Rational Approach Towards Designing Metallogels From a Urea-Functionalized Pyridyl Dicarboxylate: Anti-inflammatory, Anticancer, and Drug Delivery.

A structural rationale was adopted to design a series of metallogels from a newly synthesized urea-functionalized dicarboxylate ligand, namely, 5-[3-(pyridin-3-yl)ureido]isophthalic acid (PUIA), that produces metallogels upon reaction with various metal salts (Cu , Zn , Co , Cd , and Ni salts) at room temperature. The gels were characterized by dynamic rheology and transmission electron microscopy (TEM). The existence of a coordination bond in the gel state was probed by FTIR and H NMR spectroscopy in a Zn metallogel (i.e., MG2). Single crystals isolated from the reaction mixture of PUIA and Co or Cd salts characterized by X-ray diffraction revealed lattice inclusion of solvent molecules, which was in agreement with the hypothesis based on which the metallogels were designed. MG2 displayed anti-inflammatory response (prostaglandin E assay) in the macrophage cell line (RAW 264.7) and anticancer properties (cell migration assay) on a highly aggressive human breast cancer cell line (MDA-MB-231). The MG2 metallogel matrix could also be used to load and release (pH responsive) the anticancer drug doxorubicin. Fluorescence imaging of MDA-MB-231 cells treated with MG2 revealed that it was successfully internalized.