Supramolecular Hydrogels with Properties Tunable by Calcium Ions: A Bio-Inspired Chemical System

Abstract

Boc-L-DOPA(OBn)2-OH is a simple synthetic molecule that promotes hydrogelation through electrostatic and π–π stacking interactions. Hydrogelation can occur in alkaline conditions by the use of triggers. Four hydrogels were prepared varying the base, NaOH or Na2CO3, and the trigger, GdL or CaCl2. When the hydrogel formed in the presence of Na2CO3 and CaCl2, the concomitant production of CaCO3 crystals occurred, generating an organic/inorganic composite material. It was observed that the hydrogel once self-assembled preserved its status even if the trigger, the calcium ions, was removed. The viscoelastic behavior of the hydrogels was analyzed through rheological experiments, which showed a solid-like behavior of the hydrogels. The corresponding xerogels were analyzed mainly by scanning electron microscopy (SEM) and synchrotron X-ray diffraction analysis (XRD). They showed differences in structure, morphology, and fiber organization according to their source. This research presents a hydrogel system that can be applied as a soft biomaterial for tissue engineering, cosmetics, food, and environmental science. Moreover, it represents a model for biomineralization studies in which the hydrogel structure can act as an analogue of the insoluble matrix that confines the calcification site, provides Ca2+, and preserves its structure.