Entrapment and release of quinoline derivatives using a hydrogel of a low molecular weight gelator

Gels of low molecular weight gelators (LMWGs) are self-assembled, thermoreversible, viscoelastic materials which can also be rendered sensitive to light, pH or chemical substances by simple chemical modifications. In addition, the ability of some of these LMWGs to gelate water (hydrogelators) makes these gels interesting, new materials for drug delivery applications. In this paper, for the first time, a release study from LMWG gels is presented. This study concerns the release of small (model) drug molecules: 8-aminoquinoline (AQ) and 2-hydroxyquinoline (HQ), from gels of N,N'-dibenzoyl-L-cystine (DBC). DBC forms stable, clear gels in water, 150 mM NaCl solution and PBS (phosphate-buffered saline at pH 7.4) with gel-to-sol transition temperatures (Tgs) of 40-120 degrees C, depending on the gelator concentration (from 2.23 to 22.3 mM). The release of HQ from DBC gels was found to be approximately seven times faster than that of AQ and the initial release of the latter follows the kinetics of gel degradation. These observations indicate that AQ is preferentially retained in the gel, presumably as a result of stronger interactions with the gelator molecules (i.e. DBC-COO-+ H3N-AQ). These results indicate the potential of LMWG gels as delivery vehicles for small drug molecules and also show that the release profiles for such systems can be fine-tuned by the correct choice of gelator-drug combination.