Energy Transfer-Based Recognition of Membrane Cholesterol by Controlling Intradistance of Linker

초록

Gold nanoparticles (AuNPs) are good candidates for donor material in energy transfer systems and can easily be functionalized with various ligands on the surface with Au-S bonding. Cyclodextrin (CD) forms inclusion complexes with fluorophores due to its unique structure for host-guest interaction. In this study, we fabricated beta CD-functionalized AuNPs using different lengths of thiol ligands and recognized cholesterol to confirm the energy-transfer-based turn-on fluorescence mechanism. AuNP-beta CD conjugated with various thiol ligands and quenched the fluorescein (Fl) dye, forming beta CD-Fl inclusion complexes. As the distance between AuNPs and beta CD decreased, the quenching efficiency became higher. The quenched fluorescence was recovered when the cholesterol replaced the Fl because of the stronger binding affinity of the cholesterol with beta CD. The efficiency of cholesterol recognition was also affected by the energy transfer effect because the shorter beta CD ligand had a higher fluorescence recovery. Furthermore, we fabricated a liposome with cholesterol embedded in the lipid bilayer membrane to mimic the cholesterol coexisting with lipids in human serum. These cellular cholesterols accelerated the replacement of the Fl molecules, resulting in a fluorescence recovery higher than that of pure lipid. These discoveries are expected to give guidance towards cholesterol sensors or energy-transfer-based biosensors using AuNPs.

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