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Peroxidase-like metallo-nanozyme is developed based on multicomponent cooperative coordination among amino acid, metal ion and therapeutic agent, the metallo-nanozyme achieves synergetic chemo-catalytic therapy through depleting high-level glutathione in tumor cell and converting Fe3+ to Fe2+ for catalyzation of hydrogen peroxide into highly cytotoxic hydroxyl radical, as well as the specific activation of chemical drugs for enhanced chemotherapy. [Display omitted] • Peroxidase-like metallo-nanozymes are simply constructed by amino acid-based cooperative coordinated self-assembly. • The biomimetic nanozymes demonstrate tumor in-site activated catalytic-chemotherapy. • The metallo-nanozymes suppress remarkably tumor growth and without any systemic toxicity. Simple biomolecules-based supramolecular self-assembly hold great promise on the fabrication of nanozyme for mimicking natural enzyme, both structurally and functionally. However, it remains a formidable challenge to design of tumor-specific nanozyme with promoted therapeutic efficiencies starting from such small biological molecule combinations and their cooperative interactions. Inspired by the metalloenzyme in living systems, i.e., peroxidase, herein the construction of metallo-nanozyme through a facile multicomponent coordination self-assembly based on the combination of amino acid, chemotherapeutic motif and metal ions is reported. The resulting metallo-nanozyme possess uniform size distribution, well-defined spherical nanostructure and high chemical drugs contents. Most importantly, the metallo-nanozyme depletes specifically high-level glutathione (GSH) in tumor cell and converts Fe3+ to Fe2+ for subsequent transformation of overproduced hydrogen peroxide (H 2 O 2) into highly cytotoxic hydroxyl radical (·OH) in peroxidase-like catalytic manner. Meanwhile, the metallo-nanozyme are also activated in situ to release the chemical drugs in tumor cell for enhanced chemotherapy. In vitro and in vivo evaluations demonstrate that the supramolecular metallo-nanozyme suppresses remarkably tumor growth via combined catalytic-chemotherapy and without any systemic toxicity. Therefore, this study demonstrates that the tumor-specific biomimetic nanozyme with advanced catalytic therapeutic efficacy could be achieved through cooperative coordination of small biomolecules or therapeutic drugs, opening up opportunities in the development of catalytic anticancer nanozyme for efficiently combat cancers. [ABSTRACT FROM AUTHOR]

Abstract: Ultrathin platinum-coated gold (Pt@Au) nanoparticles with core@shell structure have been developed by under-potential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt2+ produced a uniform Pt monolayer on the surface of gold nanoparticles, which are immobilized on glassy carbon electrode (GCE) surface based on electrostatic interaction. The ultrathin Pt@Au nanoparticles were confirmed by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Voltammetry and amperometric methodologies were used to evaluate the electrocatalytic activity of the Pt@Au nanoparticles modified electrode towards the reduction of hydrogen peroxide under the physiological condition. The present results show that ultrathin Pt coating greatly enhances the electrocatalytic activity towards the reduction of hydrogen peroxide, which can be utilized to fabricate the hydrogen peroxide sensor. Chronoamperometric experiments showed that at an applied potential of 0.08V (vs. Ag/AgCl), the current reduction of hydrogen peroxide was linear to its concentration in the range of 1–450μΜ, and the detection limit was found to be 0.18μM (signal-to-noise ratio, S/N=3). [Copyright &y& Elsevier]

