Artificial enzyme

An artificial enzyme is a synthetic, organic molecule or ion that recreate some function of an enzyme. The area promises to deliver catalysis at rates and selectivity observed in many 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 molecule 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 as characteristic molecular moieties have expanded the field of artificial enzymes or enzyme mimics. For instance, scaffolded histidine residues mimics certain metalloproteins and -enzymes such as hemocyanin, tyrosinase, and catechol oxidase).

In December 2014, it was announced that active enzymes had been produced that were made from artificial molecules which do not occur anywhere in nature. In 2017, a book chapter entitled "Artificial Enzymes: The Next Wave" was published.[1]

Nanozymes are nanomaterials with enzyme-like characteristics. They have been widely explored for various applications, such as biosensing, bioimaging, tumor diagnosis and therapy, antibiofouling. In 1996 and 1997, Dugan et al. discovered the superoxide dismutase (SOD) mimicking activiteis of fullerene derivatives. In 2004, the term "nanozymes" was coined by Flavio Manea, Florence Bodar Houillon, Lucia Pasquato, and Paolo Scrimin. In 2006, nanoceria (i.e., CeO2 nanoparticles) was used for preventing retinal degeneration induced by intracellular peroxides. In 2007, Xiyun Yan and coworkers reported that ferromagnetic nanoparticles possessed intrinsic peroxidase-like activity. In 2008, Hui Wei and Erkang Wang developed an iron oxide nanozyme based sensing platform for bioactive molecules (such as hydrogen peroxide and glucose). In 2012, recombinant human heavy-chain ferritin coated iron oxide nanoparticle with peroxidase-like activity was prepared and used for targeting and visualizing tumour tissues. In 2012, vanadium pentoxide nanoparticles with vanadium haloperoxidase mimicking activities were used for preventing marine biofouling. In 2014, it was demonstrated that carboxyfullerene could be used to treat neuroprotection postinjury in Parkinsonian nonhuman primates. In 2015, a supramolecular regulation strategy was proposed to modulate the activity of gold-based nanozymes for imaging and therapeutic applications. A nanozyme-strip for rapid local diagnosis of Ebola was developed. An integrated nanozyme has been developed for real time monitoring the dynamic changes of cerebral glucose in living brains. A book entitled "Nanozymes: Next Wave of Artificial Enzymes" was published.Oxidase-like nanoceria has been used for developing self-regulated bioassays. Histidine was used to modulate iron oxide nanoparticles' peroxidase mimicking activities. Gold nanoparticles' peroxidase mimicking activities were modulated via a supramolecular strategy for cascade reactions. A molecular imprinting strategy was developed to improve the selectivity of Fe3O4 nanozymes with peroxidase-like activity.

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