Deamidation of pseudopeptidic molecular hydrogelators and its application to controlled release

Abstract

Hypothesis: The incorporation of a succinic acid-derived moiety in amino acid derivatives would favor an intramolecular catalysis of a deamidation reaction. Such reaction would permit controlled disassembly of molecular hydrogelators and the use of the hydrogels for controlled release of actives. Experimental: Low molecular weight hydrogelators containing a succinic acid-derived moiety were prepared by conventional organic synthesis procedures. Hydrogels were examined by electron microscopy and 1 H NMR studies were carried out to evaluate the solubility in water of the hydrogelators and the deamidation reaction. Liberation of Rose Bengal entrapped in the hydrogels was monitored by UV–Vis spectroscopy. Findings: Molecular hydrogels formed by pseudopeptidic derivatives of L-valine suffer a thermal deamidation reaction, leading to partial disassembly. The succinic acid-derived moiety present in the gelators is responsible of intramolecular catalysis of a deamidation reaction. Such neighboring group effect is reminiscent of biochemical processes such as protein deamidation and self-excision of inteins. It has been found that the thermodynamic equilibrium of the deamidation reaction is regulated by the efficiency of hydrogelation. As a proof of concept, the thermally promoted deamidation is applied to controlled release of Rose Bengal.