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1.
Phytochemistry ; 170: 112199, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31759269

RESUMO

The Mediterranean crop Olea europaea is often exposed to high UV-B irradiation conditions. To understand how this species modulates its enzymatic and non-enzymatic antioxidant system under high UV-B radiation, young O. europaea plants (cultivar "Galega Vulgar") were exposed, for five days, to UV-B radiation (6.5 kJ m-2 d-1 and 12.4 kJ m-2 d-1). Our data indicate that UV-doses slightly differ in the modulation of the antioxidant protective mechanisms. Particularly, superoxide dismutase (SOD), guaiacol peroxidase (GPox) and catalase (CAT) activities increased contributing to H2O2 homeostasis, being more solicited by higher UV-B doses. Also, glutathione reductase (Gr) activity, ascorbate (AsA) and reduced glutathione (GSH) pools increased particularly under the highest dose, suggesting a higher mobilization of the antioxidant system in this dose. The leaf metabolites' profile of this cultivar was analysed by UHPLC-MS. Interestingly, high levels of verbascoside were found, followed by oleuropein and luteolin-7-O-glucoside. Both UV-B treatments affected mostly less abundant flavonoids (decreasing 4'-methoxy luteolin and 4' or 3'-methoxy luteolin glucoside) and hydroxycinnamic acid derivatives (HCAds, increasing ß-hydroxyverbascoside). These changes show not only different mobilization with the UV-intensity, but also reinforce for the first time the protective roles of these minor compounds against UV-B, as reactive oxygen species (ROS) scavengers and UV-B shields, in complement with other antioxidant systems (e.g. AsA/GSH cycle), particularly for high UV-B doses. Secoiridoids also standout in the response to both UV-B doses, with decreases of oleuropein and increases 2''-methoxyoleuropein. Being oleuropein an abundant compound, data suggest that secoiridoids play a more important role than flavonoids and HCAds, in O. europaea protection against UV-B, possibly by acting as signalling molecules and ROS scavengers. This is the first report on the influence of UV-B radiation on the secoiridoid oleuropein, and provides a novel insight to the role of this compound in the O. europaea antioxidant defence mechanisms.


Assuntos
Antioxidantes/metabolismo , Flavonoides/metabolismo , Iridoides/metabolismo , Olea/enzimologia , Raios Ultravioleta , Antioxidantes/química , Catalase/química , Catalase/metabolismo , Flavonoides/química , Iridoides/química , Peroxidase/química , Peroxidase/metabolismo , Compostos Fitoquímicos/química , Compostos Fitoquímicos/metabolismo , Superóxido Dismutase/química , Superóxido Dismutase/metabolismo
2.
Proc Natl Acad Sci U S A ; 117(2): 923-930, 2020 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-31879351

RESUMO

The driving force for active physical and biological systems is determined by both the underlying landscape and nonequilibrium curl flux. While landscape can be experimentally quantified from the histograms of the collected real-time trajectories of the observables, quantifying the experimental flux remains challenging. In this work, we studied the single-molecule enzyme dynamics of horseradish peroxidase with dihydrorhodamine 123 and hydrogen peroxide (H2O2) as substrates. Surprisingly, significant deviations in the kinetics from the conventional Michaelis-Menten reaction rate were observed. Instead of a linear relationship between the inverse of the enzyme kinetic rate and the inverse of substrate concentration, a nonlinear relationship between the two emerged. We identified nonequilibrium flux as the origin of such non-Michaelis-Menten enzyme rate behavior. Furthermore, we quantified the nonequilibrium flux from experimentally obtained fluorescence correlation spectroscopy data and showed this flux to led to the deviations from the Michaelis-Menten kinetics. We also identified and quantified the nonequilibrium thermodynamic driving forces as the chemical potential and entropy production for such non-Michaelis-Menten kinetics. Moreover, through isothermal titration calorimetry measurements, we identified and quantified the origin of both nonequilibrium dynamic and thermodynamic driving forces as the heat absorbed (energy input) into the enzyme reaction system. Furthermore, we showed that the nonequilibrium driving forces led to time irreversibility through the difference between the forward and backward directions in time and high-order correlations were associated with the deviations from Michaelis-Menten kinetics. This study provided a general framework for experimentally quantifying the dynamic and thermodynamic driving forces for nonequilibrium systems.


