Oxidase-like Activity Research Articles

Trimetallic FeCoNi Metal-Organic Framework with Enhanced Peroxidase-like Activity for the Construction of a Colorimetric Sensor for Rapid Detection of Thiophenol in Water Samples.

In recent years, nanozymes have attracted particular interest and attention as catalysts because of their high catalytic efficiency and stability compared with natural enzymes, whereas how to use simple methods to further improve the catalytic activity of nanozymes is still challenging. In this work, we report a trimetallic metal-organic framework (MOF) based on Fe, Co and Ni, which was prepared by replacing partial original Fe nodes of the Fe-MOF with Co and Ni nodes. The obtained FeCoNi-MOF shows both oxidase-like activity and peroxidase-like activity. FeCoNi-MOF can not only oxidize the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) to its blue oxidation product oxTMB directly, but also catalyze the activation of H2O2 to oxidize the TMB. Compared with corresponding monometallic/bimetallic MOFs, the FeCoNi-MOF with equimolar metals hereby prepared exhibited higher peroxidase-like activity, faster colorimetric reaction speed (1.26-2.57 folds), shorter reaction time (20 min) and stronger affinity with TMB (2.50-5.89 folds) and H2O2 (1.73-3.94 folds), owing to the splendid synergistic electron transfer effect between Fe, Co and Ni. Considering its outstanding advantages, a promising FeCoNi-MOF-based sensing platform has been designated for the colorimetric detection of the biomarker H2O2 and environmental pollutant TP, and lower limits of detection (LODs) (1.75 μM for H2O2 and 0.045 μM for TP) and wider linear ranges (6-800 μM for H2O2 and 0.5-80 μM for TP) were obtained. In addition, the newly constructed colorimetric platform for TP has been applied successfully for the determination of TP in real water samples with average recoveries ranging from 94.6% to 112.1%. Finally, the colorimetric sensing platform based on FeCoNi-MOF is converted to a cost-effective paper strip sensor, which renders the detection of TP more rapid and convenient.

Programming of a Portable Digital Monitoring System-Integrated DNA Aptamer Reversely Regulated Oxidase-Like Nanozyme for Real-Time Dynamic Analysis of Atmospheric Perfluorooctanoic Acid.

Timely and efficient analysis of the fluorinated per- and polyfluoroalkyl substances (PFAS) in an atmospheric environment is critical to environmental pollution traceability, early warnings, and governance. Here, a portable, reliable, and intelligent digital monitoring device for onsite real-time dynamic analysis of atmospheric perfluorooctanoic acid (PFOA) is proposed. The sensing mechanism is attributed to the oxidase-like activity of PtCoNPs@g-C3N4 that is reversely regulated by the surface modification of a PFOA-recognizable DNA aptamer, engineering a PFOA-activated oxidase-like activity of nanozyme (Apt-PtCoNPs@g-C3N4) to combine the nonfluorescence o-phenylenediamine (OPD) as the dual-modality response system. The present PFOA interacts with its DNA aptamer and dissociates from the surface of Apt-PtCoNPs@g-C3N4, restoring the oxidase-like activity of PtCoNPs@g-C3N4 to oxidize OPD into yellow fluorescence 2,3-diphenylaniline (DAP), thereby observing a PFOA-triggered colorimetric as well as fluorescence dual-modality change. Then, a hydrogel kit-programmed Apt-PtCoNPs@g-C3N4 + OPD system is used as the sensitive element to incorporate into this homemade portable device, automatically gathering and processing the PFOA-triggered hydrogel colorimetric and fluorescence image gray values by our self-weaving software, ultimately realizing the onsite real-time dynamic analysis of atmospheric PFOA surrounding a fluorochemical production plant. This work provides a direction and theoretical foundation for designing portable onsite screening devices that cater to other atmospheric contaminants detection requirements.

Colorimetric aptasensor for Listeria monocytogenes detection using dual functional Fe3O4@MIL-100(Fe) with magnetic separation and oxidase-like activities in food samples.

