Selective Oxidation of Halophenols Catalyzed by an Artificial Miniaturized Peroxidase.

The development of artificial enzymes for application in sustainable technologies, such as the transformation of environmental pollutants or biomass, is one of the most challenging goals in metalloenzyme design. In this work, we describe the oxidation of mono-, di-, tri- and penta-halogenated phenols catalyzed by the artificial metalloenzyme Fe-MC6*a. It promoted the dehalogenation of 4-fluorophenol into the corresponding 1,4-benzoquinone, while under the same experimental conditions, 4-chloro, 4-bromo and 4-iodophenol were selectively converted into higher molecular weight compounds. Analysis of the 4-chlorophenol oxidation products clarified that oligomers based on C-O bonds were exclusively formed in this case. All results show that Fe-MC6*a holds intriguing enzymatic properties, as it catalyzes halophenol oxidation with substrate-dependent chemoselectivity.

ROS Consumers or Producers? Interpreting Transcriptomic Data by AlphaFold Modeling Provides Insights into Class III Peroxidase Functions in Response to Biotic and Abiotic Stresses.

Participating in both biotic and abiotic stress responses, plant-specific class III peroxidases (PERs) show promise as candidates for crop improvement. The multigenic PER family is known to take part in diverse functions, such as lignin formation and defense against pathogens. Traditionally linked to hydrogen peroxide (H2O2) consumption, PERs can also produce reactive oxygen species (ROS), essential in tissue development, pathogen defense and stress signaling. The amino acid sequences of both orthologues and paralogues of PERs are highly conserved, but discovering correlations between sequence differences and their functional diversity has proven difficult. By combining meta-analysis of transcriptomic data and sequence alignments, we discovered a correlation between three key amino acid positions and gene expression in response to biotic and abiotic stresses. Phylogenetic analysis revealed evolutionary pressure on these amino acids toward stress responsiveness. Using AlphaFold modeling, we found unique interdomain and protein-heme interactions involving those key amino acids in stress-induced PERs. Plausibly, these structural interactions may act as "gate keepers" by preventing larger substrates from accessing the heme and thereby shifting PER function from consumption to the production of ROS.

Bimetallic AuPt alloy/rod-like CeO2 nanojunctions with high peroxidase-like activity for colorimetric sensing of organophosphorus pesticides.

Organophosphorus pesticides (OP) have extensive applications in agriculture, while their overuse causes inevitable residues in food, soil, and water, ultimately being harmful to human health and even causing diverse dysfunctions. Herein, a novel colorimetric platform was established for quantitative determination of malathion based on peroxidase mimic AuPt alloy decorated on CeO2 nanorods (CeO2@AuPt NRs). The synthesized nanozyme oxidized colorless 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. Besides, the oxidized TMB was inversely reduced by ascorbic acid (AA), which were originated from hydrolysis of L-ascorbic acid-2-phosphate (AA2P) with the assistance of acid phosphatase (ACP). Based upon this observation ACP analysis was explored by colorimetry, showing a wid linear range of 0.2 ~ 3.5 U L-1 and a low limit of detection (LOD = 0.085 U L-1, S/N = 3). Furthermore, malathion present in the colorimetric system inhibited the activity of ACP and simultaneously affected the generation of AA, in turn promoting the recovery of the chromogenic reaction. Based on this, the LOD was decreased to 1.5 nM (S/N = 3) for the assay of malathion with a wide linear range of 6 ~ 100 nM. This simple colorimetric platform provides some informative guidelines for determination of other pesticides and disease markers.

Adaptable graphitic C6N6-based copper single-atom catalyst for intelligent biosensing.