Assuntos
Enzimas/química , Modelos Químicos , Simulação de Dinâmica Molecular , Termodinâmica , Fenômenos Químicos , Entropia , Enzimas/metabolismo , Peróxido de Hidrogênio/metabolismo , Cinética , Peroxidase/química , Peroxidase/metabolismo , Rodaminas/metabolismo
3.
Biosci Biotechnol Biochem ; 84(1): 118-125, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31516066

RESUMO

We developed an enzymatic assay system enabling easy quantification of 4-aminobutyric acid (GABA). The reaction of GABA aminotransferase obtained from Streptomyces decoyicus NBRC 13977 was combined to those of the previously developed glutamate assay system using glutamate oxidase and peroxidase. The three-enzyme system allowing GABA-dependent dye formation due to the oxidative coupling between 4-aminoantipyrine and Trinder's reagent enabled accurate quantification of 0.2 - 150 mg/L GABA. A pretreatment mixture consisting of glutamate oxidase, ascorbate oxidase and catalase eliminating glutamate, ascorbate, and hydrogen peroxide, respectively, was also prepared to remove those inhibitory substances from samples. Thus, constructed assay kit was used to measure the GABA content in tomato samples. The results were almost the same as that obtained by the conventional method using liquid chromatography-tandem mass spectrometry. The kit will become a promising tool especially for the on-site measurement of GABA content in agricultural products.


Assuntos
4-Aminobutirato Transaminase/química , Aminoácido Oxirredutases/química , Colorimetria/métodos , Ensaios Enzimáticos/métodos , Peroxidase/química , Ácido gama-Aminobutírico/análise , Ampirona/química , Ascorbato Oxidase/química , Catalase/química , Cromatografia Líquida , Ensaios Enzimáticos/economia , Compostos Férricos/química , Ácido Glutâmico/química , Peróxido de Hidrogênio/química , Lycopersicon esculentum/química , Acoplamento Oxidativo , Proteínas Recombinantes , Streptomyces/enzimologia , Espectrometria de Massas em Tandem
4.
Biochim Biophys Acta Proteins Proteom ; 1868(1): 140249, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31295557

RESUMO

Human peroxidasin 1 is a multidomain peroxidase situated in the basement membrane. The iron enzyme with covalently bound heme oxidizes bromide to hypobromous acid which facilitates the formation of distinct sulfilimine cross-links in the collagen IV network and therefore contributes to its mechanical stability. Additional to the catalytically active peroxidase domain peroxidasin comprises a leucine rich repeat domain, four Ig domains and a C-terminal von Willebrand factor type C module (VWC). Peroxidasin has been shown to form homotrimers involving two redox-sensitive cysteine residues and to undergo posttranslational C-terminal proteolytic cleavage. The present study on several recombinantly produced truncated peroxidasin variants showed that the VWC is not required for trimer formation whereas the alpha-helical linker region located between the peroxidase domain and the VWC is crucial for trimerization. Our data furthermore implies that peroxidasin oligomerization occurs intracellularly before C-terminal cleavage. For the first time we present overall solution structures of monomeric and trimeric truncated peroxidasin variants which were determined by rotary shadowing combined with transmission electron microscopy and by small-angle X-ray scattering (SAXS). A triangular arrangement of the peroxidase domains to each other within the homotrimer was revealed and this structure was confirmed by a model of trimeric peroxidase domains. Our SAXS data showed that the Ig domains are highly flexible and interact with the peroxidase domain and that within the homotrimer each alpha-helical linker region interacts with the respective adjacent peroxidase domain. The implications of our findings on the structure-function relationship of peroxidasin are discussed.


