Reversible self-assembly of gels through metal-ligand interactions

Metal-ligand interactions with various proteins form in vivo metal assemblies. In recent years, metallosupramolecular approaches have been utilized to forge an assortment of fascinating two- and three-dimensional nano-architectures, and macroscopic materials, such as metal-ligand coordination polymeric materials, have promise in artificial systems. However to the best of our knowledge, the self-assembly of macroscopic materials through metal-ligand interactions has yet to be reported. Herein we demonstrate a gel assembly formed via metal-ligand interactions using polyacrylamide modified with Fe-porphyrin and L-histidine moieties. The stress values for the assembly increase as the concentration of Fe-porphyrin or L-histidine in the gels increases. Moreover, agitation of Fe-porphyrin gel, Zn-porphyrin gel, and L-histidine gel in an 80 mM Tris-acetate buffer (pH 9.0) results in selective adhesion of the Fe-porphyrin gel to the L-histidine gel based on the affinities of Fe-porphyrin and Zn-porphyrin with L-histidine.