Here, an integrated cascade nanozyme with a formulation of Pt@PCN222-Mn is developed to eliminate excessive reactive oxygen species (ROS). This nanozyme mimics superoxide dismutase by incorporation of a Mn–[5,10,15,20-tetrakis(4-carboxyphenyl)porphyrinato]–based metal-organic framework compound capable of transforming oxygen radicals to hydrogen peroxide. The second mimicked functionality is that of catalase by incorporation of Pt nanoparticles, which catalyze hydrogen peroxide disproportionation to water and oxygen. Both in vitro and in vivo experimental measurements reveal the synergistic ROS-scavenging capacity of such an integrated cascade nanozyme. Two forms of inflammatory bowel disease (IBD; i.e., ulcerative colitis and Crohn’s disease) can be effectively relieved by treatment with the cascade nanozyme. This study not only provides a new method for constructing enzyme-like cascade systems but also illustrates their efficient therapeutic promise in the treatment of in vivo IBDs.

One of the current challenges in nanozymebased technology is to rationally control the enzyme mimicking activities with suitable modulation strategies to mimic the complexity and functions of natural systems. In this regard, nanoceria has recently emerged as a promising nanozyme because of its unique enzyme mimicking properties. Herein, we demonstrated that the oxidase-like catalytic activity of nanoceria was rationally modulated in situ via protonproducing/consuming enzyme-catalyzed bioreactions, which formed the basis of self-regulated bioassays for determining the corresponding enzyme activity, as well as other important targets, such as nerve agents, drugs, and bioactive ions. More interestingly, the oxidase-like activity of nanoceria was cooperatively modulated with the aid of adenosine triphosphate, thus improving the analytical performance of such selfregulated bioassays. The current study not only demonstrated regulatory strategies to modulate the nanozymes' activities, but also established a facile approach to designing self-regulated bioassays.

Efficient electrocatalytic overall water splitting is achieved with commercially-available and low-cost nickel foam and stainless steel mesh as cathode and anode electrodes.

Heme post-translational modification plays a key role in tuning the structure and function of heme proteins. We herein report a novel tyrosine-heme covalent C−O bond in an artificially produced sperm whale myoglobin (Mb) mutant, F43Y Mb, which formed spontaneously in vivo between the Tyr43 hydroxy group and the heme 4-vinyl group. This highlights the diverse chemistry of heme post-translational modifications, and lays groundwork for further investigation of the structural and functional diversity of covalently-bound heme proteins.