Protein-Assisted Osmium Nanoclusters with Intrinsic Peroxidase-like Activity and Extrinsic Antifouling Behavior

Glucose Oxidase Energized Osmium with Dual-Active Centers and Triple Enzyme Activities for Infected Diabetic Wound Management

Diabetic wounds are susceptible to bacterial infections, largely linked to high blood glucose levels (hyperglycemia). To treat such wounds, enzymes like glucose oxidase (GOx) can be combined with nanozymes (nanomaterials mimic enzymes) to use glucose effectively for purposes. However, there is still room for improvement in these systems, particularly in terms of process simplification, enzyme activity regulation, and treatment effects. Herein, the approach utilizes GOx to directly facilitate the biomineralized growth of osmium (Os) nanozyme (GOx-OsNCs), leading to dual-active centers and remarkable triple enzyme activities. Initially, GOx-OsNCs use vicinal dual-active centers, enabling a self-cascaded mechanism that significantly enhances glucose sensing performance compared to step-by-step reactions, surpassing the capabilities of other metal sources such as gold and platinum. In addition, GOx-OsNCs are integrated into a glucose-sensing gel, enabling instantaneous visual feedback. In the treatment of infected diabetic wounds, GOx-OsNCs exhibit multifaceted benefits by lowering blood glucose levels and exhibiting antibacterial properties through the generation of hydroxyl free radicals, thereby expediting healing by fostering a favorable microenvironment. Furthermore, the catalase-like activity of GOx-OsNCs aids in reducing oxidative stress, inflammation, and hypoxia, culminating in improved healing outcomes. Overall, this synergistic enzyme-nanozyme blend is user-friendly and holds considerable promise for diverse applications.

Synthesis of Os@ZIF-8 nanocomposites with enhanced peroxidase-like activity for detection of Hg2

Metal organic framework (MOF)-derived nanostructures display remarkable characteristics and have broad application potential. Os@ZIF-8 nanocomposites were prepared by a depositional method. The Os nanoparticles distributed on the surface of ZIF-8. The nanocomposites displayed enhanced peroxidase-like activity with smaller Km for both 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 compared to Os NPs due to the confinement effect and large surface area that ZIF-8 provided. From the average reaction rate constants obtained from three different temperatures, the activation energy values were determined. The kinetic data indicated that the Os@ZIF-8 NCs are catalytically more active than Os NPs. In addition, quantitative measurement of Hg2+ was performed based on the formation of Os-Hg alloy. Os@ZIF-8 NCs had a wide detection range between 0 μM and 71.43 μM for Hg2+ with a limit of detection (LOD) of 2.29 μM. Using a MOF with a large surface area to load Os nanoparticles to achieve enhanced nanozyme activity is the novelty of this work.

Biodegradable Osmium Nanoantidotes for Photothermal-/Chemo- Combined Treatment and to Prevent Chemotherapy-Induced Acute Kidney Injury

Acute kidney injury (AKI) is a common adverse event in chemotherapy patients. AKI is accompanied by the generation of reactive oxygen species (ROS) and inflammation. Therefore, the management of ROS and inflammation is a potential strategy for AKI mitigation. Herein, polyethylene glycol-coated osmium nanozyme-based antidotes (Os) are developed for imaging-guided photothermal therapy (PTT) in combination with cisplatin (Pt); while, avoiding AKI induced by high-dose Pt. Os nanoantidotes can enhance the efficiency of tumor treatment during combined PTT and chemotherapy and inhibit tumor metastasis by improving the hypoxic and inflammatory tumor microenvironment. Os nanoantidotes preferentially accumulate in the kidney because of their 2-nm size distribution; and then, regulate inflammation by scavenging ROS and generating oxygen to alleviate Pt-induced AKI. Os nanoantidotes can be cleared from the kidneys by urine excretion but can be degraded under hydrogen peroxide stimulation, reducing the bio-retention of these compounds. By integrating PTT with inflammatory regulation, Os nanoantidotes have the potential to reduce the side effects of chemotherapy, offering an alternative route for the clinical management of cancer patients with chemotherapy-induced AKI.

NLISA versus enzyme-linked immunosorbent assay: Nanozyme-linked immunosorbent array based on platinum sub-nanocluster nanozyme for α-fetoprotein detection

Rapid and accurate identification of tumor metabolic markers is important for early tumor diagnosis and individualized treatment. Here, a stable monodisperse sub-nanometer platinum (Pt) material was developed as a highly efficient nanozyme with a specific activity of peroxidase as high as 20.86 U mg-1 through the growth of in situ domain-limited Pt quantum dots via the polymer polyvinylpyrrolidone. Further, the synthesis of large quantities of Pt-loaded SiO2 (Pt-SiO2 ) was determined by silylation reaction and used for naked eye colorimetric testing of human alpha-fetoprotein (AFP). In particular, the immunization incubation process occurred in preprepared microplates. A nanozyme-based immunomodel was constructed in the presence of the target AFP, and a chromogenic reaction occurred with exogenous hydrogen peroxide and the chromogenic substrate tetramethylbenzidine. On optimization of experimental conditions, the dynamic working response range for AFP was found to be 0.05-20 ng mL-1 , with a limit of detection of 38.7 pg mL-1 . This work provides a new strategy to design efficient nanozyme-based enzyme-linked immunochromatographic platforms to meet the practical use of replacing natural enzymes.

