Multi-enzyme mimics - cracking the code of subcellular cascade reactions and their potential biological applications

In this review, we discuss the emerging new field of multi-enzyme mimics or multi-nanozymes from a critical perspective portraying the unique characteristics and design strategies that endow a nanomaterial with its multi-enzymatic properties. In order to provide a comprehensive review, distinct and widely used nanomaterials such as metals/metal oxides, low dimensional carbons, Prussian blue analogues (PBAs), metal organic frameworks (MOFs), single-atom catalysts (SACs) and smart assemblies/nanohybrids have been selected as the basis for the discussion on transformation of these materials into multi-nanozymes. Studies reported so far on this fascinating new field have been glanced through with a critical perspective and a debate on the limitations, gaps and general misconceptions that can be found related to these nanomaterials and their properties has been initiated. A thorough discussion on the often-confused cascade mechanisms of redox reactions driven by these multi-nanozymes has been brought into the limelight for the first time and the examples of various multi-nanozymes that have been employed in biological applications have been evaluated categorically. The cascade-like cycle of reactive oxygen species (ROS) generation and consumption by various nanomaterials to mimic multiple natural enzymes depending on the reaction conditions and environmental stimuli.