A facile one-pot method to prepare peroxidase-like nanogel artificial enzymes for highly efficient and controllable catalysis.

Novel artificial enzymes are highly desired to overcome the shortcomings of natural enzymes during industrial or biological applications. Here we designed and prepared nanogel-based artificial enzymes (NAEs) to mimic natural horseradish peroxidase (HRP) using a facile one-pot, scalable method. The poly(N-isopropylacrylamide) (PNIPAM) matrix provided a temperature-responsive and size-controllable scaffold for the NAEs, and 1-vinylimidazole (Vim) moieties stabilized the enzymatic centers (Hemin) through coordination interaction. The feeding ratios of the components to prepare NAEs were subsequently studied and optimized to ensure the NAEs possess the highest catalytic activity and stability. The optimized NAEs were quite stable and can maintain their catalytic activities over a broad range of heat or pH treatments, and a long storage period as well. The NAEs are active to catalytic oxidation of several azo compounds and their activities can easily be switched on/off by changing the surrounding temperature. Taken together, these easily made, highly stable, efficient and activity-switchable NAEs could mimic natural HRP while overcoming their shortcomings and have a potential in wastewater treatment and controllable catalysis.

A biocompatible cobaltporphyrin-based complex micelle constructed via supramolecular assembly for oxygen transfer.

Herein, a complex micelle as an oxygen nano-carrier is constructed through the hierarchical assembly of the diblock copolymer poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLys), tetrakis(4-sulfonatophenyl)porphinato cobalt(ii) (Co(ii)TPPS), a heptapeptide (Cys-His-His-His-His-His-His) and heptakis(2,3,6-tri-O-methyl)-ß-cyclodextrin (TM-ß-CD). Co(ii)TPPS was encapsulated into the cavities of TM-ß-CDs driven by the host-guest interaction so that the irreversible formation of a µ-oxo-dimer of Co(ii)TPPS can be effectively prevented. The imidazole groups of the heptapeptide were selected as good axial ligands coordinating to the centric cobalt of Co(ii)TPPS, which subtly constituted the five-coordinated precursor serving as an active functional centre for oxygen binding. The sixth position of Co(ii)TPPS can bind oxygen. Furthermore, the host-guest inclusion (TM-ß-CD/Co(ii)TPPS) was loaded into the hydrophobic core of the complex micelle and tightly fixed with PLys chains. The hydrophilic PEG blocks stretched in the aqueous solution constitute the shells which stabilize the structure of the complex micelle as well as impart the complex micelle sufficient blood circulation time. Moreover, the complex micelle exhibited excellent biocompatibility and cellular uptake. Therefore, the rationally designed amphiphilic structure can work as promising artificial O2 carriers in vivo. Potentially, the complex micelle can be expected to change the anaerobic microenvironment and find applications in the repair of the cells damaged by cellular hypoxia.