Natural Horseradish Peroxidase Research Articles

Pt deposited on sea urchin-like CuCo2O4 nanowires: Preparation, the excellent peroxidase-like activity and the colorimetric detection of sulfide ions

Detecting of sulfur ions (S2-) in environment is critical to human health. In this work, a fast and convenient colorimetric sensing platform for S2- was developed. In detail, Pt deposited on sea urchin-like CuCo2O4 nanostructures (Pt/CuCo2O4) was synthesized and demonstrated to possess enhanced peroxidase-like performance, similar to the natural horseradish peroxidase (HRP). Pt/CuCo2O4 can catalyze colorless 3, 3, 5, 5-Tetramethylbenzidine (TMB) to be oxidized by H2O2 into a blue product (oxTMB). When the above system encounters sulfur ions (S2-), the peroxidase-like activity of Pt/CuCo2O4 is inhibited, accompanied with the color change of reaction solutions. On this basis, a colorimetric sensing platform for S2- can be established. Kinetic experiments verified Pt/CuCo2O4 possessed a higher affinity with substrate than that of HPR. The excellent peroxidase-like performance of Pt/CuCo2O4 was attributed to two active species including hydroxyl radical (•OH) and superoxide radical (•O2-) in the catalytic process. The linear range of the proposed sensing platform for S2- was 0.5–10 μM as well as the low limit of detection is 85.9 nM, much lower than the World Health Organization regulations. The sensing platform had been successfully applied to the detection of S2- in tap water and lake water, which provided a convenient method for detecting S2- in wastewater.

Biomimetic iron-imidazole sites into metal organic framework nanoflowers as high-affinity peroxidase mimic for colorimetric biosensing

The active site of natural horseradish peroxidase (HRP) comprises iron coordinated equatorially by a porphyrin ring and axially by the imidazole group of His170. The low water solubility of porphyrin rings inspired us to investigate the potential of the iron-imidazole group as peroxidase mimic. Herein, iron-imidazole (Fe-MIM) was one-pot constructed using ascorbic acid stabilized Fe2+ and 2-methylimidazole in the presence of zinc acetate at room temperature in aqueous medium, along with the formation of ZIF-8 framework around Fe-MIM sites. Fe-MIM/ZIF-8 was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller surface measurements. Fe-MIM/ZIF-8 exhibits high peroxidase-like activity, efficiently catalyzing the redox reaction between H2O2 and 3, 3′, 5, 5′-tetramethylbenzidine, as made evident by the appearance of a UV–Vis signal at 652 nm. Fe-MIM/ZIF-8 displays higher catalytic activity than the material (Fe + MIM) prepared by ascorbic acid stabilized Fe2+ and MIM, due to its rich biomimetic architecture and large BET surface area. The Km of Fe-MIM/ZIF-8 for H2O2 was 28 μM, which is 132 and 98 times lower than those of HRP and hemin (ironIII porphyrin), respectively. This low Km value indicates the strong affinity of Fe-MIM/ZIF-8 for H2O2, which proves the superiority of biomimetic Fe-MIM sites and suggests Fe-MIM/ZIF-8′s potential for H2O2-related biosensing. The highly sensitive colorimetric methods for H2O2 and H2O2-related glucose detection has been proposed. The applicability of this method to glucose detection in serum samples was tested with satisfactory results.

Investigation on the peroxidase-mimic activity of adenine phosphate and its applications

The peroxidase-like activity of adenine phosphate (AP) was investigated for the first time using chromogenic substrate 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the presence of H2O2. Effects of different reaction conditions, including pH, temperature, AP concentration and incubation time on the catalytic property of AP, were investigated. The peroxidase-like activity of AP complies with Michaelis-Menten kinetics, and the calculated kinetic parameter (Km, 0.038 mM) of AP catalysis exhibits higher affinity to H2O2 than natural horseradish peroxidase and some of the other small-molecule peroxidase mimics. The radical scavenging results confirm that hydroxyl radical (•OH) is the active specie of catalytic process. Based on the excellent catalytic performance of AP, a facile colorimetric method for the H2O2 and ascorbic acid detection with good sensitivity and selectivity was established at the linear ranges of 2.0–50.0 μM and 20.0–70.0 μM, respectively. In addition, the developed method was applied to detect H2O2 and ascorbic acid in practical samples. In short, this work will not only broaden the understanding of biological function of AP, but also facilitate the development of new category of small-molecule enzyme mimics.

Colorimetric and Fluorescent Dual-Modality Sensing Platform Based on Fluorescent Nanozyme.

