Facile strategy to prepare a metalloporphyrin-based hydrophilic porous organic polymer with enhanced peroxidase-like activity and high stability for colorimetric detection of H2O2 and glucose

Versatile self-assembled near-infrared SERS nanoprobes for multidrug-resistant bacterial infection-specific surveillance and therapy

The rise of multidrug-resistant bacteria (MDRB) has made bacterial infection one of the biggest health threats, causing numerous antibiotics to fail. Real-time monitoring of bacterial disease treatment efficacy at the infection site is required. Herein, we report a versatile Raman tag 3,3'-diethylthiatricarbocyanine iodide (DTTC)-conjugated star-shaped Au-MoS2@hyaluronic acid (AMD@HA) nanocomposite as a surface-enhanced Raman scattering (SERS) nanoprobe for quick bacterial identification and in-situ eradication. Localized surface plasmon resonance (LSPR) from the hybrid metallic nanostructure makes AMD@HA highly responsive to the near-infrared laser, enabling it to demonstrate a photothermal (PTT) effect, increased SERS activity, and peroxidase-like catalytic reaction to release reactive oxygen species. The tail vein injection of AMD@HA nanoprobes is invasive, however SERS imaging for bacterial identification is non-invasive and sensitive, making it an efficient residual bacteria monitoring method. The detection limit for methicillin-resistant Staphylococcus aureus (MRSA) is as low as 102 CFU·mL-1, and the substrates allow for taking 120 s to acquire a Raman image of 1600 (40 × 40) pixels. In mouse models of MRSA-induced wound infection and skin abscess, the combination of AMD@HA-mediated PTT and catalytic therapy demonstrates a synergistic effect in promoting wound healing through rapid sterilization. This SERS-guided therapeutic approach exhibits little toxicity and does not cause considerable collateral damage, offering a highly promising intervention for treating diseases caused by MDRB. STATEMENT OF SIGNIFICANCE: This research introduces a SERS nanoprobe, AMD@HA, for the rapid identification and eradication of multidrug-resistant bacteria (MDRB), a critical health threat. The nanoprobe leverages localized surface plasmon resonance for photothermal therapy and enhanced Raman signals, offering a sensitive, non-invasive diagnostic tool. With a low detection limit for MRSA and a synergistic therapeutic effect in mouse models, our approach holds significant promise for treating MDRB-driven infections with minimal toxicity, advancing the field of antimicrobial strategies.

Porphyrin-based porous organic polymers synthesized using the Alder-Longo method: the most traditional synthetic strategy with exceptional capacity

Porphyrin is a typical tetrapyrrole chromophore-based pigment with a special electronic structure and functionalities, which is frequently introduced into various porous organic polymers (POPs). Porphyrin-based POPs are widely used in various fields ranging from environmental and energy to biomedicine-related fields. Currently, most porphyrin-based POPs are prepared via the copolymerization of specific-group-functionalized porphyrins with other building blocks, in which the tedious and inefficient synthesis procedure for the porphyrin greatly hinders the development of such materials. This review aimed to summarize information on porphyrin-based POPs synthesized using the Alder-Longo method, thereby skipping the complex synthesis of porphyrin-bearing monomers, in which the porphyrin macrocycles are formed directly via the cyclic tetramerization of pyrrole with monomers containing multiple aldehyde groups during the polymerization process. The representative applications of porphyrin-based POPs derived using the Alder-Longo method are finally introduced, which pinpoints a clear relationship between the structure and function from the aspect of the building blocks used and porous structures. This review is therefore valuable for the rational design of efficient porphyrin-based porous organic polymer systems that may be utilized in various fields from energy-related conversion/storage technologies to biomedical science.

Recent advancements in chemosensors for the detection of food spoilage

The need for reliable sensors has become a major requirement to confirm the quality and safety of food commodities. Chemosensors are promising sensing tools to identify contaminants and food spoilage to ensure food safety. Chemosensing materials are evolving and becoming potential mechanisms to enable onsite and real-time monitoring of food safety. This review summarizes the information about the basic four types of chemosensors (colorimetric, optical, electrochemical, and piezoelectric) employed in the food sector, the latest advancements in the development of chemo-sensing mechanisms, and their food applications, with special emphasis on the future outlook of them. In this review, we discuss the novel chemosensors developed from the year 2018 to 2022 to detect spoilage in some common types of food like fish, meat, milk, cheese and soy sauce. This work will provide a fundamental step toward further development and innovations of chemosensors targeting different arenas in the food industry.

