Location of 7-Aminoactinomycin D in Micellar Medium Depends on Ionic Nature of the Surfactant Head Group

Abstract

7-Aminoactinomycin D (7AAMD) is the fluorescent analogue of the anticancer drug actinomycin D (AMD). In order to overcome toxic side effects and enhanced bioavailability of 7AAMD, micellar drug carrier systems could be useful. We have used cationic (hexadecetyltrimethylammonium bromide [CTAB]), anionic (sodium dodecyl sulphate [SDS]) and non-ionic (t-octylphenoxypolyoxyethanol, Triton-X100 [TX 100]) surfactants to prepare micelle. We have explored the mechanism of the interaction of 7AAMD with micelles using steady-state and time-resolved fluorescence spectroscopy. Our results revealed that the Stokes' shift values of 7AAMD were decreased in all three micellar medium compared to that in the absence of any micelle. Thus, 7AAMD is localized in less polar microenvironment of micelles than bulk water. In addition, from the time-resolved fluorescence study of 7AAMD, we found that the relative contribution of the conformers of 7AAMD depended on the surfactant head group. Furthermore, acrylamide induced fluorescence quenching study shows differential accessibility of the quencher molecules towards 7AAMD depending on the ionic nature of the surfactant head group. In the presence of acrylamide, 7AAMD was expelled out from the non-ionic TX 100 micelle but not in CTAB and SDS micelle. Thus, our results are valuable to design new drug delivery system for AMD-like antitumor agents.