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1.
Food Chem ; 317: 126361, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32070846

RESUMO

A rapid, sensitive, and highly selective method for determining nitrite in food has been developed. This method is based on the reaction of nitrite with the amino group of 3,3,5,5-tetramethylbenzidine (TMB) to form a diazonium salt, and then the diazonium salt and glucosamine hydrochloride are coupled to each other to form an orange compound. The optimal conditions for maximum color and other analytical parameters were studied. A colorimetric method for nitrite detection has been developed with an outstanding correlation coefficient (R2 = 0.9944), a wide linear range (1-75 µM) and 0.73 µM limit of detection (at S/N = 3) for nitrite ions. This method was successfully applied to the determination of nitrite in a variety of foods and gave recoveries in the range between 100.16% and 103.07%, demonstrating that the accuracy, reliability and potential application of this assay for monitoring nitrite in foods.


Assuntos
Benzidinas/química , Análise de Alimentos/métodos , Nitritos/análise , Colorimetria/métodos , Glucosamina/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Nitritos/química , Reprodutibilidade dos Testes
2.
N Biotechnol ; 54: 71-79, 2020 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-31473254

RESUMO

The heme domain of cytochrome P450 116B5 from Acinetobacter radioresistens (P450 116B5hd), a self-sufficient class VII P450, was functionally expressed in Escherichia coli, purified and characterised in active form. Its unusually high reduction potential (-144 ±â€¯42 mV) and stability in the presence of hydrogen peroxide make this enzyme a good candidate for driving catalysis with the so-called peroxide shunt, avoiding the need for a reductase and the expensive cofactor NAD(P)H. The enzyme is able to carry out the peroxide-driven hydroxylation of aromatic compounds such as p-nitrophenol (KM = 128.85 ±â€¯29.51 µM and kcat = 2.65 ±â€¯0.14 min-1), 10-acetyl-3,7-dihydroxyphenoxazine (KM = 6.01 ±â€¯0.32 µM and kcat = 0.33 ±â€¯0.03 min-1), and 3,5,3',5'tetramethylbenzidine (TMB). Moreover, it catalyses different reactions on well-known drugs such as hydroxylation of diclofenac (KM = 49.60 ±â€¯6.30 µM and kcat = 0.06 ±â€¯0.01 min-1) and N-desmethylation of tamoxifen (KM = 57.20 ±â€¯7.90 µM and kcat = 0.79 ±â€¯0.04 min-1). The data demonstrate that P450 116B5hd is an efficient biocatalyst for sustainable applications in bioremediation and human drug metabolite production.


Assuntos
Acinetobacter/enzimologia , Benzidinas/metabolismo , Biocatálise , Sistema Enzimático do Citocromo P-450/metabolismo , Nitrofenóis/metabolismo , Oxazinas/metabolismo , Peróxidos/metabolismo , Benzidinas/química , Sistema Enzimático do Citocromo P-450/química , Sistema Enzimático do Citocromo P-450/isolamento & purificação , Escherichia coli/metabolismo , Heme/química , Heme/metabolismo , Estrutura Molecular , Nitrofenóis/química , Oxazinas/química , Oxirredução , Peróxidos/química
3.
Talanta ; 206: 120250, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514846

RESUMO

The development of a simple and economical spectrophotometric system based on the use of a device created by 3D printing and the electronics necessary to control the intensity of the radiation source was described. The measurements are made with a low-cost digital webcam. The entire system is only powered through the USB outputs of a computer, which makes the portable and really practical system for the measurements in the field. This method was applied to determine iron (II) in waters using o-phenanthroline as chromogenic reagent giving a red complex, and also to hypochlorite determination using tetramethylbenzidine as the reagent providing a yellow color. The calibration curves were built using a mathematical algorithm making a RGB deconvolution. The intense of colors obtained from a webcam in each concentration of analyte had a relationship with the absorbance values. In order to confirm the accuracy and precision of this method, a traditional spectrophotometer was used for validation.