Self-adaptability is highly envisioned for artificial devices such as robots with chemical noses. For this goal, seeking catalysts with multiple and modulable reaction pathways is promising but generally hampered by inconsistent reaction conditions and negative internal interferences. Herein, we report an adaptable graphitic C6N6-based copper single-atom catalyst. It drives the basic oxidation of peroxidase substrates by a bound copper-oxo pathway, and undertakes a second gain reaction triggered by light via a free hydroxyl radical pathway. Such multiformity of reactive oxygen-related intermediates for the same oxidation reaction makes the reaction conditions capable to be the same. Moreover, the unique topological structure of CuSAC6N6 along with the specialized donor-π-acceptor linker promotes intramolecular charge separation and migration, thus inhibiting negative interferences of the above two reaction pathways. As a result, a sound basic activity and a superb gain of up to 3.6 times under household lights are observed, superior to that of the controls, including peroxidase-like catalysts, photocatalysts, or their mixtures. CuSAC6N6 is further applied to a glucose biosensor, which can intelligently switch sensitivity and linear detection range in vitro.

Photoluminescent gold nanoclusters as two-photon excited ratiometric pH sensor and photoactivated peroxidase.

A two-photon excited ratiometric fluorescent pH sensor is reported by combining L-cysteine-protected AuNCs (Cys@AuNCs) with fluorescein isothiocyanate (FITC). Cys@AuNCs were synthesized through a one-step self-reduction route and showed pH-responsive photoluminescence at 650 nm. Benefiting from the opposite pH response of Cys@AuNCs and FITC, the fluorescence ratio (F515 nm/F650 nm) of FITC&Cys@AuNCs provided a large dynamic range of 200-fold for pH measurement in the response interval of pH 5.0-8.0. Based on the excellent two-photon absorption coefficient of Cys@AuNCs, the sensor was expected to achieve sensitive quantitation of pH in living cells under two-photon excitation. In addition, colorimetric biosensing based on enzyme-like metal nanoclusters has attracted wide attention due to their low-cost, simplicity, and practicality. It is crucial to develop high catalytic activity nanozyme from the viewpoint of practical application. The synthesized Cys@AuNCs exhibited excellent photoactivated peroxidase-like activity with high substrate affinity and catalytic reaction rate, promising for rapid colorimetric biosensing of field analysis and the control of catalytic reactions by photostimulation.

Antieosinophil Antibodies Alone or in Combination with Antineutrophil Cytoplasmic Antibodies (ANCA) Detected in Different Autoimmune Conditions.

Circulating antieosinophil antibodies (AEOSA) have been associated with various autoimmune conditions affecting the liver, kidneys, lungs, and joints but are not part of routine clinical diagnostics. While analyzing human sera for antineutrophil cytoplasmic antibodies (ANCA) by indirect immunofluorescence (IIF) on granulocytes, 0.8% of analyzed samples were found to be reactive with eosinophils. Our aim was to determine the diagnostic relevance and antigenic specificity of AEOSA. AEOSA were seen either in combination with an myeloperoxidase (MPO)-positive p-ANCA (44%; AEOSA+/ANCA+) or on their own (56%; AEOSA+/ANCA-). AEOSA/ANCA positivity was seen in patients with thyroid disease (44%) or vasculitis (31%), while AEOSA+/ANCA- pattern was more common in patients with autoimmune disorders of the gastrointestinal tract and/or liver. Eosinophil peroxidase (EPX) was the main target recognized in 66% of the AEOSA+ sera by enzyme-linked immunosorbent assay (ELISA). Eosinophil cationic protein (ECP) and eosinophil-derived neurotoxin (EDN) were also identified as target antigens but less frequently and only in combination with EPX. In conclusion, we confirmed that EPX is a major target of AEOSA, illustrating the high antigenic potential of EPX. Our results also demonstrate the presence of concomitant AEOSA/ANCA positivity in a defined patient group. Further research should aim to elucidate the association of AEOSA with autoimmunity.

Platinum Nanoparticles Loaded Graphitic Carbon Nitride Nanosheets with Enhanced Peroxidase-like Activity for H2O2 and Oxidase-Based Sensing.

