“…These enzymes include SOD, catalase, oxidase, and peroxidase. Numerous materials of various structures and compositions have been found to mimic such enzymes including metallic nanoparticles (Ag, Au, and Pd), − metal oxides (Co 3 O 4 , CeO 2 , and V 2 O 5 ), − metal chalcogenides (FeS, MoS 2 , and WS 2 ), − clays, , carbon materials (fullerenes and carbon nanotubes), biopolymers, , and metal–organic frameworks . The surface functionalities and parameters of nanoparticles such as metal oxides often result in the aggregation of the bare and primary particles into clusters of various sizes, depending on the experimental conditions in the system such as ionic strength, the presence of polyelectrolytes, and the nature of the solvents. − In addition, many metal oxide particles are characterized by an isoelectric point (IEP), , at which the particles have no surface charge and tend to undergo heavy aggregation that results in the loss of the surface area, which could lead to a significant reduction of the enzymatic activity.…”