Galactose functionalized diketopyrrolopyrrole as NIR fluorescent probes for lectin detection and HepG2 cell targeting based on aggregation-induced emission mechanism

Since the elucidation that sugar-lectin interactions contribute to the understanding of "Glycomics", how to construct glycosensors with rapid response, excellent sensitivity and selectivity is of intense research interest. Herein, we report the design of three NIR emissive glyco-probes based on diketopyrrolopyrrole (DPPs) conjugated with two (DPPG), four (DPPF-G) and six (DPPS-G) galactose groups. All three molecules could probe lectins with excellent sensitivity and selectivity. The increase of glyco-DPP emission in NIR region upon interaction with lectin is due to the aggregates formation induced by sugar-lectin interactions, which have been verified by dynamic light scattering (DLS) and scanning electronic microscope (SEM) analysis. Due to the multiple glyco-ligands on DPPS-G, it has been successfully used to stain HepG2 cells through interactions between galactose and asialogly-coprotein (ASGP-R), which are overexpressed on the surface of HepG2 cells.