Assuntos
Proteínas da Matriz Extracelular/química , Peroxidase/química , Multimerização Proteica , Proteínas da Matriz Extracelular/genética , Humanos , Modelos Moleculares , Peroxidase/genética , Proteínas Recombinantes/química
5.
Anal Bioanal Chem ; 412(4): 963-972, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31853600

RESUMO

In this study, palladium/carbon dot composites (Pd-CDs) were fabricated via a facial hydrothermal route using ethanediamine and palladium chloride dihydrate as precursors. The obtained Pd-CDs showed an excellent intrinsic peroxidase-like activity, which could catalyze the oxidization of 3,3'5,5'-tetramethylbenzidine with the assistance of hydrogen peroxide (H2O2) and thus resulted in color change, accompanied by an absorption peak which appeared at 652 nm. Such response is H2O2 concentration-dependent and allows for the assay of H2O2 in the range of 0.1 to 30 µM with a limit of detection of 0.03 µM. Simultaneously, by combination of enzymatic oxidation of glucose with glucose oxidase and Pd-CD catalytic reaction, a colorimetric sensing platform was also constructed for glucose detection with high selectivity and sensitivity (limit of detection as low as 0.2 µM). Additionally, the proposed method exhibited capability for determination of glucose in real samples (fruit juice) with satisfactory recovery (98.5-103%), indicating potential application prospects in biochemical analysis.


Assuntos
Carbono/química , Glucose/análise , Peróxido de Hidrogênio/análise , Paládio/química , Benzidinas/química , Materiais Biomiméticos/química , Técnicas Biossensoriais/métodos , Colorimetria/métodos , Análise de Alimentos/métodos , Sucos de Frutas e Vegetais/análise , Limite de Detecção , Oxirredução , Peroxidase/química
6.
Anal Bioanal Chem ; 412(4): 861-870, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31865416

RESUMO

In this paper, we report the use of a smartphone and B, N, and S co-doped carbon dots (BNS-CDs) as a promising peroxidase mimic to quantify hydrogen peroxide (H2O2). The synthesized BNS-CDs exhibited excellent peroxidase-like activity to catalyze the reaction of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) with H2O2 to generate a blue oxide product (ox-TMB) with maximum absorption at 652 nm. Steady-state kinetic analysis demonstrated that the BNS-CDs showed much higher affinity than natural horseradish peroxidase (HRP) for H2O2 due to their small size and larger specific surface area. A smartphone colorimetric readout device was employed to record the RGB (red green blue) value of the ox-TMB solution via the Android application Color Grab for quantitative detection. A good linear relationship (R2 = 0.9970) between the H2O2 concentration and |R-Rblank| value was obtained in the range of 3-30 µM with a limit of detection (LOD) of 0.8 µM. The current method was successfully applied to determine H2O2 in mouthwash and milk with recoveries of 92.70-108.30%. The developed assay is a promising portable detection platform for H2O2 with good sensitivity and selectivity, simple operation, fast response, and low cost. Graphical abstract.


Assuntos
Carbono/química , Colorimetria/instrumentação , Peróxido de Hidrogênio/análise , Leite/química , Antissépticos Bucais/análise , Animais , Benzidinas/química , Materiais Biomiméticos/química , Catálise , Desenho de Equipamento , Análise de Alimentos/instrumentação , Limite de Detecção , Peroxidase/química , Smartphone/instrumentação
7.
Nanoscale ; 11(39): 18393-18406, 2019 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-31573583

