Ultrasmall Gold Nanoclusters-Enabled Fabrication of Ultrafine Gold Aerogels as Novel Self-Supported Nanozymes

Iridium nanoparticles supported on polyaniline nanotubes for peroxidase mimicking towards total antioxidant capacity assay of fruits and vegetables

In this study, a straightforward approach is presented for the first time to anchor Ir nanoparticles on the surface of uniform polyaniline (PANi) nanotubes (NTs), which can be used as an efficient peroxidase (POD)-like catalyst. The morphology and chemical structure of the PANi-Ir nanocomposite are characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), Raman and X-ray photoelectron spectroscopy (XPS) measurements. Owing to the strong interaction between Ir nanoparticles and PANi, a remarkable catalytic enhancement is achieved compared to the bare Ir black catalyst and individual PANi NTs, dominating withan electron transfer mechanism. Furthermore, an efficient colorimetric sensor for ascorbic acid (AA) is developed with a low detection limit of 1.0 μM (S/N = 3), and a total antioxidant capacity (TAC) sensing platform is also constructed for the rigorous detection and analysis of fruits and vegetables.

Multifunctional Gold Nanozyme-Engineered Amphotericin B for Enhanced Antifungal Infection Therapy

Chronic wounds of significant severity and acute injuries are highly vulnerable to fungal infections, drastically impeding the expected wound healing trajectory. The clinical use of antifungal therapeutic drug is hampered by poor solubility, high toxicity and adverse reactions, thereby necessitating the urgent development of novel antifungal therapy strategy. Herein, this study proposes a new strategy to enhance the bioactivity of small-molecule antifungal drugs based on multifunctional metal nanozyme engineering, using amphotericin B (AmB) as an example. AmB-decorated gold nanoparticles (AmB@AuNPs) are synthesized by a facile one-pot reaction strategy, and the AmB@AuNPs exhibit superior peroxidase (POD)-like enzyme activity, with maximal reaction rates (Vmax ) 3.4 times higher than that of AuNPs for the catalytic reaction of H2 O2 . Importantly, the enzyme-like activity of AuNPs significantly enhanced the antifungal properties of AmB, and the minimum inhibitory concentrations of AmB@AuNPs against Candida albicans (C. albicans) and Saccharomyces cerevisiae (S. cerevisiae) W303 are reduced by 1.6-fold and 50-fold, respectively, as compared with AmB alone. Concurrent in vivo studies conducted on fungal-infected wounds in mice underscored the fundamentally superior antifungal ability and biosafety of AmB@AuNPs. The proposed strategy of engineering antifungal drugs with nanozymes has great potential for enhanced therapy of fungal infections and related diseases.

Strain Effects in Ru-Au Bimetallic Aerogels Boost Electrocatalytic Hydrogen Evolution

To improve the sluggish kinetics of the hydrogen evolution reaction (HER), a key component in water-splitting applications, there is an urgent desire to develop efficient, cost-effective, and stable electrocatalysts. Strain engineering is proving an efficient strategy for increasing the catalytic activity of electrocatalysts. This work presents the development of Ru-Au bimetallic aerogels by a simple one-step in situ reduction-gelation approach, which exhibits strain effects and electron transfer to create a remarkable HER activity and stability in an alkaline environment. The surface strain induced by the bimetallic segregated structure shifts the d-band center downward, enhancing catalysis by balancing the processes of water dissociation, OH* adsorption, and H* adsorption. Specifically, the optimized catalyst shows low overpotentials of only 24.1 mV at a current density of 10 mA cm-2 in alkaline electrolytes, surpassing commercial Pt/C. This study can contribute to the understanding of strain engineering in bimetallic electrocatalysts for HER at the atomic scale.

Advances in the Application of Transition-Metal Composite Nanozymes in the Field of Biomedicine

Due to the limitation that natural peroxidase enzymes can only function in relatively mild environments, nanozymes have expanded the application of enzymology in the biological field by dint of their ability to maintain catalytic oxidative activity in relatively harsh environments. At the same time, the development of new and highly efficient composite nanozymes has been a challenge due to the limitations of monometallic particles in applications and the inherently poor enzyme-mimetic activity of composite nanozymes. The inherent enzyme-mimicking activity is due to Au, Ag, and Pt, along with other transition metals. Moreover, the nanomaterials exhibit excellent enzyme-mimicking activity when composited with other materials. Therefore, this paper focuses on composite nanozymes with simulated peroxidase activity that have been prepared using noble metals such as Au, Ag, and Pt and other transition metal nanoparticles in recent years. Their simulated enzymatic activity is utilized for biomedical applications such as glucose detection, cancer cell detection and tumor treatment, and antibacterial applications.

