Peroxidase-like Catalytic Activity Research Articles

Iron Single-Atom Nanozyme with Inflammation-Suppressing for Inhibiting Multidrug-Resistant Bacterial Infection and Facilitating Wound Healing.

Infection with drug-resistant bacteria and the formation of biofilms are the main factors contributing to wound healing insufficiency. Antibacterial agents with enzyme-like properties have exhibited considerable potential for efficient eradication of drug-resistant microorganisms due to their superior sensitivities and minimal side effects. In this work, we prepared a kind of Fe-centered single-atom nanozyme (Fe-SAzyme) with high biocompatibility and stability via a facile one-pot hydrothermal method, which was suitable for the treatment of wounds infected with drug-resistant bacteria. The Fe-SAzyme exhibited remarkable peroxidase-like catalytic activities, catalyzing the conversion of hydrogen peroxide (H2O2) to highly toxic hydroxyl radicals (•OH), which could not only damage bacterial cells but also inhibit, disrupt, and eradicate the formation of bacterial biofilms. Thus, Fe-SAzyme demonstrated a broad-spectrum antibacterial performance capable of effectively eliminating multidrug-resistant bacteria. The coexistence of ferrous (Fe2+) and ferric (Fe3+) ions in Fe-SAzyme conferred the nanozyme with anti-inflammatory activity, effectively suppressing excessive inflammation. Meanwhile, Fe-SAzyme could significantly downregulate inflammatory cytokines tumor necrosis factor-α and interleukin-1β and upregulate growth factors VEGF and epidermal growth factor, which can prevent bacterial infection, mitigate inflammation, promote fibroblast proliferation, and improve wound closure. Thus, Fe-SAzyme had shown favorable therapeutic efficiency in promoting bacteria-infected wound healing. This study provides Fe-SAzyme as a promising candidate for the development of new strategies to treat multidrug-resistant bacterial infections.

CRISPR/Cas12a-Sheared ZIF-Based Heterojunction to Allow Polarity-Switchable Photoelectrochemical and Nanozyme-Enabled Colorimetric Dual-Modal Biosensing.

Modulating the migration of interfacial carriers in heterojunctions is critical for driving the signal response of high-performance optical biosensors. In this study, a polarity-switchable photoelectrochemical (PEC) and nanozyme-enabled colorimetric dual-modal biosensor is designed to modulate the interfacial carrier migration of the zeolitic imidazolate framework (ZIF)-based heterojunction by exploiting stem-loop DNA and the CRISPR/Cas12a system. Specifically, ZIF-hemin (ZIF-Hemin) is assembled at the CdSe/NH2-rGO interface via stem-loop DNA to form a ZIF-based heterojunction. Stem-loop DNA with a reinforcing rib effect enhances binding and accelerates the interfacial carrier migration of the heterojunction. In the presence of the target Cry1Ab, the CRISPR/Cas12a system is activated to shear the ZIF-based heterojunction, resulting in the disintegration of the heterojunction and the disappearance of interfacial carrier migration. At this point, ZIF-Hemin is released from the CdSe/NH2-rGO interface, with the photocurrent switching from the anode to the cathode. Meanwhile, due to its rich accessible active sites, the released ZIF-Hemin nanosheet shows high peroxidase-like catalytic activity and generates colorimetric signals. The dual-modal biosensor demonstrates excellent performance in selectivity and sensitivity, with low detection limits of 0.05 pg mL-1 (PEC) and 0.4 pg mL-1 (colorimetric). This work provides a general strategy to improve the performance of optical biosensors by modulating the migration of interfacial carriers in heterojunctions.

Au@Pt nanoparticles-based signal-enhanced lateral flow immunoassay for ultrasensitive naked-eye detection of SARS-CoV-2.

