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Time-resolved nanosecond fluorescence lifetime imaging and picosecond infrared spectroscopy of combretastatin A-4 in solution and in cellular systems

Bisby, RH; Botchway, SW; Greetham, GM; Hadfield, JA; Mcgown, A; Parker, AW; Scherer, KM; Towrie, M

Authors

RH Bisby

SW Botchway

GM Greetham

JA Hadfield

A Mcgown

AW Parker

KM Scherer

M Towrie



Abstract

Fluorescence lifetime images of intrinsic fluorescence obtained with two-photon excitation at 630 nm are shown following uptake of a series of E-combretastatins into live cells, including human umbilical vein endothelial cells (HUVECs) that are the target for the anticancer activity of combretastatins. Images show distribution of the compounds within the cell cytoplasm and in structures identified as lipid droplets by comparison with images obtained following Nile red staining of the same cells. The intracellular fluorescent lifetimes are generally longer than in fluid solution as a consequence of the high viscosity of the cellular environment. Following incubation the intracellular concentrations of a fluorinated derivative of E combretastatin A4 in HUVECs are up to between 2 and 3 orders of magnitude higher than the concentration in the surrounding medium. Evidence is presented to indicate that at moderate laser powers (up to 6 mW) it is possible to isomerize up to 25% of the combretastatin within the femtolitre focal volume of the femtosecond laser beam. This suggests that it may be possible to activate the E-combretastatin (with low cellular toxicity) to the Z-isomer with high anticancer drug activity using two-photon irradiation. The isomerization of Z- and E-combretastatins by 266 nm irradiation has been probed by ultrafast time-resolved infrared spectroscopy. Results for the E-isomer show a rapid loss of excess vibrational energy in the excited state with a lifetime of 7 ps, followed by a slower process with a lifetime of 500 ps corresponding to the return to the ground state as also determined from the fluorescence lifetime. In contrast the Z-isomer, whilst also appearing to undergo a rapid cooling of the initial excited state, has a much shorter overall excited state lifetime of 14 ps.

Citation

Bisby, R., Botchway, S., Greetham, G., Hadfield, J., Mcgown, A., Parker, A., …Towrie, M. (2012). Time-resolved nanosecond fluorescence lifetime imaging and picosecond infrared spectroscopy of combretastatin A-4 in solution and in cellular systems. Measurement Science and Technology, 23, 084001. https://doi.org/10.1088/0957-0233/23/8/084001

Journal Article Type Article
Publication Date Jan 1, 2012
Deposit Date Jun 21, 2012
Publicly Available Date Apr 5, 2016
Journal Measurement Science and Technology
Print ISSN 0957-0233
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 23
Pages 084001
DOI https://doi.org/10.1088/0957-0233/23/8/084001
Keywords fluorescence, lifetime, imaging, microscopy, two-photon, combretastatin, live cell,
time resolved, infrared, spectroscopy, ultrafast
Publisher URL http://dx.doi.org/10.1088/0957-0233/23/8/084001
Related Public URLs http://iopscience.iop.org/0957-0233

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