Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 20.177
Filtrar
1.
Biotechniques ; 70(4): 218-225, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33820475

RESUMEN

Evaluation of the performance of a new set of primers defined from the ORF1ab sequence, and its combination with a previously published set of primers from the N sequence, to detect SARS-CoV-2 RNA by the loop-mediated isothermal amplification technique is presented. The ORF1ab primer set enables visual detection of SARS-CoV-2 RNA in 16 min. In addition, a simultaneous reaction with both ORF1ab and N primers allows for higher sensitivity of detection, particularly when low numbers of copies are present (250 viral RNA copies). Further, the protocol is able to detect viral RNA in saliva samples. The procedure reported could be easily implemented in the generation of a new and sensitive rapid point-of care device for SARS-CoV-2 RNA visual detection.


Asunto(s)
/métodos , Colorimetría/métodos , Técnicas de Diagnóstico Molecular/métodos , Técnicas de Amplificación de Ácido Nucleico/métodos , /genética , /virología , Cartilla de ADN , Humanos , Poliproteínas/genética , Proteínas Virales/genética
2.
Sensors (Basel) ; 21(5)2021 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-33807562

RESUMEN

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) can serve as biochemical markers of various pathologies like liver disfunction and poisonings by nerve agents. Ellman's assay is the standard spectrophotometric method to measure cholinesterase activity in clinical laboratories. The authors present a new colorimetric test to assess AChE and BChE activity in biological samples using chromogenic reagents, treated 3D-printed measuring pads and a smartphone camera as a signal detector. Multiwell pads treated with reagent substrates 2,6-dichlorophenolindophenyl acetate, indoxylacetate, ethoxyresorufin and methoxyresorufin were prepared and tested for AChE and BChE. In the experiments, 3D-printed pads containing indoxylacetate as a chromogenic substrate were optimal for analytical purposes. The best results were achieved using the red (R) channel, where the limit of detection was 4.05 µkat/mL for BChE and 4.38 µkat/mL for AChE using a 40 µL sample and a 60 min assay. The major advantage of this method is its overall simplicity, as samples are applied directly without any specific treatment or added reagents. The assay was also validated to the standard Ellman's assay using human plasma samples. In conclusion, this smartphone camera-based colorimetric assay appears to have practical applicability and to be a suitable method for point-of-care testing because it does not require specific manipulation, additional education of staff or use of sophisticated analytical instruments.


Asunto(s)
Acetilcolinesterasa , Butirilcolinesterasa , Inhibidores de la Colinesterasa , Colorimetría , Humanos , Teléfono Inteligente , Espectrofotometría
3.
Sensors (Basel) ; 21(5)2021 Mar 03.
Artículo en Inglés | MEDLINE | ID: mdl-33802387

RESUMEN

Meat is often wasted due to the perceived concerns of its shelf life and preservation. Specifically, in meat formation, biogenic amines (BAs) are the major agents to spoil them. Herein, we have developed a carbon disulfide (CS2) added colloidal gold nanoparticles-based colorimetric sensor for the rapid and on-site detection of biogenic amines. Transmission electron microscopy is used to observe the morphological changes in colloidal gold nanoparticles and aggregation behavior of CS2 added to the colloidal gold nanoparticles' solution. Raman spectroscopic analysis is further used to characterize the peaks of CS2, Cad and CS2-Cad molecules. Absorption spectroscopy is used to estimate the colorimetric differences and diffuse reflectance spectra of the samples. The sensing analysis is performed systematically in the presence and absence of CS2. CS2 added colloidal gold nanoparticles colorimetric sensor detected the BAs with a limit of detection (LOD) value of 50.00 µM. Furthermore, the developed sensor has shown an LOD of 50.00 µM for the detection of multiple BAs at a single time. The observed differences in the colorimetric and absorption signals indicate that the structure of BAs is converted to the dithiocarbamate (DTC)-BA molecule, due to the chemical reactions between the amine groups of BAs and CS2. Significantly, the developed colorimetric sensor offers distinct features such as facile fabrication approach, on-site sensing strategy, rapid analysis, visual detection, cost-effective, possibility of mass production, availability to detect multiple BAs at a single time and appreciable sensitivity. The developed sensor can be effectively used as a promising and alternative on-site tool for the estimation of BAs.