RESUMO

Iron oxide nanoparticles (IONPs) are frequently used in biomedical applications due to their magnetic properties and putative chemical stability. Nevertheless, their well-known ability to mimic some features of the peroxidase enzyme activity under specific conditions of pH and temperature could lead to the formation of potentially harmful free radical species. In addition to the intrinsic enzyme-like activity of IONPs, the buffer solution is an important external factor that can alter dramatically the IONP activity because the buffer species can interact with the surface of the particles. In our study, IONP activity was evaluated in different buffering solutions under different experimental conditions and predominant free radical species were measured by electron paramagnetic resonance using the spin-trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The formation kinetics of the reactive oxygen species were studied by UV-visible spectroscopy with TMB and DAB peroxidase substrates. We found that the highest catalytic oxidation of peroxidase substrates and free radical generation were achieved in acetate buffer, while phosphate buffer inhibited the peroxidase-like activity of IONPs in a concentration dependent manner. When emulating the physiological conditions, a lower catalytic activity was observed at pH 7.4 when compared to that at pH 5.0. Also, in phosphate buffered saline (PBS), we observed an enhancement in the peroxidase substrate oxidation rate that was not accompanied by an increase in DMPO/adduct formation which could be related to a non-specific oxidation catalyzed by the chloride ion. Similar observations were found after the addition of a bicarbonate to HEPES buffer. TMB oxidation did not occur when the reaction was conducted with free iron ions from metal salts with the same concentration of the IONPs (0.33 Fe2+ and 0.66 Fe3+). However, we observed even higher catalytic activities than those when doubling the IONP concentration when they are combined with the free iron salts. These results indicate that biological buffering solutions need to be carefully considered when evaluating IONP catalytic activity and their potential toxicological effects since under physiological conditions of pH, salinity and buffering species, the peroxidase-like activity of IONPs is dramatically reduced.


Assuntos
Nanopartículas de Magnetita/química , Peroxidase/química , Espécies Reativas de Oxigênio/química , Tampões (Química) , Espectroscopia de Ressonância de Spin Eletrônica , Oxirredução
8.
Mater Sci Eng C Mater Biol Appl ; 104: 110000, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499984

RESUMO

Nanomaterials with enzyme-like activity have attracted much attention recently. Herein, we report the synthesis of a new type of 2D MXene-Ti3C2/CuS nanocomposites with peroxidase-like activity using a simple hydrothermal approach. Significantly, compared with the individual MXene-Ti3C2 nanosheets or CuS nanoparticles, the MXene-Ti3C2/CuS nanocomposites show a synergistically enhanced peroxidase-like activity and can be used as an efficient mimetic peroxidase to catalyze the reaction of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), causing a blue color change. Kinetic studies reveal that the MXene-Ti3C2/CuS nanocomposites have a higher catalytic activity to TMB than their single components, and the catalytic reaction follows the ping-pong mechanism. The MXene-Ti3C2/CuS nanocomposites are used for the colorimetric determination of cholesterol with a linear range of 10-100 µM and a limit of detection (LOD) of 1.9 µM. Our results show that the MXene-Ti3C2/CuS nanocomposites based colorimetric cholesterol biosensor is cost-effective, sensitive, and selective, which has potential application in H2O2 and cholesterol detection and clinic medicine diagnostics.


Assuntos
Colesterol/química , Cobre/química , Nanocompostos/química , Nanopartículas/química , Peroxidase/química , Titânio/química , Benzidinas/química , Técnicas Biossensoriais/métodos , Catálise/efeitos dos fármacos , Colorimetria/métodos , Peróxido de Hidrogênio/química , Cinética , Limite de Detecção , Oxirredução , Peroxidases/química
9.
Molecules ; 24(16)2019 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-31395798

RESUMO

The micro sequential injection analysis / lab-on-valve (µSIA-LOV) system is a miniaturized SIA system resulting from the implementation of a lab-on-valve (LOV) atop of the selection valve. It integrates the detection cell and the sample processing channels into the same device, promoting the reduction of reagent consumption and waste generation, the improvement of the versatility, and the reduction of the time of analysis. All of these characteristics are really relevant to the implementation of enzymatic reactions. Additionally, the evaluation of cholesterol in serum samples is widely relevant in clinical diagnosis, since higher values of cholesterol in human blood are actually an important risk factor for cardiovascular problems. An automatic methodology was developed based on the µSIA-LOV system in order to evaluate its advantages in the implementation of enzymatic reactions performed by cholesterol esterase, cholesterol oxidase and peroxidase. Considering these reactions, the developed methodology was also used for the evaluation of cholesterol in human serum samples, showing reliable and accurate results. The developed methodology presented detection and quantification limits of 1.36 and 4.53 mg dL-1 and a linear range up to 40 mg dL-1. This work confirmed that this µSIA-LOV system is a simple, rapid, versatile, and robust analytical tool for the automatic implementation of enzymatic reactions performed by cholesterol esterase, cholesterol oxidase, and peroxidase. It is also a useful alternative methodology for the routine determinations of cholesterol in real samples, even when compared with other automatic methodologies.