Assuntos
Computadores , Fotografação/instrumentação , Impressão Tridimensional , Espectrofotometria/instrumentação , Benzidinas/química , Calibragem , Ácido Hipocloroso/análise , Ferro/análise , Limite de Detecção , Fenantrolinas/química , Espectrofotometria/métodos
4.
Talanta ; 206: 120211, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514873

RESUMO

Urinary glucose determination using a glucose test strip is simple and convenient in daily self-monitoring of diabetes. However, diabetic patients exhibit acquired impaired color vision (ICV), which results in the inability to discriminate between hues. Even with the assistance of a color chart, it is still not easy for these patients to read the urinary glucose results with the naked eye. In this study, a smartphone camera using an image-based colorimetric detection method was successfully developed for quantitative analysis of urine glucose. A horseradish peroxidase-hydrogen peroxide-3,3'5,5'-tetramethylbenzidine (HRP-H2O2-TMB) system was optimized for a reliable and gradual color fading process via a glucose oxidase (GOD) catalyzed oxidation reaction. The color changes of the peroxidase-H2O2 enzymatic reactions in the 96-well microplate were captured by a smartphone RGB camera with subsequent detection of red, green, and blue (RGB) intensities decreasing at each image pixel. The highly quantitative relationships between the glucose concentrations and the color characteristic values of the blue channel of the captured images were successfully established. The high accuracy of this method was demonstrated in urine glucose measurements with a linear response over the 0.039 mg mL-1 to 10.000 mg mL-1 glucose concentration range and a 0.009 mg mL-1 detection limit. The method has great potential as a point-of-need platform for diabetic patients with defective color vision and features high accuracy and low cost.


Assuntos
Diabetes Mellitus/urina , Glucose/análise , Glicosúria/diagnóstico , Smartphone , Armoracia/enzimologia , Benzidinas/química , Compostos Cromogênicos/química , Colorimetria/métodos , Glucose/química , Glucose Oxidase/química , Peroxidase do Rábano Silvestre/química , Humanos , Peróxido de Hidrogênio/química , Limite de Detecção , Fotografação/instrumentação , Testes Imediatos
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.
Anal Chim Acta ; 1093: 150-159, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31735208

RESUMO

As a powerful tool for medical diagnosis and bioanalysis, conventional optical spectrometers are generally expensive, bulky and always require an accompanying data processing device. In this work, we developed a novel smartphone-based CD-spectrometer (SCDS) for high sensitive and ultra-portable colorimetric analysis, with the advantage of cost-effective and simplicity. The distance between the light source and slit, the structure of SCDS and the parameters of camera in the smartphone were all optimized to ensure the best analytical performance. Besides, the SCDS employed HSV color model and utilized the overall intensity calculated by summing V-value of adjacent position for the absorbance measurement. In this way the errors caused by the low resolution of CD-grating can effectively be eliminated to promote the sensitivity of the SCDS. The performance of the SCDS was first validated for colorimetric detection of BSA with a detection limit of 0.0073 mg/mL, which is superior compared to that of the microtiter plate reader (MTPR). Moreover, by combining with 3,3',5,5'-tetramethylbenzidine-manganese dioxide (TMB-MnO2) nanosheets reaction, a high sensitive and specific system for ascorbic acid detection was established. The SCDS gives a detection range from 0.6250 µM to 40 µM with a detection limit of 0.4946 µM for AA detection. Compared to other studies, the SCDS features wide detection range and very low detection limit with low cost instrument. Therefore, the SCDS will be an ideal and promising colorimetric system for point-of-care (POC) application in food security, disease diagnosis and environmental monitoring.


Assuntos
Ácido Ascórbico/análise , Colorimetria/métodos , Discos Compactos , Smartphone , Análise Espectral/métodos , Animais , Benzidinas/química , Bebidas/análise , Bovinos , Colorimetria/instrumentação , Desenho de Equipamento , Limite de Detecção , Compostos de Manganês/química , Nanoestruturas/química , Óxidos/química , Testes Imediatos , Soroalbumina Bovina/análise , Análise Espectral/instrumentação
8.
Chemphyschem ; 21(5): 450-458, 2020 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-31875355

RESUMO

Experimental and kinetic modelling studies are presented to investigate the mechanism of 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by hydrogen peroxide (H2 O2 ) catalyzed by peroxidase-like Pt nanoparticles immobilized in spherical polyelectrolyte brushes (SPB-Pt). Due to the high stability of SPB-Pt colloidal, this reaction can be monitored precisely in situ by UV/VIS spectroscopy. The time-dependent concentration of the blue-colored oxidation product of TMB expressed by different kinetic models was used to simulate the experimental data by a genetic fitting algorithm. After falsifying the models with abundant experimental data, it is found that both H2 O2 and TMB adsorb on the surface of Pt nanoparticles to react, indicating that the reaction follows the Langmuir-Hinshelwood mechanism. A true rate constant k, characterizing the rate-determining step of the reaction and which is independent on the amount of catalysts used, is obtained for the first time. Furthermore, it is found that the product adsorbes strongly on the surface of nanoparticles, thus inhibiting the reaction. The entire analysis provides a new perspective to study the catalytic mechanism and evaluate the catalytic activity of the peroxidase-like nanoparticles.