Compared with natural enzymes, nanozymes based on carbonaceous nanomaterials are advantages due to high stability, good biocompatibility, and the possibility of multifunctionalities through materials engineering at an atomic level. Herein, we present a sensing platform using a nitrogen-doped graphene quantum dot (NGQD) as a highly efficient fluorescent peroxidase mimic, which enables a colorimetric/fluorescent dual-modality platform for detection of hydrogen peroxide (H2O2) and biomolecules (ascorbic acid-AA, acid phosphatase-ACP) with high sensitivity. NGQD is synthesized using a simple hydrothermal process, which has advantages of high production yield and potential for large-scale preparation. NGQD with uniform size (3.0 ± 0.6 nm) and a single-layer graphene structure exhibits bright and stable fluorescence. N-doping and ultrasmall size endow NGQD with high peroxidase-mimicking activity with an obviously reduced Michaelis–Menten constant (K m) in comparison with natural horseradish peroxidase. Taking advantages of both high nanozyme activity and unique fluorescence property of NGQD, a colorimetric and fluorescent dual-modality platform capable of detecting H2O2 and biomolecules (AA, ACP) with high sensitivity is developed as the proof-of-concept demonstration. Furthermore, the mechanisms underlying the nanozyme activity and biosensing are investigated.

Peroxidase-mimetic activity of a nanozyme with uniformly dispersed Fe3O4 NPs supported by mesoporous graphitized carbon for determination of glucose.

A Fe3O4/mesoporous graphitized carbon (Fe3O4/m-GC) composite was prepared through a facile calcination method with iron-based metal-organic frameworks (Fe-MOFs) as a sacrificial template. After carbonization, the Fe3O4 nanoparticles were uniformly dispersed in the mesoporous carbon support, resulting in spatial structural stability. The mesoporous carbon support obtained was highly graphitized and exhibited eminent electrical conductivity, which accelerated the electron transfer between the Fe3O4 nanoparticles by Fe(II)/Fe(III) redox cycles and m-GC by C = Csp2/C-Csp3 redox cycles, leading to the excellent peroxidase-mimetic activity of Fe3O4/m-GC. Km values for tetramethylbenzidine (TMB) and H2O2 were 26.8 and 15.8 times lower than that of natural horseradish peroxidase, respectively. Taking advantage of the peroxidase-mimetic activity of Fe3O4/m-GC, a colorimetric assay was fabricated for detecting glucose in the range 0.5 ~ 200μM, with a limit of detection of 0.24μM. Fig 1 A Schematic illustration of the preparation process of Fe3O4/m-GC, B schematic illustration of a proposed synergistic catalytic mechanism of TMB oxidation by Fe3O4/m-GC.

Zwitterionic daptomycin stabilized palladium nanoparticles with enhanced peroxidase-like properties for glucose detection

Mimic enzymes, especially noble metal nanomaterials, replace natural horseradish peroxidase due to the artificial regulation of catalytic activity by adjusting particle size and morphology. However, the existing mimic enzymes still have disadvantages such as large particle size, easy clustering and poor biocompatibility. Herein, well-dispersed daptomycin stabilized palladium nanoparticles (Dap-Pdn NPs) were synthesized by using daptomycin as a biological template. The average particle size of palladium nanoparticles of Dap-Pd0.25 NPs was 1.73 nm, the hydrodynamic size of Dap-Pd0.25 NPs detected by DLS method was 49.97 nm, Dap-Pd0.25 NPs were stable in fibrinogen solution. In addition, Dap-Pd0.25 NPs had excellent peroxidase-like activity, which effectively catalyzed the colorimetric oxidation reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2. Dap-Pd0.25 NPs were used to detect glucose concentration based on the colorimetric reaction of TMB, which had a wide detection range (0.02–1 mM) and low detection limit (5.6 μM) for glucose. Besides, fluorescence experiments proved that Dap-Pdn NPs catalyzed H2O2 to generate·OH. Taken together, a simple, green and inexpensive synthesis method of palladium nanoparticles with enhanced peroxidase-like activity was proved in this research. Dap-Pdn NPs will have great application prospects in biological detection in the future.

Bifunctional nanozyme of copper organophyllosilicate for the ultrasensitive detection of hydroquinone.

