Multifunctional Proximity Labeling Strategy for Lipid Raft-Specific Sialic Acid Tracking and Engineering

Lipid raft-specific glycosylation has been implicated in many biological processes, including intracellular trafficking, cell adhesion, signal transduction, and host–pathogen interactions. The major predicament in lipid raft-specific glycosylation research is the unavailability of tools for tracking and manipulating glycans on lipid rafts at the microstructural level. To overcome this challenge, we developed a multifunctional proximity labeling (MPL) platform that relies on cholera toxin B subunit to localize horseradish peroxidase on lipid rafts. In addition to the prevailing electron-rich amino acids, modified sialic acid was included in the horseradish peroxidase-mediated proximity labeling substrate via purposefully designed chemical transformation reactions. In combination with sialic acid editing, the self-renewal of lipid raft-specific sialic acid was visualized. The MPL method enabled tracking of lipid raft dynamics under methyl-β-cyclodextrin and mevinolin treatments; in particular, the alteration of lipid rafts markedly affected cell migration. Furthermore, we embedded functional molecules into the method and implemented raft-specific sialic acid gradient engineering. Our novel strategy presents opportunities for tailoring lipid raft-specific sialic acids, thereby regulating interactions associated with lipid raft regions (such as cell–virus and cell–microenvironment interactions), and can aid in the development of lipid raft-based therapeutic regimens for tumors

Design and Synthesis of Fluorinated Amphiphile as ¹⁹F MRI/Fluorescence Dual-Imaging Agent by Tuning the Self-Assembly

Both ¹⁹F MRI and optical imaging are powerful noninvasive molecular imaging modalities in biomedical applications. To integrate these two complementary imaging modalities, the design and synthesis of a novel ¹⁹F MRI/fluorescence dual-modal imaging agent is reported herein. Through Sonogashira coupling reaction between the fluorinated phenylacetylene and 1,2,4,5-tetraiodobenzene, a fluorophore with 48 symmetrical fluorines at its periphery was constructed with high efficacy. High aqueous solubility was achieved by PEGylation of the fluorophore with monodisperse PEGs. However, an unexpected self-assembly of the PEGylated amphiphilic fluorophore in water “turned off” the ¹⁹F NMR signal. However, hydrogenation of the triple bonds or introduction of branched monodisperse PEGs was able to efficiently tune the self-assembly, resulting in the “turning on” of the ¹⁹F NMR signal. One of these amphiphiles combines the advantages of label-free fluorescence, high ¹⁹F MRI sensitivity, biocompatibility, and excellent aqueous solubility. The results demonstrate the great potential of such amphiphiles for real-time ¹⁹F MRI and fluorescence dual-modality imaging