By incorporating hemin into G-quadruplex (G4) during cation-templated self-assembly between guanosine and KB(OH)4, we have constructed an artificial enzyme hydrogel (AEH)-based system for the highly sensitive and selective detection of Pb2+. The sensing strategy is based on a Pb2+-induced decrease in AEH activity. Because of the higher efficiency of Pb2+ for stabilizing G4 compared with K+, the Pb2+ ions substitute K+ and trigger hemin release from G4, thus giving rise to a conformational interconversion accompanied by the loss of enzyme activity. The Pb2+-induced catalytic interconversion endows the AEH-based system with high sensitivity and selectivity for detecting Pb2+. As a result, the AEH-based system shows an excellent response for Pb2+ in the range from 1 pM to 50 nM with a limit of detection of ∼0.32 pM, which is much lower than that of the previously reported G4-DNAzyme. We also demonstrate that this AEH-based system exhibits high selectivity toward Pb2+ over other metal ions. Furthermore, two two-input INHIBIT logic gates have been constructed via switching of the catalytic interconversion induced by K+ and Pb2+ or K+ and pH. Given its versatility, this AEH-based system provides a novel platform for sensing and biomolecular computation.
Keywords: G-quadruplex; Pb2+ detection; artificial enzyme hydrogel; catalytic interconversion; logic gate.