Platinum nanoparticles (PtNPs) are classical peroxidase-like nanozyme; self-agglomeration of nanoparticles leads to the undesirable reduction in stability and catalytic activity. Herein, a hybrid peroxidase-like nanocatalyst consisting of PtNPs in situ growing on g-C3N4 nanosheets with enhanced peroxidase-mimic catalytic activity (PtNP@g-C3N4 nanosheets) was prepared for H2O2 and oxidase-based colorimetric assay. g-C3N4 nanosheets can be used as carriers to solve the problem of poor stability of PtNPs. We observed that the catalytic ability could be maintained for more than 90 days. PtNP@g-C3N4 nanosheets could quickly catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), and the absorbance of blue color oxidized TMB (oxTMB) showed a robust linear relationship with the concentration of H2O2 (the detection limit (LOD): 3.33 µM). By utilizing H2O2 as a mediator, this strategy can be applied to oxidase-based biomolecules (glucose, organophosphorus, and so on, that generate or consume hydrogen peroxide) sensing. As a proof of concept, a sensitive assay of cholesterol that combined PtNP@g-C3N4 nanosheets with cholesterol oxidase (ChOx) cascade catalytic reaction was constructed with an LOD of 9.35 µM in a widespread range from 10 to 800 µM (R2 = 0.9981). In addition, we also verified its ability to detect cholesterol in fetal bovine serum. These results showed application prospect of PtNP@g-C3N4 nanosheets-based colorimetry in sensing and clinical medical detection.

Dual-mode colorimetric and homogeneous electrochemical detection of intracellular/extracellular H2O2 based on FeSx/SiO2 nanoparticles with high peroxidase-like activity.

Abnormal expression of hydrogen peroxide (H2O2) elucidates cell dysfunctions and might induce the occurrence and deterioration of various diseases. However, limited by its ultralow level under pathophysiological conditions, intracellular and extracellular H2O2 was difficult to be detected accurately. Herein, a colorimetric and homogeneous electrochemical dual-mode biosensing platform was constructed for intracellular/extracellular H2O2 detection based on FeSx/SiO2 nanoparticles (FeSx/SiO2 NPs) with high peroxidase-like activity. In this design, FeSx/SiO2 NPs were synthesized with excellent catalytic activity and stability compared to natural enzymes, which improved the sensitivity and stability of sensing strategy. 3,3',5,5'-Tetramethylbenzidine (TMB), as a multifunctional indicator, was oxidized in the presence of H2O2, generated color changes and realized visual analysis. In this process, the characteristic peak current of TMB decreased, which could realize the ultrasensitive detection of H2O2 by homogeneous electrochemistry. Accordingly, by integrating visual analysis ability of colorimetry and the high sensitivity of homogeneous electrochemistry, the dual-mode biosensing platform exhibited high accuracy, sensitivity and reliability. The detection limits of H2O2 were 0.2 µM (S/N = 3) for the colorimetric method and 2.5 nM (S/N = 3) for the homogeneous electrochemistry assay. Therefore, the dual-mode biosensing platform provided a new opportunity for highly accurate and sensitive detection of intracellular/extracellular H2O2.

RLS-0071 Moderated Elevated Myeloperoxidase Level and Activity in an Asymptomatic Subject in Clinical Trial RLS-0071-101.

BACKGROUND RLS-0071 is a dual-targeting peptide developed for the regulation of humoral and cellular inflammation via inhibition of neutrophil effectors, including myeloperoxidase and neutrophil extracellular trap formation (NETosis). The safety, pharmacokinetics, and pharmacodynamics of single and multiple doses of RLS-0071 were evaluated in a first-in-human clinical trial in healthy volunteers. Myeloperoxidase is the major peroxidase enzyme present in neutrophilic granules and contributes to cellular inflammation. Extracellular myeloperoxidase has been associated with chronic inflammation in a variety of diseases, including atherosclerosis. RLS-0071 has previously been shown to inhibit extracellular myeloperoxidase function both in vitro and in vivo in animal disease models. CASE REPORT Healthy subjects participating in the RLS-0071-101 study were screened for baseline myeloperoxidase level, leading to the identification of a 21-year-old woman with elevated baseline levels. After randomization, the subject received 9 intravenous infusions of 10 mg/kg RLS-0071. The subject tolerated the peptide infusions well with no adverse changes in vital signs, significantly abnormal clinical laboratory results, or severe adverse events. Analysis of this subject's myeloperoxidase plasma concentrations demonstrated that her myeloperoxidase levels decreased by 43% and myeloperoxidase activity levels decreased 49% after infusions of RLS-0071. The reduction in the patient's plasma myeloperoxidase levels demonstrated a partial return to baseline levels 24 hours after cessation of dosing. There were no other clinically meaningful safety observations for this subject. CONCLUSIONS This observation suggests RLS-0071 has the therapeutic potential to moderate plasma myeloperoxidase levels and activity and modulate diseases in which myeloperoxidase contributes to pathogenesis.

