Hemin-micelles immobilized in alginate hydrogels as artificial enzymes with peroxidase-like activity and substrate selectivity

Artificial enzymes are widely investigated to mimic the active center and the recognition center of natural enzymes. The active center is responsible for the catalytic activity of enzymes, and the recognition center provides enzymes with specificity. Most of the previous studies on artificial enzymes preferred to solve the problem of activity rather than specificity due to the complexity of the enzyme structures related to substrate recognition. Inspired by the multilevel structures of enzymes and the unique net-structures of hydrogels, hemin-micelles immobilized in alginate hydrogels (HM-AH) were constructed by multistep self-assembly. The hemin-micelle was the active center and mimicked the microenvironment of the catalytic site in horseradish peroxidase (HRP). The alginate hydrogel further enhanced the catalytic activity and stability of hemin-micelles and endowed the artificial enzymes with a catalytic capability in harsh water conditions and non-polar organic solvents. The hydrogel also served as the recognition center, which exhibited substrate selectivity owing to the diffusivity differentiations of substrates in hydrogel fibers. It is the first example of constructing a micelle-hydrogel complex system as an artificial enzyme with both catalytic activity and substrate selectivity by the method of multistep self-assembly.