The rapid development of nanozymes for ultrasensitive detection of contaminate has resulted in considerable attention. Herein, a carboxyl- and aminopropyl-functionalized copper organophyllosilicate (Cu-CAP) was synthesized by a facile, one-pot sol-gel method. The bifunctional groups endow it with superior catalytic activity than that of natural enzyme. Besides, it possesses outstanding catalytic stability under harsh conditions such as high temperature, extremely high or low pH, and high salinity. Apart from laccase-mimetic activity, Cu-CAP also shows oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to the blue-colored TMBox in the presence of H2O2, which is similar to natural horseradish peroxidase (HRP). Interestingly, this colorimetric system was suppressed by hydroquinone (HQ) specifically. Inspired by this, Cu-CAP was used to develop a highly sensitive and selective colorimetric method for the determination of HQ. This assay displayed an extremely low detection limit of 23nM and was applied for the detection of HQ in environmental water with high accuracy. This approach offers a new route for the rational design of high performance nanozymes for environmental and biosensing applications.

Peroxidase-like and oxidase-like nanozyme activities of reusable Mn–Co–S–Se/Ni foam for antibacterial application

Developing a stable and reusable material for antibacterial application in an enzyme-like system is still a challenge. Herein, Mn–Co–S–Se (MnCo2SxSe4–x)/Ni foam (NF) are synthesized by introducing S2– and Se2– in MnCo2O4/NF with a facile hydrothermal approach. With the different molar ratios of S/Se, the surface morphology of MnCo2SxSe4–x/NF shows different growth and the catalytic activity also presents regular changes. MnCo2S3.1Se0.9/NF possesses a high enzyme-like ability with higher Vmax than natural horseradish peroxidase. Due to the outstanding peroxidase-like activity, MnCo2S3.1Se0.9/NF also exhibits broad-spectrum bactericidal performance towards Escherichia coli and Staphylococcus aureus which stems from the formation of ·O2– from H2O2. In the reutilization experiment, the enzyme-like activity keeps a stable value after 25 cyclic tests and the bactericidal performance is still stable after 10 cyclic tests, proving that MnCo2S3.1Se0.9/NF possesses relative stability and reusability. This research showed the great prospect of new energy and environmental catalysis.

Colorimetric Detection of Hydrogen Peroxide and Glutathione Based on Peroxidase Mimetic Activity of Fe3O4-sodium Lignosulfonate Nanoparticles

The sodium lignosulfonate (SL) modified Fe3O4 (Fe3O4-SL) nanoparticles with excellent peroxidase-like activity were prepared by one-step solvothermal method, which were applied to sensing hydrogen peroxide (H2O2) and glutathione (GSH) with color change. Firstly, the morphology and composition of Fe3O4-SL nanoparticles were characterized. The results showed that the synthesized Fe3O4-SL nanoparticles had a spherical structure with an average diameter of 220 nm. Subsequently, the peroxidase-like activity of Fe3O4-SL nanoparticles was investigated by catalyzing the formation of blue-colored oxidized TMB (ox-TMB) by 3,3’,5,5’-tetramethylbenzidine (TMB) in the presence of H2O2. Mechanism studies showed that the Fe3O4-SL nanoparticles exhibited better catalytic activity than natural horseradish peroxidase (HRP), and the catalytic pathway abode by the ping-pong mechanism. Finally, the colorimetric sensor for H2O2 was established, which had a linear range of 0.5–150 μmol/L, a detection limit of 0.139 μmol/L and good selectivity. In addition, according to the decolorization reaction of ox-TMB and GSH and the scavenging effect of GSH on hydroxyl radicals, a colorimetric GSH sensor was further constructed. Based on the above results, a colorimetric detection platform for GSH was built, by which a detection range of 0.5–25 μmol/L and a detection limit of 0.08 μmol/L were obtained. The results above showed that the colorimetric sensing system constructed here had a wide detection range, good selectivity and stability for detection of GSH, which would provide an important reference in food monitoring, biomolecule detection and other fields.

Amorphous RuTe2 nanorods as efficient peroxidase mimics for colorimetric immunoassay