With SARS-CoV-2 N protein as a model target, a signal-enhanced LFIA based on Au@Pt nanoparticles (NPs) as labelsis proposed. This Au@Pt NPs combined the distinguished localized surface plasma resonance (LSPR) effect of Au NPs and the ultrahigh peroxidase-like catalytic activity of Pt NPs. Au@Pt NPs could trigger substrate chromogenic reaction, generating acolor signal orders of magnitude darker than their intrinsic color. In the detection, after the coloration of the strips, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 were added, and adark blue chelate (OxTMB) was produced soon, enhancing the band color significantly. After the signal amplification, the naked-eye detection limit for N protein reached 40pg/mL. The detection sensitivity enhanced more than 1000 times than that without signal amplification. Compared with mainstream LFIA requiring complex readout instruments, theAu@Pt-based LFIA achieved a comparable sensitivity usingnaked eyesdetection. This point is crucial, especially for unprofessional users or low-resource areas. Hence, this signal-enhanced LFIA may serve as a sensitive, cost-effective, and user-friendly detection method. It can shorten the testing window period and help identify early infections.

Hydroxyl functionalized hexagonal boron nitride quantum dots as nanozyme for pesticides sensing through dual colorimetric and fluorometric platform: A combined experimental and theoretical study

The Hydroxyl-functionalized hexagonal boron nitride quantum dots (h-BN QDs) were synthesized using a hydrothermal technique in a water medium, exhibiting stability in water for over 90 days. The present study demonstrates two simple fluorescence and colorimetric techniques for sensing organophosphorus (OP) and organochloride (OC) pesticides (atrazine, simazine and chlorpyrifos) in an aqueous medium using hydroxyl-functionalized h-BN QDs. The sensing capability of h-BN QDs for these pesticides was determined to be in the range of 5–10 µM using both techniques. The hydroxyl groups on the surface of the QDs enhanced dispersibility and enabled peroxidase-like catalytic activity in acidic conditions. The radical generation using hydroxyl-functionalized h-BN QDs in the presence of H2O2 upon 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) oxidation plays a significant role in the peroxidase reaction. The hydrogen bonding and π-π interactions between the pesticide molecules and ABTS can enhance the pesticide sensing performance. The limit of detection (LOD) using ABTS for atrazine, simazine, and chlorpyrifos was 6.11, 6.56, and 2.47 µM, respectively. Fluorescence sensing, based on a turn ON/OFF mechanism, demonstrated high specificity and sensitivity with LODs of 5.59, 6.45, and 8.08 µM for the same pesticides. The DFT studies revealed non-covalent bonding, such as hydrogen bonding, π-π interactions between the pesticides and the h-BN QDs, indicating binding affinities and stabilization energies of the complexes which can detect pesticides effectively. Atrazine exhibited higher binding affinity towards h-BN QDs, followed by simazine and chlorpyrifos. The h-BN QDs provide a new insight into bonding with pesticides, enhancing the peroxidase mimetic and fluorescence activity.

Single-Atom Iridium Nanozyme-Based Persistent Luminescence Nanoparticles for Multimodal Imaging-Guided Combination Tumor Therapy.

Persistent luminescence nanoparticles (PLNPs) can achieve autofluorescence-free afterglow imaging, while near-infrared (NIR) emission realizes deep tissue imaging. Nanozymes integrate the merits of nanomaterials and enzyme-mimicking activities with simple preparation. Here PLNPs are prepared of Zn1.2Ga1.6Ge0.2O4:Cr0.0075 with NIR emission at 700 nm. The PLNPs are then incubated with IrCl3 solution, and the nanoparticles are collected and annealed at 750 °C to obtain iridium@PLNPs. Iridium is observed on the PLNPs at the atomic level as a single-atom nanozyme with peroxidase-like catalytic activity, photothermal conversion, and computed tomography (CT) contrast capability. After coating with exosome membrane (EM), the Ir@PLNPs@EM composite exhibits long-lasting NIR luminescence, peroxidase-like catalytic activity, photothermal conversion, and CT contrast capability, with the targeting capability and biocompatibility from EM. Thus, NIR afterglow/photothermal/CT trimodal imaging-guided photothermal-chemodynamic combination therapy is realized as validated with the in vitro and in vivo inhibition of tumor growth, while toxicity and side effects are avoided as drug-free treatment. This work offers a promising avenue for advanced single-atom nanozyme@PLNPs to promote the development of nanozymes and PLNPs for clinical applications.

Freeze-Driven Adsorption of Oligonucleotides with polyA-Anchors on Au@Pt Nanozyme.