Porphyrin/phthalocyanine-based porous organic polymers for pollutant removal and detection: Synthesis, mechanisms, and challenges

The growing global concern about environmental threats due to environmental pollution requires the development of environmentally friendly and efficient removal/detection materials and methods. Porphyrin/phthalocyanine (Por/Pc) based porous organic polymers (POPs) as a newly emerging porous material are prepared through polymerizing building blocks with different structures. Benefiting from the high porosity, adjustable pore structure, and enzyme-like activities, the Por/Pc-POPs can be the ideal platform to study the removal and detection of pollutants. However, a systematic summary of their application in environmental treatment is still lacking to date. In this review, the development of various Por/Pc-POPs for pollutant removal and detection applications over the past decade was systematically addressed for the first time to offer valuable guidance on environmental remediation through the utilization of Por/Pc-POPs. This review is divided into two sections (pollutants removal and detection) focusing on Por/Pc-POPs for organic, inorganic, and gaseous pollutants adsorption, photodegradation, and chemosensing, respectively. The related removal and sensing mechanisms are also discussed, and the methods to improve removal and detection efficiency and selectivity are also summarized. For the future practical application of Por/Pc-POPs, this review provides the emerging research directions and their application possibility and challenges in the removal and detection of pollutants.

Recent theranostic applications of hydrogen peroxide-responsive nanomaterials for multiple diseases

It is well established that hydrogen peroxide (H2O2) is associated with the initiation and progression of many diseases. With the rapid development of nanotechnology, the diagnosis and treatment of those diseases could be realized through a variety of H2O2-responsive nanomaterials. In order to broaden the application prospects of H2O2-responsive nanomaterials and promote their development, understanding and summarizing the design and application fields of such materials has attracted much attention. This review provides a comprehensive summary of the types of H2O2-responsive nanomaterials including organic, inorganic and organic-inorganic hybrids in recent years, and focused on their specific design and applications. Based on the type of disease, such as tumors, bacteria, dental diseases, inflammation, cardiovascular diseases, bone injury and so on, key examples for above disease imaging diagnosis and therapy strategies are introduced. In addition, current challenges and the outlook of H2O2-responsive nanomaterials are also discussed. This review aims to stimulate the potential of H2O2-responsive nanomaterials and provide new application ideas for various functional nanomaterials related to H2O2.

Copper(II)-Incorporated Porphyrin-Based Porous Organic Polymer for a Nonenzymatic Electrochemical Glucose Sensor

To date, the fabrication of multifunctional nanoplatforms based on a porous organic polymer for electrochemical sensing of biorelevant molecules has received considerable attention in the search for a more active, robust, and sensitive electrocatalyst. Here, in this report, we have developed a new porous organic polymer based on porphyrin (TEG-POR) from a polycondensation reaction between a triethylene glycol-linked dialdehyde and pyrrole. The Cu(II) complex of the polymer Cu-TEG-POR shows high sensitivity and a low detection limit for glucose electro-oxidation in an alkaline medium. The characterization of the as-synthesized polymer was done by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and ¹³C CP-MAS solid-state NMR. The N₂ adsorption/desorption isotherm was carried out at 77 K to analyze the porous property. TEG-POR and Cu-TEG-POR both show excellent thermal stability. The Cu-TEG-POR-modified GC electrode shows a low detection limit (LOD) value of 0.9 μM and a wide linear range (0.001-1.3 mM) with a sensitivity of 415.8 μA mM^-1 cm^-2 toward electrochemical glucose sensing. The interference of the modified electrode from ascorbic acid, dopamine, NaCl, uric acid, fructose, sucrose, and cysteine was insignificant. Cu-TEG-POR exhibits acceptable recovery for blood glucose detection (97.25-104%), suggesting its scope in the future for selective and sensitive nonenzymatic glucose detection in human blood.