With great progress in the development of nanozymes, the effect of size, composition and structure on the catalytic activity of nanozymes have been studied extensively, while the effect of phase has rarely been reported. Herein, phase-engineered RuTe2 nanorods are synthesized with different phase structures and peroxidase (POD)-like activities, which enables an in-depth understanding of their structure-activity relationship. Amorphous RuTe2 (a-RuTe2) nanorods exhibit superior POD-like activity, which is 3.77 times higher than that of their crystalline counterpart (c-RuTe2 nanorods). The amorphous phase composed of a large amount of disordered atoms endows the a-RuTe2 nanozyme with impressive performance. Significantly, given many POD-like nanozymes also show oxidase (OXD)-like activities, the interferences of O2 limit their applications in colorimetric assay. The proposed a-RuTe2 nanorods were found to possess negligible OXD-like activity. As a proof-of-concept, an enzyme-linked immunosorbent assay (ELISA) was constructed utilizing a-RuTe2 nanorods as labels for the detection of prostate-specific antigen (PSA). This a-RuTe2 nanorods-based ELISA possesses a low detection limit of 32.6 pg mL−1, which is at least one order of magnitude lower than that of conventional ELISA based on natural horseradish peroxidase. This work provides new insights into the design of high-performance nanozymes based on phase engineering.

Colorimetric Detection of Cholesterol Based on the Peroxidase‐Like Activity of Metal‐Organic Framework MIL‐101(Cr)

AbstractEfficient quantitative determination of cholesterol has important application value in drug testing and clinical diagnosis of cardiovascular diseases. In this work, a metal‐organic framework MIL‐101(Cr) (MIL=Materials of Institute Lavoisier) was synthesized and developed as a peroxidase mimic for colorimetric detection of cholesterol. Kinetic analysis indicated that the MIL‐101(Cr) nanoparticles showed a higher Vmax (2.27*10−7 MS−1) and a lower Km (0.07 mM) than the natural horseradish peroxidase (HRP). An effective colorimetric sensor has been proven to detect cholesterol. Based on the outstanding catalytic activity, the colorimetric sensor displayed a linear response for cholesterol in the concentration range from 1.1 μM to 22.9 μM and the detection limit as low as 0.86 μM. Furthermore, the proposed method based on MIL‐101(Cr) nanoparticles showed a favorable reproducibility and recovery. The sensor had been successfully applied to determine serum cholesterol level in mice and human, respectively.

Peroxidase-mimetic activity of FeOCl nanosheets for the colorimetric determination of glutathione and cysteine

Forthe first time the enzyme mimic activity of iron oxychloride (FeOCl) nanosheets has been studied. The intrinsic peroxidase-mimetic activity of the nanosheets in the presence of H2O2 was approved by the efficient oxidation of tetramethylbenzidine (TMB). The Michaelis-Menten constant of the nanosheets toward TMB was about six times lower than that of natural horseradish peroxidase. The superiority of the nanosheets' catalytic property ascribes to their H2O2 activation ability. Based on the inhibition of the nanozymes' catalytic reaction, an assay was developedfor the quantitative measurement of glutathione (GSH) and cysteine (Cys). The linear range for both biomolecules was over the range of 3-33 μM. The LOD values (3σ/slope) for GSH and Cys were 2.23 μM and 2.76 μM, respectively. Importantly, we succeeded in colorimetric discrimination of GSH and Cys kinetically. We achieved high selectivity toward GSH and Cys. This work extends the feasibility of using FeOCl as nanozymes to construct biosensors, colorimetric probes for medical diagnosis, and nanozyme-based cancer therapy.

Fe-Coordinated Carbon Nanozyme Dots as Peroxidase-Like Nanozymes and Magnetic Resonance Imaging Contrast Agents.

The catalytic activities of currently developed peroxidase-mimic nanozymes are generally limited. Therefore, further efforts are still needed to improve the catalytic performance of peroxidase nanozymes. Herein, we synthesized Fe-coordinated carbon nanozyme dots (Fe-CDs) that can serve as both efficient peroxidase nanozymes and T2-magnetic resonance imaging (MRI) contrast agents. The intrinsic peroxidase-like activity of the Fe-CDs was explored by catalytic oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H2O2). The product showed better performance over natural horseradish peroxidase (HRP) and other mimetic peroxidases. Quantification of glucose and ascorbic acid detection showed that this nanozyme could be used to detect a minimum limit as low as 5 μM glucose. Moreover, the colorimetric detection technique was used to detect serum glucose in mice, and the detection result was comparable with autobiochemistry analyzer results using a glucose assay kit. Furthermore, the Fe-CDs showed good magnetism properties and provided promising MR imaging of tumors with excellent biocompatibility.