A novel colorimetric aptasensor assay based on the excellent magnetic responsiveness and oxidase-like activity of Fe3O4@MIL-100(Fe) was developed. Fe3O4@MIL-100(Fe) absorbed with aptamer and blocked by BSA served as capture probe for selective isolation and enrichment of Listeria monocytogenesone of the most common and dangerous foodborne pathogenic bacteria. The aptamer absorbed on Fe3O4@MIL-100(Fe) was further used as signal probe that specifically binds with target bacteria conjugation of capture probe for colorimetric detection of Listeria monocytogenes, taking advantages of its oxidase-like activity. The linear range of the detection of Listeria monocytogenes was from 102 to 107CFUmL-1, with the limit of detection as low as 14CFUmL-1. The approach also showed good feasibility for detection of Listeria monocytogenes in milk and meat samples. The spiked recoveries were in the range 81-114% with relative standard deviations ranging from 1.28 to 5.19%. Thus, this work provides an efficient, convenient, and practical tool for selective isolation and colorimetric detection of Listeria monocytogenes in food.

Development of a Zn-Based Single-Atom Nanozyme for Efficient Hydrolysis of Glycosidic Bonds.

Hydrolytic enzymes are essential components in second-generation biofuel technology and food fermentation processes. Nanozymes show promise for large-scale industrial applications as replacements for natural enzymes due to their distinct advantages. However, there remains a research gap concerning glycosidase nanozymes. In this study, a Zn-based single-atom nanozyme (ZnN4-900) is developed for efficient glycosidic bond hydrolysis in an aqueous solution. The planar structure of the class-porphyrin N4 material approximatively mimicked the catalytic centers of natural enzymes, facilitating oxidase-like (OXD-like)activity and promoting glycosidic bond cleavage. Theoretical calculations show that the Zn site can act as Lewis acids, attacking the C─O bond in glycosidic bonds. Additionally, ZnN4-900 has the ability to degrade starch and produce reducing sugars that increased yeast cell biomass by 32.86% and ethanol production by 14.56%. This catalyst held promising potential for enhancing processes in ethanol brewing and starch degradation industries.

Bimetallic metal-organic framework-based molecularly imprinted sensors for selective on-site detection of 2,4-dichlorophenoxyacetic acid

Designing and constructing simple and selective sensors for the on-site recognition of 2,4-dichlorophenoxyacetic acid (2,4-D) is both significant and challenging. Here, we report the development of molecularly imprinted sensors (Zn/Co-MOF@MIPs) utilizing bimetallic metal-organic frameworks as supporting carriers and catalysts, constructed via surface imprinting for the rapid detection and determination of 2,4-D. Zn/Co-MOF@MIPs exhibited oxidase-like activity, catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to yield a blue-colored oxidized TMB in the absence of H2O2. The high affinity of the imprinted layer for 2,4-D selectively reduced the oxidase-like activity of Zn/Co-MOF@MIPs in the presence of 2,4-D, resulting in a significant decrease in blue color intensity. The absorbance at 650 nm gradually decreased with increasing 2,4-D concentration. Furthermore, we established a colorimetric method based on Zn/Co-MOF@MIPs for the rapid detection of 2,4-D in environmental water. This sensing platform exhibited sensitivity and selectivity for detecting 2,4-D, with a low detection limit of 2.26 μM. These findings underscore the outstanding potential of Zn/Co-MOF@MIPs for environmental chemistry sensing applications.

