The self-crosslinked ufasome of conjugated linoleic acid: Investigation of morphology, bilayer membrane and stability

Unsaturated fatty acid liposomes (Ufasomes) have attracted interests because of the ready availability of unsaturated fatty acids and the simple assembly strategy. However, the colloidal instability of the ufasomes hinders them from applying in the fields of drug delivery and food additives. In the present work, conjugated linoleic acid (CIA) with triple activities of bioactive, assembling and crosslinking was employed as a new molecular building block to construct ufasome and afterwards crosslinked ufasome. First, CIA ufasome was self-assembled from CIA molecules in response to pH variation, and the suitable CIA concentrations and pH ranges were determined by surface tension measurement and acid-base titration. Subsequently, the self-crosslinked CLA ufasome was prepared by intra-ufasomal crosslinking of conjugated double bonds in the CIA molecules. The morphologies of the self-crosslinked CIA ufasomes were imaged using transmission electron microscopy (TEM), from which the size of 20-50 nm and the bilayer thickness of 2.7 +/- 0.5 nm were detected. Most importantly, based on the comparison of the bilayer thicknesses of the different fatty acids, the molecular arrangement in the bilayer membrane of the self-crosslinked CIA ufasome is named "side-by-side" model contrary to the ordinary "tail-to-tail" model. The pH stability of the self-crosslinked CIA ufasome was examined in virtue of dynamic light scattering tests. Finally, in vitro release results of 5-fluorouracil from the self-crosslinked CIA ufasome showed that the process was slow and sustainable. (C) 2014 Elsevier B.V. All rights reserved.