Supramolecular Metal-Phenolic Gels for the Crystallization of Active Pharmaceutical Ingredients

The use of supramolecular gel media for the crystallization of active pharmaceutical ingredients (APIs) is of interest for controlling crystal size, morphology, and polymorphism, as these features determine the performance of pharmaceutical formulations. In contrast to supramolecular systems prepared from synthetic gelators, herein, supramolecular metallogels based on a natural polyphenol (tannic acid) are used for the crystallization of APIs. The gel-grown API crystals exhibit considerable differences in size, morphology, and polymorphism when compared with those formed in solutions. These physical features can also be tailored by varying the gel composition and additives, suggesting an influence of the gel medium on the crystallization outcomes. Furthermore, these gel-API crystal composites can be used for sustained drug release, indicating their potential as drug delivery systems. The facile preparation of these supramolecular gels and the use of naturally abundant components in their synthesis provide a generic platform for studying gel-mediated crystallization of diverse APIs.