Fluorescent Carbon Dots Functionalized With Self-Assembled Glycan Monolayers For Probing Interactions Across The Glyco- Interactome

Multivalent protein-glycan interactions are widespread in biology and are vital for initial recognition in cell-cell communication, host immune regulation, and viral and bacterial infection. Recently, fluorescent nanomaterials such as quantum dots (QDs) have been identified as a capable scaffold for multivalent carbohydrate immobilization. Carbon dots (CDs) are essentially heavy-metal-free QDs, offering a low-toxicity alternative for bioimaging and biosensing applications. Herein, we report a simple and versatile route for linker functionalization of lactose with (3-glycidyloxypropyl)-trimethoxysilane (GOPTS) for conjugation to various CDs. CDs derived by thermal treatment of polyethylenimine (PEI) with citric acid and lactose, as the glycan, were employed in a number of detailed biological applications and evaluations. The self-assembled glycan monolayer (SAGM) method described here resulted in a high yield of lactose-conjugated CDs. Specific interactions of our lactose-coated CDs with cells, lectin microarrays, and as internalized bioimaging nanolights were demonstrated, with intracellular localization in a variety of cell lines observed. This present study offers a facile, one-pot, green, and low-cost synthesis of fluorescent multivalent nanoparticles that can be applied in the study of diverse interactions across the glycointeractome.