dual fluorescence imaging of mucin 1 and its glycoform in tumor cells.

The most efficient approach for cancer identification and monitoring is the detection of cancer-associated protein biomarkers but an accurate diagnosis requires multiple analyses. Glycosylation profiling can provide important biological information since different glycoforms are involved in malignant transformation. Here, a near-infrared (NIR) light activated fluorescence resonance energy transfer (FRET) strategy for the efficient and reliable simultaneous dual imaging of the mucin 1 (MUC1) protein backbone and MUC1-specific sialic acid (Sia) is reported. MUC1, an important tumor biomarker, is overexpressed and under-glycosylated in most tumor cells. Two aptamer-functionalized nanoprobes, Cy5-labeled Sia aptamer-functionalized gold nanostars (Sia-GNSs) and MUC1 aptamer-functionalized quantum dots (MUC1-QDs), were successfully constructed with high specificity and biocompatibility. Upon excitation with NIR light, Sia-GNSs endothermically released the Cy5-labeled Sia aptamer that specifically binds to Sia. The Cy5 fluorescence can be observed due to the FRET effect when the Cy5-labeled Sia aptamer and MUC1-QDs bind to the same MUC1 molecule. Dual imaging and relative quantification of MUC1 and its sialylation were achieved , and in clinical tissue samples. This efficient platform allows for the simultaneous detection of protein biomarkers and their glycosylation pattern, with significant potential for clinical cancer diagnostics.