Elucidating chlorin e6-sucrose ester interaction using coarse-grain modeling and fluorescence spectroscopic technique

Abstract

This study aimed at visualization and elucidation of aggregate-to-monomer conversion of chlorin e6 (Ce6) by non-ionic surfactant sucrose esters. Excitation-emission matrix (EEM) fluorescence spectra of Ce6 were recorded in the presence of different concentrations of the surfactants with alkyl substituents of various chain lengths [lauryl (SEL)/myristyl (SEM)/palmityl (SEP)]. The EEM spectra were deconvoluted and parallel factor (PAFARAC) algorithm was applied to determine the concentrations of the underlying constituents (aggregates and monomers) for each Ce6-sucrose ester system. The experimental results were further correlated by dissipative particle dynamics (DPD), a coarse grain simulation technique. The results showed that disruption of Ce6 aggregates was primarily initiated at sub-micellar concentration of the sucrose ester and completed at concentrations higher than their corresponding critical micelle concentrations. Thermodynamic study revealed that Ce6 monomers were encased in the hydrophobic micellar cores of the sucrose esters. PARAFAC analysis and DPD response parameters substantiated the overall disaggregation rank order as SEP. >. SEM. >. SEL. This study successfully demonstrated Ce6-surfactant interaction using a novel multivariate technique while DPD simulation served as a visualization tool for illustrating underlying changes in the Ce6-sucrose ester systems at different surfactant concentrations. © 2014 Elsevier B.V.