PtCo with oxidase-like activity and laccase for synergistic catalytic degradation of phthalic acid esters

Phthalic acid esters (PAEs) as common plasticizers, providing convenience to humans. However, they also present a potential threat to ecosystems and human health as emerging contaminants. In this study, co-immobilization of nanozyme (PtCo) and laccase (Lac) into dendritic mesoporous silica (DMSN) constitutes nanomaterials (Lac@PtCo@DMSN). PtCo with an atomic ratio of 3:1 has the highest oxidizing activity. DMSN exhibited a maximum Lac loading capacity of 365 mg/g and activity of Lac@PtCo@DMSN exhibits excellent pH, temperature, and storage stability and reusability, and demonstrated greater recoverability. Remarkably, Lac@PtCo@DMSN (50 mg) achieved 81.83% degradation of total PAEs within 72 h and maintained 72.44% degradation of dimethyl phthalate (DMP) in the fifth cycle. Electron transfer between Pt, Co and adsorbed oxygen (O2ads) in PtCo can generate •OH and •O2−, which were the dominant reactants for PAEs degradation. •OH could degrade PAEs to phthalic acid via H-abstration and •OH addition. •OH effectively enhanced Lac activity, and promoted the synergistic catalytic performance of nanozymes and natural enzymes. The degradation of phthalic acid by Lac accelerated the release of PtCo@DMSN reaction sites, resulting in significantly enhanced PAEs degradation. Thus, artificial/natural enzymes can degrade PAEs without exogenous additives to solve the limitation of Lac application, providing a new strategy for degrading contaminants in water.

Artificial-Cofactor-Mediated Hydrogen and Electron Transfer Endows AuFe/Polydopamine Superparticles with Enhanced Glucose Oxidase-Like Activity.

Various applications related to glucose catalysis have led to the development of functional nanozymes with glucose oxidase (GOX)-like activity. However, the unsatisfactory catalytic activity of nanozymes is a major challenge for their practical applications due to their inefficient hydrogen and electron transfer. Herein, we present the synthesis of AuFe/polydopamine (PDA) superparticles that exhibit photothermal-enhanced GOX-like activity. Experimental investigations and theoretical calculations reveal that the glucose oxidation process catalyzed by AuFe/PDA follows an artificial-cofactor-mediated hydrogen atom transfer mechanism, which facilitates the generation of carbon-centered radical intermediates. Rather than depending on charged Au surfaces for thermodynamically unstable hydride transfer, Fe(III)-coordinated PDA with abundant amino and phenolic hydroxyl groups serves as cofactor mimics, facilitating both hydrogen atom and electron transfer in the catalytic process. Finally, leveraging the photothermal-enhanced GOX-like and catalase-like activities of AuFe/PDA, we establish a highly sensitive and accurate point-of-care testing blood glucose determination with exceptional anti-jamming capabilities.

Designing Fe8-N2 Catalytic Sites of Nitrogen-Doped Iron-Based Nanoparticles with Oxidase-Like Activity: Characterization, Calculation and Application.

Designing metal nanoparticles with oxidase-mimicking capabilities has garnered significant attention due to their promising attributes. However, understanding the intricate catalytic mechanisms underlying these nanoparticles poses a formidable challenge. In this study, a straightforward pyrolysis procedure was employed to synthesize nitrogen-doped iron-based nanoparticles (Fe NPs-N@C) with Fe8-N2 serving as active sites. The confirmation of these sites was thoroughly confirmed through density functional theory (DFT) calculations complemented by experimental validation. The resulting Fe NPs-N@C nanoparticles, averaging 5.45 nm in size, exhibited excellent oxidase-mimicking activity, with vmax=1.11×10-7 M s-1and km=1.67 mM, employing 3,3',5,5'-tetramethylbenzidine as a substrate. The oxidation pathway and catalytic mechanism of Fe NPs-N@C involved 1O2⋅ radicals, validated through electron paramagnetic resonance analysis and DFT calculations. Furthermore, Fe NPs-N@C/TMB system was devised for ascorbic acid and nitrite quantitative detection. This method demonstrated the capability to detect ascorbic acid within concentrations ranging from 1 to 55 μM, with a limit of detection (LOD) of 0.81 μM, and nitrite within concentrations from 1 to 160 μM, with a LOD value of 0.45 μM. These findings offer a comprehensive understanding of the catalytic mechanisms of Fe NPs-N@C nanoparticles at the atomic level, along with its potential for colorimetric sensor in future.

