BIOPHYSICAL THEORY AND MODELING |
Modeling leakage kinetics from multilamellar vesicles for membrane permeability determination: application to glucose
Chrystel Faure 1*, Frederic Nallet 2, Didier Roux 3, Scott Milner 4, Fabienne Gauffre 5, David Olea 6 and Olivier Lambert 7
1 Centre de Recherche Paul Pascal
2 CRPP(CNRS)
3 Saint Gobain
4 Exxon
5 IMRCP
6 CRPP
7 IECB
* To whom correspondence should be addressed. E-mail: faure{at}crpp-bordeaux.cnrs.fr.
Submitted on May 3, 2006
Revised on June 23, 2006
Accepted on 28 August 2006
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Abstract |
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The glucose permeability of bilayers formed from phosphatidylcholine, Brij®30 and sodium octadecyl sulfate has been determined via an enzymatic reaction. Glucose was encapsulated either in uni- or multi-lamellar vesicles (MLV) and its concentration in the dispersion medium was monitored through the rate of glucose oxidase-catalyzed reaction of oxidation of glucose by spectrophotometry analysis. A kinetic model of leakage, taking explicitly into account one, two, or nw walls (nw>>1) for the vesicles and assuming an enzymatic Michaelis-Menten behavior, is proposed and used to fit the experimental data. The 2-wall model was used chosen to fit experimental data obtained on MLV since an average value of 1.7 bilayers was estimated for MLV by cryo-TEM imaging. A permeability value of 5.8±4.4 10-9 cm.s-1 was found. The proposed model is validated by the measurement of the bilayer permeability deduced from the modeling of glucose leakage from uni-lamellar vesicles with the same composition. In this latter case, a value of 8.3±0.7 10-9 cm/s-1 is found for the permeability, which is within the error bar of the value found with MLV.
Key Words:
enzyme activity, glucose oxidase, liposomes, modeling of leak kinetics, multilamellar vesicles, permeability coefficient