Nano-CeO2-Loaded Polyzwitterionic Double-Network High-Strength Hydrogel for Highly Enhanced Synergistic Marine Antifouling

Although many antibiofouling materials have been developed based on either bacterial-killing or antiadhesion effects, the integration of both the effects in one material remains challenging for achieving highly enhanced synergistic antibiofouling. In this study, we have explored a nano-CeO2-loaded double-network hydrogel by introducing CeO2 nanorods into a polyzwitterionic hydrogel via a simple one-pot method for achieving highly efficient antifouling. First, the CeO2 nanorods dispersed in the hydrogel, as an outstanding nanozyme, have highly efficient bacterial-killing performance. Second, the superhydrophilic polyzwitterionic hydrogel provides a dense hydrated layer on the surface and subsequently excellent broad-spectrum antiadhesion behavior. Most importantly, the bacterial killing and antiadhesion of this hydrogel can work synergistically to largely improve the marine-antifouling performance. Moreover, the double-network structure of this hydrogel, including the covalently cross-linked polyzwitterion hard network and the physically cross-linked poly(vinyl alcohol) soft network, can provide greatly improved mechanical properties (2.44 MPa of tensile strength reaches and 21.87 MPa of compressive strength). As a result, among the existing marine-antifouling hydrogels, the CeO2-loaded polyzwitterionic double-network hydrogel can achieve outstanding antifouling performance, which can sustain for over 6 months in a real marine environment. This work provides a promising marine-antifouling hydrogel, which will also inspire antifouling research of a new strategy and materials.

Protein-Templated Metal Nanoclusters: Molecular-like Hybrids for Biosensing, Diagnostics and Pharmaceutics

The use of proteins as biomolecular templates to synthesize atomically precise metal nanoclusters has been gaining traction due to their appealing properties such as photoluminescence, good colloidal- and photostability and biocompatibility. The synergistic effect of using a protein scaffold and metal nanoclusters makes it especially attractive for biomedical applications. Unlike other reviews, we focus on proteins in general as the protective ligand for various metal nanoclusters and highlight their applications in the biomedical field. We first introduce the approaches and underlined principles in synthesizing protein-templated metal nanoclusters and summarize some of the typical proteins that have been used thus far. Afterwards, we highlight the key physicochemical properties and the characterization techniques commonly used for the size, structure and optical properties of protein-templated metal nanoclusters. We feature two case studies to illustrate the importance of combining these characterization techniques to elucidate the formation process of protein-templated metal nanoclusters. Lastly, we highlight the promising applications of protein-templated metal nanoclusters in three areas-biosensing, diagnostics and therapeutics.

Structural Analysis and Intrinsic Enzyme Mimicking Activities of Ligand-Free PtAg Nanoalloys

Nanozymes are nanomaterials with biocatalytic properties under physiological conditions and are one class of artificial enzymes to overcome the high cost and low stability of natural enzymes. However, surface ligands on nanomaterials will decrease the catalytic activity of the nanozymes by blocking the active sites. To address this limitation, ligand-free PtAg nanoclusters (NCs) are synthesized and applied as nanozymes for various enzyme-mimicking reactions. By taking advantage of the mutual interaction of zeolitic imidazolate frameworks (ZIF-8) and Pt precursors, a good dispersion of PtAg bimetal NCs with a diameter of 1.78 ± 0.1 nm is achieved with ZIF-8 as a template. The incorporation of PtAgNCs in the voids of ZIF-8 is confirmed with structural analysis using the atomic pair-distribution function and powder X-ray diffraction. Importantly, the PtAgNCs present good catalytic activity for various enzyme-mimicking reactions, including peroxidase-/catalase- and oxidase-like reactions. Further, this work compares the catalytic activity between PtAg NCs and PtAg nanoparticles with different compositions and finds that these two nanozymes present a converse dependency of Ag-loading on their activity. This study contributes to the field of nanozymes and presents a potential option to prepare ligand-free bimetal biocatalysts with sizes in the nanocluster regime.

Osmium and OsO x nanoparticles: an overview of syntheses and applications

Precious metal nanoparticles are key for a range of applications ranging from catalysis and sensing to medicine. While gold (Au), silver (Ag), platinum (Pt), palladium (Pd) or ruthenium (Ru) nanoparticles have been widely studied, other precious metals are less investigated. Osmium (Os) is one of the least studied of the precious metals. However, Os nanoparticles are interesting materials since they present unique features compared to other precious metals and Os nanomaterials have been reported to be useful for a range of applications, catalysis or sensing for instance. With the increasing availability of advanced characterization techniques, investigating the properties of relatively small Os nanoparticles and clusters has become easier and it can be expected that our knowledge on Os nanomaterials will increase in the coming years. This review aims to give an overview on Os and Os oxide materials syntheses and applications.

A bifunctional immunosensor based on osmium nano-hydrangeas as a catalytic chromogenic and tinctorial signal output for folic acid detection

As a neglected member of the platinum group elements, osmium, the metal with the highest density in the earth, is very suitable for the preparation of a peroxidase with high catalytic activity and stability, and can also be associated with the development of a sensor. In this study, we accessed Os nano-hydrangeas (OsNHs) with one-pot synthesis and utilized them in a bifunctional immunosensor that can present both catalytic chromogenic and tinctorial signal for nanozyme-linked immunosorbent assay (NLISA) and lateral flow immunoassay (LFIA) for use in folic acid (FA) detection. In the OsNHs-NLISA, the linear range is from 9.42 to 167.53 ng mL^-1. The limit of detection (LOD) is 4.03 ng mL^-1 and the IC₅₀ value is 39.73 ng mL^-1. In OsNHs-LFIA, the visual cut-off value and limit of detection (v-LOD) are 100 ng mL^-1 and 0.01 ng mL^-1, respectively. Additionally, the outcome from the specificity and spiked sample analysis offered recovery from the spiked milk powder sample ranging from 93.9 to 103.6% with a coefficient of variation under 4.9%, compared with UPLC-MS/MS for a correlation of R² = 0.999 and admirable validation. The promising application of the OsNHs can also be used in other bioprobes, and this bifunctional immunosensor analysis mode is suitable for diversified analytes.