Imaging specific cell-surface sialylation using DNA dendrimer-assisted FRET

Sialylation plays a vital role in multiple different physiologic processes, aberrant sialylation is highly related to disease development. Especially in cancer development, changed states of specific cell-surface sialylation implies rich cancer-related information. Therefore, it is necessary to image specific cell-surface sialylation for better understanding biological functions of sialylation. To meet this purpose, we designed a DNA dendrimer-assisted fluorescence resonance energy transfer (FRET) strategy in this work. By labeling multiple FRET donors and acceptors on the target molecules through metabolic oligosaccharide engineering (MOE) and targeted recognition of aptamer-tethered DNA dendrimer, the FRET was significantly improved. With the DNA dendrimer-assisted FRET strategy, specific imaging of cell-surface sialylation on SMMC-7721 and CEM cells were successfully achieved. The obtained FRET signal intensity was approximately four times higher than the control without the assistance of DNA dendrimer. Moreover, this method is competent to monitor changed states of PTK7-specific sialylation induced by tunicamycin. The proposed imaging strategy may provide a powerful tool to explore the physiological roles of specific cell-surface sialylation and the related mechanism of diseases.