In situ scanometric assay of cell surface carbohydrate by glyconanoparticle-aggregation-regulated silver enhancement

A convenient and label-free scanometric approach for in situ cell surface carbohydrate assay was designed by integrating the bioconjugation and aggregation of glyconanoparticles, silver signal amplification, and spot test. The novel glyconanoparticles were prepared by a one-pot procedure. In the presence of lectin, using concanavalin A and mannose as a couple of model, the glyconanoparticles exhibited fast aggregation. The aggregation process could be inhibited by the specific recognition of lectin by the carbohydrate on the cell surface. Combining the gold nanoparticle catalyzed silver enhancement and scanometric detection, the number of cell surface carbohydrate groups could be conveniently read out. The average number of mannose units on a single living intact BGC cell was detected to be (4.5 +/- 0.4) x 10(7). This largely noninstrumental method took the advantages of a nanoparticle-based recognition and an aggregation-regulated signal amplification and avoided cell pretreatment and labeling processes. It could determine cell surface densities of different carbohydrates in parallel and thus would contribute considerably to meeting the challenges in decipherment of the glycomic codes.