Asunto(s)
Disulfuro de Carbono , Nanopartículas del Metal , Aminas Biogénicas , Colorimetría , Oro , Oro Coloide
4.
ACS Sens ; 6(3): 1086-1093, 2021 03 26.
Artículo en Inglés | MEDLINE | ID: mdl-33683104

RESUMEN

The outbreak of COVID-19 caused a worldwide public health crisis. Large-scale population screening is an effective means to control the spread of COVID-19. Reverse transcription-polymerase chain reaction (RT-qPCR) and serology assays are the most available techniques for SARS-CoV-2 detection; however, they suffer from either less sensitivity and accuracy or low instrument accessibility for screening. To balance the sensitivity, specificity, and test availability, here, we developed enhanced colorimetry, which is termed as a magnetic pull-down-assisted colorimetric method based on the CRISPR/Cas12a system (M-CDC), for SARS-CoV-2 detection. By this method, SARS-CoV-2 RNA from synthetic sequences and cultured viruses can be detected by the naked eye based on gold nanoparticle (AuNP) probes, with a detection limit of 50 RNA copies per reaction. With CRISPR/Cas12a-assisted detection, SARS-CoV-2 can be specifically distinguished from other closely related viruses. M-CDC was further used to analyze 41 clinical samples, whose performance was 95.12%, consistent with that of an approved Clinical RT-qPCR Diagnosis kit. The developed M-CDC method is not dependent on sophisticated instruments, which makes it potentially valuable to be applied for SARS-CoV-2 screening under poor conditions.


Asunto(s)
/métodos , ARN Viral/análisis , /genética , Proteínas Bacterianas , Proteínas Asociadas a CRISPR , Sistemas CRISPR-Cas , Línea Celular Tumoral , Colorimetría , ADN/química , Sondas de ADN , Endodesoxirribonucleasas , Oro/química , Humanos , Nanopartículas del Metal/química
5.
Nat Commun ; 12(1): 1467, 2021 03 05.
Artículo en Inglés | MEDLINE | ID: mdl-33674580

RESUMEN

Efforts to contain the spread of SARS-CoV-2 have spurred the need for reliable, rapid, and cost-effective diagnostic methods which can be applied to large numbers of people. However, current standard protocols for the detection of viral nucleic acids while sensitive, require a high level of automation and sophisticated laboratory equipment to achieve throughputs that allow whole communities to be tested on a regular basis. Here we present Cap-iLAMP (capture and improved loop-mediated isothermal amplification) which combines a hybridization capture-based RNA extraction of gargle lavage samples with an improved colorimetric RT-LAMP assay and smartphone-based color scoring. Cap-iLAMP is compatible with point-of-care testing and enables the detection of SARS-CoV-2 positive samples in less than one hour. In contrast to direct addition of the sample to improved LAMP (iLAMP), Cap-iLAMP prevents false positives and allows single positive samples to be detected in pools of 25 negative samples, reducing the reagent cost per test to ~1 Euro per individual.


Asunto(s)
/métodos , /virología , Colorimetría/métodos , Técnicas de Diagnóstico Molecular/métodos , Técnicas de Amplificación de Ácido Nucleico/métodos , Hibridación de Ácido Nucleico/métodos , Pruebas en el Punto de Atención , /aislamiento & purificación , /genética , Humanos , Fosfoproteínas/genética , ARN Viral/genética , Sensibilidad y Especificidad
6.
Biosens Bioelectron ; 182: 113173, 2021 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-33773383

RESUMEN

Respiratory syncytial virus (RSV) infection is the most common clinical infectious disease threatening the safety of human life. Herein, we provided a sensitive and specific method for detection and differentiation of RSV subgroups A (RSVA) and B (RSVB) with colorimetric toehold switch sensors in a paper-based cell-free system. In this method, we applied the toehold switch, an RNA-based riboswitch, to regulate the translation level of ß-galactosidase (lacZ) gene. In the presence of target trigger RNA, the toehold switch sensor was activated and the expressed LacZ hydrolyzed chromogenic substrates to produce a colorimetric result that can be observed directly with the naked eye in a cell-free system. In addition, nucleic acid sequence-based amplification (NASBA) was used to improve the sensitivity by amplifying target trigger RNAs. Under optimal conditions, our method produced a visible result for the detection of RSVA and RSVB with the detection limit of 52 aM and 91 aM, respectively. The cross-reaction of this method was validated with other closely related respiratory viruses, including human coronavirus HKU1 (HCoV-HKU1), and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Furthermore, we used the paper-based carrier material that allows stable storage of our detection elements and rapid detection outside laboratory. In conclusion, this method can sensitively and specifically differentiate RSVA and RSVB and generate a visible colorimetric result without specialized operators and sophisticated equipment. Based on these advantages above, this method serves as a simple and portable detector in resource-poor areas and point-of-care testing (POCT) scenarios.


