Manipulation and characterization of photo-induced transient states of Merocyanine 540 by fluorescence correlation spectroscopy
2000 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 2, no 15, 3435-3441 p.Article in journal (Refereed) Published
In this study, fluorescence correlation spectroscopy (FCS) is used to investigate the photo-induced transient states of Merocyanine 540 (MC540), a fluorescent agent for photodynamic therapy. Two relaxation processes are observed in the FCS measurements, which can be attributed to trans-cis isomerization and triplet state formation. Under the photostationary conditions present in the detection volume of the FCS measurements, the steady state populations of the photo-isomer and the triplet state, as well as their relaxation rates, can be determined. The population of the triplet states was noticeably reduced by light-induced deactivation at 515 nm excitation, and by simultaneous excitation at 647 nm the triplet state build-up could be almost eliminated with a concomitant increase in fluorescence intensity. By applying a simplified kinetic model for the measured fluorescence fluctuations it is possible to determine the rates for intersystem crossing, triplet state decay, as well as photo-induced isomerization and back-isomerization. In relation to other present techniques, FCS offers a relatively simple way to monitor photo-induced trans-cis isomerization, and cis-trans back-isomerization. For MC540, it is desirable to increase the triplet state formation at the expense of trans-cis isomerization in order to optimize the photodynamic action. FCS is well suited to monitor these processes on a microscopic scale, and thus to follow the local potency of MC540 as a photodynamic agent, at its site of action in target cells.
Place, publisher, year, edition, pages
2000. Vol. 2, no 15, 3435-3441 p.
indodicarbocyanine dyes, iodide dodci, photoisomerization, dynamics, carbocyanines, fluctuations, temperature, relaxation, singlet, system
IdentifiersURN: urn:nbn:se:kth:diva-19930ISI: 000088407700011OAI: oai:DiVA.org:kth-19930DiVA: diva2:338622
QC 201005252010-08-102010-08-10Bibliographically approved