Bimetallic ZIF‐Derived Nitrogenous Porous Carbon Co 3 O 4 as a Peroxidase Mimetic for the Sensitive Detection of L‐Cysteine

Hydrogen-Bonding-Induced H-Aggregation of Charge-Transfer Complexes for Ultra-Efficient Second Near-Infrared Region Photothermal Conversion

Adenosine triphosphate (ATP) is produced mainly in the mitochondrion, and its primary task is to function as a ubiquitous energy currency to meet the cellular metabolic demands in biological system...

In this study, 3,3',5,5'-tetramethylbenzidine (TMB) was selected as a chromogenic substrate to evaluate the light-responsive oxidase-like activity of different zeolitic imidazolate frameworks (ZIFs). The synthesized ZIFs were systematically characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infraredspectroscopy, and X-ray diffraction analysis. Several main operational parameters, including ZIFs and TMB concentrations, pH value, radiation time, and working current, in the reaction process were optimized. The kinetic measurement results show that ZIF-90 exhibits higher affinity to thesubstrate than horseradish peroxidase. Furthermore, given that adenosine triphosphate (ATP) can specifically combine with Zn2+ binding site and destroy the structure of ZIF-90, a specific and sensitive colorimetric method was established for the quantitative detection of ATP within the range 10 - 240μM. In addition, on the basis that phenolic pollutants can impact the reaction kinetics diversely on different ZIFs, a sensor array was constructed and successfully applied to differentiate five phenolic pollutants in lake water samples. This work is expected to shed light on the establishment of ZIF-based light-responsive oxidase-like nanozymes for the highly selective colorimetric detection and sensor array.

Anode-Driven Controlled Release of Cathodic Fuel via pH Response for Smart Enzymatic Biofuel Cell.

Nanozymes, despite their promising stability and cost-effectiveness, often suffer from lower catalytic activity compared to natural enzymes, limiting their practical applications. Herein, we report the rational design, synthesis, and comprehensive characterization of novel bimetallic palladium-iron nanoparticles supported on nitrogen-doped mesoporous carbon (Fe-Pd@N-MC) as a highly efficient peroxidase-mimicking nanozyme. Structural and morphological analyses using XRD, HR-TEM, XPS, and N2 physisorption confirmed the successful formation of uniformly dispersed, superparamagnetic bimetallic nanoparticles composed of Pd0 and Fe3O4. Benefiting from the synergistic effect between Pd and Fe species, Fe-Pd@N-MC exhibited markedly enhanced peroxidase-like activity compared to its monometallic counterparts (Fe@N-MC and Pd@N-MC) toward both 3,3',5,5'-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD). Kinetic studies revealed excellent catalytic efficiency and high substrate affinity, with Km values of 0.156 mM for TMB and 0.088 mM for OPD. Mechanistic investigations identified hydroxyl radicals (˙OH) as the dominant reactive species driving the oxidation processes. Exploiting its robust and rapid catalytic performance, Fe-Pd@N-MC was further employed to construct a sensitive and selective colorimetric platform for the detection of dopamine and ascorbic acid, achieving limits of detection of 3.44 μM and 2.87 μM, respectively. The practical applicability of this nanozyme-based sensor was demonstrated through the accurate quantification of ascorbic acid in fresh fruit juice samples, highlighting its potential for application in biosensing, food analysis and clinical diagnostics.

Electron spin resonance (ESR) spectroscopy has been used to investigate hydroxyl radical generation in rats with chronic dietary iron loading. A secondary radical spin-trapping technique was used where hydroxyl radical forms methyl radical upon reaction with DMSO. The methyl radical was then detected by ESR spectroscopy as its adduct with the spin trap alpha-phenyl-N-t-butylnitrone (PBN). This adduct was detected in the bile of rats 10 wk after being fed an iron-loading diet and 40 min after the i.p. injection of the spin trap PBN dissolved in DMSO. Bile samples were collected into a solution of the ferrous stabilizing chelator 2,2'-dipyridyl in order to prevent the generation of radical adducts ex vivo during bile collection. Identification of the ESR spectrum of the major radical adduct as that of PBN/.CH3 provides evidence for the generation of the hydroxyl radical during iron supplementation. Desferal completely inhibited in vivo hydroxyl radical generation stimulated by high dietary iron intake. No radical adducts were detected in rats which were fed the control diet for the same period of time. This is the first evidence of hydroxyl radical generation in chronic iron-loaded rats.