Lacking ARHGAP25 mitigates the symptoms of autoantibody-induced arthritis in mice.

Objective: Despite intensive research on rheumatoid arthritis, the pathomechanism of the disease is still not fully understood and the treatment has not been completely resolved. Previously we demonstrated that the GTPase-activating protein, ARHGAP25 has a crucial role in the regulation of basic phagocyte functions. Here we investigate the role of ARHGAP25 in the complex inflammatory process of autoantibody-induced arthritis. Methods: Wild-type and ARHGAP25 deficient (KO) mice on a C57BL/6 background, as well as bone marrow chimeric mice, were treated i.p. with the K/BxN arthritogenic or control serum, and the severity of inflammation and pain-related behavior was measured. Histology was prepared, leukocyte infiltration, cytokine production, myeloperoxidase activity, and superoxide production were determined, and comprehensive western blot analysis was conducted. Results: In the absence of ARHGAP25, the severity of inflammation, joint destruction, and mechanical hyperalgesia significantly decreased, similarly to phagocyte infiltration, IL-1ß, and MIP-2 levels in the tibiotarsal joint, whereas superoxide production or myeloperoxidase activity was unchanged. We observed a significantly mitigated phenotype in KO bone marrow chimeras as well. In addition, fibroblast-like synoviocytes showed comparable expression of ARHGAP25 to neutrophils. Significantly reduced ERK1/2, MAPK, and I-κB protein signals were detected in the arthritic KO mouse ankles. Conclusion: Our findings suggest that ARHGAP25 has a key role in the pathomechanism of autoantibody-induced arthritis in which it regulates inflammation via the I-κB/NF-κB/IL-1ß axis with the involvement of both immune cells and fibroblast-like synoviocytes.

Sulforaphane Attenuates Neutrophil ROS Production, MPO Degranulation and Phagocytosis, but Does Not Affect NET Formation Ex Vivo and In Vitro.

Sulforaphane has several effects on the human body, including anti-inflammation, antioxidation, antimicrobial and anti-obesity effects. In this study, we examined the effect of sulforaphane on several neutrophil functions: reactive oxygen species (ROS) production, degranulation, phagocytosis, and neutrophil extracellular trap (NET) formation. We also examined the direct antioxidant effect of sulforaphane. First, we measured neutrophil ROS production induced by zymosan in whole blood in the presence of 0 to 560 µM sulforaphane. Second, we examined the direct antioxidant activity of sulforaphane using a HOCl removal test. In addition, inflammation-related proteins, including an azurophilic granule component, were measured by collecting supernatants following ROS measurements. Finally, neutrophils were isolated from blood, and phagocytosis and NET formation were measured. Sulforaphane reduced neutrophil ROS production in a concentration-dependent manner. The ability of sulforaphane to remove HOCl is stronger than that of ascorbic acid. Sulforaphane at 280 µM significantly reduced the release of myeloperoxidase from azurophilic granules, as well as that of the inflammatory cytokines TNF-α and IL-6. Sulforaphane also suppressed phagocytosis but did not affect NET formation. These results suggest that sulforaphane attenuates neutrophil ROS production, degranulation, and phagocytosis, but does not affect NET formation. Moreover, sulforaphane directly removes ROS, including HOCl.