Excellent performance of Ag6Si2O7 oxidase mimic endowed by self-released ions for rapid colorimetric determination with reduced operational interference

Increasing attention has been directed towards oxidase mimics due to their catalytic ability toward enzyme substrates in the absence of H2O2, offering great colorimetric sensing potential in assays and diagnostics. However, slow electron-transfer and unstable absorbance over time often lead to unsatisfactory enzymatic reaction rates and unreliable readouts, significantly reducing detection efficiency and accuracy. Herein, we report on an Ag6Si2O7 nanozyme utilizing 3,3′,5,5′-tetramethylbenzidine (TMB) as a chromogenic substrate, demonstrating excellent oxidase-like activity and long-term stable colorimetric signals. Experimental results reveal that the excellent catalytic kinetics of Ag6Si2O7 (Km = 0.197 mM, Vmax = 5.1 × 10−7 M/s) are attributed to ultrafast electron transfer between Ag+ and TMB, mediated by Ag2O intermediates formed from self-released alkaline ions. Additionally, self-released H2SiO42− improves the stability of the oxidized substrate, resulting in a long-term stable colorimetric signal (∼20 min), which exhibits reliable accuracy regardless of the time point at which analyte is added within 20 min, thus eliminating the interference of individual operation time errors. Ascorbic acid (AA) is selected as the target molecule to assess the performance of the Ag6Si2O7-TMB colorimetric sensing system. This approach demonstrates a wide detection range from 5 to 300 μM and a detection limit of 0.452 μM. The developed colorimetric sensing strategy exhibits good stability, specificity, rapidity, and potential application in real sample detection.

The Identification of Oral Cariogenic Bacteria through Colorimetric Sensor Array Based on Single-Atom Nanozymes.

Effective identification of multiple cariogenic bacteria in saliva samples is important for oral disease prevention and treatment. Here, a simple colorimetric sensor array is developed for the identification of cariogenic bacteria using single-atom nanozymes (SANs) assisted by machine learning. Interestingly, cariogenic bacteria can increase oxidase-like activity of iron (Fe)─nitrogen (N)─carbon (C) SANs by accelerating electron transfer, and inversely reduce the activity of Fe─N─C further reconstruction with urea. Through machine-learning-assisted sensor array, colorimetric responses are developed as "fingerprints" of cariogenic bacteria. Multiple cariogenic bacteria can be well distinguished by linear discriminant analysis and bacteria at different genera can also be distinguished by hierarchical cluster analysis. Furthermore, colorimetric sensor array has demonstrated excellent performance for the identification of mixed cariogenic bacteria in artificial saliva samples. In view of convenience, precise, and high-throughput discrimination, the developed colorimetric sensor array based on SANs assisted by machine learning, has great potential for the identification of oral cariogenic bacteria so as to serve for oral disease prevention and treatment.

Electrochemical identification of reductive enantiomers in wood channels: A low-cost and scalable platform for chiral sensing

Chirality, an inherent characteristic of natural substances (such as sugars, peptides, proteins, and nucleic acid), plays a vital role in human metabolism and exerts substantial impacts. In general, chiral drugs can display diverse pharmacological and pharmacokinetic properties. One enantiomer may exhibit therapeutic effects, while the other could cause adverse reactions. Selective recognition of enantiomers is thus a significant task in the biomolecular and pharmaceutical fields. Despite the development of several chiral identification techniques, low-cost enantioselective sensing methods remain highly desirable. Here, we designed and developed an electrochemical sensing device for reductive enantiomer identification using natural wood channels as the substrate. The wood channels were endowed with oxidase-like activity through the in-situ growth of cerium oxide nanoparticles (CeO2). Chiral recognition capability was further introduced by incorporating a layer of chiral ZIF-8 (L-ZIF) as the chiral selector. To demonstrate the enantioselective sensing performance, 3,4-dihydroxyphenylalanine (DOPA) enantiomers were employed as model analytes. Due to the oxidase-like activity and the confinement effect of the proposed channels, the captured DOPA enantiomers were effectively oxidized to their quinone structure, and the Ce(IV) in CeO2 was reduced to Ce(III). These changes led to alterations in the surface charge of the channels, thereby modulating their ionic transport properties. This sensing mechanism also proved useful for the identification of other reductive enantiomers. The limits of detection for l-DOPA and d-DOPA were determined as 2.41 nM and 1.56 nM, respectively. The resulting wood channel-based sensing device not only can be used for the recognition and detection of reductive enantiomers, but also is expected to be applied to the non-electochemically active substances. Moreover, this study offers a novel type of solid-state channel material with low cost, reproducibility, and easy accessibility for electrochemical chiral sensing.

