Artificial enzyme
An artificial enzyme is a synthetic organic molecule or ion that recreates one or more functions of an enzyme. It seeks to deliver catalysis at rates and selectivity observed in naturally occurring enzymes. Enzyme catalysis of chemical reactions occur with high selectivity and rate. The substrate is activated in a small part of the enzyme's macromolecule called the active site. There, the binding of a substrate close to functional groups in the enzyme causes catalysis by so-called proximity effects. It is possible to create similar catalysts from small molecules by combining substrate-binding with catalytic functional groups. Classically, artificial enzymes bind substrates using receptors such as cyclodextrin, crown ethers, and calixarene. Artificial enzymes based on amino acids or peptides have expanded the field of artificial enzymes or enzyme mimics. For instance, scaffolded histidine residues mimic certain metalloproteins and enzymes such as hemocyanin, tyrosinase, and catechol oxidase). Artificial enzymes have been designed from scratch via a computational strategy using Rosetta. A December 2014 publication reported active enzymes made from molecules that do not occur in nature. In 2016, a book chapter entitled "Artificial Enzymes: The Next Wave" was published. Nanozymes are nanomaterials with enzyme-like characteristics. They have been explored for applications such as biosensing, bioimaging, tumor diagnosis and therapy, and anti-biofouling. In 1996 and 1997, Dugan et al. discovered superoxide dismutase (SOD)-mimicking activities of fullerene derivatives. The term "nanozyme" was coined in 2004 by Flavio Manea, Florence Bodar Houillon, Lucia Pasquato, and Paolo Scrimin. A 2005 review article attributed this term to "analogy with the activity of catalytic polymers (synzymes)", based on the "outstanding catalytic efficiency of some of the functional nanoparticles synthesized". In 2006, nanoceria (CeO2 nanoparticles) was reported to prevent retinal degeneration induced by intracellular peroxides (toxic reactive oxygen intermediates) in rat.