Analytical studies on photochemical behavior of phototoxic substances; effect of detergent additives on singlet oxygen generation.
OBJECTIVE
Monitoring of reactive oxygen species (ROS) generation from photoirradiated compounds would be effective for the prediction of the phototoxic potential. The aim of this investigation was to clarify the possible role of biomimetic vehicle systems on the photochemical properties of phototoxic compounds, focusing on the singlet oxygen generation.


METHODS
Nine phototoxic and one non-phototoxic compounds (200 microM), dissolved in Tween 20, sodium laurate, or sodium dodecyl sulfate (SDS) micellar solution, were exposed to UVA/B light (250 W/m2), and singlet oxygen generation was monitored by RNO bleaching methodology. Photochemical properties of photosensitizers were also evaluated by UV measurement, and the interaction of photosensitizers with surfactant micelles was assessed by Z-potential and NMR spectroscopic analyses.


RESULTS
All phototoxic compounds tended to generate singlet oxygen under light exposure in the all micellar solutions tested. There appeared to be some differences in photoreactivity of both cationic and anionic photosensitizers among the micelles tested, whereas ROS data on anthracene, dissolved in three micellar solutions, were found to be quite similar. Photosensitizers exhibited no significant changes in UV spectral patterns among the dissolving micellar solutions. Addition of cationic photosensitizer at the final concentration of 100 microM into 100 mM SDS solution resulted in the 20 mV increase of zeta potential and transition of NMR spectral pattern, which would reflect the electrostatic interaction with anionic micelles.


CONCLUSIONS
Based on the data obtained, the photoreactivity of photosensitizing molecules, especially cationic and anionic photosensitizers, strongly depends on the physicochemical properties of the microenvironment.
Onoue
Satomi
S
Analytical Research and Development, Pfizer Global Research and Development, Nagoya Laboratories, Pfizer Japan Inc., 5-2 Taketoyo, Aichi, 470-2393, Japan. onoue@u-shizuoka-ken.ac.jp
Yamauchi
Yukinori
Y
Kojima
Takashi
T
Igarashi
Naoko
N
Tsuda
Yoshiko
Y
D000818:Animals; D017484:Dermatitis, Phototoxic / Q000209:etiology* / Q000378:metabolism; D003902:Detergents / Q000737:chemistry*; D006801:Humans; D007850:Lauric Acids / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D011136:Polysorbates / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry* / Q000378:metabolism; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D012995:Solubility; D055672:Static Electricity; D013997:Time Factors; D014466:Ultraviolet Rays
D003902:Detergents; D007850:Lauric Acids; D008823:Micelles; D017319:Photosensitizing Agents; D011136:Polysorbates; C030358:lauric acid; D026082:Singlet Oxygen; D012967:Sodium Dodecyl Sulfate