A metalloporphyrin and hydantoin functionalized nanozyme with synergistically enhanced bacterial inhibition

An elaborate design of multimodal antibacterial agents has been revealed to be a promising strategy to address bacterial resistance, originating from the abuse of antibiotics. In this work, we have developed a positively charged and porous material, FePPOP_Hydantoin, as a disinfectant via introducing 1,3-dibromo-5,5-dimethylhydantoin (Hydantoin) and porphyrin iron units into a polymer framework. The extended π conjugated networks of FePPOP_Hydantoin endowed the material with strong near-infrared (NIR) absorption, high density of surface catalytic active centers, superior stability, and reproducibility. FePPOP_Hydantoin exhibits high peroxidase mimetic and photo-Fenton activity, which can catalyze the biologically allowable maximum concentrations of hydrogen peroxide (100 μM) to produce a vast amount of hydroxyl radicals. Simultaneously, the effective electrostatic interaction between the positively charged FePPOP_Hydantoin and the negatively charged bacteria facilitates the binding of FePPOP_Hydantoin on the bacterial membrane, restricting bacteria within the destruction range of hydroxyl radicals and thus making the bacteria more vulnerable. Finally, further close contact between bacteria and Hydantoin units in FePPOP_Hydantoin gave the material an antibacterial efficiency of over 99.999%. Compared with chemical therapy, photo-Fenton therapy, or peroxidase catalytic therapy alone, FePPOP_Hydantoin had a noteworthy multi-amplified antibacterial efficiency. Furthermore, FePPOP_Hydantoin exhibited good biocompatibility and negligible cytotoxicity. The in vivo antibacterial therapy on the Staphylococcus aureus (S. aureus) infected mouse wound model clearly proved the effectiveness of FePPOP_Hydantoin for fighting bacterial infections. This work highlights opportunities for the design of nanozymes with enhanced bacteriostatic activity, providing a new avenue for the construction of novel antibiotics.

Organic-Inorganic Porphyrinoid Frameworks for Biomolecule Sensing

Porphyrinoids and their analogous compounds play an important role in biosensing applications on account of their unique and versatile catalytic, coordination, photophysical, and electrochemical properties. Their remarkable arrays of properties can be finely tuned by synthetically modifying the porphyrinoid ring and varying the various structural parameters such as peripheral functionalization, metal coordination, and covalent or physical conjugation with other organic or inorganic scaffolds such as nanoparticles, metal-organic frameworks, and polymers. Porphyrinoids and their organic-inorganic conjugates are not only used as responsive materials but also utilized for the immobilization and embedding of biomolecules for applications in wearable devices, fast sensing devices, and other functional materials. The present review delineates the impact of different porphyrinoid conjugates on their physicochemical properties and their specificity as biosensors in a range of applications. The newest porphyrinoid types and their synthesis, modification, and functionalization are presented along with their advantages and performance improvements.

Cerium oxide nanoparticles with antioxidative neurorestoration for ischemic stroke

Oxidative stress and mitochondrial damage are the main mechanisms of ischemia-reperfusion injury in ischemic stroke. Herein, cerium oxide nanoparticles with powerful free radical scavenging ability were used as carriers to load dl-3-n-butylphthalide (NBP-CeO2 NPs) for the combined treatment of ischemic stroke. NBP-CeO2 NPs could eliminate reactive oxygen species (ROS) in mouse brain microvascular endothelial cells and hippocampal neurons after oxygen-glucose deprivation/reoxygenation (OGD/R), and also save mitochondrial membrane potential, morphology, and function, thus alleviating the in vitro blood brain barrier (BBB) disruption and neuronal apoptosis. In the middle cerebral artery embolization/recanalization (MCAO/R) mouse model, the NBP-CeO2 NPs also possessed superior ROS scavenging ability, protected mitochondria, and preserved BBB integrity, thereby reducing cerebral infarction and cerebral edema and inhibiting neuroinflammation and neuronal apoptosis. The long-term neurobehavioral tests indicated that the NBP-CeO2 NPs significantly improved sensorimotor function and spatial learning ability by promoting angiogenesis after ischemic stroke. Therefore, the NBP-CeO2 NPs provided a novel therapeutic approach for ischemic stroke by combining antioxidant and neurovascular repair abilities, highlighting its wide application in ischemia-reperfusion injury.

Colorimetric detection of H2O2 with Fe3O4@Chi nanozyme modified µPADs using artificial intelligence