Adaptive Responses of a Peroxidase-like Polyoxometalate-Based Tri-Assembly to Bacterial Microenvironment (BME) Significantly Improved the Anti-Bacterial Effects.

The present study presents the tertiary assembly of a POM, peptide, and biogenic amine, which is a concept to construct new hybrid bio-inorganic materials for antibacterial applications and will help to promote the development of antivirus agents in the future. To achieve this, a Eu-containing polyoxometalate (EuW10) was first co-assembled with a biogenic amine of spermine (Spm), which improved both the luminescence and antibacterial effect of EuW10. Further introduction of a basic peptide from HPV E6, GL-22, induced more extensive enhancements, both of them being attributed to the cooperation and synergistic effects between the constituents, particularly the adaptive responses of assembly to the bacterial microenvironment (BME). Further intrinsic mechanism investigations revealed in detail that the encapsulation of EuW10 in Spm and further GL-22 enhanced the uptake abilities of EuW10 in bacteria, which further improved the ROS generation in BME via the abundant H2O2 involved there and significantly promoted the antibacterial effects.

Cerium and samarium blocked antioxidant enzymes in wheat plants.

This work was conducted to study positive and negative impacts of cerium (Ce) and samarium (Sm) on two cultivars (Arta and Baharan) in wheat plant. Symbols of stress such as proline, malondialdehyde (MDA) and antioxidant enzymes, which may be complicated in the suppression responses of plants, were also studied. Wheat plants were exposed to 0, 2500, 5000, 7500, 10,000 and 15,000 µM of Ce and Sm for 7 days. The growth enhanced in plants treated with lesser Ce and Sm concentration (2500 µM) and declined in plants treated with upper concentrations as compared to untreated plants. The treatment with 2500 µM of Ce and Sm increased dry weigh in Arta by 68.42 and 20% and in Baharan by 32.14% and 27.3%. Thus, Ce and Sm had hormesis effect on growth in wheat plants. According to plant's growth parameter patterns, Arta cultivar had more sensitive to Sm than to Ce, whereas Baharan cultivar had sensitive to Ce than to Sm. Our results indicated impact of Ce and Sm on proline accumulation depended on the dosage of Ce and Sm. It was observed that Ce and Sm accumulated in wheat plants at higher exposure doses. Increment of MDA content by Ce and Sm treatments showed that these metals caused oxidative stress in wheat plants. Ce and Sm blocked enzymatic antioxidant system (superoxide dismutases, peroxidase and polyphenol peroxidase) in wheat. In wheat plants treated with lower Ce and Sm concentrations higher amounts of non-enzymatic antioxidant metabolites were detected. Thus, we showed the potential negative impact of unsuitable utilization of REEs in plants and suggested growth and interruption in physiological and biochemical mechanisms as a possible factor to recognize the underlying toxicological processes.

Effects of probiotics on pancreatic inflammation and intestinal integrity in mice with acute pancreatitis.

BACKGROUND: Severe acute pancreatitis is a potentially life-threatening disease. Despite being a common disorder, acute pancreatitis lacks a specific treatment. The present study aimed to examine the effects of probiotics on pancreatic inflammation and intestinal integrity in mice with acute pancreatitis. METHODS: Male ICR mice were randomly divided into 4 groups (n = 6 per group). The control group received two intraperitoneal (i.p.) injections of normal saline as a vehicle control. The acute pancreatitis (AP) group received two i.p. injections of L-arginine 450 mg/100 g body weight. AP plus probiotics groups received L-arginine to induce acute pancreatitis as above. In the single-strain and mixed-strain groups, mice received 1 mL of Lactobacillus plantarum B7 1 × 108 CFU/mL and 1 mL of Lactobacillus rhamnosus L34 1 × 108 CFU/mL and Lactobacillus paracasei B13 1 × 108 CFU/mL by oral gavage, respectively for 6 days starting 3 days prior to the AP induction. All mice were sacrificed 72 h after L-arginine injection. Pancreatic tissue was obtained for histological evaluation and immunohistochemical studies for myeloperoxidase, whereas ileal tissue was used for immunohistochemical studies for occludin, and claudin-1. Blood samples were collected for amylase analysis. RESULTS: Serum amylase levels and pancreatic myeloperoxidase levels in the AP group were significantly higher than in controls and significantly decreased in probiotic groups compared with the AP group. Ileal occludin and claudin-1 levels were significantly lower in the AP group than in controls. Ileal occludin levels significantly increased, whereas ileal claudin-1 levels did not significantly change in both probiotic groups as compared with the AP group. The pancreatic histopathology showed significantly higher degree of inflammation, edema, and fat necrosis in the AP group, and these changes improved in mixed-strained probiotic groups. CONCLUSIONS: Probiotics, particularly the mixed-strain ones, attenuated AP via the reduction of inflammation and the maintenance of intestinal integrity.