Assuntos
Colesterol Oxidase/química , Colesterol/sangue , Dispositivos Lab-On-A-Chip , Peroxidase/química , Esterol Esterase/química , Humanos , Limite de Detecção
10.
Chem Commun (Camb) ; 55(66): 9865-9868, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31364624

RESUMO

Au hydrogel with a well-defined nanowire network was rationally designed through one-step dopamine-induced self-assembly. Due to the porous nanostructure along with the polydopamine induced accumulation and interfacial electron transfer effects, the resulting Au hydrogel nanozyme exhibits enhanced glucose oxidase-like activity and peroxidase-like activity, with a biomimetic cascade catalysis.


Assuntos
Biomimética , Dopamina/química , Glucose Oxidase/química , Ouro/química , Hidrogéis/química , Nanopartículas Metálicas/química , Peroxidase/química , Catálise , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Oxirredução
11.
ACS Appl Mater Interfaces ; 11(34): 30542-30550, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31362494

RESUMO

Biodegradation is a mild and efficient way to protect humans and animals from mycotoxins. However, microbes and enzymes are susceptible to environmental change, lack of stability, and reusability. In this work, three peroxidase-like metal-organic frameworks (MOFs), as artificial substitutes of natural peroxidase, are used for aflatoxin B1 (AFB1) removal, demonstrating the strong removal ability for AFB1 and anti-interference ability toward other substances. There are distinct adsorption and catalytic properties among these MOFs that are mainly because of the differences in structure and Fe ion active sites. Then, we immobilized these MOFs into ultrafiltration membranes to form a multifunctional membrane (i.e., filtration, adsorption, and catalysis) for AFB1 removal with good reusability that can be operated in simultaneous adsorption/catalysis or adsorption followed by catalysis/regeneration modes. Physicochemical analysis and animal experiments showed that the degradation products are probably several low-carbon substances whose toxic groups are cleaved.


Assuntos
Aflatoxina B1 , Membranas Artificiais , Estruturas Metalorgânicas , Peroxidase , Aflatoxina B1/química , Aflatoxina B1/toxicidade , Animais , Catálise , Humanos , Masculino , Estruturas Metalorgânicas/química , Estruturas Metalorgânicas/farmacologia , Camundongos , Camundongos Endogâmicos ICR , Peroxidase/química , Peroxidase/farmacologia
12.
Prep Biochem Biotechnol ; 49(10): 1033-1039, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31407950

RESUMO

In many occasions it is necessary to use fast and simple methods, different to the chromatographic techniques, for the quantification of biomolecules such as flavonoids. Also, the flavonoid levels in some foodstuffs can be influenced by industrial extraction processes such as pressing and squeezing, resulting in modification of their functional value. For this purpose, we have developed a rapid method to analyze flavonoids, based on a coupling reaction between ABTS and flavonoid mediated by peroxidase. The present method can be used to detect and measure flavonoids with hydroxyl moieties on A- or B-rings, not adjacent to methoxy or oxo substitutions. The visible spectrum of the ABTS-flavonoid complex, the calibration curve (within the range 5-50 µM) and the molar absorption coefficients for isosakuranetin, isonaringin, rhoifolin, hyperoside, rutin, hesperetin, quercetin, kaempherol and naringenin are given. The method has been applied to complex culture media and is sensitive, accurate, quick and easy to apply. This method can be used in laboratories that do not have sophisticated and expensive techniques such as liquid chromatography and also as a quick, simple and inexpensive technique for student practice laboratories.


