Interactions of the β-blocker drug, propranolol, with detergents, β-cyclodextrin and living cells studied using fluorescence spectroscopy and imaging

Abstract

Interactions of theβ-blocker drug, propranolol, with amphipathic systems have been studied using fluorescence spectroscopy. The results show a strong binding of propranolol with micelles of sodium dodecyl sulfate revealed through changes in the fluorescence spectrum and an increase in fluorescence lifetime. Quenching of propranolol fluorescence by iodide is used to demonstrate interaction withβ-cyclodextrin. At high concentrations, self-quenching of propranolol fluorescence was also observed withκq=2.5×109dm3mol–1s–1. Two-photon excited (630 nm) fluorescence lifetime imaging of propranolol in cells showed propranolol to be widely distributed in the cell cytoplasm, with fluorescence lifetimes shorter than in solution. The results suggest that intracellular propranolol is mainly confined within the aqueous cytoplasm and rather than membrane associated.

Two-photon excitation with pico-second fluorescence lifetime imaging to detect nuclear association of flavanols

“…In fluorescence life-time imaging microscopy (FLIM) both fluorescence intensities and fluorescence lifetimes of specific compounds can be measured at each pixel in the image [21,22]. In addition, variations in fluorescence lifetime can provide further image contrast: lifetime shifts can serve as sensitive probes for detecting molecular interactions and may yield information on a compound's environment, such as pH or oxygen concentration [23][24][25]. Lifetime, τ, is derived from the time-constant of the fluorescence decay (Fig.…”

“…Thus, 2PE at 560 nm mimics UV excitation at 280 nm [23,27]. In FLIM ultrafast lasers providing pulse lengths of the order of 200 femtoseconds (200 x 10 -15 s) enable time-resolved measurements, which can detect molecular interactions in solution and cells [23][24][25]28] Here we describe 2PE experiments designed to eliminate any doubts regarding the results from previous histological studies that employed the DMACA staining reagent. Twophoton excitation coupled to 3-D fluorescence lifetime imaging microscopy enabled examination of intact biological tissues and highly localised, non-destructive and selective detection of flavanols.…”

Fluorescence lifetime imaging microscopy (FLIM) to demonstrate the nuclear binding of flavanols and (–-epigallocatechin gallate

“…New Such analytical developments will facilitate new types of biological experiments that can test how these compounds, when present in plant foods, can impact on mammalian cells and health. Although FLIM is a new technique to both mammalian and plant cell biologists alike, its application is growing rapidly [23][24][25][26]28], particularly in protein-protein interactions that involve energy transfer processes. However, this is the first study to report FLIM for other plant components and as the technique becomes more readily available, its impact can only grow.…”

“…1 and In fluorescence life-time imaging microscopy (FLIM) both fluorescence intensities and fluorescence lifetimes of specific compounds can be measured at each pixel in the image [21,22]. In addition, variations in fluorescence lifetime can provide further image contrast: lifetime shifts can serve as sensitive probes for detecting molecular interactions and may yield information on a compound's environment, such as pH or oxygen concentration [23][24][25]. Lifetime, τ, is derived from the time-constant of the fluorescence decay ( Fig.…”

Fluorescence Lifetime Imaging of Propranolol Uptake in Living Glial C6 Cells

“…It is known that propranolol exhibits intrinsic fluorescence in the ultraviolet region with a solventdependent maximum between 320 and 360 nm [8][9][10][11]. This has been used for a number of purposes, including quantification of propranolol in drug assays, detection during microchip electrophoresis, and monitoring binding to imprinted polymers.…”