Deoxycholic acid and l-Phenylalanine enrich their hydrogel properties when combined in a zwitterionic derivative

Leana Travaglini; Maria Chiara di Gregorio; Emilia Severoni; Andrea D'Annibale; Simona Sennato; Franco Tardani; Mauro Giustini; Marta Gubitosi; Alessandra Del Giudice; Luciano Galantini

doi:10.1016/j.jcis.2019.07.019

Deoxycholic acid and l-Phenylalanine enrich their hydrogel properties when combined in a zwitterionic derivative

J Colloid Interface Sci. 2019 Oct 15:554:453-462. doi: 10.1016/j.jcis.2019.07.019. Epub 2019 Jul 8.

Affiliations

¹ Department of Chemistry, Sapienza University of Rome, P. le A. Moro 5, 00185 Rome, Italy.
² Department of Chemistry, Sapienza University of Rome, P. le A. Moro 5, 00185 Rome, Italy. Electronic address: maria-chiara.di-gregorio@weizmann.ac.il.
³ CNR-ISC UOS Sapienza, Sapienza University of Rome, P. le A. Moro 5, 00185 Roma, Italy; Department of Physics, Sapienza University of Rome, P. le A. Moro 5, 00185 Roma, Italy.
⁴ CNR-ISC UOS Sapienza, Sapienza University of Rome, P. le A. Moro 5, 00185 Roma, Italy.
⁵ Department of Chemistry, Sapienza University of Rome, P. le A. Moro 5, 00185 Rome, Italy. Electronic address: luciano.galantini@uniroma1.it.

PMID: 31325679
DOI: 10.1016/j.jcis.2019.07.019

Abstract

Hypothesis: Sodium Deoxycholate (NaDC) and Phenylalanine (Phe) are important biological hydrogelators. NaDC hydrogels form by lowering the pH or by increasing the ionic strength. Phe gels form from saturated solution by thermal induction and slow kinetics. The resulting gels hold great potential in medicine and biology as drug carriers and models for fundamental self-assembly in pathological conditions. Based on this background it was hypothesized that a Phe substituted NaDC could provide a molecule with expanded gelling ability, merging those of the precursors.

Experiments: We coupled both building blocks in a zwitterionic derivative bearing a Phe residue at the C3 carbon of NaDC. The specific zwitterionic structure, the concurrent use of Ca²⁺ ions for the carboxyl group coordination and the pH control generate conditions for the formation of hydrogels. The hydrogels were analyzed by combining UV and circular dichroism spectroscopies, rheology, small angle X-ray scattering and atomic force microscopy.

Findings: Hydrogel appearance occurs in conditions that are uncovered in the case of the pure Phe and NaDC: self-standing gels form instantaneously at room temperature, in the 10-12 pH range and down to concentration of 0.17 wt%. Both thixotropic and shake resistant gels can form depending on the derivative concentration. The gels show an uncommon thermal stability in the scanned range of 20-60 °C. The reported system concurrently enriches the hydrogelation properties of two relevant building blocks. We anticipate some potential applications of such gels in materials science where coordination of metal ions can be exploited for templating inorganic nanostructures.

Keywords: Bile salts; Hydrogels; Metallogels; Phenylalanine; Zwitterionic gels.