Imaging-Guided Antibacterial Based on Gold Nanocrystals and Assemblies

Bacterial infection becomes a severe threat to human life and health worldwide. Antibiotics with the ability to resist pathogenic bacteria are therefore widely used, but the misuse or abuse of antibiotics can generate multidrug-resistant bacteria or resistant biofilms. Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria. With the excellent optical properties, engineerable surface chemistry, neglectable biotoxicity, gold nanocrystals are particularly attractive in biomedicine for cancer therapy and antibacterial therapy, as well as nanoprobes for bioimaging and disease diagnosis. In this perspective, gold nanocrystal-based antibacterial performance and deep-tissue imaging are summarized, including near-infrared-light excited photoacoustic imaging and fluorescence imaging through deep tissue infections. On the basis of integrating "imaging-therapy-targeting" in single nanotheranostic, the current challenges of imaging-guided antibacterial and therapy based on gold nanocrystals are discussed, and some insights are provided into the gold nanocrystal-based nanoplatform that integrates antibacterial activity and therapy. This perspective is expected to provide comprehensive guidance for diagnosing and combating bacterial infections based on gold nanostructures.

Leveraging Ligand and Composition Effects: Morphology-Tailorable Pt-Bi Bimetallic Aerogels for Enhanced (Photo-)Electrocatalysis

Metal aerogels (MAs) are emerging porous materials displaying unprecedented potential in catalysis, sensing, plasmonic technologies, etc. However, the lack of efficient regulation of their nano-building blocks (NBBs) remains a big hurdle that hampers the in-depth investigation and performance enhancement. Here, by harmonizing composition and ligand effects, Pt- and Bi-based single- and bimetallic aerogels bearing NBBs of controlled dimensions and shapes are obtained by facilely tuning the metal precursors and the applied ligands. Particularly, by further modulating the electronic and optic properties of the aerogels via adjusting the content of the catalytically active Pt component and the semiconducting Bi component, both the electrocatalytic and photoelectrocatalytic performance of the Pt-Bi aerogels can be manipulated. In this light, an impressive catalytic performance for electro-oxidation of methanol is acquired, marking a mass activity of 6.4-fold higher under UV irradiation than that for commercial Pt/C. This study not only sheds light on in situ manipulating NBBs of MAs, but also puts forward guidelines for crafting high-performance MAs-based electrocatalysts and photoelectrocatalysts toward energy-related electrochemical processes.

Implantable 3D Printed Hydrogel Scaffolds Loading Copper-Doxorubicin Complexes for Postoperative Chemo/Chemodynamic Therapy

Biomaterial-based implants hold great potential for postoperative cancer treatment due to the enhanced drug dosage at the disease site and decreased systemic toxicity. However, the elaborate design of implants to avoid complicated chemical modification and burst release remains challenging. Herein, we report a three-dimensional (3D) printed hydrogel scaffold to enable sustained release of drugs for postoperative synergistic cancer therapy. The hydrogel scaffold is composed of Pluronic F127 and sodium alginate (SA) as well as doxorubicin (DOX) and copper ions (F127-SA/Cu-DOX hydrogel scaffold). Benefiting from the coordination of Cu(II) with both SA and DOX, burst release of DOX can be overcome, and prolonged release time can be achieved. The therapeutic efficiency can be adjusted by altering the amount of DOX and Cu(II) in the scaffolds. Moreover, apoptosis and ferroptosis of cancer cells can be induced through the combination of chemotherapy and chemodynamic therapy. In addition, DOX supplies excess hydrogen peroxide to enhance the efficiency of Cu-based chemodynamic therapy. When implanted in the resection site, hydrogel scaffolds effectively inhibit tumor growth. Overall, this study may offer a new strategy for fabricating local implants with synergistic therapeutic performance for preventing postoperative cancer recurrence.

An Oligopeptide-Protected Ultrasmall Gold Nanocluster with Peroxidase-Mimicking and Cellular-Imaging Capacities

Recent decades have witnessed the rapid progress of nanozymes and their high promising applications in catalysis and bioclinics. However, the comprehensive synthetic procedures and harsh synthetic conditions represent significant challenges for nanozymes. In this study, monodisperse, ultrasmall gold clusters with peroxidase-like activity were prepared via a simple and robust one-pot method. The reaction of clusters with H₂O₂ and 3,3',5,5'-tetramethylbenzidine (TMB) followed the Michaelis-Menton kinetics. In addition, in vitro experiments showed that the prepared clusters had good biocompatibility and cell imaging ability, indicating their future potential as multi-functional materials.

Copper–carbon dot aerogel: a high-performance mimetic peroxidase and its application for versatile colorimetric bioassays

Benefiting from the electron transfer process and generation of hydroxyl radical, copper–carbon dot aerogels exhibit high-performance peroxidase-like activity and are applied for versatile colorimetric bioassays based on multienzyme cascade reactions.