Dodab - dppc vesicles characterization

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Elsevier Editorial System(tm) for Chemistry and Physics of Lipids

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Manuscript Number: Title: Characterization of DODAB/DPPC Vesicles Article Type: Research Paper Section/Category: Keywords: dipalmitoylphosphatidylcholine; dioctadecyldimethylammonium bromide; large vesicles; zetaaverage diameter; zeta-potential; phase transition; colloid stability Corresponding Author: Prof.Ana María Carmona-Ribeiro, Corresponding Author's Institution: First Author: Cecília N C Sobral, Undergraduate student Order of Authors: Cecília N C Sobral, Undergraduate student; Marco A Soto; Ana María Carmona-Ribeiro Manuscript Region of Origin: Abstract: Dioctadecyldimethylammonium bromide (DODAB) / dipalmitoylphosphatidylcholine (DPPC) large and cationic vesicles obtained by vortexing a lipidfilm in aqueous solution and above the mean phase transition temperature (Tm) are characterized by means of determination of phase behaviour, size distribution, zeta-potential analysis and colloid stability. The effect of increasing % DODAB over the 0-100 % range was a nonmonotonic phase behaviour. At 50 % DODAB, the mean phase transition temperature and the colloid stability were at maximum.There is an intimate relationship between stability of the bilayer structure and colloid stability. In 1, 50 and 150 mM NaCl, the colloid stability for pure DPPC or pure DODAB vesicles was very low as observed by sedimentation or flocculation, respectively. In contrast, at 50 % DODAB, remarkable colloid stability was achieved in 1, 50 or 150 mM NaCl for the DODAB/DPPC

composite vesicles. Thismight be important for several biotechnological applications currently being attempted with cationic bilayer systems.

Manuscript

Characterization of DODAB/DPPC Vesicles

Cecília N. C. Sobral,1 Marco A. Soto2 and Ana M. Carmona-Ribeiro1*

1

Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo,

P. O. Box 26077, 05513-970, São Paulo, SP, Brazil. Telephone: 55 113091 3810 Ext 237. Fax: 0055 11 3818 5579. e-mail: mcribeir@iq.usp.br

2

Departamento de Química Física, Facultad de Química, Pontifícia Universidad Católica de

Chile, Casilla 306, Correo 22, Santiago, Chile.

*

To whom correspondence should be addressed

Keywords: dipalmitoylphosphatidylcholine; dioctadecyldimethylammonium bromide; large vesicles; zeta-average diameter;zeta-potential; phase transition; colloid stability.

Abstract Dioctadecyldimethylammonium bromide (DODAB) / dipalmitoylphosphatidylcholine (DPPC) large and cationic vesicles obtained by vortexing a lipid film in aqueous solution and above the mean phase transition temperature (Tm) are characterized by means of determination of phase behaviour, size distribution, zeta-potential analysis and colloidstability. The effect of increasing % DODAB over the 0-100 % range was a nonmonotonic phase behaviour. At 50 % DODAB, the mean phase transition temperature and the colloid stability were at maximum. There is an intimate relationship between stability of the bilayer structure and colloid stability. In 1, 50 and 150 mM NaCl, the colloid stability for pure DPPC or pure DODAB vesicles was very low asobserved by sedimentation or flocculation, respectively. In contrast, at 50 % DODAB, remarkable colloid stability was achieved in 1, 50 or 150 mM NaCl for the DODAB/DPPC composite vesicles. This might be important for several biotechnological applications currently being attempted with cationic bilayer systems.

Introduction In recent years, it has become apparent that cationic lipidlike compounds canbe used to deliver DNA to cells, a procedure that may become clinically important in gene therapy and drug delivery (Felgner and Ringold, 1989; Zhu et al., 1993; Felgner, 1997). A large variety of such compounds has been synthesized and tested, and although described as ‘‘cationic lipids’’, they are not natural products but rather are almost always cationic amphiphiles or detergents, i.e.,...
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