Supramolecular Hydrogel Inspired from DNA Structures Mimics Peroxidase Activity

We herein report that hydrogels can be prepared from guanosine and boronic acids in the presence of K⁺ and Pb²⁺ ions. These supramolecular hydrogels are formed via G-quartet like self-assembly of guanosine and its boronate esters. The potential of this hydrogel construct in mimicking enzyme-like activity has been demonstrated for the first time. We have observed that the self-assembled structure present in K⁺ stabilized hydrogel binds to iron(III)-hemin and shows peroxidase activity, catalyzing oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H₂O₂. Furthermore, the conformation of the G-quartet assemblies in the hydrogel can be altered by varying the stabilizing cations K⁺ and Pb²⁺. This conformational switching has been used to devise a molecular logic gate for sensing of toxic Pb²⁺ ions.