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Effect of aggregation on bacteriochlorin a triplet-state formation: A laser flash photolysis study

Authors
Publication Date
Keywords
  • Bacteriochlorin
  • Photodynamic Therapy
  • Laser Flash Phtolysis
  • Life Sciences :: Biochemistry
  • Biophysics & Molecular Biology [F05]
  • Sciences Du Vivant :: Biochimie
  • Biophysique & Biologie Mol√©culaire [F05]
Disciplines
  • Medicine
  • Physics

Abstract

Bacteriochlorin a (BCA) is a potential photosensitizer for photodynamic therapy of cancer. It has been shown previously that the photoefficiency of the dye is mainly dependent on singlet oxygen (O-1(2)) generation. Nanosecond laser flash photolysis was used to produce and to investigate the excited triplet state of the dye in methanol, phosphate buffer and dimiristoyl-L-alpha-phosphatidylcholine (DMPC) liposomes. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients and formation quantum yield of singlet-triplet intercrossing. The lifetime of the BCA triplet state was measured at room temperature. The triplet-state quantum yield is quite high in methanol (0.7) and in DMPC (0.4) but only 0.095 in phosphate buffer. In the last case, BCA is in a monomer-dimer equilibrium, and the low value of the quantum yield observed was ascribed to the fact the triplet state is only formed by the monomers.

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