Assuntos
Benzidinas/química , Peróxido de Hidrogênio/química , Nanopartículas Metálicas/química , Platina/química , Polieletrólitos/química , Catálise , Cinética , Estrutura Molecular , Oxirredução , Tamanho da Partícula , Propriedades de Superfície
9.
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
10.
J Agric Food Chem ; 67(34): 9658-9666, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31381330

RESUMO

The biomimetic enzyme-linked immunosorbent assay (BELISA) is widely used for detection of small-molecule compounds as a result of low cost and reagent stability of molecularly imprinted polymers (MIPs). However, enzyme labels used in BELISA still suffer some drawbacks, such as high production cost and limited stability. To overcome the drawbacks, a biomimetic nanozyme-linked immunosorbent assay (BNLISA) based on MIPs and nanozyme labels was first proposed. For nanozyme labels, platinum nanoparticles (PtNPs) acted as peroxidase by catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) into an ideal surface-enhanced Raman scattering (SERS) marker. Blue TMB2+ and bovine serum albumin (BSA)-hapten showed superior selectivity when competing with targets for binding sites on MIPs, named the Pt@BSA-hapten probe. The BNLISA method was employed to detect triazophos with a limit of detection of 1 ng mL-1 via colorimetric and SERS methods. Replacing traditional enzymes with nanozymes for combination with MIPs may bring about a new prospect for other compound analyses.


Assuntos
Colorimetria/métodos , Organotiofosfatos/análise , Praguicidas/análise , Análise Espectral Raman/métodos , Triazóis/análise , Benzidinas/química , Materiais Biomiméticos/química , Colorimetria/instrumentação , Frutas/química , Ouro/química , Imunoadsorventes/química , Nanopartículas Metálicas/química , Platina/química , Pyrus/química , Sensibilidade e Especificidade , Análise Espectral Raman/instrumentação , Poluentes Químicos da Água/análise
11.
Biosens Bioelectron ; 142: 111565, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31404878

RESUMO

We investigated sequence-specific and simultaneous microRNA (miRNA) detections by surface plasmon resonance (SPR) imaging measurements on SPR chips possessing an Au spot array modified with probe DNAs based on a miRNA-detection-selective SPR signal amplification method. MiRNAs were detected with the detection limit of the attomole level by SPR imaging measurements for different miRNA concentrations on a single chip. SPR signals were enhanced based on a combination process of sequence-specific hybridization of the miRNA to the probe DNAs, extension reaction of polyadenine (poly(A)) tails by poly(A) polymerase, binding of a ternary complex of T30-biotin/horseradish peroxidase (HRP)-biotin/streptavidin to the poly(A) tails, and the oxidation reaction of tetramethylbenzidine (TMB) on the HRP by providing a blue precipitate on the surface. This process sequence-specifically and dramatically amplified the SPR signals. This is a simple, cost-effective, and feasible signal amplification method based on the organic compound TMB instead of metal nanoparticles.


Assuntos
MicroRNAs/análise , Ressonância de Plasmônio de Superfície/instrumentação , Benzidinas/química , Sondas de DNA/química , Desenho de Equipamento , Humanos , Limite de Detecção , Hibridização de Ácido Nucleico , Análise de Sequência com Séries de Oligonucleotídeos/instrumentação
12.
Analyst ; 144(17): 5284-5291, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31372627

RESUMO

5,10,15,20-Tetrakis(4-carboxyl phenyl)porphyrin (Por) modified Co(OH)2 deposited on the surface of GO nanocomposites (Por/Co(OH)2/GO) were prepared and characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and XRD. For the first time, H2TCPP/Co(OH)2/GO is found to have enhanced peroxidase-like activity and catalyze the oxidation of the substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2). Notably, the colorless TMB rapidly transformed into blue oxTMB in just 60 s, which was easily observed visually. The catalytic kinetics of H2TCPP/Co(OH)2/GO is in accord with the Michaelis-Menten equation. The catalytic mechanism of H2TCPP/Co(OH)2/GO nanocomposites is attributed to hydroxyl radicals (˙OH), due to decomposition of H2O2, which is verified by using terephthalic acid as a fluorescent probe. What's more, H2O2 can be detected in a wide linear detection range from 5 to 35 mM with a detection limit of 0.385 mM. Furthermore, based on the excellent peroxidase-like activity of H2TCPP/Co(OH)2/GO, a colorimetric sensor is established to sensitively detect glutathione (GSH) in a linear range from 10 to 300 µM with a low detection limit of 9.5 µM.