A promising and sought-after class of nanozymes for various applications is Pt-containing nanozymes, primarily Au@Pt, due to their easy preparation and remarkable catalytic properties. This study aimed to explore the freeze-thaw method for functionalizing Pt-containing nanozymes with oligonucleotides featuring a polyadenine anchor. Spherical gold nanoparticles ([Au]NPs) were synthesized and subsequently used as seeds to produce urchin-like Au@Pt nanoparticles ([Au@Pt]NPs) with an average diameter of 29.8 nm. The nanoparticles were conjugated with a series of non-thiolated DNA oligonucleotides, each consisting of three parts: a 5'-polyadenine anchor (An, with n = 3, 5, 7, 10; triple-branched A3, or triple-branched A5), a random sequence of 23 nucleotides, and a linear polyT block consisting of seven deoxythymine residues. The resulting conjugates were characterized using transmission electron microscopy, spectroscopy, dynamic light scattering, and emission detection of the fluorescent label at the 3'-end of each oligonucleotide. The stability of the conjugates was found to depend on the type of oligonucleotide, with decreased stability in the row of [Au@Pt]NP conjugates with A7 > A5 > 3A3 > 3A5 > A10 > A3 anchors. These [Au@Pt]NP-oligonucleotide conjugates were further evaluated using lateral flow test strips to assess fluorescein-specific binding and peroxidase-like catalytic activity. Conjugates with A3, A5, A7, and 3A3 anchors showed the highest levels of signals of bound labels on test strips, exceeding conjugates in sensitivity by up to nine times. These findings hold significant potential for broad application in bioanalytical systems.

Colorimetric detection of benzoate in the beverage using the peroxidase-like properties of single-atom Fe-N-C nanozymes

Overuse of benzoate as a preservative is bad for human health. Therefore, we need to achieve quantitative detection of benzoate. Colorimetric nanozyme sensors have garnered significant interest owing to their exceptional efficacy and affordability. In this article, Fe-N-C dodecahedral nanozymes with superior peroxidase-like catalytic activity are prepared using ZIF-8 as a precursor. Therefore, we construct a colorimetric sensor for benzoate detection with a detection limit of 0.33 μM through integrating the inhibitory impact of benzoate on D-amino acid oxidase activity with the Fe-N-C-catalyzed 3,3′,5,5′-tetramethylbenzidine (TMB)–H2O2 system, and this reaction is completed within 10 min. It is noteworthy that a recovery rate of 96.8–109 % has been attained for the detection of benzoate in beverages.

Enhanced peroxidase-like activity via Pt loading of Ni-MOF for colorimetric and smartphone-based bimodal determination of antioxidant capacity in aging cells

Total antioxidant capacity (TAC) serves as a vital indicator for evaluating cell senescence. Here, we synthesized a platinum-loaded nickel-based metal–organic framework material (Ni-MOF@Pt) via a solvothermal method for bimodal determination of TAC in aging cells. The Pt nanoparticle incorporation substantially enhanced the peroxidase-like catalytic activity of Ni-MOF. Ni-MOF@Pt exhibited a strong affinity for 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, with lower Km values compared to horseradish peroxidase (HRP). The Ni-MOF@Pt-TMB-H2O2 system was successfully applied for detecting antioxidants, including glutathione (GSH), ascorbic acid (AA), and cysteine (Cys) with impressive detection limits (121 nM for GSH, 119 nM for AA, 72 nM for Cys), highlighting the high sensitivity of this system. Additionally, a smartphone-assisted visual detection sensor was established using Ni-MOF@Pt for rapid, sensitive, and on-site TAC detection. Moreover, our established Ni-MOF@Pt method effectively determined the TAC of aging cells and demonstrated its ability to differentiate between normal, senescent, and cancerous cells. This research offers novel insight on fabricating nanozymes with potent peroxidase-like properties and manifests their practicality in TAC analysis.

Poly(ionic liquid)/Wood Composite-Derived B/N-Codoped Porous Carbons Possessing Peroxidase-like Catalytic Activity.