Hydrogen peroxide (H 2 O 2) is a common oxidant that plays an important role in many biological processes and is also an important medium analysis in various fields. In this work, a new electrochemical nanosensor capable of detecting and quantifying hydrogen peroxide was introduced. This nanosensor was fabricated by electrodepositing prussian blue (PB)/graphene quantum dots (GQDs)/polypyrrole (PPy) on single nanopore electrode etched from single gold nanoelectrode. This prepapred nanosensor exhibits good electrochemical response to hydrogen peroxide with high sensitivity and stability, with a linear response in the 2.0 and 80 μM by using amperometric method and differential pulse voltammetry (DPV) method. The limit of detections are 0.33 μM (S/N = 3) for amperometric method and 0.67 μM (S/N = 3) for differential pulse voltammetry (DPV) method, respectively. This nanosensor can be used for the determination of hydrogen peroxide in human urine, and can serve as a new electrochemical platform to monitor H 2 O 2 release from single living cells due to its small overal dimension and high sensitivity. [Display omitted] • Nanosensor was fabricated on single nanopore electrode filled with Prussian blue and graphene quantum dots coated by Polypyrrole. • New nanosensor shows good electrocatalytic activity towards H2O2 oxidation. • This nanosensor can serve as a new electrochemical platform to monitor H2O2 release from single living cells due to its small overal dimension. [ABSTRACT FROM AUTHOR]

A new nanozyme (CuGaa) with switchable enzyme-like activity of peroxidase and polyphenol oxidase was successfully prepared based on guanidinoacetic acid and copper. The two enzyme-like activities can be easily switched by changing temperature or adding MnCl 2. At 4 °C, polyphenol oxidase-like activity decreased to nearly 1%, and the material is mainly characterized by peroxidase-like activity at this point. However, at 60 °C in the presence of 20 mM MnCl 2 , the peroxidase-like activity decreased to nearly 10%, and the polyphenol oxidase-like activity of the materials increased to 140%. Based on the switchable enzyme-like activity of CuGaa, detection methods for thymol and hydrogen peroxide were developed. In addition, a rapid combination strategy was further established combined with logic gate technology for the facile identification of complex contamination in honey, which provided new ideas for low-cost and rapid honey identification. The graphic descriptives that CuGaa has polyphenol oxidase-like and peroxidase-like activities, and that under different conditions, CuGaa can be made to exhibit only one enzyme activity. [Display omitted] • Nanozyme with switchable enzyme-like activity. • Thymol detection at high temperature based on the nanozyme. • A sensing strategy combined with logic gate technology. • A facile identification of complex contamination in honey. [ABSTRACT FROM AUTHOR]

Abstract: Based on the enhancement of chemiluminescence (CL) of luminol-hydrogen peroxide-gold nanoparticles system by fluoroquinolones (FQs), a novel and rapid CL method is reported for the determination of FQs derivatives. Under the optimum conditions, the CL intensity is proportional to the concentration of FQs derivative in solution. The corresponding linear regression equations are established over the range of 0.08–1.28μg/mL for norfloxacin, 0.013–1.32μg/mL for ciprofloxacin, 0.014–1.4μg/mL for lomefloxacin, 0.029–1.46μg/mL for fleroxacin, 0.02–1.0μg/mL for ofloxacin and 0.01–1.44μg/mL for levofloxacin, respectively. The limits of detection (S/N =3) are 3.2, 9.5, 7.0, 9.0, 8.0, and 8.0ng/mL with the relative standard deviation (n =11) 4.3, 1.5, 1.9, 1.3, 1.6 and 2.1% for norfloxacin, ciprofloxacin, lomefloxacin, fleroxacin, ofloxacin and levofloxacin, respectively. This proposed method has been applied to detect FQs derivatives in human urine successfully. [Copyright &y& Elsevier]