Asunto(s)
Técnicas Biosensibles , Sistema Libre de Células , Colorimetría/métodos , Virus Sincitial Respiratorio Humano/aislamiento & purificación , Betacoronavirus/aislamiento & purificación , Humanos , ARN Viral , /aislamiento & purificación
7.
J Esthet Restor Dent ; 33(2): 323-340, 2021 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-33769698

RESUMEN

OBJECTIVE: To investigate the color difference using both ΔE*ab and CIEDE2000 formulas of all combinations of all enamel and dentin shades of three different composite systems with three different shade guides, to compare the coverage error (CE) of the shade guides for each composite and to investigate whether coverage error is affected by enamel shade layer thickness (0.5 vs 1 mm). MATERIALS AND METHODS: Disk specimens from all enamel and dentin shades of Essentia, Enamel Plus HRi, and IPS Empress Direct composites were fabricated. Color measurements were performed for all enamel-dentin combinations and for two thicknesses per enamel shade: 0.5 and 1 mm. Color was measured for three shade guides: Vitapan Classical, 3DMaster, and Ivoclar. Minimum color difference between layered composites and shade tabs, closest shade tab match and CE of all shade guides were calculated for all composite shade combinations. RESULTS: In most cases, the closest match was a mismatch. CE of 3DMaster was significantly lower for IPS Empress Direct and Enamel Plus HRi at 0.5 mm enamel thickness. Shade guides exhibited higher lightness values compared to composites and composites lower chroma values compared to shade guides. CONCLUSIONS: Shade guides do not match well to the layered composites. 3DMaster performed better than the other two shade guides, in most cases.


Asunto(s)
Resinas Compuestas , Esmalte Dental , Color , Colorimetría , Coloración de Prótesis , Espectrofotometría
8.
Food Chem ; 345: 128560, 2021 May 30.
Artículo en Inglés | MEDLINE | ID: mdl-33601648

RESUMEN

An efficient and convenient detection method for organophosphorus pesticide (OP) residues is needed because of their high neurotoxicity and severe threat to food safety. OPs effectively reduce the production of thiocholine in the acetylcholinesterase/acetylthiocholine reaction by inhibiting the activity of acetylcholinesterase. Therefore, we developed a feasible and convenient fluorescent and colorimetric dual-response sensor based on the competitive complexation of Cu2+ between graphitic carbon nitride nanosheets and thiocholine for the rapid detection of OPs with high sensitivity. Malathion was used as a model OP, and a linear range of 70-800 nM with a detection limit of 6.798 nM for a fluorescent signaling platform and 2.5-25 nM with a detection limit of 1.204 nM for a colorimetric probe were attained. The constructed probe was successfully applied to determine OP in actual samples of cabbages leaves and tap water. The results indicated that the dual-response probe was reliable and sensitive to actual samples.


Asunto(s)
Colorimetría/métodos , Cobre/química , Grafito/química , Nanoestructuras/química , Compuestos de Nitrógeno/química , Compuestos Organofosforados/análisis , Acetilcolinesterasa/química , Acetilcolinesterasa/metabolismo , Agua Dulce/análisis , Peróxido de Hidrógeno/química , Concentración de Iones de Hidrógeno , Límite de Detección , Malatión/análisis , Residuos de Plaguicidas/análisis , Espectrometría de Fluorescencia
9.
Sensors (Basel) ; 21(3)2021 Feb 02.
Artículo en Inglés | MEDLINE | ID: mdl-33540523

RESUMEN

Recently, aptamers have attracted attention in the biosensing field as signal recognition elements because of their high binding affinity toward specific targets such as proteins, cells, small molecules, and even metal ions, antibodies for which are difficult to obtain. Aptamers are single oligonucleotides generated by in vitro selection mechanisms via the systematic evolution of ligand exponential enrichment (SELEX) process. In addition to their high binding affinity, aptamers can be easily functionalized and engineered, providing several signaling modes such as colorimetric, fluorometric, and electrochemical, in what are known as aptasensors. In this review, recent advances in aptasensors as powerful biosensor probes that could be used in different fields, including environmental monitoring, clinical diagnosis, and drug monitoring, are described. Advances in aptamer-based colorimetric, fluorometric, and electrochemical aptasensing with their advantages and disadvantages are summarized and critically discussed. Additionally, future prospects are pointed out to facilitate the development of aptasensor technology for different targets.