The pursuit of efficient and cost-effective metal-free heterogeneous catalytic systems remains a challenging task in materials research. Heteroatom-doped carbonaceous materials are increasingly recognized as powerful metal-free catalysts, often demonstrating catalytic performance comparable to or even surpassing metal-based alternatives. This is attributed to their tunable physicochemical properties, tailorable structural features, and environmentally friendly profile. In a straightforward single-step synthetic approach, we utilized wood as an eco-friendly and renewable carbon source, in conjunction with a poly(ionic liquid) as a heteroatom source and pore-making agent. The combination of both biobased and synthetic polymers in this method yielded sustainable, high-performance catalysts characterized by enhanced stability and reusability. The inclusion of sacrificial pore-inducing templates resulted in the formation of abundant defects serving as catalytically active sites, while codoping with boron and nitrogen further enhanced these sites, significantly impacting catalytic activities, as established by peroxidase-like activity in this study. The optimized codoped porous carbon membrane exhibited excellent peroxidase-type activity and catalyzed the oxidation reaction of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide. This high activity was largely due to the dual heteroatom codoping effect and the mixed micro/macroporous structure of the membrane. Our work presents a versatile and eco-friendly method for fabricating hierarchically porous B/N codoped carbon membranes, offering a manageable, convenient, and recyclable biomimetic artificial enzyme with superior catalytic capabilities. This work introduces a practical and robust colorimetric method that can be used in healthcare and environmental rehabilitation.

Bioinspired synergy strategy based on the integration of nanozyme into a molecularly imprinted polymer for improved enzyme catalytic mimicry and selective biosensing

Nanozymes offer many advantages such as good stability and high catalytic activity, but their selectivity is lower than that of enzymes. This is because most of enzymes have a protein component (apoenzyme) for substrate affinity to enhance selectivity and a non-protein element (coenzyme) for catalytic activity to improve sensitivity. The synergy between molecularly imprinted polymers (MIPs) and nanozymes can mimic natural enzymes, with MIP acting as the apoenzyme and nanozyme as the coenzyme. Despite researchers' attempts to associate MIPs with nanozymes, the full potential of this combination remains not well explored. This study addresses this gap by integrating Fe3O4-Lys-Cu nanozymes with peroxidase-like catalytic activities within appropriate MIPs for L-DOPA and dopamine. The catalytic performance of the nanozyme was improved by the presence of Cu in Fe3O4-Lys-Cu and further enhanced by MIP. Indeed, the exploration of the pre-concentration property of MIP has increased twenty-fold the catalytic activity of the nanozyme. Moreover, this synergistic combination facilitated the template removal process during MIP production by reducing the extraction time from several hours to just 1 min thanks to the addition of co-substrates which trigger the reaction with nanozyme and release the template. Overall, the synergistic combination of MIPs and nanozymes offers a promising avenue for the design of artificial enzymes.

Defect engineering synergistically boosts the catalytic activity of Fe-MoOv for highly efficient breast mesh antitumor therapy

The demand for breast mesh with antitumor properties is critical in post-mastectomy breast reconstruction to prevent local tumor recurrence. Molybdenum-based oxide (MoOx) exhibits enzyme-like activities by catalyzing endogenous hydrogen peroxide to produce reactive oxygen species for inducing tumor cell apoptosis. However, its catalytic activity is limited by insufficient active sites. Herein, a defect engineering strategy is proposed to create redox nanozymes with multiple enzymatic activities by incorporating Fe into MoOx (Fe-MoOv). Fe-MoOv is subsequently integrated into polycaprolactone (PCL) to fabricate breast meshes for establishing an enzyme-catalyzed antitumor platform. The doping of Fe into MoOx formed numerous defect sites, including oxygen vacancies (OV) and Fe substitution sites, synergistically boosting the binding capacity and catalytic activity of Fe-MoOv. Density functional theory calculations demonstrated that the outstanding peroxidase-like catalytic activity of Fe-MoOv resulted from the synergy between OV and Fe sites. Additionally, OV contributes to the localized surface plasmon resonance effect, enhancing the photothermal capability of the PCL/Fe-MoOv mesh. Upon near-infrared laser exposure, the catalytic activity of the PCL/Fe-MoOv mesh is further improved, leading to increased generation of reactive oxygen species and enhanced antitumor efficacy, achieving 86.7% tumor cell mortality, a 264% enhancement compared to the PCL/MoOx mesh.

Synthesis of Mo-Pt/CeO2 Dual Single-Atom Nanozyme for Multifunctional Biochemical Detection Applications.