Inspired by the very popular demonstration, Elephant's Toothpaste, we developed a cost-effective, portable foam immunoassay for quantitative detection of Escherichia coli O157:H7 (E. coli O157:H7) by measuring foam volume changes using a low-cost ruler. This quantitative immunoassay for E. coli O157:H7 is built by integrating a catalyzed foam-generation reaction with pathogen recognition component. E. coli O157:H7 was enriched and captured by monoclonal antibody to E. coli O157:H7 (mAb1) modified Fe 3 O 4 magnetic nanoparticles (MNP). The peroxidase-like nanozymes gold and platinum nanoparticles (Au@Pt NP) were loaded on silica nanoparticle (SiO 2 NP), forming Au@Pt/SiO 2 NP. The Au@Pt/SiO 2 NP were functionalized by antibody against E. coli O157:H7 (mAb2-Au@Pt/SiO 2 NP) and used as signal labels. In the final sandwich immune complex, Au@Pt NP catalyzes the hydrolysis of hydrogen peroxide (H 2 O 2) to produce oxygen (O 2). In the presence of sodium dodecyl sulfate (SDS), O 2 is trapped by SDS forming thick foam. The foam rises in an acrylic tube and produces sensitive height readout. There is a linear relationship between the foam height and the logarithm of E. coli O157:H7 concentration. Under the optimum conditions, the detection limit was 2.16 × 102 CFU·mL−1 (3σ) in the range of 1.19 × 103–1.19 × 107 CFU·mL−1. This method demonstrates good practical application potential during detection of E. coli O157:H7 in milk samples. This new signaling strategy opens up a new way for portable, simple and sensitive on-site analysis in various environments. Schematic illustration of the fabrication process of Au@Pt NP, mAb2-Au@Pt/SiO 2 NP, sandwich immune reaction for detection of E. coli O157:H7 using MIcs and mAb2-Au@Pt/SiO 2 NP and the principle of quantitative detection strategy of Escherichia coli O157:H7 with an foam immunoassay based on distance readout. Unlabelled Image • A cost-effective foam immunoassay for quantitative detection of Escherichia coli O157:H7 without using any instrument. • Au@Pt NP catalyzed hydrogen peroxide to produce a large amount of oxygen. • O 2 is trapped by SDS producing foam in an acrylic tube, which is measured by distance readout. [ABSTRACT FROM AUTHOR]

Highlights • A novel method for the sensing of H 2 O 2 and choline was developed. • The detection was based on near infrared luminescent UCNPs. • The upconversion luminescence was quenched to 3% of its original intensity by Fe3+. • UCNPs can avoid the interference of fluorescent substances in complex samples. Abstract Choline is an essential nutrient for the growth and development of the baby, and therefore it is often added to infant formula. In this paper, a novel sensor for choline determination in infant formula is developed based on upconverting nanoparticles (UCNPs) with near infrared luminescence. UCNPs-based detection can avoid the interference of background fluorescence from complex samples, and thus provide high selectivity and sensitivity. It was observed that in the presence of Fe3+, polyacrylic acid coated UCNPs were quenched to 3% of its original intensity. The degree of quenching was among the best for UCNPs. Hydrogen peroxide could oxidize Fe2+ to Fe3+, which caused quenching of the upconversion luminescence. A new H 2 O 2 detection method was thus established. In addition, choline could be hydrolyzed to betaine by choline oxidase, and at the same time produced H 2 O 2 , which also caused luminescence quenching through Fe2+ oxidation. Therefore, selective choline sensing was achieved. [ABSTRACT FROM AUTHOR]

Solid-nanopores/nanopipettes have the exquisite ability to reveal the changes in molecular volume due to the advantages of adjustable size, good rigidity and low noise. Herein, a new platform for sensing application was established based on G-quadruplex-hemin DNAzyme (GQH) functionalized gold-coated nanopipettes. In this method, GQH was immobilized on gold-coated nanopipette, which could be used as a catalyst for the reaction of H 2 O 2 with 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) to promote the conversion of ABTS to ABTS+ ions inside gold-coated nanopipette, and the change of transmembrane ion current could be monitored in real time. At the optimal conditions, there was a correlation between the ion current and the concentration of H 2 O 2 in a certain range, which could be used for the hydrogen peroxide sensing. The GQH immobilized nanopipette provides a useful platform to investigate enzymatic catalysis in confined environment, which can be used in electrocatalysis, sensing and fundamental electrochemistry. [Display omitted] • GQH-functionalized gold-coated nanopipettes was fabricated successfully. • GQH-functionalized nanopipettes was used as a catalyst for H 2 O 2 and ABTS reaction. • The conversion of ABTS to ABTS + ions resulted the change of ICR. • A H 2 O 2 sensor was established using the GQH-functionalized nanopipettes platform. [ABSTRACT FROM AUTHOR]