Assuntos
Cobalto/química , Grafite/química , Hidróxidos/química , Nanocompostos/química , Peroxidases/química , Porfirinas/química , Benzidinas/química , Materiais Biomiméticos , Técnicas Biossensoriais/métodos , Catálise , Glutationa/análise , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Cinética , Limite de Detecção , Oxirredução , Sensibilidade e Especificidade , Propriedades de Superfície
13.
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
14.
Analyst ; 144(19): 5748-5754, 2019 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-31432061

RESUMO

A sensitive electrochemical immunoassay (e-ELISA) has been developed for the detection of the gastrointestinal parasitic nematode Ostertagia ostertagi (brown stomach worm) in infected and control serum samples. An antigen-indirect immunoassay format was employed to detect the presence of O. ostertagi antibodies, coupled with an anti-species monoclonal horseradish peroxidase (HRP) conjugate. ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) and TMB (3,3',5,5'-tetramethylbenzidine/hydrogen peroxide) were investigated as both chromogenic visualising reagents for optical ELISA and electroactive substrates for electrochemical ELISA in the HRP catalysed oxidation reaction. Coulometry was applied for the detection of O. ostertagi antibodies (via TMB electrochemistry) and compared with the commercial optical ELISA (ABTS based SVANOVIR® O. ostertagi-Ab ELISA kit). Cost-effective in-house sensors were designed and fabricated using polyester and chemical adhesive materials with the aid of stencil printing and laser machining techniques. The performance of the electrochemical ELISA and sensor was evaluated by investigating redox mediators (ABTS vs. TMB), stop solutions (sodium dodecyl sulfate vs. sulfuric acid) and incubation times (150 min vs. 70 min vs. 25 min). For a total assay incubation time of 70 minutes, the TMB/H2SO4 based e-ELISA was able to differentiate between positive (P) and negative (N) control serum samples, with a P/N70 control ratio 1.6 times higher than that of optical ELISA (TMB/H2SO4 combination) and 2.9 times higher than that of the commercial ELISA kit (ABTS/SDS combination). Furthermore, the e-ELISA approach is quicker and required only 25 min (total incubation time) with even better response (P/N25 = 14.7), which is approximately 4-fold higher than the optical immunoassay (P/N25 = 3.8). The proposed e-ELISA is specific (selective Ab-Ag interactions) and highly sensitive - capable of detecting up to 16-fold dilutions of a positive control serum sample. The electrochemical ELISA approach has the potential for rapid sample screening in a portable, disposable format, contributing to the quest for effective prevention and control of parasitic Ostertagia ostertagi infections in cattle.


Assuntos
Anticorpos Anti-Helmínticos/sangue , Doenças dos Bovinos/diagnóstico , Técnicas Eletroquímicas/veterinária , Ensaio de Imunoadsorção Enzimática/veterinária , Ostertagíase/veterinária , Animais , Benzidinas/química , Benzotiazóis/química , Bovinos , Doenças dos Bovinos/parasitologia , Técnicas Eletroquímicas/métodos , Ensaio de Imunoadsorção Enzimática/métodos , Peroxidase do Rábano Silvestre/química , Peróxido de Hidrogênio/química , Imunoglobulina G/química , Ostertagia , Ostertagíase/diagnóstico , Ostertagíase/parasitologia , Ácidos Sulfônicos/química
15.
Food Chem ; 298: 125034, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31261013

RESUMO

A wash-free and label-free colorimetric biosensor for the amplified detection of aflatoxin B1 (AFB1) has been constructed by the integration of an ingenious hairpin DNA probe with exonuclease III (Exo III)-assisted signal amplification. The presence of the AFB1 activates the continuous cleavage reactions by Exo III toward a hairpin probe, resulting in the autonomous accumulation of numerous free G-quadruplex sequences, which can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by H2O2 to produce a colorimetric response. The naked-eye biosensor is ultrasensitive, enabling the visual detection of trace amounts of AFB1 as low as 1 pM without instrumentation. The sensor is robust and can work even when challenged with complex sample matrices such as peanut samples. With the advantages of simple operation, wash-free and label-free format, visible and intuitive output, and low cost, the naked-eye based colorimetric biosensor is expected to have potential applications for in-field detection of AFB1.


