We report a synthetic route to BODIPY–cholesterol conjugates in which the key steps were Suzuki or Liebeskind–Srogl cross-coupling of cholesterol phenyl moieties with structurally diverse BODIPY scaffolds. All conjugates feature single-bonded and hydrophobic linkages between the fluorophore and sterol that are devoid of heteroatoms. Using HeLa cells, we show that these BODIPY–cholesterol analogues can be used simultaneously with the parent BODIPY–cholesterol for cell imaging and flow cytometry. The BODIPY–cholesterol analogues exhibit similar cellular localization in HeLa cells and show similar cholesterol efflux properties from THP-1 cells to HDL acceptors. These results demonstrate that the red-shifted BODIPY–cholesterol analogues behave in a manner similar to unlabeled cholesterol and are useful probes for simultaneous visualization of intracellular cholesterol pools and for monitoring cholesterol efflux from cells to extracellular acceptors.

Model membrane systems have become invaluable tools to investigate specific features of cellular membranes. Although a variety of different experimental assays does exist, many of them are rather complicated in their preparation and difficult in their practical realisation. Here, we propose a new simple miniaturised monolayer assay that can easily be combined with standard analytical techniques such as confocal fluorescence microscopy and fluorescence correlation spectroscopy (FCS).