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Modulation of Drug Transport Properties by Multicomponent Diffusion in Surfactant Aqueous Solutions

Summary: Modulation of Drug Transport Properties by Multicomponent
Diffusion in Surfactant Aqueous Solutions
Huixiang Zhang,
and Onofrio Annunziata*,
Department of Chemistry, Texas Christian UniVersity, Fort Worth, Texas 76129, and Alcon Research, Ltd.,
Fort Worth, Texas 76134
ReceiVed May 27, 2008. ReVised Manuscript ReceiVed July 1, 2008
Diffusion coefficients of drug compounds are crucial parameters used for modeling transport processes. Interestingly,
diffusion of a solute can be generated not only by its own concentration gradient but also by concentration gradients
of other solutes. This phenomenon is known as multicomponent diffusion. A multicomponent diffusion study on
drug-surfactant-water ternary mixtures is reported here. Specifically, high-precision Rayleigh interferometry was
used to determine multicomponent diffusion coefficients for the hydrocortisone-tyloxapol-water system at 25 C.
For comparison, diffusion measurements by dynamic light scattering were also performed. In addition, drug solubility
was measured as a function of tyloxapol concentration, and drug-surfactant thermodynamic interactions using the
two-phase partitioning model were characterized. The diffusion results are in agreement with a proposed coupled
multicomponent diffusion model for ternary mixtures relevant to nonionic drug and surfactant molecules. Theoretical
examination of diffusion-based drug transport in the presence of concentration gradients of micelles shows that drug
fluxes and drug concentration profiles are significantly affected by coupled multicomponent diffusion. This work
provides guidance for the development of accurate models of diffusion-based controlled release in multicomponent
systems and for the applications of micelle concentration gradients to the modulation of diffusion-based drug transport.


Source: Annunziata, Onofrio - Department of Chemistry, Texas Christian University


Collections: Chemistry