Self‐assembled CoSe2 Microspheres with Intrinsic Peroxidase Mimicking Activity for Efficient Degradation of Variety of Dyes

AbstractIn this investigation, we report a new and greener self‐assembly of CoSe2 microsphere (CoSe2 MS) without assistance of harmful reducing and structure‐directing agents (SDA). Intrinsic peroxidase mimicking activity of synthesized CoSe2 MS was evaluated for 3,3,5,5′‐tetramethylbenzidine as a substrate by monitoring the absorbance of oxidized product at 653 nm. The smaller Michalis Menten constant (Km) for CoSe2 MS catalyzed reaction (0.371 mM), than the natural Horse Radish Peroxidase (HRP) enzyme, signifies the high substrate affinity of CoSe2 MS than HRP. Further, intrinsic peroxidase activity was assessed using emission intensity enhancement of terephthalic acid (TA) in presence of CoSe2 MS and H2O2 with time due to the production of .OH radicals and subsequent hydroxylation of TA. CoSe2 MS was further employed for organic dyes degradation in presence of H2O2, where cationic and anionic dyes degraded within 120 min with the highest degradation efficiency of 99.45 % for malachite green.

Palygorskite@Co3O4 nanocomposites as efficient peroxidase mimics for colorimetric detection of H2O2 and ascorbic acid

Nanomaterials with intrinsic enzyme-like activities have attracted extensive research interest as promising alternatives to natural biological enzymes due to their advantages of low cost and high stability. Many artificial enzyme mimics have been successfully applied in the fields of sensing, environmental treatment, and oncotherapy. Herein, novel palygorskite@Co3O4 nanocomposites (Pal@Co3O4 NCs) were fabricated by modifying Pal with Co3O4 nanoparticles through a facile hydrothermal method. The obtained Pal@Co3O4 nanocomposites as nanozymes displayed enhanced peroxidase-like activity, which can catalyze the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to obtain colored products. Kinetic assay indicated that the Pal@Co3O4 peroxidase mimics showed a higher affinity towards TMB than that of natural horseradish peroxidase (HRP). Moreover, a sensitive and selective sensor for colorimetric determination of H2O2 and ascorbic acid (AA) was successfully constructed by using Pal@Co3O4 nanocomposites as peroxidase mimics. Furthermore, the proposed assay for sensing of AA in model samples was evaluated with satisfactory results, demonstrating the potential applications in complex biological systems.

Highly Sensitive Fluorescent Detection of Acetylcholine Based on the Enhanced Peroxidase-Like Activity of Histidine Coated Magnetic Nanoparticles.

Inspired by the active site structure of natural horseradish peroxidase having iron as a pivotal element with coordinated histidine residues, we have developed histidine coated magnetic nanoparticles (His@MNPs) with relatively uniform and small sizes (less than 10 nm) through one-pot heat treatment. In comparison to pristine MNPs and other amino acid coated MNPs, His@MNPs exhibited a considerably enhanced peroxidase-imitating activity, approaching 10-fold higher in catalytic reactions. With the high activity, His@MNPs then were exploited to detect the important neurotransmitter acetylcholine. By coupling choline oxidase and acetylcholine esterase with His@MNPs as peroxidase mimics, target choline and acetylcholine were successfully detected via fluorescent mode with high specificity and sensitivity with the limits of detection down to 200 and 100 nM, respectively. The diagnostic capability of the method is demonstrated by analyzing acetylcholine in human blood serum. This study thus demonstrates the potential of utilizing His@MNPs as peroxidase-mimicking nanozymes for detecting important biological and clinical targets with high sensitivity and reliability.

Sensitive colorimetric assay for the determination of alkaline phosphatase activity utilizing nanozyme based on copper nanoparticle-modified Prussian blue

Nanozyme based on Prussian blue nanocubes (PB NCs) loaded with copper nanoparticles (Cu@PB NCs) was synthesized. The peroxidase (POD)-like activity of Cu@PB NCs was studied and utilized for detecting the activity of alkaline phosphatase (ALP). The Cu@PB NCs possess higher POD-like activity compared with PB NCs and natural horseradish peroxidase (HRP) due to the loading of copper nanoparticles. 3,3',5,5'-Tetramethylbenzidine (TMB) can be oxidized to oxTMB in the presence of Cu@PB NCs and H2O2, generating blue-colored compound, while introduction of pyrophosphate (PPi) leads to the POD-like activity of Cu@PB NCs decreased obviously. In the presence of ALP, PPi was hydrolyzed and then the POD-like activity of Cu@PB NCs was restored. So, according to the change of the POD-like activity of Cu@PB NCs, a sensitive colorimetric assay for ALP activity was reported. The limit of detection of the assay is 0.08mU/mL, with linear range from 0.1 to 50mU/mL. In addition, the assay was also applied for screening the inhibitors of ALP. Nanozyme based on Prussian blue nanocube (PB NCs) loaded with copper nanoparticles was synthesized and utilized for detecting the activity of alkaline phosphatase (ALP).

