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The Scientific World Journal
Volume 2014 (2014), Article ID 152972, 10 pages
Research Article

The Effect of Hydroxyl Moieties and Their Oxosubstitution on Bile Acid Association Studied in Floating Monolayers

1Department of Physical Chemistry and Materials Science, University of Szeged, Aradi Vt. 1, Szeged 6720, Hungary
2Department of Chemistry and Chemical Informatics, University of Szeged, Boldogasszony Sugárút 6, Szeged 6720, Hungary
3Laboratory of Physical Pharmacy, Department of Pharmacy, Faculty of Medicine, University of Novi Sad, Hajduk Veljkova 3, 21000 Novi Sad, Serbia
4Department of Chemistry, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovica 3, 21000 Novi Sad, Serbia

Received 29 July 2014; Revised 4 December 2014; Accepted 9 December 2014; Published 25 December 2014

Academic Editor: Timothy G. Strein

Copyright © 2014 Márta Szekeres et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Bile salt aggregates are promising candidates for drug delivery vehicles due to their unique fat-solubilizing ability. However, the toxicity of bile salts increases with improving fat-solubilizing capability and so an optimal combination of efficient solubilization and low toxicity is necessary. To improve hydrophilicity (and decrease toxicity), we substituted hydroxyl groups of several natural bile acid (BA) molecules for oxogroups and studied their intrinsic molecular association behavior. Here we present the comparative Langmuir trough study of the two-dimensional (2D) association behavior of eight natural BAs and four oxoderivatives (traditionally called keto-derivatives) floated on an aqueous subphase. The series of BAs and derivatives showed systematic changes in the shape of the compression isotherms. Two types of association could be distinguished: the first transition was assigned to the formation of dimers through H-bonding and the second to the hydrophobic aggregation of BA dimers. Hydrophobic association of BA molecules in the films is linked to the ability of forming H-bonded dimers. Both H-bond formation and hydrophobic association weakened with increasing number of hydroxyl groups, decreasing distance between hydroxyl groups, and increasing oxosubstitution. The results also show that the Langmuir trough method is extremely useful in selecting appropriate BA molecules to design drug delivery systems.