Bifunctional 3D-MOF-based nanoprobes for electrochemical sensing and nanozyme enhanced with peroxidase mimicking for colorimetric detection of acetaminophen

Recent advances and synergistic effect of bioactive zeolite imidazolate frameworks (ZIFs) for biosensing applications

N, N, N′, N′‐tetramethyl‐p‐phenylenediamine (TMPD) and N, N, N′, N′‐tetramethylbenzidine (TMB) were used as probe molecules to examine their interactions with catalytically active sites generated after thermal treatment at 600 °C under O2 of acidic H6ZSM‐5 zeolite with chemical composition H6(AlO2)6(SiO2)90. The aromatic amines were merely exposed as powders at room temperature under argon to activated acidic H6ZSM‐5 molecular sieve. The course of adsorption and subsequent reactions were monitored by the application of diffuse reflectance, UV–visible absorption, electron paramagnetic resonance (EPR) and Raman scattering spectroscopy. The experimental investigations provided specific evidence of TMPD·+ or TMB·+ radical cations as major durable species and TMB2+ as minor species after complete adsorption. No direct evidence of trapped electrons within the zeolite framework resulting from the ionization was provided by EPR and electronic absorption spectroscopy. The aromatic amines through resonance Raman spectroscopy appear to be a sensitive and specific tool to probe the concentration, strength and accessibility of electron acceptor Lewis acid sites created during thermal treatment under O2. In contrast, no evidence of Brønsted acid sites of H6ZSM‐5 was found during the sorption of TMPD or TMB through the generation of protonated species. Copyright © 2002 John Wiley & Sons, Ltd.

Separately, Fenton and starvation cancer therapies have been recently reported as impressive methods for tumor destruction. Here, we introduce natural hemoglobin and glucose oxidase (GOx) for efficient cancer treatment following combined Fenton and starvation therapies. GOx and hemoglobin were encapsulated in zeolitic imidazolate frameworks 8 (ZIF-8) to fabricate a pH-sensitive MOF activated by tumor acidity. In the slightly acidic environment of cancer cells, GOx is released and it consumes d-glucose and molecular oxygen, nutrients essential for the survival of cancer cells, and produces gluconic acid and hydrogen peroxide, respectively. The produced gluconic acid increases the acidity of the tumor microenvironment leading to complete MOF destruction and enhances hemoglobin and GOx release. The Fe ions from the heme groups of hemoglobin also release in the presence of both endogenous and produced H2O2 and generate hydroxyl radicals. The produced OH˙ radical can rapidly oxidize the surrounding biomacromolecules in the biological system and treat the cancer cells. In vitro experiments demonstrate that this novel nanoparticle is cytotoxic to cancer cells HeLa and MCF-7, at very low concentrations (<2 μg mL-1). In addition, the selectivity index values are 5.52 and 11.04 for HeLa and MCF-7 cells, respectively, which are much higher than those of commercial drugs and those of similar studies reported by other research groups. This work thus demonstrates a novel pH-sensitive system containing hemoglobin and GOx for effective and selective cancer treatment using both radical generation and nutrient starvation.

Hollow Cu-Co/N-doped carbon spheres derived from ZIFs as an efficient catalyst for peroxymonosulfate activation

Aims: This study evaluated the connection between the progression of hepatic fibrosis and trace metals, the distribution profiles of copper(Cu) and Zinc (Zn) and the generation of hydroxyl radicals from Cu- metallothionein (MT) purified from human hepatocellular carcinoma (HCC). Methods: We measured the metal contents in HCC tissue and liver parenchyma in patients with HCC. The content of metals in the liver was measured by particle induced X-ray emission (PIXE). Distribution profiles of Cu and Zn in human liver was evaluated by high-performance liquid chromatography (HPLC). The generation of hydroxyl radicals was measured by electron spin resonance (ESR) spin-trapping technique. Results: Hepatic copper content increased with the progression of hepatic fibrosis. Copper level in liver parenchyma was higher in patients with HCC than in those without HCC (p &lt; 0.01). MT was mainly present as Zn-MT in normal liver, Cu,Zn-MT in surrounding liver parenchyma and Cu-MT in HCC (p &lt; 0.01). The signal intensity of the ESR spectrum in HCC was stronger than those in normal liver and surrounding liver parenchyma. Conclusions: Copper accumulation in the liver parenchyma seems to relate to hepatocarcinogenesis.

Extra virgin olive oil (EVOO) is recognized as one of the healthiest foods for its high content of antioxidants, which forestall and slow down radical formation. Free radical-initiated oxidation is considered one of the main causes of rancidity in fats and oils. As a consequence, reliable protocols for the investigation of oil oxidation based on selective, noninvasive, and fast methods are highly desirable. Here we report an experimental approach based on UV-Vis absorbance, steady-state fluorescence, and electron paramagnetic resonance (EPR) spectroscopy for studying oxidation processes induced by temperature for a period up to 35 d on Sicilian EVOO samples. We followed the decrease in β-carotene content during incubation time and observed changes in polyphenols and tocopherols during the oxidation processes, focusing on the time scale of those changes. Using EPR spectroscopy, the free radical formation in different oil samples is reported, providing a fingerprint for both the antioxidant content and temporal features of the oxidation process at its early stage. We monitor β-carotene and chlorophyll in an auto-oxidation process. A protocol based on spectroscopic measurements is presented and can be used for the quality control process of commercial olive oil.

In Vivo ESR Spin Trapping Evidence for Hydroxyl Radical-Mediated Toxicity of Paraquat and Copper in Rats

Promoting sensitive colorimetric detection of hydroquinone and Hg2+ via ZIF-8 dispersion enhanced oxidase-mimicking activity of MnO2 nanozyme