A two-photon fluorescent lipid raft probe derived from dicyanostilbene and similar to cholesterol's structure

Lipid raft is a microdomain being rich in cholesterol and sphingolipid and closely related to neurodegenerative diseases such as Alzheimer's disease and prion disease. Hence the study on the physiological mechanism of lipid raft is helpful to reveal its biological role and its correlations with diseases. Two-photon fluorescence probe for lipid raft is a sharp tool to achieve this goal. A dicyanocarbazolylstilbene-derived two-photon fluorescence probe for lipid raft (DLR) was developed. Both DLR and lipid raft belong to D-π-A (donor-π-acceptor; π: C = C) type rigid planar molecule, and contain four fused carbon rings (one five-membered ring and three six-membered ring), and bear a long carbon chain (C₈H₁₇). The excellent comparability between the rigid plane of the probe molecule and the rigid lipid raft could significantly enhance the specific affinity to lipid rafts. DLR's maximum emission wavelength increased with medium polarity while its fluorescence intensity (FI) augmented with viscosity, and FI in DPPC (dipalmitoylphosphatidylcholine) was 20 times higher than that in DOPC (dioleoylphosphatidylcholine). DLR's fluorescence lifetime in DPPC was more than 2.2 times longer than that in DOPC. These indicate that DLR can distinguish DPPC from DOPC. Φδs of DLR in DPPC and DOPC were 1350 GM and 67 GM, respectively. DLR can image lipid raft distribution in cells and tissues. Graphic abstract: