Newly Constructed NiCo2O4 Derived from ZIF-67 with Dual Mimic Enzyme Properties for Colorimetric Detection of Biomolecules and Metal Ions

Rapid visual detection of glutathione in vegetables and distinguishing multiple sulfur-containing compounds by smartphone-assisted sensor based on calcined PPy@CuNi-ZIF-67 nanozyme with enhanced oxidase-like activity

In this work, polypyrrole-coated Cu, Ni co-doped ZIF-67 (PPy@CuNi-ZIF-67) was designed and prepared via a facile method. Calcined PPy@CuNi-ZIF-67 exhibited highly efficient oxidase-like activity and possessed excellent capacity to oxidize colorless 3,3',5,5'-tetramethyl benzidine (TMB) into blue oxidation products (oxTMB) within 4 min. Glutathione (GSH) and sulfur-containing compounds can inhibit its oxidase-like activity. Based on this principle, an effective colorimetric method was developed in combination with a smartphone for efficient, sensitive, and visual detection of GSH. Under optimal conditions, good linearity was achieved in the range of 0.83-33.33 μM, and the visual detection limit was 0.27 μM. Moreover, based on the response difference of different sulfur-containing compounds to different chromogenic substrates, a new array sensor was constructed with three chromogenic substrates. The array sensor was proven to quickly distinguish five sulfur-containing compounds at a concentration as low as 8.3 μM in combination with principal component analysis and hierarchical clustering analysis.

Signal "Off-On Model'' for Colorimetric Sensing Proanthocyanidin B2 Achieved by the Organic Solvent-Processed Amorphous BiVO4 Nanozyme

Here, we report a "off-on model"-based colorimetric sensor without the assistance of H2O2, achieved by organic solvent-processed amorphous BiVO4 nanoparticles favorable for large-scale manufacturing. The amorphous material beyond traditional crystalline nanozymes has both vanadium vacancy (Vv) and oxygen vacancy (Ov), as well as single oxidase-like activity with both hydroxyl radical (•OH) and superoxide anion (O2•-) as electron acceptors. Despite the high enzymatic performance, the dual-defect-rich amorphous BiVO4 preserves good long-term activity in either buffer solution or the solid state. The specially designed BiVO4 is capable of accelerating TMB oxidation in the presence of polyphenols, thus leading to an interesting signal-intensified colorimetric response. This is probably due to the coordination of the ortho dihydroxyl group in polyphenols with the catalyst by replacing the surface-adsorbed NO3-, which results in faster charge transfer between BiVO4 and substrate and, thus, more rapid depletion of radicals for TMB oxidation. Based on these findings, a sensor platform for proanthocyanidin (PAC) B2 is established with a limit of detection (LOD) as low as 65 nM and good specificity. The sensor shows higher sensitivity than the standard Porter method (LOD: 0.29 μM) and comparable accuracy when analyzing PAC B2 in commercially available grape seed capsules, with quantitative recoveries varying from 104.0 to 108.3% and relative standard deviations ranging from 1.7 to 5.7%. To date, this is the only nanozyme-based chemical sensor that is active for the signal "off-on model" for the detection of reducing polyphenols. Also, this method seems quite general, and it can be used for sensing of a series of specific polyphenols in addition to PAC B2.

Rational design of redox active metal organic frameworks for mediated electron transfer of enzymes

The efficient immobilization of redox mediators remains a major challenge in the design of mediated enzyme electrode platforms. In addition to stability, the ability of the redox-active material to mediate electron transfer from the active-site buried enzymes, such as flavin adenine dinucleotide-dependent glucose dehydrogenase (FADGDH) and lactate oxidase (LOx), is also crucial. Conventional immobilization techniques can be synthetically challenging, and immobilized mediators often exhibit limited durability, particularly in continuous operation. Here, we design a novel redox-active cobalt-based metal-organic framework (raMOF) obtained via the partial ligand substitution of 2-methylimidazole (MeIm) with a 1,2-naphthoquinone-4-sulfonate (NQSO) redox probe, as a promising platform for high-performance enzyme electrodes. This nanostructured raMOF, combined with multi-walled carbon nanotubes (CNTs), provided a high current density of up to 2.06 mA cm-2 during enzymatic reactions and maintained remarkable operational stability, retaining 100% of its current over 54 hours. This stability far exceeded that of adsorbed NQSO on CNTs, which experienced a complete loss of the initial current, highlighting the significant advantage of the raMOF-based platform for high-performance enzyme electrodes.

Smartphone-assisted colorimetric biosensor for the rapid visual detection of natural antioxidants in food samples

Quantitative monitoring of the concentrations of epigallocatechin gallate (EGCG) and cysteine (Cys) is of great significance for promoting human health. In this study, iron/aluminum bimetallic MOF material MIL-53 (Fe, Al) was rapidly prepared under room temperature using a co-precipitation method, followed by investigating the peroxidase-like (POD-like) activity of MIL-53(Fe, Al) using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic substrate. The results showed that the Michaelis -Menten constants of TMB and H2O2 as substrates were 0.167 mM and 0.108 mM, respectively. A colorimetric sensing platform for detecting EGCG and Cys was developed and successfully applied for analysis and quantitative detection using a smartphone. The linear detection range for EGCG was 15∼80 μM (R2=0.994) and for Cys was 7∼95 μM (R2=0.998). The limits of detection (LOD) were 0.719 μM and 0.363 μM for EGCG and Cys, respectively. This work provides a new and cost-effective approach for the real-time analysis of catechins and amino acids.

Construction and synthesis of NiCo2O4nanozyme for enhanced antibacterial performance

Developing effective and low-cost enzyme-like nanomaterials to kill bacteria is vital for human health. Herein, nanorod-assembled NiCo2O4microspheres were prepared though a facile hydrothermal method, andshowed highly enhanced peroxidase-like activity compared to pure Co3O4due to its large surface area and abundant active sites. The NiCo2O4possess the ability to catalyze H2O2to generate large amounts of •O2-, which can be used for bacteriostatic applications. In particular, the antibacterial system combining the spiky NiCo2O4particles and a low concentration of H2O2(100μM) exhibits an excellent bacteriostatic efficiency against bothEscherichia coli(94.44%) andStaphylococcus aureus(93.45%).

A Microenvironment-Responsive Graphdiyne-Iron Nanozyme Hydrogel with Antibacterial and Anti-Inflammatory Effect for Periodontitis Treatment

Periodontitis is a chronic inflammatory disease caused by dental plaque, which leads to tooth loosening and shifting or even tooth loss. Current treatments, including mechanical debridement and antibiotics, often fail to eradicate recalcitrant biofilms and mitigate excessive inflammation. Moreover, these interventions can disrupt the oral microbiome, potentially compromising long-term treatment outcomes. To address these limitations, an injectable nanoenzyme hydrogel composed of a dopamine (DA)-modified hyaluronic acid (HA) scaffold and a graphdiyne-iron (GDY-Fe) complex, named GDY-Fe@HA-DA, exhibits excellent tissue adhesion, self-healing, antibacterial properties, and biocompatibility. Under near-infrared laser irradiation, GDY-Fe@HA-DA effectively eradicates a variety of pathogens, including Escherichia coli, Staphylococcus aureus, and Porphyromonas gingivalis, through a synergistic combination of chemodynamical and photothermal therapies. The hydrogel's efficacy is further validated in both bacterial-infected skin wounds and rat periodontitis models. It effectively alleviates the inflammatory environment and promotes wound healing and periodontal tissue recovery. This findings highlight the potential of GDY-Fe@HA-DA as a promising therapeutic material for periodontitis and other tissue injuries.

Zeolitic imidazole framework-derived rich-Zn-Co3O4/N-doped porous carbon with multiple enzyme-like activities for synergistic cancer therapy

Reactive oxygen species (ROS)-centered chemodynamic therapy (CDT) holds significant potential for tumor-specific treatment. However, insufficient endogenous H2O2 and extra glutathione within tumor microenvironment (TME) severely deteriorate the CDT's effectiveness. Herein, rich-Zn-Co3O4/N-doped porous carbon (Zn-Co3O4/NC) was fabricated by two-step pyrolysis, and applied to build high-efficiency nano-platform for synergistic cancer therapy upon combination with glucose oxidase (GOx), labeled Zn-Co3O4/NC-GOx for clarity. Specifically, the multiple enzyme-like activities of the Zn-Co3O4/NC were scrutinously investigated, including peroxidase-like activity to convert H2O2 to O2∙-, catalase-like activity to decompose H2O2 into O2, and oxidase-like activity to transform O2 to O2∙-, which achieved the CDT through the catalytic cascade reaction. Simultaneously, GOx reacted with intracellular glucose to produce gluconic acid and H2O2, realizing starvation therapy. In the acidic TME, the Zn-Co3O4/NC-GOx rapidly caused intracellular Zn2+ pool overload and disrupted cellular homeostasis for ion-intervention therapy. Additionally, the Zn-Co3O4/NC exhibited glutathione peroxidase-like activity, which consumed glutathione in tumor cells and reduced the ROS consumption for ferroptosis. The tumor treatments offer some constructive insights into the nanozyme-mediated catalytic medicine, coupled by avoiding the TME limitations.

Cationic regulation of specificity and activity of defective MCo2O4 nanozyme (M=Fe, Co, Ni, Cu) for colorimetric detection of caffeic acid

Spinel oxide has great promise in constructing highly active nanozymes due to its tunable crystal structure. However, it still faces the problems of poor specificity and insufficient enzyme activity, which limits its application in the field of analysis. Herein, a series of transition metal spinel oxides were synthesized by cation regulation strategy, and their enzymatic activity and catalytic mechanism were analyzed. Interestingly, FeCo2O4, Co3O4 and NiCo2O4 had oxidase-like activity and peroxidase-like activity, while CuCo2O4 had specific and high oxidase-like activity. Their oxidase-like activities follow the order of FeCo2O4 < Co3O4 < NiCo2O4 < CuCo2O4, which is consistent with their cation radius. The smaller the cation radius of tetrahedral site, the more beneficial it is to increase the oxidase-like activity. The high oxidase-like activity of CuCo2O4 may be attributed to the production of 1O2, •O2- and •OH. EPR results showed the presence of abundant oxygen vacancies in CuCo2O4. Upon the introduction of EDTA, TMB color reaction fades because of oxygen vacancies elimination by EDTA, indicating that oxygen vacancies played an important role in the reaction. Based on the inhibition effect of caffeic acid on the high oxidase-like activity of CuCo2O4, a simple and sensitive caffeic acid colorimetric sensing platform was developed. The linear range for the detection of caffeic acid is 0.02-15 μM, with a detection limit as low as 13 nM. The constructed sensor enables the detection of caffeic acid in caffeic acid tablets and actual water samples, providing a new strategy for the detection of caffeic acid and drug quality control.

Co(II)-Based Metal-Organic Framework Derived CA-CoNiMn-CLDHs with Peroxidase-like Activity for Colorimetric Detection of Phenol

Given the serious harm of toxic phenol to human health and the ecological environment, it is urgent to develop an efficient, low-cost and sensitive nanoenzyme-based method to monitor phenol. MOF-derived nanozyme has attracted wide interest due to its hollow polyhedra structure and porous micro-nano frameworks. However, it is still a great challenge to synthesize MOF-derived multimetal synergistic catalytic nanoenzymes in large quantities with low cost. Herein, we reported the synthetic strategy of porous hollow CA-CoNiMn-CLDHs with ZIF-67 as templates through a facile solvothermal reaction. The prepared trimetallic catalyst exhibits excellent peroxidase-like activity to trigger the oxidative coupling reaction of 4-AAP and phenol in the presence of H2O2. The visual detection platform for phenol based on CA-CoNiMn-CLDHs is constructed, and satisfactory results are obtained. The Km value for CA-CoNiMn-CLDHs (0.21 mM) is lower than that of HRP (0.43 mM) with TMB as the chromogenic substrate. Because of the synergistic effect of peroxidase-like activity and citric acid functionalization, the built colorimetric sensor displayed a good linear response to phenol from 1 to 100 μM with a detection limit of 0.163 μM (3σ/slope). Additionally, the CA-CoNiMn-CLDHs-based visual detection platform possesses high-chemical stability and excellent reusability, which can greatly improve economic benefits in practical applications.

Covalent organic framework-supported ultrasmall Rh nanoparticles as peroxidase mimics for colorimetric sensing of cysteine

Covalent organic frameworks (COFs), as a novel porous organic polymer with periodic and highly ordered structure, are ideal carrier matrix for metal nanoparticles due to high specific surface area, good stability, controllable pore size, and structural tunability. In this work, COFs are used as a carrier to in-situ grow ultrasmall rhodium nanoparticles (Rh NPs, ∼2.4 nm), which are uniformly distributed in the pores and on the surfaces of the COFs. The formed composite (COF-Rh) shows excellent peroxidase-mimetic activity benefiting from the good catalytic activity of ultrafine and highly dispersed Rh NPs as well as the high affinity of COFs to organic molecules (i.e., catalytic substrates). Cysteine (Cys) can inhibit the peroxidase-like activity of COF-Rh due to the interaction of -SH in Cys with Rh and the reduction of oxidized peroxidase substrate by Cys. By regulating the peroxidase-like activity of the system, a colorimetric method is successfully developed for Cys detection. Using smartphone as a readout, a portable strategy is further proposed for rapid and visual sensing of Cys.

Rational regulation of peroxymonosulfate activation over porous Co3O4 with carbon coating to boost utilization efficiency of peroxymonosulfate and achieve rapid removal of pollutants

It is of great significance to regulate rationally the activation mechanism of persulfate for promoting the development of sulfate radical-based advanced oxidation processes in wastewater treatment. Herein, carbon coated porous Co₃O₄ with hollow structure was synthesized. Notably, the formation of porous hollow structure improved specific surface area of Co₃O₄ and offered more redox couples of Co²⁺/Co³⁺, thereby reducing electron transfer resistance. Thus, the generation of reactive oxygen species and the role of high-valent transition metal complexes (namely Co₃O₄Co⁴⁺) were improved. The formation of carbon layer on the Co₃O₄ surface can avoid the release of Co ion during reaction process. Benefiting from the role of carbon layer in electron transport, catalyst-mediated the direct electron transfer from pollutant to PMS was boosted. Radical and nonradical pathways worked in coordination each other and realized the rapid removal of various organic pollutants in the presence of a little PMS. In short, current work revealed that modulating rationally the microstructure of catalyst was an efficient strategy for achieving controllable regulation of PMS activation process. More significantly, whether the direct electron transfer process can occur or not depended on both catalyst structure and electronic density of pollutants.

Switching on-off-on colorimetric sensor based on Fe-N/S-C single-atom nanozyme for ultrasensitive and multimodal detection of Hg2

Single-atom nanozymes (SAzymes) as a new class of efficient nanozymes have attracted extensive research interest due to their high catalytic activity and specificity. However, it is challenging to develop a novel nanoenzyme with high activity, good stability and reproducibility. In this paper, the nitrogen and sulfur coordinated Fe-N/S-C SAzymes were synthesized using peanuts shells as carbon, nitrogen and sulfur source. It shows high oxidase-like activities due to the doping of S induced geometric and electronic effects, which is further confirmed by density functional theory calculations. The prepared Fe-N/S-C SAzymes with the remarkable oxidase-mimicking activity could oxidize TMB to blue oxTMB, but the GSH can inhibit the oxidation of TMB resulting in blue fading. However, when Hg²⁺ is added into above system, Hg²⁺-SH complexes are generated attributed to a high affinity between GSH and Hg²⁺, ultimately leading to blue recovery. Based on this phenomenon, we constructed a novel "on-off-on" colorimetric sensor for the simultaneous detection of GSH (off) and Hg²⁺ (on), and the signal is acquired by various modes such as naked eye, UV-Vis spectrometer and smartphone. The colorimetric detection mode based on a smartphone showed a good linear response from 10 to 80 μM for GSH with a detection limit of 3.92 μM, and for Hg²⁺ with a linear range of 1 nM-10 μM and LOD of 0.17 nM, which is more suitable for routine laboratory applications. More importantly, the proposed colorimetric sensor has been successfully applied to the detection of GSH and Hg²⁺ in real samples with good analytical performance. This work not only provides a simple and cost-effective method to detect GSH and Hg²⁺ but also makes a certain contribution to environmental protection.

Colorimetric assay based on NiCo2S4@N,S-rGO nanozyme for sensitive detection of H2O2 and glucose in serum and urine samples

Traditional bimetallic sulfide-based nanomaterials often have a small specific surface area (SSA), low dispersion, and poor conductivity, thereby limiting their wide applications in the nanozyme-catalytic field. To address the above issues, we herein integrated NiCo2S4 with N,S-rGO to fabricate a nanocomposite (NiCo2S4@N,S-rGO), which showed a stronger peroxidase-mimetic activity than its pristine components. The SSA (155.8 m2 g-1) of NiCo2S4@N,S-rGO increased by ∼2-fold compared to NiCo2S4 with a pore size of 7-9 nm, thus providing more active sites and charge transfer channels. Based on the Michaelis-Menten equation, the affinity of this nanocomposite increased 40% and 1.1∼10.6-fold compared with NiCo2S4 with N,S-rGO, respectively, highlighting the significant enhancement of the peroxidase-like activity. The enhanced activity of this nanocomposite is derived from the joint participation of ˙OH, ˙O2 -, and photogenerated holes (h+), and was dominated by h+. To sum up, N,S-codoping, rich S-vacancies, and multi-valence states for this nanocomposite facilitate electron transfer and accelerate reaction processes. The nanocomposite-based colorimetric sensor gave low detection limits for H2O2 (12 μM) and glucose (0.3 μM). In comparison with the results detected by a common glucose meter, this sensor provided the relative recoveries across the range of 97.4-101.8%, demonstrating its high accuracy. Moreover, it exhibited excellent selectivity for glucose assay with little interference from common co-existing macromolecules/ions, as well as high reusability (>6 times). Collectively, the newly developed colorimetric sensor yields a promising methodology for practical applications in H2O2 and glucose detection with advantages of highly visual resolution, simple operation, convenient use, and satisfactory sensitivity.