“Dual lock-and-key”-controlled ceria nanotubes-based nanozymes for tumor-specific photothermal therapy

Tumor-specific activatable therapy has gained more and more attention due to its improved therapeutic efficacy and minimized side effects. However, most of these nanomedicines only utilized one stimulus as the switch of the therapeutic process, which may have the issue of low selectivity. Herein, we develop a “dual lock-and-key” type activatable nanotherapeutic platform (ABTS@PAH-CNts) for tumor-specific photothermal therapy (PTT). Such nanoplatform can only be activated under both H2O2 and acidic pH, thus achieving higher selectivity towards tumor than single stimulus-activated nanomedicine. The nanoplatform is prepared by adsorbing 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) onto the surface of ceria nanotubes. We demonstrate that ceria nanotubes have analogous peroxidase activity with natural horseradish peroxidase (HRP). Under both H2O2 and acidic pH, ceria nanotubes can catalyze ABTS into its oxidized form, showing enhanced near-infrared (NIR) absorption with good photothermal effect. ABTS@PAH-CNts shows good in vitro biocompatibility without laser irradiation, while has good anticancer efficiency under 808 nm laser irradiation. In addition, in vivo study indicates that the photothermal temperature of ABTS@PAH-CNts can reach up to 55 °C in the tumor site, while only can reach 40 °C for normal tissue, demonstrating its good tumor specificity. Our work not only develops a nanozyme-based “dual lock-and-key”-controlled PTT system, but also provides a nanoplatform for activatable theranostics.

High-Performance Self-Cascade Pyrite Nanozymes for Apoptosis–Ferroptosis Synergistic Tumor Therapy

As next-generation artificial enzymes, nanozymes have shown great promise for tumor catalytic therapy. In particular, their peroxidase-like activity has been employed to catalyze hydrogen peroxide (H2O2) to produce highly toxic hydroxyl radicals (•OH) to kill tumor cells. However, limited by the low affinity between nanozymes with H2O2 and the low level of H2O2 in the tumor microenvironment, peroxidase nanozymes usually produced insufficient •OH to kill tumor cells for therapeutic purposes. Herein, we present a pyrite peroxidase nanozyme with ultrahigh H2O2 affinity, resulting in a 4144- and 3086-fold increase of catalytic activity compared with that of classical Fe3O4 nanozyme and natural horseradish peroxidase, respectively. We found that the pyrite nanozyme also possesses intrinsic glutathione oxidase-like activity, which catalyzes the oxidation of reduced glutathione accompanied by H2O2 generation. Thus, the dual-activity pyrite nanozyme constitutes a self-cascade platform to generate abundant •OH and deplete reduced glutathione, which induces apoptosis as well as ferroptosis of tumor cells. Consequently, it killed apoptosis-resistant tumor cells harboring KRAS mutation by inducing ferroptosis. The pyrite nanozyme also exhibited favorable tumor-specific cytotoxicity and biodegradability to ensure its biosafety. These results indicate that the high-performance pyrite nanozyme is an effective therapeutic reagent and may aid the development of nanozyme-based tumor catalytic therapy.

Construction and stabilization of a peptide-based peroxidase mimic for the colorimetric detection of uric acid and sarcosine

Abstract Peptide assembly provides a new approach for the construction of enzyme-like catalysts. However, low stability is still a big challenge for the peptide-based enzyme mimics because the non-covalently driven structures are often destroyed when exposed to environmental changes. Inspired by the catalytic centre of natural horseradish peroxidase (HRP) and the biological function of dityrosine in structural proteins, in this study, we presented the construction of a stable peptide-based HRP mimic (CCA-YH) through introducing covalent bonds. CCA-YH was obtained through the co-assembly of YYHYY and hemin, followed by a ruthenium-mediated photo-crosslinking reaction. Catalytic activity assay demonstrated that CCA-YH displayed enhanced catalytic ability than the non-covalent co-assemblies (CA-YH). Remarkably, CCA-YH exhibited superior long-term stability than CA-YH and natural HRP under different pH, temperature, ion strength and organic medium environments, as well as a favorable reusability. Finally, CCA-YH was applied to the colorimetric detection of uric acid and sarcosine in human urine, which displayed satisfactory sensitivity, specificity and reproducibility. This is the first report the construction of stable peptide-based enzyme mimic based on covalent co-assembly strategy.