Peroxidase-Like Reactivity at Iron-Chelation Sites in a Mesoporous Synthetic Melanin

Abstract

High catalytic activity and substrate specificity make enzymes a rich source of inspiration for catalyst development. Co-opting the advantages of natural materials while tuning them to a modified form and purpose, however, is not a straightforward synthetic task. Polymerization of L-3,4-dihydroxyphenylalanine (L-DOPA) results in amorphous polymer nanoparticles that are similar in many ways to natural eumelanin. Herein, the authors introduce mesoporosity and iron ion chelation to synthesize a variant of the L-DOPA polymer with high peroxidase-like activity. Our results indicate catalytic reaction with peroxide under mildly acidic conditions (pH 5.4 and 6) with a greater maximum reaction velocity (V max ) than horseradish peroxidase (HRP) at optimal pH 3.5-4.5. Comparison between Fe(III) and Fe(II) loading indicates that either can be used as a starting point to trigger reactivity, though Fe(II) loading leads to materials with twice the V max of the Fe(III)-loaded sample. The lack of catalyst degradation despite the redox changes and presence of radical species is consistent with the robust nature and redox versatility of polydopamine-based materials and demonstrates strong potential as a versatile redox-catalysis platform.

Fe3O4/Ag/Bi2MoO6 Photoactivatable Nanozyme for Self‐Replenishing and Sustainable Cascaded Nanocatalytic Cancer Therapy

“…Moreover, nanozymes may be designed to be photoactivatable for localized treatment. [11][12][13][14][15] But most of current nanozymes mimic peroxidase (POD) and a few simulate catalase (CAT) to convert H 2 O 2 into •OH for chemodynamic therapy (CDT) or into oxygen to enhance O 2 -dependent photodynamic therapy (PDT). [16][17][18] The effectiveness of these strategies is, however, not sustainable owing to limited supply of H 2 O 2 and suppression of the generated reactive oxygen species (ROS) by the elevated antioxidants in TME.…”

Quaternary Ammonium Assisted Synthesis of Melanin-like Poly(l-DOPA) Nanoparticles with a Boosted Photothermal Effect

“…Inspired by nature, polydopamine nanoparticle (PDA NP)-based melanin-like materials have been popularly shining in biomedical, − energy, − and other fields. ,,− It is worth noting that poly­(levodopa) nanoparticles (P­( l -DOPA) NPs), as another typical kind of melanin mimetic, have also emerged in recent years, showing superior performance and great potential in many areas. − Several methods have been developed for the preparation of P­( l -DOPA) NPs, such as employing ammonia, strong oxidants, and enzymes. ,,,, However, these strategies are plagued by problems including poor controllability, high cost, or damaged functional groups. Very recently, metal ions were found to be efficient in achieving the controlled synthesis of P­( l -DOPA) NPs .…”

Integrating a Copper–Histidine Brace in a Mimetic Nanozyme Streamlines the Tyrosinase Recognition Moiety to Achieve Chiral Differentiation

“…Nanozymes can be defined as nanomaterials with intrinsic enzyme-like activity that catalyze the conversion of substrates by following the same kinetics and mechanisms as natural enzymes under physiological conditions. − Nanozymes also have the advantages of high catalytic activity, high stability, reusability, easy preparation, good biocompatibility, and controllable physicochemical properties. Consequently, they have broad application prospects in many fields, such as chemical synthesis, biomedicine, and environmental treatment. ,− Important to the present work is that nanozymes are potential materials that can be designed as alternative candidates for traditional bioenzymes. However, the design and construction of nanozymes with chirality, i.e., mimetic bioenzymes, mean first understanding how natural bioenzymes perform (1) chiral recognition, whereby chiral stationary phases interact differently with mirror-image molecules, leading to their separation; and (2) chiral differentiation, whereby one chiral molecule can distinguish an identical molecule, i.e., the molecule that it matches in order to accelerate chemical reactions.…”