Estimation of Critical Micelle Concentrations of Lysolecithins with Fluorescent Probes

Abstract

The estimation of the critical micelle concentration (cmc) of various lysolecithins with 2-p-toluidinylnaphthalene-6-sulfonate (TNS) and l-anilinonaphthalene-8-sulfonate (ANS) as fluorescent probes was investigated. The fluorescence yield of TNS in palmitoyl lysolecithin micellar phase was found to be somewhat larger than that of ANS. Further, the fluorescence yield of TNS in the aqueous phase is known to be much smaller than that of ANS. Thus, TNS should be useful for estimating very small cmc values of surfactants such as lysolecithins. The cmc values of lysolecithins estimated by using TNS were 0.5 mM for lauroyl lysolecithin, 63 μM for myristoyl lysolecithin, 8.3 μM for palmitoyl lysolecithin and 6.6 μM for oleoyl lysolecithin, in 20 mM Tris-HCl buffer solution (pH 7.0) at 25 °C. It was also found that stearoyl lysolecithin does not form micelles at room temperature, and the Krafft point is about 60 °C. © 1986, The Pharmaceutical Society of Japan. All rights reserved.