Re: P7 Microemulsions

From: Luis Martinez.
Date: 11/26/97
Time: 1:07:30 PM
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Thanks for your comments, Chris. Of course, it is quite difficult to extrapolate results in microemulsions to the biological situation, althoug you can get very valuable information. We think that the absorption spectra indicate that the most probable location of the NSAID is the interface in W/O and O/W microemulsions, somewhat more towards the oil phase in case of W/O. As you say, this is confirmed by a similar trend for the series for W/O and O/W. For the sensitizing drugs (excepting TA), the quantum yields given are, in fact, absolute quantum yields. Only for TA the singlet oxygen luminescence signal depends on the concentration of the drug; we have to determine the rate constant of singlet oxygen quenching by TA itself in order to obtain the absolute quantum yield. We also think that the quantum yield depends both on the environment and on the nature of the sensitizer (drug). In aqueous solution, measurements have shown that the quantum yield is pH dependent and, in general, 2 to 4 times lower than in microemulsions (even O/W), whereas measurements in acetonitrile are closer to those obtained in heterogeneous systems. Finally, it seem to us that the environment affects the NSAID behavior in a similar way.


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