Elaborated structural modulation of Pt-based artificial nanozymes can efficiently improve their catalytic activity and expand their applications in clinical diagnosis and biochemical sensing. Herein, a highly efficient dual-site peroxidase mimic composed of highly dispersed Pt and Mo atoms is reported. The obtained Mo-Pt/CeO2 exhibits exceptional peroxidase-like catalytic activity, with a Vmax as high as 34.16 × 10-8 m s-1, which is 37.5 times higher than that of the single-site counterpart. Mechanism studies suggest that the Mo atoms can not only serve as adsorption and activation sites for the H2O2 substrate but also regulate the charge density of Pt centers to promote the generation ability of •OH. As a result, the synergistic effect between the dual active sites significantly improves the catalytic efficiency. Significantly, the application of the Mo-Pt/CeO2 catalyst's excellent peroxidase-like activity is extended to various biochemical detection applications, including the trace detection of glucose and cysteine, as well as the assessment of antioxidants' antioxidant capacity. This work reveals the great potential of rational design dual-site active centers for constructing high-performance artificial nanozymes.

H2O2-Activatable Liposomal Nanobomb Capable of Generating Hypoxia-Irrelevant Alkyl Radicals by Photo-Triggered Cascade Reaction for High-Performance Elimination of Biofilm Bacteria.

High H2O2 levels are widely present at the infection sites or in the biofilm microenvironment. Herein, hemin with peroxidase-like catalytic activity and its substrate, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), are simultaneously introduced into a liposomal nanoparticle containing thermosensitive 2,2'-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIBI)-loaded bovine serum albumin (BAG), rationally constructing an H2O2-activatable liposomal nanobomb (Lipo@BHA) for combating biofilm-associated bacterial infections with high performance. In the presence of H2O2, hemin can catalyze the conversion of ABTS into its oxidized form (ABTS·+) with strong near-infrared (NIR) absorption, which produces photonic hyperpyrexia to cause the decomposition of AIBI into oxygen-independent alkyl radicals (·R) and nitrogen (N2) microbubbles. The former not only directly damage bacterial cells but also significantly accelerates the oxidization of ABTS to ABTS·+ for augmenting photothermal-triggered generation of ·R. Interestingly, the released N2 can induce transient cavitation to rupture lysosomal nanoparticle and improve the biofilm permeability, thereby enhancing the antibiofilm effect of Lipo@BHA. The proposed Lipo@BHA exhibits satisfactory multi-mode combination antibacterial properties. Through endogenous H2O2-activated cascade reaction, Lipo@BHA achieves remarkable hypoxia-irrelevant ·R therapy of biofilm-associated wound infections with low cytotoxicity and good in vivo biosafety. Therefore, this work presents a versatile H2O2-activatable cascade ·R generation strategy for biofilm-specific therapeutic applications.

Discovery of FeP/Carbon Dots Nanozymes for Enhanced Peroxidase-Like Catalytic and Antibacterial Activity.

Iron phosphide/carbon (FeP/C) serving as electrocatalysts exhibit excellent activity in oxygen reduction reaction (ORR) process. H2O2 catalyzed by peroxidase (POD) is similar to the formation of new electron transfer channels and the optimization of adsorption of oxygen-containing intermediates or desorption of products in ORR process. However, it is still a challenge to discover FeP/C with enhanced POD-like catalytic activity in the electrocatalytic database for biocatalysis. The discovery of FeP/carbon dots (FeP/CDs) nanozymes driven by electrocatalytic activity for enhanced POD-like ability is demonstrated. FeP/CDs derived from CDs-Fe3+ chelates show enhanced POD-like catalytic and antibacterial activity. FeP/CDs exhibit enhanced POD-like activities with a specific activity of 31.1 Umg-1 that is double higher than that of FeP. The antibacterial ability of FeP/CDs nanozymes with enhanced POD-like activity is 98.1%. The antibacterial rate of FeP/CDs nanozymes (250µgmL-1) increased by 5%, 15%, and 36% compared with FeP, Fe2O3/CDs, and Cu3P/CDs nanozymes, respectively. FeP/CDs nanozymes will attract more efforts to discover or screen transition metal phosphide/C nanozymes with enhanced POD-like catalytic activity for biocatalysis in the electrocatalytic database.