Architecting an indirect Z-scheme NiCo2O4@CdS-Ag photocatalytic system with enhanced charge transfer for high-efficiency degradation of emerging pollutants

Bimetallic oxides with spinel structure show great prospects in the photocatalysis owing to many active sites. Herein, a novel 500NiCo₂O₄@CdS-5%Ag composite was fabricated via a feasible strategy. Interestingly, the combination with NiCo₂O₄ could significantly enhance the absorption ability of CdS for visible light. Benefiting from the formation of heterojunction structure between NiCo₂O₄ and CdS, the recombination of photogenerated electrons and holes was remarkably restrained. As an effective mediator, deposition of Ag could further promote the transfer of photogenerated charge carriers, thereby accelerating the reaction rate. Meanwhile, light absorption capacity of composite was also improved, owing to the surface plasmon resonance effect of metallic Ag. More importantly, 500NiCo₂O₄@CdS-5%Ag composite with great stability displayed an excellent performance in the photocatalytic degradation of OFX, and its highest removal efficiency was as high as 99.14%. Possible degradation pathways of OFX were given, and most of OFX could be degraded into CO₂, H₂O and other by-products with no toxicity. Significantly, the separation and transfer of photogenerated charge carriers followed indirect Z-scheme heterojunction mechanism. The O₂^-, OH and ¹O₂ were main active species in photocatalytic reaction system. All in all, current work inspired some new ideas for designing novel photocatalytic system in wastewater treatment.

N, S-co-doped carbon/Co1-xS nanocomposite with dual-enzyme activities for a smartphone-based colorimetric assay of total cholesterol in human serum

We fabricated a novel N,S-co-doped carbon/Co_1-xS nanocomposite (NSC/Co_1-xS) using a facile sol-gel approach, which featured a multiporous structure, abundant S vacancies and Co-S nanoparticles filling the carbon-layer pores. When the Co_1-xS nanoparticles were anchored onto the surface of N,S-co-doped carbon, a synergistic catalysis action occurred. The NSC/Co_1-xS nanocomposites possessed both peroxidase-like and oxidase-mimetic dual-enzyme activities, in which the oxidase-mimetic activity dominated. By scavenger capture tests, the nanozyme was demonstrated to catalyze H₂O₂ to produce h⁺, •OH and •O₂^-, among which the strongest and weakest signals were h⁺ and •OH, respectively. The multi-valence states of Co atoms in the NSC/Co_1-xS structure facilitated electronic transfer that enhanced redox reactions, thereby improving the resultant color reaction. Based on the NSC/Co_1-xS's enzyme-mimetic catalytic reaction, a visual colorimetric assay and Android "Thing Identify" application (app), installed on a smartphone, offered detection limits of 1.93 and 2.51 mg/dl, respectively, in human serum samples. The selectivity/interference experiments, using fortified macromolecules and metal ions, demonstrated that this sensor had high selectivity and low interference potential for cholesterol analysis. Compared to standard assay kits and previously reported visual detection, the Android smartphone-based assays provided higher accuracy (recoveries up to 93.6-104.1%), feasibility for trace-level detection, and more convenient on-site application for cholesterol assay due to the superior enzymatic activity of NSC/Co_1-xS. These compelling performance metrics lead us to posit that the NSC/Co_1-xS-based nanozymic sensor offers a promising methodology for several practical applications, such as point-of-care diagnosis and workplace health evaluations.

Versatile Sensing Platform of Innovative Copper Oxide Assisted Cu-Phenolic Coordination Nanosheet mediated Fluorophore tagged GT-rich SSA based Fluorescence ON-OFF Biosensor for Subsequent Detection of Cd2+ and S2− Ions

Increased levels of toxic metal/non-metal ions Cadmium (Cd2+) and Sulfide (S2−) in the environment can be detrimental to human health. Given the circumstances, the detection and measurement of Cd2+ and...