Assuntos
Benzotiazóis/química , Colorimetria/métodos , Flavonoides/análise , Peroxidase/química , Ácidos Sulfônicos/química , Cromatografia Líquida de Alta Pressão
13.
J Appl Oral Sci ; 27: e20180453, 2019 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-31411261

RESUMO

OBJECTIVE: This study was designed for the chemical activation of a 35% hydrogen peroxide (H2O2) bleaching gel to increase its whitening effectiveness and reduce its toxicity. METHODOLOGY: First, the bleaching gel - associated or not with ferrous sulfate (FS), manganese chloride (MC), peroxidase (PR), or catalase (CT) - was applied (3x 15 min) to enamel/dentin discs adapted to artificial pulp chambers. Then, odontoblast-like MDPC-23 cells were exposed for 1 h to the extracts (culture medium + components released from the product), for the assessment of viability (MTT assay) and oxidative stress (H2DCFDA). Residual H2O2 and bleaching effectiveness (DE) were also evaluated. Data were analyzed with one-way ANOVA complemented with Tukey's test (n=8. p<0.05). RESULTS: All chemically activated groups minimized MDPC-23 oxidative stress generation; however, significantly higher cell viability was detected for MC, PR, and CT than for plain 35% H2O2 gel. Nevertheless, FS, MC, PR, and CT reduced the amount of residual H2O2 and increased bleaching effectiveness. CONCLUSION: Chemical activation of 35% H2O2 gel with MC, PR, and CT minimized residual H2O2 and pulp cell toxicity; but PR duplicated the whitening potential of the bleaching gel after a single 45-minute session.


Assuntos
Peróxido de Hidrogênio/química , Peróxido de Hidrogênio/toxicidade , Clareadores Dentários/química , Clareadores Dentários/toxicidade , Clareamento Dental/métodos , Análise de Variância , Catalase/química , Sobrevivência Celular , Células Cultivadas , Cloretos/química , Cor , Polpa Dentária/química , Polpa Dentária/diagnóstico por imagem , Dentina/química , Dentina/efeitos dos fármacos , Compostos Ferrosos/química , Compostos de Manganês/química , Odontoblastos/efeitos dos fármacos , Peroxidase/química , Valores de Referência , Reprodutibilidade dos Testes , Estatísticas não Paramétricas , Fatores de Tempo
14.
Analyst ; 144(18): 5455-5461, 2019 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-31432811

RESUMO

Over the past few years, artificial enzymes have attracted enormous attention due to their high stabilities and cost-effective productions. In this work, metal-organic framework-derived SiW12@Co3O4 was synthesized in large quantities by stirring the mixture at ambient temperature and calcination. The obtained SiW12@Co3O4 exhibited a highly inherent peroxidase-like activity and excellent stability. Kinetic studies demonstrated that the synthesized SiW12@Co3O4 had a strong binding affinity to 3,3',5,5'-tetramethylbenzidine (TMB), stronger than HRP had. Specifically, the peroxidase-like activity of SiW12@Co3O4 in an aqueous solution was well maintained after incubation at an elevated temperature, at an extreme pH and for a long time. A SiW12@Co3O4-based method was further developed for H2O2 and one-pot glucose detection with good sensitivity and reliability. The facile synthesis approach is expected to facilitate the practical use of metal-organic frameworks and their derivatives as enzyme mimics in the future.


Assuntos
Glucose/análise , Peróxido de Hidrogênio/análise , Estruturas Metalorgânicas/química , Benzidinas/química , Colorimetria/métodos , Glucose/química , Glucose Oxidase/química , Peróxido de Hidrogênio/química , Limite de Detecção , Estruturas Metalorgânicas/síntese química , Oxirredução , Peroxidase/química
15.
Chemistry ; 25(51): 11940-11944, 2019 Sep 12.
Artigo em Inglês | MEDLINE | ID: mdl-31317582

RESUMO

In addition to superior enzyme-mimicking abilities, nanozymes also have intrinsic physicochemical properties. Integrating the enzyme-like activities and tunable physicochemical properties into a single nanoparticle is a promising strategy for versatile nanozyme design and application. Herein, a composite nanozyme in which Au nanoparticles are encapsulated by Au nanoclusters (AuNP@AuNCs) is presented. By integrating the peroxidase-mimicking ability of fluorescent Au NCs with the glucose oxidase-like activity of Au NPs, the composite nanozyme realized cascade assay of glucose without the aid of external indicators. Compared to traditional multistep colorimetric methods, the analytical process was highly simplified by using the self-responsive nanozyme. This synthetic strategy provided valuable insights into exploring talented nanozymes for sensing diverse targets.