A novel fluorescent and photothermal probe based on nanozyme-mediated cascade reaction for detecting organophosphorus pesticide residues

In this study, a nanozyme (ZIF-Co-Cys) with high oxidase-like catalytic activity was prepared, and a ratiometric fluorescent/photothermal dual-mode probe was constructed for organophosphorus pesticides (OPs) detection based on the competitive effect of ZIF-Co-Cys and the enzymatic reaction product of acid phosphatase (ACP) on o-phenylenediamine and the inhibition effect of OPs on ACP activity. Using dimethyl dichloroviny phosphate (DDVP) as the model, both the fluorescence intensity ratio and the temperature change of the probe solution exhibited an excellent correlation with OPs concentration. The detection limits were 1.64 ng/mL and 0.084 ng/mL, respectively. Additionally, the detection of DDVP residues in real samples verified the outstanding anti-interference and accuracy of the probe. This work not only provided a complementary dual-mode method for the accurate and rapid detection of OPs residues in complex samples, but also supplied a new insight into the design of a multi-mode sensing platform based on the cascade reaction of nanozyme.

Bringing Cerium Oxysulfate Clusters into Nanozymes by Saturated Fatty Acid Regulation for Oxidase-like Activity

Bringing Cerium Oxysulfate Clusters into Nanozymes by Saturated Fatty Acid Regulation for Oxidase-like Activity

Platinum nanoparticle oxidase-like enzyme for colorimetric and photothermal dual-mode detection of sulfide ions

Monitoring sulfide ions (S2-) in environmental matrices is critical for environmental safety and pollution control. In this work, a novel dual-mode colorimetric and photothermal (PT) point-of-care testing (POCT) platform was developed for S2- assay. The synthesized platinum nanoparticles (Pt NPs) exhibited exceptional oxidase-like activity, catalyzing the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to its oxidized form (oxTMB), causing a color change from colorless to blue. Additionally, oxTMB exhibits significant PT effects under near-infrared 808 nm laser irradiation. The presence of S2- induced the aggregation of Pt NPs, markedly inhibiting their oxidase-like activity, thereby establishing an inverse relationship between the concentration of S2- and both the RGB value and temperature change in TMB solution. The limits of detection (LODs) were calculated to be 1.5 μM and 4.4 μM for colorimetric and photothermal analysis using a digital thermometer and smartphone, respectively. The S2- in lake water and fuel residue was analyzed, yielding satisfactory results. This method offers low-cost, straightforward, and swift advantages, underscoring its potential for POCT in environmental monitoring.

