Abstract:
:The photophysical properties of Piroxicam, a nonsteroidal anti-inflammatory drug (NSAID), were investigated at different pHext values in reversed micelles of Aerosol-OT (AOT) in iso-octane, using both steady-state and picosecond time-resolved fluorescence spectroscopy. In contrast with the very complex data obtained in aqueous media, where several prototropic species are in equilibrium, the reversed micellar system essentially favors two species. The absorption spectra shows only one isosbestic point at lambda = 348 nm. Excited-state intramolecular proton transfer (ESIPT), also detected in water, is promoted at low water pool contents measured by omega 0 = [H2O]/[AOT]. A strongly shifted (lambda em = 470 nm) tautomeric emission is found. Upon the gradual increase of omega 0, striking differences with pHext are found. At pHext = 4, the drug preferentially locates itself in the interfacial region partitioning between a hydrophobic and a hydrophilic domain. Global analysis was applied to the decay data and the results were interpreted by the "two-state excited-state" formalism. At pHext = 7, the anionic species is prevalent and the probe locates itself deeper inside the water core of the reversed micelles. Thus, a strong dependence on water content is detected, approaching a behavior similar to that observed in free aqueous solutions.
journal_name
Photochem Photobioljournal_title
Photochemistry and photobiologyauthors
Andrade SM,Costa SM,Pansu Rsubject
Has Abstractpub_date
2000-04-01 00:00:00pages
405-12issue
4eissn
0031-8655issn
1751-1097journal_volume
71pub_type
杂志文章abstract::To improve the understanding of human skin autofluorescence emission, the spectroscopic and microscopic characteristics of skin autofluorescence were studied using a combined fluorescence and reflectance spectroanalyzer and a fiber optic microspectrophotometer. The autofluorescence spectra of in vivo human skin were m...
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