Application of\nRedox-Responsive Cysteine-Based Organogels\nas a Drug Delivery System for Doxorubicin

Cysteine derivatives having disulfide bonds in their\nside chains\ncan be used as redox-responsive organogelators. The disulfide bond\ncan be cleaved in the presence of certain reducing agents like thiol\nderivatives such as glutathione (GSH), which is a tripeptide that\nconsists of cysteine, glutamic acid, and glycine. Studies show that\ncells of certain cancers have higher levels of glutathione due to\nincreased production of reactive oxygen species (ROS). This feature\nallows targeted cancer therapy using glutathione-responsive drug delivery\nsystems. This study showed the drug delivery property of l-Cys(<i>t</i>-dodecyl-sulfanyl)–OH and l-Cys-(S<i>t</i>Bu)–OH-based organogels. The drug-release\nproperties of these organogels were measured in the presence of GSH\nand were compared with the drug-release property of the l-Cys-(<i>t</i>Bu)–OH-based organogel. The biocompatibility\nof the organogelators was measured <i>in vitro</i> by MTT\nassay and the characterization of microstructures and gel behaviors\nwere studied using transmission electron microscopy (TEM) imaging,\nX-ray diffraction spectroscopy (XRD), Fourier-transform infrared spectroscopy\n(FTIR), and rheological measurements. The results indicated that the\norganogelators were able to form nanofibers by hydrogen bonds and\nvan der Waals interactions between their hydrophobic groups and were\nable to release doxorubicin in the presence of GSH. The <i>in\nvitro</i> biocompatibility studies did not show significant toxicity\nto the L929 cells for l-Cys-(S<i>t</i>Bu)–OH\nand showed low concentrations of l-Cys(<i>t</i>-dodecyl-sulfanyl)–OH.