Sensitive Chemiluminescent Imaging for Chemoselective Analysis of Glycan Expression on Living Cells Using a Multifunctional Nanoprobe

A novel sensitive chemiluminescent (CL) imaging method was developed for in situ monitoring of cell surface glycan expression through chemoselective labeling of carbohydrate motifs and then binding to a multifunctional nanoprobe. The nanoprobe was fabricated by assembling biotin-DNA and a large amount of horseradish peroxidase (HRP) on gold nanoparticles (AuNPs). The chemoselective labeling was performed by selective oxidization of the hydroxyl sites of sialyl and galactosyl groups on cell surfaces into aldehydes by periodate and galactose oxidase, respectively, and then aniline-catalyzed hydrazone ligation with biotin hydrazide for specific recognition to avidin. With the biotin avidin system, the multifunctional nanoprobe could conveniently be bound to the glycan sites on the cell surface. The DNA chain presenting between the AuNPs and biotin assembled on the nanoprobe could obviate the steric effect, and HRP acted to trigger the CL emission of the luminal-H2O2 system. Therefore the expression of both sialyl and galactosyl groups could be selectively monitored by CL imaging with high sensitivity due to the high amount of HRP. Using human liver cancer HCCC-9810 cells as a model, this CL imaging strategy could detect HCCC cells ranging from 6 x 10(2) to 1 X 10(7) cells mL(-1) with a detection limit down to 12 cells. More importantly, this method could be used for distinguishing cancer cells from normal cells and monitoring of dynamic carbohydrate expression on living cells, providing promising application in clinical diagnosis and treatment of cancer.