Assuntos
Glucose Oxidase/química , Glucose/metabolismo , Ouro/química , Nanopartículas Metálicas/química , Peroxidase/química , Colorimetria/métodos , Glucose/química , Glucose Oxidase/metabolismo
16.
Analyst ; 144(15): 4472-4476, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31257395

RESUMO

RNA G-quadruplexes (rG4s) are important RNA secondary structures considering their significance in regulating numerous cellular processes. Described herein is an rG4 detecting and isolation method, which exploits the complex of rG4 and hemin to mimic peroxidase. In the presence of biotin tyramide and hydrogen peroxide, rG4s can be selectively self-biotinylated and easily isolated from a complex RNA mixture using streptavidin magnetic beads.


Assuntos
Quadruplex G , RNA Catalítico/isolamento & purificação , Materiais Biomiméticos/química , Materiais Biomiméticos/isolamento & purificação , Biotina/análogos & derivados , Biotina/química , Biotinilação , Catálise , Hemina/química , Peróxido de Hidrogênio/química , Fenômenos Magnéticos , Mutação , Oxirredução , Peroxidase/química , RNA Catalítico/química , RNA Catalítico/genética , Estreptavidina/química , Tiramina/análogos & derivados , Tiramina/química
17.
Biosens Bioelectron ; 142: 111495, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31310943

RESUMO

Due to robustness, easy large-scale preparation and low cost, nanomaterials with enzyme-like characteristics (defined as 'nanozymes') are attracting increasing interest for various applications. However, most of currently developed nanozymes show much lower activity in comparison with natural enzymes, and the deficiency greatly hinders their use in sensing and biomedicine. Single-atom catalysts (SACs) offer the unique feature of maximum atomic utilization, providing a potential pathway to improve the catalytic activity of nanozymes. Herein, we propose a Fe-N-C single-atom nanozyme (SAN) that exhibits unprecedented peroxidase-mimicking activity. The SAN consists of atomically dispersed Fe─Nx moieties hosted by metal-organic frameworks (MOF) derived porous carbon. Thanks to the 100% single-atom active Fe dispersion and the large surface area of the porous support, the Fe-N-C SAN provided a specific activity of 57.76 U mg-1, which was almost at the same level as natural horseradish peroxidase (HRP). Attractively, the SAN presented much better storage stability and robustness against harsh environments. As a proof-of-concept application, highly sensitive biosensing of butyrylcholinesterase (BChE) activity using the Fe-N-C SAN as a substitute for natural HRP was further verified.


Assuntos
Materiais Biomiméticos/química , Técnicas Biossensoriais/métodos , Butirilcolinesterase/análise , Carbono/química , Estruturas Metalorgânicas/química , Peroxidase/química , Animais , Catálise , Cavalos , Ferro/química , Porosidade
18.
Talanta ; 204: 278-284, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357294

RESUMO

Two-dimensional WO3 nanosheets were prepared by ultrasonic exfoliation of bulk WO3·2H2O in water and characterized by transmission electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman, dynamic light scattering. The nanosheets were discovered to possess the peroxidase-like catalytic activity, which can catalyze the oxidation of 3, 3', 5, 5'-tetramethylbenzidine by H2O2. The catalytic mechanism was also investigated by the scavenger experiments. Taking advantage of the peroxidase-like activity of WO3 nanosheets, a facile colorimetric method for xanthine was developed by combining the oxidation reaction of xanthine catalyzed by xanthine oxidase. The linear range for xanthine was ranged from 25 to 200 µmol L-1. The limit of detection for xanthine was 1.24 µmol L-1. The colorimetric method was applied to determine xanthine in urine samples.


