Minireview doi.org/10.1002/ejoc.202000356 EurJOC European Journal of Organic Chemistry Supramolecular Catalysis | Very Important Paper | Hydrolytic Nanozymes Luca Gabrielli, [a] Leonard J. Prins, [a] Federico Rastrelli, [a] Fabrizio Mancin, [a] and Paolo Scrimin* [a] In memory of Umberto Tonellato, the scientific father of our group Abstract: In 2004 we first reported catalytic nanoparticles, that are able to cleave phosphate diesters with very high efficiency (Angew. Chem. Int Ed, 2004, 43, 6165–6169) and dubbed them “nanozymes” for the similarity of their behavior with natural enzymes, both in terms of efficiency and mechanism of action. Since then the field has impressively expanded and a search on the web of science at the time of submitting this contribution returned almost 1,000 entries. This minireview highlights what has been done in the field focusing specifically on hydrolytic nanozymes, the focal point of the research in our group since 1. Introduction Nanozymes are nanoscale systems endowed with the property of catalyzing a chemical reaction by interacting with the sub- strate they transform via a pre-transformation complexation process. [1–5] The reactions follow, hence, the same steps of an enzyme-catalyzed transformation: the equilibrium towards the enzyme/substrate complex (ES) followed by its evolution into products with the final release of the enzyme. The analogy with enzymes is also supported by the dimensions of these systems (typically 2–50 nm), not much different from those of a catalytic protein. As an example, the diameter of trypsin is ca. 5 nm. Most of these nanosystems, are intrinsically multivalent, since they feature a collection of identical (or similar) functionali- ties. [6,7] These functional groups may be held together by weak interactions or by covalent bonds. Examples of the first are mi- cellar or vesicular aggregates while examples of the second are functional polymers, dendrimers or monolayer-protected nano- particles. Multivalency is particularly important in binding. Nu- merous reports show these systems interact very strongly with [a] Dr. L. Gabrielli, Dr. Prof. L. J. Prins, Dr. Prof. F. Rastrelli, Dr. Prof. F. Mancin, Dr. Prof. P. Scrimin Department of Chemical Sciences, University of Padova, via Marzolo, 1, 35131 Padova, Italy E-mail: paolo.scrimin@unipd.it luca.gabrielli@unipd.it leonard.prins@unipd.it federico.rastrelli@unipd.it fabrizio.mancin@unipd.it http://wwwdisc.chimica.unipd.it/paolo.scrimin/pubblica/ http://wwwdisc.chimica.unipd.it/leonard.prins/pubblica/ http://wwwdisc.chimica.unipd.it/federico.rastrelli/pubblica/ http://wwwdisc.chimica.unipd.it/fabrizio.mancin/pubblica/index.htm ORCID(s) from the author(s) for this article is/are available on the WWW under https://doi.org/10.1002/ejoc.202000356. Eur. J. Org. Chem. 2020, 5044–5055 © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 5044 its very beginning. Special emphasis is given to the advantage of bringing catalytic units in the confined space of a nanosys- tem in terms of inducing the cooperation between them, favor- ing the interaction with substrates, and altering the local envi- ronment. We will try to answer to questions like: why can a lipophilic substrate be transformed by these catalysts even in an aqueous environment? Why may the pH in the catalytic loci of the nanosystem be different from that of the bulk solution even in the presence of buffers? Why are most of these nano- systems better than monovalent ones? multivalent counterparts. Multivalency is a property well-ex- ploited by natural systems to achieve astonishingly high bind- ing constants just by summing up contributions of several units, individually capable only of a very weak binding interaction. Benefits of these interactions, driven by multivalency, are en- hanced selectivity and even specificity in recognition. It is thus not surprising that multivalent systems are able to govern cell- cell, protein–protein, protein-cell interactions, critical processes for the occurrence of life as we know it. [8] The connection of multivalency to catalysis is obvious, because catalysis requires the binding of the transition state of a reaction thus lowering its energy. [9] Thus multivalent nanozymes, if properly designed, may enjoy the advantage of a strong interaction with the transi- tion state of the catalyzed reaction. Furthermore, in the catalytic process several functional units may operate in a concerted, cooperative [10] fashion, often with complementary roles. This last aspect mimics what happens in the catalytic site of natural enzymes. Although natural enzymes are typically not multiva- lent species, intriguing examples of multivalent enzymes are emerging. [11] The minireview discusses two classes of hydrolytic reactions: the hydrolysis of carboxylic- and phosphoric-acid esters. Ac- cordingly, in the different paragraphs several nanosystems per- forming the same or similar tasks are reported. We have taken advantage of this to highlight, whenever possible, common as- pects and differences pertaining to each class of nanosystems discussed. 2. Assessing the Catalytic Performance of Nanozymes Quite often the assessment of the catalytic performance of a nanozyme is poorly performed and does not allow a correct