Peroxidase mimicking Fe₃O₄@Chitosan (Fe₃O₄@Chi) nanozyme was synthesized and used for high-sensitive enzyme-free colorimetric detection of H₂O₂. The nanozyme was characterized in comparison with  Fe₃O₄ nanoparticles (NPs) using X-ray diffraction, Fourier-transform infrared spectroscopy, dynamic light scattering, and thermogravimetric analysis. The catalytic performance of Fe₃O₄@Chi nanozyme was first evaluated by UV-Vis spectroscopy using 3,3',5,5'-tetramethylbenzidine. Unlike Fe₃O₄NPs, Fe₃O₄@Chi nanozyme exhibited an intrinsic peroxidase activity with a detection limit of 69 nM. Next, the nanozyme was applied to a microfluidic paper-based analytical device (µPAD) and colorimetric analysis was performed at varying concentrations of H₂O₂ using a machine learning-based smartphone app called "Hi-perox Sens++ ." The app with machine learning classifiers made the system user-friendly as well as more robust and adaptive against variation in illumination and camera optics. In order to train various machine learning classifiers, the images of the µPADs were taken at 30 s and 10 min by four smartphone brands under seven different illuminations. According to the results, linear discriminant analysis exhibited the highest classification accuracy (98.7%) with phone-independent repeatability at t = 30 s and the accuracy was preserved for 10 min. The proposed system also showed excellent selectivity in the presence of various interfering molecules and good detection performance in tap water.

Explaining chemical clues of metal organic framework-nanozyme nano-/micro-motors in targeted treatment of cancers: benchmarks and challenges

Nowadays, nano-/micro-motors are considered as powerful tools in different areas ranging from cleaning all types of contaminants, to development of Targeted drug delivery systems and diagnostic activities. Therefore, the development and application of nano-/micro-motors based on metal-organic frameworks with nanozyme activity (abbreviated as: MOF-NZs) in biomedical activities have received much interest recently. Therefore, after investigating the catalytic properties and applications of MOF-NZs in the treatment of cancer, this study intends to point out their key role in the production of biocompatible nano-/micro-motors. Since reducing the toxicity of MOF-NZ nano-/micro-motors can pave the way for medical activities, this article examines the methods of making biocompatible nanomotors to address the benefits and drawbacks of the required propellants. In the following, an analysis of the amplified directional motion of MOF-NZ nano-/micro-motors under physiological conditions is presented, which can improve the motor behaviors in the propulsion function, conductivity, targeting, drug release, and possible elimination. Meanwhile, by explaining the use of MOF-NZ nano-/micro-motors in the treatment of cancer through the possible synergy of nanomotors with different therapies, it was revealed that MOF-NZ nano-/micro-motors can be effective in the treatment of cancer. Ultimately, by analyzing the potential challenges of MOF-NZ nano-/micro-motors in the treatment of cancers, we hope to encourage researchers to develop MOF-NZs-based nanomotors, in addition to opening up new ideas to address ongoing problems.

Nanozyme Applications: A Glimpse of Insight in Food Safety

Nanozymes own striking merits, including high enzyme-mimicking activity, good stability, and low cost. Due to the powerful and distinguished functions, nanozymes exhibit widespread applications in the field of biosensing and immunoassay, attracting researchers in various fields to design and engineer nanozymes. Recently, nanozymes have been innovatively used to bridge nanotechnology with analytical techniques to achieve the high sensitivity, specificity, and reproducibility. However, the applications of nanozymes in food applications are seldom reviewed. In this review, we summarize several typical nanozymes and provide a comprehensive description of the history, principles, designs, and applications of nanozyme-based analytical techniques in food contaminants detection. Based on engineering and modification of nanozymes, the food contaminants are classified and then discussed in detail via discriminating the roles of nanozymes in various analytical methods, including fluorescence, colorimetric and electrochemical assay, surface-enhanced Raman scattering, magnetic relaxing sensing, and electrochemiluminescence. Further, representative examples of nanozymes-based methods are highlighted for contaminants analysis and inhibition. Finally, the current challenges and prospects of nanozymes are discussed.

Pt Nanoparticles Anchored on NH2-MIL-101 with Efficient Peroxidase-Like Activity for Colorimetric Detection of Dopamine

Dopamine (DA) is an important catecholamine neurotransmitter that plays a highly relevant role in regulating the central nervous system, and abnormal DA content can cause many immune-related diseases. Hence, it is of significance to sensitively and specifically identify DA for clinical medicine. In this work, Pt/NH2-MIL-101 hybrid nanozymes with bimetallic catalytic centers were fabricated by forming coordinate bonds between Pt nanoparticles (Pt NPs) and –NH2 on metal–organic frameworks (MOF). The catalytic activity of Pt/NH2-MIL-101 was increased by 1.5 times via enlarging the exposure of more active sites and improving the activity of the active sites through the strategy of forming bimetallic catalytic centers. In the presence of DA, competing with 3, 3′, 5, 5′-tetramethylbenzidine (TMB) for the generated hydroxyl radicals (•OH), the blue oxidation state TMB (Ox-TMB) is reduced to colorless TMB, showing dramatic color changes. The Pt/NH2-MIL-101-based colorimetric assay enables the sensitive and robust detection of DA molecules with a detection limit of only 0.42 μM and has an observable potential in clinical applications.