Insights into the degradation of emerging organic pollutants by peroxydisulfate activated with Co3O4@NiO: role of each component and catalytic mechanism

A novel Co3O4@NiO as a high-efficiency catalyst was employed to activate peroxydisulfate for degrading antibiotics, and the catalytic mechanism was investigated.

Sensitive electrochemical biosensor for Uracil-DNA glycosylase detection based on self-linkable hollow Mn/Ni layered doubled hydroxides as oxidase-like nanozyme for cascade signal amplification

Nanozymes have been widely used in biosensors instead of natural enzymes because of low cost, high stability and ease of storage. However, few works use oxidase-like nanozymes to fabricate electrochemical biosensors. Herein, we proposed a sensitive electrochemical biosensor to detect uracil-DNA glycosylase (UDG) based on the hollow Mn/Ni layered doubled hydroxides (h-Mn/Ni LDHs) as oxidase-like nanozyme. Briefly, the h-Mn/Ni LDHs, which was prepared by a facile hydrothermal method, exhibited excellent oxidase-like activity because the hollow structure provided rich active sites and high specific surface area. Then, the signal probes were constructed by assembling the hairpin DNA (hDNA), single DNA1 and DNA2 on the h-Mn/Ni LDHs, respectively. In the presence of UDG, the uracil bases in the stem of hDNA were specifically excised, generating apyrimidinic (AP) sites and inducing the unwinding of the hDNA. Afterwards, the h-Mn/Ni LDHs@Au-hDNA/DNA1 was connected on the electrode via hybridization between unwinded hDNA and capture DNA (cDNA). Subsequently, the self-linking process allowed the retention of numerous h-Mn/Ni LDHs through simple DNA hybridization to amplify the signal of o-phenylenediamine (o-PD). Unlike many peroxidase-like nanozyme-based electrochemical biosensors, there is no need to add H₂O₂ during the experimental process, which effectively reduced the background signal as well as improved the stability of the biosensor. As expected, the biosensor exhibited excellent performance with a wide linear range and a low detection limit. This work highlights an appealing opportunity to develop a no H₂O₂ platform based on h-Mn/Ni LDHs for future application in biological analysis and clinical diagnosis.

Construction of pH-Dependent Nanozymes with Oxygen Vacancies as the High-Efficient Reactive Oxygen Species Scavenger for Oral-Administrated Anti-Inflammatory Therapy

It is of great significance to eliminate excessive reactive oxygen species (ROS) for treating inflammatory bowel disease (IBD). Herein, for the first time, a novel nanozyme NiCo₂ O₄ @PVP is constructed via a step-by-step strategy. Noticeably, the existence of oxygen vacancy in the NiCo₂ O₄ @PVP is helpful for capturing oxygenated compounds, while both redox couples of Co³⁺ /Co²⁺ and Ni³⁺ /Ni²⁺ will offer richer catalytic sites. As expected, the obtained NiCo₂ O₄ @PVP exhibits pH-dependent multiple mimic enzymatic activities. Benefiting from the introduction of polyvinylpyrrolidone (PVP), the NiCo₂ O₄ @PVP possesses good physiological stability and excellent biosafety in stomach and intestines' environment. Meanwhile, the NiCo₂ O₄ @PVP also presents strong scavenging activities to ROS in vitro, including ^• O₂ ^- , H₂ O₂ , as well as ^• OH. Furthermore, a dextran sodium sulfate (DSS)-induced colitis model is established for evaluating the anti-inflammatory activity of NiCo₂ O₄ @PVP in vivo. Based on the size-mediated and charge-mediated mechanisms, the nanozyme can pass through the digestive tract and target the inflamed site for oral-administrated anti-inflammatory therapy. More interestingly, compared with the model group, the expression levels of inflammatory factors (e.g., Interleukin- 6 (IL-6), Interleukin- 1β (IL-1β), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS)) in colon of mice show a significant decrease after nanozyme intervention, thereby inhibiting the development of IBD. In short, current work provides an alternative therapy for patients suffering from IBD.

N-Doped carbon coated NiCo2O4 nanorods for efficient electrocatalytic oxygen evolution

Hybrid architectures composed of NiCo₂O₄ nanorods coated N-doped carbon (NiCo₂O₄@NC) are synthesized through the pyrolysis of Bi-metallic MOFs, which exhibit excellent electrochemical performance for oxygen evolution reaction.