Common clinical pattern of antineutrophil cytoplasmic antibody -associated vasculitis: An experience from a multicenter study in Saudi Arabia.

OBJECTIVES: To understand the most common type and clinical manifestations of associated vasculitis (AAV) in the Saudi Arabia. METHODS: This retrospective study was conducted at King Fahad Medical City and the Security Forces Hospital Program, Riyadh, Saudi Arabia, between January 2014 and May 2022. Patients aged ≥18 years were included in the study and diagnosed based on clinical manifestations, serology, or histopathology according to the EMA algorithm. Univariate analysis was carried out to compare different groups; a series of independent samples t-tests was applied for continuous data. RESULTS: A total of 53 patients were enrolled: eosinophilic granulomatosis with polyangiitis (EGPA), granulomatosis with polyangiitis (GPA), and microscopic polyangiitis (MPA). Overall, proteinase-3 was the most prevalent (52.8%), and myeloperoxidase, myeloperoxidase MPO was the least prevalent antineutrophil cytoplasmic antibody (ANCA)-type (18.9%) among patients; other patients showed negative ANCA test results. The clinical manifestations differed significantly between EGPA and GPA groups in pulmonary, neurological, cardiological, and renal signs and symptoms (p<0.05); there was a higher incidence of the former 3 in the EGPA group. Although upper airway was predominant in all groups, there was no statistical difference between both groups. CONCLUSION: This study validated international reports on AAV clinical manifestations in the Saudi population. The GPA was associated with more upper airway and pulmonary signs and symptoms. Further investigation is needed to understand the treatments and quality of life of patients with AAV.

Myeloperoxidase in Health and Disease.

Innate and adaptive immune responses comprise a complex network of protein-protein and protein-cell interactions that regulates commensal flora and protects organisms from foreign pathogens and transformed (proliferating) host cells under physiological conditions such as pregnancy, growth and development as well as formulating a response pathological challenge [...].

Visual Detection of Stem-Loop Primer Amplification (SPA) Products without Denaturation Using Peroxidase-like DNA Machines (PxDM).

Rapid, inexpensive, and accurate determination of nucleic acids is a decisive factor in evaluating population's health and monitoring treatment at point-of-care (POC) settings. Testing systems with visual outputs can provide instrument-free signal detection. Isothermal amplification technologies can substitute conventional polymerase chain reaction (PCR) testing due to compatibility with the POC diagnostic. Here, we have visually detected DNA fragments obtained by stem-loop-primer-assisted isothermal amplification (SPA), but not those obtained by PCR or LAMP amplification using DNA nanomachines with peroxidase-like activity (PxDM) with sensitivity to a single nucleotide substitution. Compared to the diagnostics with conventional loop-mediated isothermal amplification (LAMP), the PxDM method produces no false positive signals with the non-specific amplification products. The study suggests that PxDM, in conjunction with SPA isothermal amplification, can become a valid platform for POC testing systems.

Porous-nanozyme-based colorimetric sensor for rapid detection of kanamycin in foods under neutral condition.