Enhancing radiation-resistance and peroxidase-like activity of single-atom copper nanozyme via local coordination manipulation

The inactivation of natural enzymes by radiation poses a great challenge to their applications for radiotherapy. Single-atom nanozymes (SAzymes) with high structural stability under such extreme conditions become a promising candidate for replacing natural enzymes to shrink tumors. Here, we report a CuN3-centered SAzyme (CuN3-SAzyme) that exhibits higher peroxidase-like catalytic activity than a CuN4-centered counterpart, by locally regulating the coordination environment of single copper sites. Density functional theory calculations reveal that the CuN3 active moiety confers optimal H2O2 adsorption and dissociation properties, thus contributing to high enzymatic activity of CuN3-SAzyme. The introduction of X-ray can improve the kinetics of the decomposition of H2O2 by CuN3-SAzyme. Moreover, CuN3-SAzyme is very stable after a total radiation dose of 500 Gy, without significant changes in its geometrical structure or coordination environment, and simultaneously still retains comparable peroxidase-like activity relative to natural enzymes. Finally, this developed CuN3-SAzyme with remarkable radioresistance can be used as an external field-improved therapeutics for enhancing radio-enzymatic therapy in vitro and in vivo. Overall, this study provides a paradigm for developing SAzymes with improved enzymatic activity through local coordination manipulation and high radioresistance over natural enzymes, for example, as sensitizers for cancer therapy.

Multi-functional nanozyme-based colorimetric, fluorescence dual-mode assay for Salmonella typhimurium detection in milk.

Rapid and high-sensitive Salmonella detection in milk is important for preventing foodborne disease eruption. To overcome the influence of the complex ingredients in milk on the sensitive detection of Salmonella, a dual-signal reporter red fluorescence nanosphere (RNs)-Pt was designed by combining RNs and Pt nanoparticles. After being equipped with antibodies, the immune RNs-Pt (IRNs-Pt) provide an ultra-strong fluorescence signal when excited by UV light. With the assistance of the H2O2/TMB system, a visible color change appeared that was attributed to the strong peroxidase-like catalytic activity derived from Pt nanoparticles. The IRNs-Pt in conjunction with immune magnetic beads can realize that Salmonella typhimurium (S. typhi) was captured, labeled, and separated effectively from untreated reduced-fat pure milk samples. Under the optimal experimental conditions, with the assay, as low as 50 CFU S. typhi can be converted to detectable fluorescence and absorbance signals within 2 h, suggesting the feasibility of practical application of the assay. Meanwhile, dual-signal modes of quantitative detection were realized. For fluorescence signal detection(emission at 615 nm), the linear correlation between signal intensity and the concentration of S. typhi was Y = 83C-3321 (R2 = 0.9941), ranging from 103 to 105 CFU/mL, while for colorimetric detection(absorbamce at 450 nm), the relationship between signal intensity and the concentration of S. typhi was Y = 2.9logC-10.2 (R2 = 0.9875), ranging from 5 × 103 to 105 CFU/mL. For suspect food contamination by foodborne pathogens, this dual-mode signal readout assay is promising for achieving the aim of convenient preliminary screening and accurate quantification simultaneously.

Colorimetric aptasensor based on Fe3O4@MOF@Pt nanozymes for ultrasensitive detection of histamine in fish

The accurate determination of histamine in fish is imperative for food safety, given the toxic nature of this biogenic amine. This study presents an innovative colorimetric aptasensor for the ultrasensitive detection of histamine in fish, utilizing nanozymes based on magnetic metal-organic frameworks coated with Pt nanoparticles (Fe3O4@MOF@Pt), which exhibit high peroxidase-like catalytic activity, magnetism, and superior optical properties. The surface of Fe3O4@MOF@Pt nanozymes were modified with DNA strands complementary to the histamine aptamer, creating effective colorimetric probes. In the presence of histamine, these colorimetric probes compete with histamine molecules for aptamer binding on the enzyme plate. Color development is triggered by adding a TMB and H2O2 substrate solution to the enzyme plate. This competitive binding-based aptasensor allows for rapid and accurate histamine quantification within a linear range of 10 pM to 10 μM, and a notable detection limit of 6.23 pM. Furthermore, the sensor demonstrated excellent specificity, distinguishing histamine from l-histidine and other biogenic amines. Tested on mackerel samples, the aptasensor showed spiked recoveries of 91.4%–109.6%, validating its practical applicability. This sensor offers an ultrasensitive, specific, and reusable tool for histamine detection, representing a significant advancement in ensuring the safety of fish products.