Assuntos
Aflatoxina B1/análise , Técnicas Biossensoriais/métodos , Colorimetria/métodos , Contaminação de Alimentos/análise , Benzidinas/química , Sondas de DNA/química , Exodesoxirribonucleases/química , Análise de Alimentos/métodos , Quadruplex G , Peróxido de Hidrogênio/química , Limite de Detecção
16.
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
17.
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
18.
Talanta ; 204: 542-547, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357331

RESUMO

The repeatable immobilization of molecular recognition elements onto particle surfaces has a strong impact on the outcomes of affinity-based assays. In this work, an automatic method for the immobilization of immunoglobulin G (IgG) onto protein A-Sepharose microbeads was established through the flow programming features of the portable lab-on-valve platform using micro-bead injection spectroscopy. The reproducible packing of protein A-microbeads between two optic fibers was feasible, allowing on-column probing of IgG retention. The automation of solutions handling and the precise control of time of IgG interaction with the beads rendered repeatable immobilization cycles, within a short timeframe (<2 min). The proposed method featured the preparation of disposable immunosorbents for downstream analytical applications, such as immunosensing or microenrichment of target analytes. In-situ quantification of IgG@protein A-microbeads was carried out using a horseradish peroxidase-labeled detection IgG. The colorimetric oxidation of 3,3',5,5'-tetramethylbenzidine was monitored on-column. Quantitation of mouse and human IgG immobilized@protein A-microbeads was achieved for loading masses between 0.1 and 0.4 µg per ca. 5.5 mg of sorbent. The implemented detection strategy allowed the quantification of human IgG in certified human serum (ERM®- DA470k/IFCC) and spiked saliva, yielding recoveries of 102-108% and requiring minimal volume (1-15 µL) from serum and saliva.


Assuntos
Cromatografia de Afinidade/métodos , Proteínas Imobilizadas/química , Imunoglobulina G/sangue , Sefarose/análogos & derivados , Proteína Estafilocócica A/química , Animais , Armoracia/enzimologia , Benzidinas/química , Compostos Cromogênicos/química , Colorimetria/métodos , Peroxidase do Rábano Silvestre/química , Humanos , Camundongos , Microesferas , Oxirredução , Saliva/química , Sefarose/química
19.
Talanta ; 204: 833-839, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357372

RESUMO

The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.e., direct blocking with N-ethylmaleimide (NEM), or using tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to interrupt disulfide bonds then blocking thiol groups with NEM, were applied to block thiol groups of ficin, ficin-NEM (ficin-N) and ficin-TCEP-NEM (ficin-TN) were produced, respectively. The blocking of thiol groups accelerated the peroxidase activity dramatically. The peroxidase catalytic activity of ficin-N and ficin-TN toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H2O2 was about 2.5-fold and 5-fold increase compared with ficin, respectively, which accompanied a color change from colorless to blue and followed classic Michaelis-Menten model. The kinetic parameters indicated that higher affinity of ficin-N (Km = 0.31) and ficin-TN (Km = 0.39) to H2O2 compared with ficin (Km = 0.58), and ficin-TN had the highest Kcat which increased by 6.5 times and 4.5 times for TMB and H2O2, respectively. According to these findings, a colorimetric method with high sensitivity for the detection of biothiols was developed due to sulfhydryl compounds inhibited the peroxidase activity of ficin. Comparing with ficin and ficin-N, ficin-TN had the widest detection range (0.01-16 µM) and the lowest detection limit (3 nM). The practical applications of ficin-TN for biothiol determination in human serum samples have been demonstrated with satisfactory results. Ficin-N and ficin-TN are promising to apply to the bioanalysis.


Assuntos
Cisteína/sangue , Ficina/química , Glutationa/sangue , Homocisteína/sangue , Peroxidases/química , Benzidinas/química , Compostos Cromogênicos/química , Colorimetria/métodos , Etilmaleimida/química , Humanos , Peróxido de Hidrogênio/química , Indicadores e Reagentes/química , Cinética , Limite de Detecção , Fosfinas/química
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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