(208j) Effect of Concentrations on the Morphology of the Self-Assembly of Conjugated Linoleic Acid

Effect of concentrations on the morphology of the self-assembly
of conjugated linoleic acid

Di Gao, Ye Fan, Chao Chen,
Biao Jiang, Yongchun Pan, Lingyu Bao, Meng Zhu, Yun Fang*

The Key Laboratory of Food
Colloids and Biotechnology, Ministry of Education; School of Chemical & Material Engineering, Jiangnan University, 1800 Lihu
Avenue, Wuxi, Jiangsu 214122, P. R. China

Abstract: Sodium soap of fatty acids is a weak electrolyte type
of surfactant, and self-assembly of the soap in aqueous solution would be controlled
by both pH and concentration of the soap. pH-driven self-assembly of the soap
at low concentration scope was broadly studied in previous reports and the
resulting morphology of self-assemblies was micelles at higher pH but vesicles
at lower pH. In this paper, concentration-driven self-assembly of the soap near
to its pK_a is investigated. Conjugated linoleic acid (CLA) is
selected as a model fatty acid, and the self-assembly behaviors of CLA at pH
8.6 was investigated when the concentration of CLA changing. At first, the self-assemblies
of CLA are stabilized
by intra-assembly self-crosslinking of conjugated double bonds in CLA molecules
through thermal polymerization, and then the morphologies are imaged by
transmission electron microscopy (TEM). The experimental
results indicate that fatty acid vesicles(Fig. 1) with diameter of 10-20 nm
were always obtained in a wide concentration range of 20-100 mmol·L^-1 (100-500
times of critical vesiculation concentration of CLA), which providing a possibility
to prepare fatty acid vesicles in high yield.

Keywords: fatty
acid vesicle, conjugated linoleic acid, concentration-driven

Fig. 1  The TEM image of
crosslinking CLA ufasomes

(c=100 mmol°¤L^-1,
pH 8.6 , crosslinking at 80 ^oC)