A novel bromelain-MnO2 biosensor for colorimetric determination of dopamine

We report a method for determining dopamine in serum via colorimetric sensing. This new method adopts bromelain-templated MnO₂ nanosheets that possess high oxidase activity. 3,3′,5,5′-Tetramethylbenzidine (TMB) can be directly oxidized by bromelain-MnO₂ nanosheets to oxTMB products.

Ratiometric fluorescence assay for L-Cysteine based on Fe-doped carbon dot nanozymes

In this work, a ratiometric fluorescence method based on nanozyme was fabricated to determine L-Cysteine. Taking silkworm feces as a carbon source, together with Fe³⁺, Fe-doped carbon dots (Fe-CDs) were synthesized through a hydrothermal method. Fe-CDs were able to oxidize the enzyme substrate o-phenylenediamine (OPD) to produce oxidized OPD (Ox-OPD) when H₂O₂ coexisted with them. Based on the fluorescence property of Fe-CDs and Ox-OPD, a dual-emission system was built. Since L-Cysteine contains reductive thiols that can inhibit the production of Ox-OPD, the addition of L-Cysteine caused a decrease in the fluorescence intensity of Ox-OPD. The results showed that the ratio of fluorescence intensities at 450 and 560 nm (I₄₅₀/I₅₆₀) varied linearly with the concentration of L-Cysteine in the range of 0.25-90 μM and the limit of detection is as low as 0.047 μM. Furthermore, using this ratiometric fluorescence system to determine L-Cysteine in serum and tap-water samples, average recoveries were evaluated to reach 98.75%-103.27% with the relative standard deviation of no more than 4.5%. Based on the fluorescence property and nanozyme-like activity, this work provides an inspiration to open a new horizon in using natural carbon source to synthesize CDs and for the application of CDs as a nanozyme.

A colorimetric method for screening α-glucosidase inhibitors from flavonoids using 3,3',5,5'-tetramethylbenzidine as a chromogenic probe

A facile and novel colorimetric method for screening of α-glucosidase inhibitors (AGIs) from flavonoids using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogenic probe is proposed. This method is based on the colorimetric detection of ascorbic acid (AA) through the TMB oxidation reaction catalyzed by horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂). In the TMB/H₂O₂/HRP system, HRP catalyzes the oxidation of H₂O₂ to ‧OH radical which oxidizes TMB to blue-colored oxidized TMB (oxTMB). In the presence of AA, the production of ‧OH radical is suppressed and causes the decrease of oxTMB, resulting in the fading of the blue color and the decrease of absorbance at 652 nm. Based on this, the existence of AA can be facilely identified. In the 2-O-α-d-glucopyranosyl-l-ascorbic acid (AA-2 G)/α-glucosidase (α-Glu) system, the produced AA inhibits the oxidation of TMB to blue-colored oxTMB. In the presence of AGIs, the production of AA is inhibited, which inhibits the reduction of oxTMB, resulting in a blue color recovery and an increase of the absorbance at 652 nm. Based on this, the colorimetric method is developed for screening of AGIs from 7 flavonoids.

Porphyrins as Colorimetric and Photometric Biosensors in Modern Bioanalytical Systems

Advances in porphyrin chemistry have provided novel materials and exciting technologies for bioanalysis such as colorimetric sensor array (CSA), photo-electrochemical (PEC) biosensing, and nanocomposites as peroxidase mimetics for glucose detection. This review highlights selected recent advances in the construction of supramolecular assemblies based on the porphyrin macrocycle that provide recognition of various biologically important entities through the unique porphyrin properties associated with colorimetry, spectrophotometry, and photo-electrochemistry.

Metalloporphyrinic metal-organic frameworks: Controlled synthesis for catalytic applications in environmental and biological media