Most colorimetric methods based on nanozymes need to have excellent performance under acidic condition, so they are currently facing some challenges in the field of food hazard detection. Herein, a facile and rapid colorimetric sensor for kanamycin (KAN) detection in foods under neutral condition has been designed using the peroxidase-mimic activity of porous nanozyme like Co3 O4 nanodisk. Further investigations showed that the interaction mechanism between porous Co3 O4 nanodisk and substrates belongs to a ping-pong model, and the inhibition type of KAN on the peroxidase-mimic activity is noncompetitive inhibition. The constructed sensor has good sensitivity for KAN with the limit of 57 nM, and the color changes can be discerned visually when KAN exceeds 0.5 µM. Besides, the colorimetric sensor obtains excellent recovery results in chicken serum, milk, honey, and pork, which shows that the proposed sensing strategy can provide a rapid and convenient detection method for KAN in foods under neutral condition. PRACTICAL APPLICATION: The established sensing strategy can rapidly distinguish whether KAN residue exceeds the permissible level within 10 min, which meets the requirement for on-site monitoring of antibiotics in foods, and also open up a new idea for other hazards detection under neutral condition.

Fabrication of Adjustable Au/Carbon Hybrid Nanozymes with Photothermally Enhanced Peroxidase Activity and Ultra-sensitivity for Glutathione Detection.

Au nanozymes are extensively researched for their photothermal effect and catalytic performance, but overcoming the inherent defects of poor dispersibility and thermal stability through complementary materials will expand their prospects for biological applications. Herein, several novel CAu nanozymes were fabricated by in situ reduction of chloroauric acid on hollow carbon nanospheres (HCNs). Through regulating the number of reductions, sesame ball-shaped CAu (sCAu) with highly dispersed Au nanoparticles and diversity-shaped CAu (dCAu) were obtained. The number and morphology of loaded Au nanoparticles, absorption spectra, and hydrophilicity of CAu nanozymes were systematically characterized to demonstrate the flexibility of this novel method. The high-efficiency peroxidase-like sCAu0.3 nanozyme with hyperthermia-activated property was then screened for later bio-application. It is worth mentioning that its photothermal-promoted peroxidase-like activity could be achieved under near-infrared laser irradiation. Moreover, sCAu0.3 could specifically achieve glutathione detection in human blood samples. This method will provide a protocol for the regulation of CAu nanozymes to adapt to bio-detection applications.

Enhanced Peroxidase-Mimic Catalytic Activity via Cerium Doping of Strontium-Based Metal-Organic Frameworks with Design of a Smartphone-Based Sensor for On-Site Salivary Total Antioxidant Capacity Detection in Lung Cancer Patients.

The development of artificial nanozymes with superior catalytic performance and excellent stability has been a long-standing objective for chemists. The total antioxidant capacity (TAC) is one of the most important bioanalytical measures of oxidative stress in the body. The present work aims to develop a smartphone-assisted visual detection sensor using cerium-doped strontium-based metal-organic frameworks (Ce-SrMOFs) as peroxidase-like nanozymes for the rapid, low-cost, on-site detection of TAC. The pristine SrMOF functioned as a peroxidase nanozyme, and its enzymatic activity was enhanced after doping it with Ce(IV) ions because of the multivalent nature and synergistic impact of the heteroatoms. The Ce-SrMOFs were sensitive to the single electron transfer and hydrogen atom transfer processes, which implies that the Ce-SrMOFs can serve as an ideal nanozyme candidate for TAC analysis. The investigated mechanism revealed that •OH is the most active oxygen species for the peroxidase-like activity. The Ce-SrMOFs exhibited a strong affinity for 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2, with Km values of 0.082 and 0.427 mM, which are 5.29- and 8.67-fold lower than those of horseradish peroxidase (HRP), respectively. The Ce-SrMOFs were used for the detection of ascorbic acid, cysteine, and glutathione, with limits of detection of 44, 53, and 512 nM, respectively. The proposed method proved effective in measuring the TAC in saliva samples from lung cancer patients, thereby yielding results with satisfactory precision and accuracy.