Tailoring the peroxidase-like properties of Mo atom nanoclusters/N-MXene nanozymes for sensitive colorimetric detection of glutathione

Although nanozyme engineering has made tremendous progress, there is a huge gap between them and natural enzymes due to the enormous challenge of precisely adjusting the geometric and electronic structure of active sites. Considering that intentionally adjusting the metal-carrier interactions may bring the promising catalytic activity, in this work, a novel Mo atom nanocluster is successfully synthesized using nitrogen-doped Mxene (MoACs/N-MXene) nanozymes as carriers. The constructed MoACs/N-MXene displays excellent peroxidase-like catalytic activity and kinetics, outweighing its N-MXene and Mo nanoparticles (NPs)-MXene references and natural horse radish peroxidase. This work not only reports a successful example of MoACs/N-MXene nanozyme as a guide for achieving peroxidase-mimic performance of nanozymes for colorimetric glutathione sensing at 0.29 μM, but also expands the application prospects of two-dimensional MXene nanosheets by reasonably introducing metal atomic clusters and nonmetal atom doping and exploring related nanozyme properties.

Construction of chiral nanozymes with high enantioselectivity for visual detection via smartphone-based paper sensors

The development of enantioselective nanozymes holds profound significance in synthesizing chiral compounds and elevating analytical precision. Herein, we have synthesized chiral gold/iron hierarchically organized particles (Cys@Au/Fe Hops) possessing peroxidase-like catalytic activity, through a one-pot method using cysteine as a chiral inducer. The nanozymes exhibited remarkable enantioselective catalytic activity to 3,4-dihydroxy-phenylalanine (DOPA) enantiomer. Notably, L-Cys@Au/Fe Hops, comprising right-handed helical nanopetals, exhibited elevated catalytic efficiency for L-DOPA over D-DOPA, whereas the reverse held for D-Cys@Au/Fe Hops. The molecular dynamics simulations demonstrated hydrogen bonding interactions between the active site and substrate, thereby revealing how steric effects affected the enantioselective catalysis of chiral DOPA by L/D-Cys@Au/Fe Hops. Moreover, the chiral nanozymes were developed into a test paper sensor due to their exceptional stability, which can achieve the visual detection of DOPA enantiomer combined with a smartphone platform. This work is significant in advancing the design and practical utility of highly selective enzyme mimics.

Deciphering the Catalytic Mechanism of Peroxidase-like Activity of Iron Sulfide Nanozymes.

Iron sulfide nanomaterials represented by FeS2 and Fe3S4 nanozymes have attracted increasing attention due to their biocompatibility and peroxidase-like (POD-like) catalytic activity in disease diagnosis and treatments. However, the mechanism responsible for their POD-like activities remains unclear. Herein, taking the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 on FeS2(100) and Fe3S4(001) surfaces, the catalytic mechanism was investigated in detail using density functional theory (DFT) calculations and experimental characterizations. Our experimental results showed that the catalytic activity of FeS2 nanozymes was significantly higher than that of Fe3S4 nanozymes. Our DFT calculations indicated that the surface iron ions of iron sulfide nanozymes could effectively catalyze the production of HO• radicals via the interactions between Fe 3d electrons and the frontier orbitals of H2O2 in the range of -10 to 5 eV. However, FeS2 nanozymes exhibited higher POD-like activity due to the surface Fe(II) binding to H2O2, forming inner-orbital complexes, which results in a larger binding energy and a smaller energy barrier for the base-like decomposition of H2O2. In contrast, the surface iron ions of Fe3S4 nanozymes bind to H2O2, forming outer-orbital complexes, which results in a smaller binding energy and a larger energy barrier for the base-like decomposition of H2O2. The charge transfer analysis showed that FeS2 nanozymes transferred 0.12 e and Fe3S4 nanozymes transferred 0.05 e from their surface iron ions to H2O2, respectively. The simulations were consistent with the experimental observations that the FeS2 nanozymes had a greater affinity for H2O2 compared to that of Fe3S4 nanozymes. This work provides a theoretical foundation for the rational design and accurate preparation of iron sulfide functional nanozymes.