Two-dimensional β-MnOOH nanosheets with high oxidase-mimetic activity for smartphone-based colorimetric sensing

Manganese (Mn) is a versatile transition element with diverse oxidation states and significant biological importance. Mn-based nanozymes have emerged as promising catalysts in various applications. However, the direct use of manganese oxides as oxidase mimics remains limited and requires further improvement. In this study, we focus on hydroxylated manganese (MnOOH), specifically the layered form β-MnOOH which exhibits unique electronic and structural characteristics. The two-dimensional β-MnOOH nanosheets were synthesized through a hydrothermal approach and showed remarkable oxidase-like activity. These nanosheets effectively converted the oxidase substrate, 3,3′,5,5′-tetramethylbenzidine (TMB), into its oxidized form by initiating the conversion of dissolved oxygen into ·O2−, 1O2 and ·OH. However, in the presence of L-cysteine (L-Cys), the catalytic activity of β-MnOOH was significantly inhibited, enabling highly sensitive detection of L-Cys. This sensing strategy was successfully applied for smartphone-based L-Cys assay, offering potential utility in the diagnosis of Cys-related diseases. The exploration of layered β-MnOOH nanosheets as highly active oxidase mimics opens up new possibilities for catalytic and biomedical applications.

The enhanced oxidase-like activity of modified nanoceria/ZIF-67 for fluorescence and smartphone-assisted visual detection of tannic acid

As a substitute for natural enzymes, nanozymes have unique characteristics of high catalytic activity, excellent stability and low cost, making them pivotal in sensing applications. Among them, nanozymes with oxidase-like activity garner significant attention for antioxidant detection, as they efficiently catalyze the oxidation of antioxidants in the presence of oxygen. Herein, a nanozyme with an enhanced oxidase-like activity was synthesized through a 3-step strategy, that is, ceria nanoparticles were firstly modified with amino acid and oligopeptides, then combined with zeolitic imidazolate framework-67 (ZIF-67), and finally the composite was etched in neutral water. The as-synthesized nanozyme can oxidize the substrate 3,3′,5,5′-tetramethylbenzidine (TMB) or Amplex Red (AR) in the presence of oxygen, inducing a change in their color or fluorescent signals, verifying its oxidase-like activity. Tannic acid (TA), an antioxidant, competes with TMB/AR for oxidation by the nanozyme. Leveraging this competitive relationship, a fluorescent and portable trichromatic sensor was developed for the detection of tannic acid (TA) in food samples. The fluorescent sensor shows high sensitivity with detection limits (S/N = 3) of 0.011 µM, and the trichromatic sensor presents comparable performance to colorimetric sensor, exhibiting a linear range of 30–270 µM and detection limit of 1.03 µM. By using a smartphone platform, the trichromatic sensor enables convenient, rapid, inexpensive, and quantitative assessment of TA. Both two sensors were successfully applied to TA detection in 9 different foods. This study not only provides an effective strategy to enhance enzyme performance but also paves the way for their applications in food testing.

Heterostructure Nanozyme with Hyperthermia-Amplified Enzyme-Like Activity and Controlled Silver Release for Synergistic Antibacterial Therapy.

Heterostructure nanozymes as antibiotic-free antimicrobial agents exhibit great potential for multidrug-resistant (MDR) bacterial strains elimination. However, realization of heterostructure antimicrobials with enhanced interfacial interaction for synergistically amplified antibacterial therapy is still a great challenge. Herein, oxygen-vacancy-enriched glucose modified MoOx (G-MoOx) is exploited as a reducing agent to spontaneously reduce Ag (I) into Ag (0) that in situ grows onto the surface of G-MoOx. The resultant Ag doped G-MoOx (Ag/G-MoOx) heterostructure displays augmenting photothermal effect and NIR-enhanced oxidase-like activity after introducing Ag nanoparticles. What's more, NIR hyperthermia accelerate Ag+ ions release from Ag nanoparticles. Introduction of Ag greatly enhances antimicrobial activities of Ag/G-MoOx against MDR bacteria, especially the hybrid loading with 1 wt% Ag NPs exhibiting antibacterial efficacy up to 99.99% against Methicillin-resistant Staphylococcus aureus (MRSA, 1×106 CFU mL-1).

