down to three cells) and a wide linear detection range (from 10 to 1 × 10⁶ cells/mL). Therefore, this acid-activated biosensor shows great potential for analyzing glycosylation on the surfaces of different cell types.