Recently, as a new sub-family of porous coordination polymers (PCPs), porphyrinic-MOFs (Porph-MOFs) with biomimetic features have been developed using porphyrin macrocycles as ligands and/or pillared linkers. The control over the coordination of the porphyrin ligand and its derivatives however remains a challenge for engineering new tunable Porph-MOF frameworks by self-assembly methods. The key challenges exist in the following respects: (i) collapse of the large open pores of Porph-MOFs during synthesis, (ii) deactivation of unsaturated metal-sites (UMCs) by axial coordination, and (iii) the tendency of both coordinated moieties (at peripheral meso- and beta-carbon sites) and the N₄-pyridine core to coordinate with metal cations. In this respect, this review covers the advances in the design of Porph-MOFs relative to their counterpart covalent organic frameworks (Porph-COFs). The potential utility of custom-designed porphyrin/metalloporphyrins ligands is highlighted. Synthesis strategies of Porph-MOFs are also illustrated with modular design of hybrid guest@host composites (either Porph@MOFs or guest@Porph-MOFs) with exceptional topologies and stability. This review summarizes the synergistic benefits of coordinated porphyrin ligands and functional guest molecules in Porph-MOF composites for enhanced catalytic performance in various redox applications. This review shed lights on the engineering of new tunable hetero-metals open active sites within (metallo)porphyrin-MOFs as out-of-the-box platforms for enhanced catalytic processes in chemical and biological media.

Au–Hg/rGO with enhanced peroxidase-like activity for sensitive colorimetric determination of H2O2

Au–Hg/rGO is applied as a novel nanozyme to construct a sensitive sensing platform for the colorimetric determination of H₂O₂.

Cost-effective monitoring of microRNA-205 applied as a biomarker using G-quadruplex DNAzyme and 1,1'-oxalyldiimidazole chemiluminescence

Trace levels of microRNA-205, known as a biomarker of lung cancer, in human serum was quantified for the first-time using G-quadruplex DNAzyme linked to detection complementary probe and 1,1'-oxalyldiimidazole chemiluminescence (ODI-CL). First, capture complementary probes immobilized on the surface of paramagnetic bead selectively bound with microRNA-205 existing in human serum. Then, with the addition of detection complementary probe linked to hemin aptamer, a complex linked to hemin aptamer was formed with the completion of hybridization between microRNA-205 and two complementary probes. With the addition of hemin in the solution, finally, a complex linked to G-quadruplex DNAzyme was formed from the interaction of hemin aptamer and hemin. Resorufin, luminescent dye, was formed from the reaction of Amplex Red and H₂O₂ in the presence of the complex linked to DNAzyme acting as a horseradish peroxidase (HRP)-mimicking enzyme. The concentration of resorufin formed from the reaction was dependent on the concentration of microRNA-205 in human serum. Thus, the brightness of resorufin emitted in ODI-CL reaction was enhanced with the increase of microRNA-205. The limit of detection (LOD) of the biosensor with ODI-CL detection, capable of sensing microRNA-205 (dynamic range: 0.4-62.5 nM), was as low as 0.13 nM. It was confirmed that the biosensor can quantify trace levels of microRNA-205 with statistically acceptable accuracy, precision, and recovery.

Peroxidase mimetic activity of porphyrin modified ZnFe2O4/reduced graphene oxide and its application for colorimetric detection of H2O2 and glutathione

Artificial nanoenzymes which can overcome some drawbacks of natural enzymes is a challenging topic in the biosensor field. Herein, we demonstrated 5, 10, 15, 20-tetrakis (4-carboxylpheyl)-porphyrin modified magnetic ZnFe₂O₄ nanoparticles loaded on the surface of reduced graphene oxide (Por-ZnFe₂O₄/rGO), which exhibited intrinsic peroxidase-like activity and rapidly oxidized the peroxidase substrate 3, 3', 5, 5'-tetramethylbenzidine (TMB) into a blue product (OxTMB) distinguished by naked eyes. Interestingly, by comparative study of different nanomaterials ZnFe₂O₄ nanoparticles, ZnFe₂O₄/rGO and Por-ZnFe₂O₄, Por-ZnFe₂O₄/rGO was proved to possess the highest peroxidase-like activity. Electron spin resonance (ESR) verified the catalytic activity of Por-ZnFe₂O₄/rGO for H₂O₂ was due to hydroxyl radical from decomposition of H₂O₂. Temperature and pH strongly affected the peroxidase-like activity of Por-ZnFe₂O₄/rGO nanocomposites. Under optimal conditions (pH = 4, 40 °C), the constructed sensor based on the catalytic activity of the Por-ZnFe₂O₄/rGO could be conveniently used for colorimetric detection of H₂O₂ in the range of 0.7-30 μM with the detection limit of 0.54 μM. Moreover, the colorimetric sensor based on Por-ZnFe₂O₄/rGO exhibited a good linear response to glutathione (GHS) in the range of 2-40 μM with a low detection limit of 0.76 μM. The detection of GHS can be easily realized through the obvious color change by naked eyes without any complicated instrumentation.