Assuntos
Colorimetria/métodos , Nanoestruturas/química , Óxidos/química , Tungstênio/química , Xantina/urina , Animais , Benzidinas/química , Materiais Biomiméticos/química , Catálise , Bovinos , Compostos Cromogênicos/química , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Oxirredução , Peroxidase/química , Xantina/química , Xantina Oxidase/química
19.
Talanta ; 204: 285-293, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357295

RESUMO

To obtain sensitive analytical detection methods, many unique materials have been developed and made them promising candidates for biosensing. In this study, a type of core-shell gold nanorods, GNR@Au2S/AuAgS/CuS, possessing peroxidase-like activity was prepared in a simple, facile manner. A colorimetric strategy for detection of blood glucose, insulin and differentiating type 1 and type 2 diabetes was developed based on the unique GNR@Au2S/AuAgS/CuS. The sensitive colorimetric approach for detection of glucose in the dynamic range of 2.5-200 µM was first established based on the catalytic performance of GNR@Au2S/AuAgS/CuS. Meanwhile, the catalytic activity of the peroxidase-like GNR@Au2S/AuAgS/CuS can be regulated by introducing the high affinity and specific reaction between DNA aptamer and insulin on the surface of GNR@Au2S/AuAgS/CuS, which allows the colorimetric assay to be extended to the detection of insulin, and a quantitative analysis of insulin based on the specific recognition can be implemented at the range from 0.014 to 1.08 µU/mL. Furthermore, colorimetric approach coupling peroxidase-like performance and specific recognition on the surface of GNR@Au2S/AuAgS/CuS nanoparticles was developed to measure glucose/insulin ratio and directly differentiate type 1 and type 2 diabetes mellitus. Practical human serum samples were tested and only the glucose/insulin ratio greater than 2.2 (µU/mL) may lead to the appearance of color change. The coupling of this different bioassay on the same nanoparticles reflects the versatility and integration characteristics of the colorimetric assay and is highly promising for improving diabetes management.


Assuntos
Glicemia/análise , Colorimetria/métodos , Insulina/sangue , Nanotubos/química , Animais , Aptâmeros de Nucleotídeos/química , Benzidinas/química , Materiais Biomiméticos/química , Glicemia/química , DNA/química , Diabetes Mellitus Tipo 1/diagnóstico , Diabetes Mellitus Tipo 2/diagnóstico , Diagnóstico Diferencial , Glucose Oxidase/química , Ouro/química , Humanos , Peróxido de Hidrogênio , Insulina/química , Peroxidase/química , Suínos
20.
Anal Chim Acta ; 1078: 119-124, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358209

RESUMO

In this work, CaF2 nanoparticles were successfully synthesized by a simple direct precipitation method and firstly used as a peroxidase mimics for rapid and high sensitive colorimetric detection of aldosterone. The CaF2 nanoparticles were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD). The CaF2 nanoparticles can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product oxidized TMB (oxTMB) in the presence of H2O2 and this peroxidase-like activity of CaF2 is found out to follow Michaelis-Menten kinetics. Experiments showed that the catalytic mechanism of CaF2 nanoparticles was attributed to that it could result in the decomposition of H2O2 to produce hydroxyl radicals (•OH). The absorbance change value of the reaction system was linear with the aldosterone concentration in the range of 2.0-40.0 nM, and the detection limit was 0.6 nM. Moreover, the developed method was applied to detect aldosterone in human serum samples. It provides a new platform for enzyme functional simulation and analytical sensing research.


Assuntos
Aldosterona/sangue , Materiais Biomiméticos/química , Fluoreto de Cálcio/química , Nanopartículas Metálicas/química , Benzidinas/química , Materiais Biomiméticos/síntese química , Fluoreto de Cálcio/síntese química , Catálise , Colorimetria/métodos , Humanos , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Cinética , Limite de Detecção , Modelos Químicos , Oxirredução , Peroxidase/química , Temperatura
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