Structure and dynamics of a sponge phase in the methyl delta-aminolevulinate/monoolein/water/propylene glycol system
Journal article, 2008

The structural effect caused by the addition of up to 16% (w/w) of the hydrochloride salt of delta-aminolevulinic acid (ALA, HOOC-CH(2)-CH(2)-CO-CH(2)-NH(2)HCl) or its methyl ester (m-ALA) to the sponge phase formed of monoolein/water/propylene glycol was investigated by means of crossed polarizers, small angle X-ray diffraction (SAXD) and nuclear magnetic resonance diffusometry (NMRD). Inspection with crossed polarizers revealed that additions of 4-16% (w/w) m-ALA transformed the isotropic bicontinuous sponge phase partly (4-10%) or completely (13 and 16%) into an anisotropic lamellar phase, indicating that m-ALA has a flattening effect on the bilayer curvature. The addition of 16% (w/w) ALA did not show any effect on the sponge phase. By addition of water to the anisotropic m-ALA samples, isotropic liquids were re-formed. The SAXD data for the isotropic liquids showed a diffuse Bragg peak and the NMRD self-diffusion coefficients for the drug (m-ALA) and the components of the original sponge phase (monoolein, water and propylene glycol) were shown to be essentially constant for 0-16% (w/w) added m-ALA. These results confirmed the hypothesis that the re-formed isotropic phases were indeed sponge phases. Water, for example, showed a diffusion coefficient of 3.1-3.9x10(-10)m(2)s(-1) in the sponge phase, compared to 5.3-5.7x10(-10)m(2)s(-1) in relevant water/propylene glycol solutions or 2.3x10(-9)m(2)s(-1) in pure water. The reduction can be explained as a consequence of the microstructure (congruent monoolein bilayer) of the sponge phase and of the viscosity effect caused by propylene glycol and m-ALA.




Sponge phase

Propylene glycol





Johanna Bender

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Patrik Jarvoll Dae

Chalmers, Chemical and Biological Engineering

Magnus Nydén

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

SuMo Biomaterials

Sven Engström

Chalmers, Chemical and Biological Engineering, Applied Surface Chemistry

Journal of Colloid and Interface Science

0021-9797 (ISSN)

Vol. 17 2 577-584

Subject Categories

Pharmaceutical Sciences

Chemical Sciences



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