Carbon Nanotube-Amplified Optical Macro-Glycoligands for Probing Glycan−Protein Interactions

Abstract

Glycan−protein interactions play key roles in many biological processes of both physiological and pathological pathways. Studying glycan−protein interactions would enable the understanding of molecular mechanisms of biological processes and provide vast potential to discover diagnostic and therapeutic targets of various diseases. However, challenges arise from the weak affinity of glycan−protein interactions, the lack of well-defined scaffolds to amplify specific interactions, and the lack of robust, label-free assay technology. In this report, we developed novel label-free optical probes with integrated features stemming from the intrinsic near-infrared fluorescence of the carbon nanotube scaffold and unique glycan presentation of complexed glycopolymers containing native ligands, including biologically active sialic acids. We then interrogated the specific interactions of nanoprobes with various glycan-binding proteins, including viral SARS-CoV-2 spike protein and immune cell receptors of Siglec-7/9. We found that nanoprobes amplify the glycan recognition of protein receptors with high specificities and affinities with KD values in the range of 54−688 nM, despite being complexed with glycopolymers of significantly low glycan densities. This work demonstrates the potential of integrated nanoprobes for the development of a novel label-free sensor platform for detecting a wide range of pathogen and disease biomarkers in a high-throughput fashion with enhanced chemical and optical tunability.