Hydroxyl radical-mediated synthesis of carbonyl functionalized graphene quantum dots-like as enzyme mimics with tunable fluorescence emission

The synthesis of graphene quantum dots-like enriched with specific oxygenated groups (o-GQDs) exhibiting great catalytic performance offers a promising tool for diagnosis and biomedicine, but introducing specific oxygen groups remains a challenge. Here, we propose a mild synthetic protocol for producing regulated fluorescence emission (from blue to yellow) carbonyl functionalized GQDs with double catalytic function through Fe3O4-catalyzed hydroxyl radical (·OH) oxidation the precursors like graphene oxide, polyaniline (PANI) and polydopamine (PDA). The method can be carried out at room temperature than the traditional high-temperature oxidation in concentrated acid. Interestingly, o-GQDs exhibit excellent peroxidase (POD)- and ascorbate oxidase-like activity. XPS characterization showed a significant increase in carbonyl content in o-GQDs compared to the precursor, even a 14-fold increase in blue-emitting iron-doped GQDs (b-Fe-GQDs). The introduction of Fe3O4 during the synthesis process results in a minor degree of Fe doping, which enhances the catalytic activity of b-Fe-GQDs through coordination with N. Based on this feature, highly sensitive single-signal and ultra-selective dual-signal methods for alkaline phosphatase detection were developed. This low cost and safe synthesis strategy paves the way for practical usage of o-GQDs.

A cancer-targeted glutathione-gated probe for self-sufficient ST/CDT combination therapy and FRET-based miRNA imaging.

Acancer-targeted glutathione (GSH)-gated theranostic probe (CGT probe) for intracellular miRNA imaging and combined treatment of self-sufficient starvation therapy (ST) and chemodynamic therapy (CDT) was developed. TheCGT probe is constructed using MnO2 nanosheet (MS) as carrier material to adsorb the elaborately designed functional DNAs. It can be internalized by cancer cells via specific recognition between the AS1411 aptamer and nucleolin.After CGT probe entering the cancer cells, the overexpressed GSH, as gate-control, can degrade MS to Mn2+ which can be used for CDT by Fenton-like reaction. Simultaneously, Mn2+-mediated CDT can further cascade with the enzyme-like activities (catalase-like activity and glucose oxidase-like activity) of CGT probe, achieving self-sufficient ST/CDT synergistic therapy. Meanwhile, the anchored DNAs are released, achieving in situ signal amplification via disubstituted-catalytic hairpin assembly (DCHA) and FRET (fluorescence resonance energy transfer) imaging of miR-21. The in vitro and in vivo experiments demonstrated that accurate and sensitive miRNA detection can be achieved using the CGT probe. Overall, the ingenious CGT probe opens a new avenue for the development of early clinical diagnosis and cancer therapy.

Artificial Manganese Metalloenzymes with Laccase-like Activity: Design, Synthesis, and Characterization.

Laccase is an oxidase of great industrial interest due to its ability to catalyze oxidation processes of phenols and persistent organic pollutants. However, it is susceptible to denaturation at high temperatures, sensitive to pH, and unstable in the presence of high concentrations of solvents, which is a issue for industrial use. To solve this problem, this work develops the synthesis in an aqueous medium of a new Mn metalloenzyme with laccase oxidase mimetic catalytic activity. Geobacillus thermocatenulatus lipase (GTL) was used as a scaffold enzyme, mixed with a manganese salt at 50 °C in an aqueous medium. This leads to the in situ formation of manganese(IV) oxide nanowires that interact with the enzyme, yielding a GTL-Mn bionanohybrid. On the other hand, its oxidative activity was evaluated using the ABTS assay, obtaining a catalytic efficiency 300 times higher than that of Trametes versicolor laccase. This new Mn metalloenzyme was 2 times more stable at 40 °C, 3 times more stable in the presence of 10% acetonitrile, and 10 times more stable in 20% acetonitrile than Novozym 51003 laccase. Furthermore, the site-selective immobilized GTL-Mn showed a much higher stability than the soluble form. The oxidase-like activity of this Mn metalloenzyme was successfully demonstrated against other substrates, such as l-DOPA or phloridzin, in oligomerization reactions.