Fibrous Nanozyme Dressings with Catalase-Like Activity for H2O2 Reduction To Promote Wound Healing

The concentrations of the redox pair hydrogen peroxide (H2O2) and oxygen (O2) can promote or decelerate the progression and duration of the wound healing process. Although H2O2 can reach critically high concentrations and prohibit healing, a sufficient O2 inflow to the wound is commonly desired. Herein, we describe the fabrication and use of a membrane that can contemptuously decrease H2O2 and increase O2 levels. Therefore, hematite nanozyme particles were integrated into electrospun and cross-linked poly(vinyl alcohol) membranes. Within the dual-compound membrane, the polymeric mesh provides a porous scaffold with high water permeability and the nanozymes act as a catalyst with catalase-li…

A Step into the Future: Applications of Nanoparticle Enzyme Mimics.

We describe elementary concepts, up-to-date developments, and perspectives of the emerging field of nanoparticle enzyme mimics (so-called "nanozymes") at the interface of chemistry, biology, materials, and nanotechnology. The design and synthesis of functional enzyme mimics is a long-standing goal of biomimetic chemistry. Metal complexes, polymers and engineered biomolecules capturing the structure of natural enzymes or their active centers have been made to achieve high rates and enhanced selectivities. Still, the design of new "artificial enzymes" that are not related to proteins but with capacity of production and stability at industrial level, remains a goal. Inorganic nanoparticles bea…

Intrinsic superoxide dismutase activity of MnO nanoparticles enhances the magnetic resonance imaging contrast

Superoxide radicals are associated with the development of many severe diseases, such as cancer. Under nonpathogenic conditions, the natural enzyme superoxide dismutase (SOD) regulates the intracellular superoxide concentrations, but nearly all tumor tissues show reduced SOD levels. Selective imaging in early progression stages remains a key requirement for efficient cancer diagnosis and treatment. Magnetic resonance imaging (MRI) as a noninvasive tool with high spatial resolution may offer advantages here, but MRI contrast agents exhibiting a redox-triggered change in the image contrast towards superoxide radicals have not been reported so far. Here we show that manganese oxide (MnO) nanop…

From Single Molecules to Nanostructured Functional Materials: Formation of a Magnetic Foam Catalyzed by Pd@FexO Heterodimers

Multicomponent nanostructures containing purely organic or inorganic as well as hybrid organic–inorganic components connected through a solid interface are, unlike conventional spherical particles, able to combine different or even incompatible properties within a single entity. They are multifunctional and resemble molecular amphiphiles, like surfactants or block copolymers, which makes them attractive for the self-assembly of complex structures, drug delivery, bioimaging, or catalysis. We have synthesized Pd@FexO heterodimer nanoparticles (NPs) to fabricate a macroporous, hydrophobic, magnetically active, three-dimensional (3D), and template-free hybrid foam capable of repeatedly separati…

Frontispiece: A Step into the Future: Applications of Nanoparticle Enzyme Mimics

Antioxidant activity of cerium dioxide nanoparticles and nanorods in scavenging hydroxyl radicals

Cerium oxide nanoparticles (CeNPs) have been shown to exhibit antioxidant capabilities, but their efficiency in scavenging reactive oxygen species (ROS) and the underlying mechanisms are not yet well understood. In this study, cerium dioxide nanoparticles (CeNPs) and nanorods (CeNRs) were found to exhibit much stronger scavenging activity than ·OH generation in phosphate buffered saline (PBS) and surrogate lung fluid (SLF). The larger surface area and higher defect density of CeNRs may lead to higher ·OH scavenging activity than for CeNPs. These insights are important to understand the redox activity of cerium nanomaterials and provide clues to the role of CeNPs in biological and environmen…

Glycine-functionalized copper(ii) hydroxide nanoparticles with high intrinsic superoxide dismutase activity

Superoxide dismutases (SOD) are a group of enzymes that catalyze the dismutation of superoxide (O2−) radicals into molecular oxygen (O2) and H2O2 as a first line of defense against oxidative stress. Here, we show that glycine-functionalized copper(II) hydroxide nanoparticles (Gly-Cu(OH)2 NPs) are functional SOD mimics, whereas bulk Cu(OH)2 is insoluble in water and catalytically inactive. In contrast, Gly-Cu(OH)2 NPs form water-dispersible mesocrystals with a SOD-like activity that is larger than that of their natural CuZn enzyme counterpart. Based on this finding, we devised an application where Gly-Cu(OH)2 NPs were incorporated into cigarette filters. Cigarette smoke contains high concent…

Controlling the Morphology of Au–Pd Heterodimer Nanoparticles by Surface Ligands

Controlling the morphology of noble-metal nanoparticles is mandatory to tune specific properties such as catalytic and optical behavior. Heterodimers consisting of two noble metals have been synthesized, so far mostly in aqueous media using selective surfactants or chemical etching strategies. We report a facile synthesis for Au@Pd and Pd@Au heterodimer nanoparticles (NPs) with morphologies ranging from segregated domains (heteroparticles) to core-shell structures by applying a seed-mediated growth process with Au and Pd seed nanoparticles in 1-octadecene (ODE), which is a high-boiling organic solvent. The as-synthesized oleylamine (OAm) functionalized Au NPs led to the formation of OAm-Au@…

Nanozymes in Nanofibrous Mats with Haloperoxidase-like Activity To Combat Biofouling.

Electrospun polymer mats are widely used in tissue engineering, wearable electronics, and water purification. However, in many environments, the polymer nanofibers prepared by electrospinning suffer from biofouling during long-term usage, resulting in persistent infections and device damage. Herein, we describe the fabrication of polymer mats with CeO2–x nanorods that can prevent biofouling in an aqueous environment. The embedded CeO2–x nanorods are functional mimics of natural haloperoxidases that catalyze the oxidative bromination of Br– and H2O2 to HOBr. The generated HOBr, a natural signaling molecule, disrupted the bacterial quorum sensing, a critical step in biofilm formation. The pol…

CeO2−x nanorods with intrinsic urease-like activity

The large-scale production and ecotoxicity of urea make its removal from wastewater a health and environmental challenge. Whereas the industrial removal of urea relies on hydrolysis at elevated temperatures and high pressure, nature solves the urea disposal problem with the enzyme urease under ambient conditions. We show that CeO2−x nanorods (NRs) act as the first and efficient green urease mimic that catalyzes the hydrolysis of urea under ambient conditions with an activity (kcat = 9.58 × 101 s−1) about one order of magnitude lower than that of the native jack bean urease. The surface properties of CeO2−x NRs were probed by varying the Ce4+/Ce3+ ratio through La doping. Although La substit…

Pd@Fe2O3 Superparticles with Enhanced Peroxidase Activity by Solution Phase Epitaxial Growth

Compared to conventional deposition techniques for the epitaxial growth of metal oxide structures on a bulk metal substrate, wet-chemical synthesis based on a dispersible template offers advantages such as low cost, high throughput, and the capability to prepare metal/metal oxide nanostructures with controllable size and morphology. However, the synthesis of such organized multicomponent architectures is difficult because the size and morphology of the components are dictated by the interplay of interfacial strain and facet-specific reactivity. Here we show that solution-processable two-dimensional Pd nanotetrahedra and nanoplates can be used to direct the epitaxial growth of γ-Fe2O3 nanoro…