Time-resolved fluorescence spectroscopy and intracellular imaging of disulphonated aluminium phthalocyanine

M. Ambroz, A. J. MacRobertl, J. Morgan, Gary Rumbles, M. S C Foley, D. Phillips

Research output: Contribution to journalArticle

73 Citations (Scopus)

Abstract

Spectroscopic studies were carried out on the photosensitizer disulphonated aluminium phthalocyanine (AlS2Pc) which has prospective applications in photodynamic therapy. The fluorescence lifetimes of AlS2Pc were measured in a range of model systems and cultured leukaemic cells using laser excitation and time-correlated, single-photon-counting detection. In an investigation of non-covalent protein binding, we studied AlS2Pc in the presence of human serum albumin (HSA) in 0.1 M phosphate-buffered saline at pH 7.4. On addition of excess concentrations of HSA, small red shifts in the fluorescence and absorbance spectra were observed, together with an increase in fluorescence polarization anisotropy, consistent with binding of the phthalocyanine. Fluorescence decays could be resolved into two lifetimes for bound AlS2Pc with a dominant component of 5.5 ns and a minor component of 1 ns. Fluorescence imaging and time-resolved microfluorometry were carried out on intracellular AlS2Pc using leukaemic K562 cells. Microscopic imaging with a charge-coupled device (CCD) camera revealed that AlS2Pc fluorescence predominated in a discrete perinuclear region which was then probed selectively by a focused laser spot for fluorescence lifetime measurements. Bi-exponential decays with lifetime components of 6.1 and 2.2 ns were observed. On irradiation at 633 nm, the fluorescence intensity increased initially and subsequently declined due to photodegradation.

Original languageEnglish
Pages (from-to)105-117
Number of pages13
JournalJournal of Photochemistry and Photobiology B: Biology
Volume22
Issue number2
DOIs
Publication statusPublished - 1994

Keywords

  • Fluorescence imaging
  • Fluorescence lifetime
  • Photodynamic therapy
  • Phthalocyanine

ASJC Scopus subject areas

  • Plant Science
  • Bioengineering
  • Physical and Theoretical Chemistry

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