Enzymes fold into three-dimensional structures to distribute amino acid residues for catalysis, which inspired the supramolecular approach to construct enzyme-mimicking catalysts. A key concern in the development of supramolecular strategies is the ability to confine and orient functional groups to form enzyme-like active sites in artificial materials. This review introduces the design principles and construction of supramolecular nanomaterials exhibiting catalytic functions of heme-dependent enzymes, a large class of metalloproteins, which rely on a heme cofactor and spatially configured residues to catalyze diverse reactions via a complex multistep mechanism. We focus on the structure-activity relationship of the supramolecular catalysts and their applications in materials synthesis/degradation, biosensing, and therapeutics. The heme-free catalysts that catalyze reactions achieved by hemeproteins are also briefly discussed. Towards the end of the review, we discuss the outlook on the challenges related to catalyst design and future prospective, including the development of structure-resolving techniques and design concepts, with the aim of creating enzyme-mimicking materials that possess catalytic power rivaling that of natural enzymes..

Lead (Pb) is a highly toxic heavy metal of great environmental and health concerns, and interestingly Pb2+ has played important roles in nucleic acids chemistry. Since 2000, using DNA for selective detection of Pb2+ has become a rapidly growing topic in the analytical community. Pb2+ can serve as the most active cofactor for RNA-cleaving DNAzymes including the GR5, 17E and 8-17 DNAzymes. Recently, Pb2+ was found to promote a porphyrin metalation DNAzyme named T30695. In addition, Pb2+ can tightly bind to various G-quadruplex sequences inducing their unique folding and binding to other molecules such as dyes and hemin. The peroxidase-like activity of G-quadruplex/hemin complexes was also used for Pb2+ sensing. In this article, these Pb2+ recognition mechanisms are reviewed from fundamental chemistry to the design of fluorescent, colorimetric, and electrochemical biosensors. In addition, various signal amplification mechanisms such as rolling circle amplification, hairpin hybridization chain reaction and nuclease-assisted methods are coupled to these sensing methods to drive up sensitivity. We mainly cover recent examples published since 2015. In the end, some practical aspects of these sensors and future research opportunities are discussed.