Asunto(s)
Aptámeros de Nucleótidos , Técnicas Biosensibles , Colorimetría , Ligandos , Técnica SELEX de Producción de Aptámeros
10.
Food Chem ; 349: 129160, 2021 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-33550018

RESUMEN

Indigo carmine (IC) dye is hazardous and allergenic for humans even though it has been excessively used in a wide range of industries. Therefore, the quantitative determination of IC is still challenging. Herein, for the first time, we have developed fluorometric and colorimetric dual-mode nanoprobe derived from the ion-pair association complex between the negatively charged IC and positively charged N@C-dots in pH = 3.0. Consequently, the binding between N@C-dots and IC resulted in cyan blue and quenching of N@C-dots fluorescence. The dependence of the fluorescence response on IC concentrations was linear over the range of 0.73-10.0 µM (R2 = 0.9989) with LOD of 0.24 µM. On the other hand, the linearity of the colorimetric method ranged from 9.97 to 80.0 µM (R2 = 0.9986) with LOD of 3.3 µM. The sensor was applied for estimation of IC in fruit juice and soft drink without the need for exhaustive extraction steps.


Asunto(s)
Bebidas/análisis , Carbono/química , Análisis de los Alimentos/métodos , Contaminación de Alimentos/análisis , Carmin de Índigo/análisis , Límite de Detección , Nitrógeno/química , Colorimetría , Fluorometría , Humanos
11.
Spectrochim Acta A Mol Biomol Spectrosc ; 252: 119462, 2021 May 05.
Artículo en Inglés | MEDLINE | ID: mdl-33524823

RESUMEN

In this work, we report a novel protein-based nanoprobe (PNP) that can be employed for quantitative analysis of Cu2+ in pure water medium and real samples. Structurally, the proposed nanoprobe comprises a biofriendly protein (hen egg-white lysozyme (HEWL)) and a Cu2+-specific chromogenic agent, where HEWL acts as a nanocarrier encapsulating a structurally tailored rhodamine B derivate. The resulting PNP exhibits a hydrodynamic diameter of ~ 106 nm and efficiently disperses in water, enabling the detection of Cu2+ in pure aqueous systems without the aid of any organic co-solvents. The high sensitivity and selectivity of PNP allow the colorimetric detection of Cu2+ in the presence of other metal interferents with a low detection limit of 160 nM. The satisfying recovery of trace level Cu2+ in environmental samples demonstrate the great potential of employing PNP for the determination of Cu2+ in actual applications. Most importantly, the simple co-grinding method employing proteins and chromogenic agents provides a novel strategy to generate sensing systems that are useful detection of pollutants in aqueous samples.


Asunto(s)
Colorimetría , Cobre , Nanoestructuras , Proteínas , Límite de Detección , Metales , Agua
12.
Food Chem ; 351: 129238, 2021 Jul 30.
Artículo en Inglés | MEDLINE | ID: mdl-33640764

RESUMEN

The colorimetric sensors for reducing sugars based on a redox reaction between AuCl4- ions and fructose, glucose, lactose, or mannose are presented. Gold nanoparticles (AuNPs) that formed at room temperature as a product of this reaction were registered using a spectrophotometer. Lengthening reaction time had a positive effect on the sensitivity of the developed sensors. Different reducing sugars exhibited distinct reaction rates for AuNP formation, with the rate decreasing in the order fructose > glucose > lactose > mannose. LOD values after 60 min of the reaction for different sugars followed the same trend of 0.067, 0.081, 0.087, and 0.106 mM, while LOQ was 0.223, 0.270, 0.289, and 0.353 mM, respectively. The linear range 60 min since the start of the reaction varied from 0.3 up to 5.0 mM for different sugars. The colorimetric sensor was evaluated for use in real samples of beverages, milk, and saliva.


Asunto(s)
Colorimetría/métodos , Oro/química , Nanopartículas del Metal/química , Azúcares/análisis , Análisis de los Alimentos , Límite de Detección , Oxidación-Reducción , Azúcares/química
13.
Lab Chip ; 21(4): 700-709, 2021 02 23.
Artículo en Inglés | MEDLINE | ID: mdl-33554994

RESUMEN

The present study investigated ultraviolet-induced in situ gold nanoparticles (AuNPs) coupled with loop-mediated isothermal amplification (LAMP) for the point-of-care testing (POCT) of two major infectious pathogens, namely, Coronavirus (COVID-19) and Enterococcus faecium (E. faecium spp.). In the process, gold ions in a gold chloride (HAuCl4) solution were reduced using trisodium citrate (Na3Ct), a reducing agent, and upon UV illumination, red-colored AuNPs were produced in the presence of LAMP amplicons. The nitrogenous bases of the target deoxyribonucleic acid (DNA) acted as a physical support for capturing gold ions dissolved in the sample. The high affinity of gold with the nitrogenous bases enabled facile detection within 10 min, and the detection limit of COVID-19 plasmid DNA was as low as 42 fg µL-1. To ensure POCT, we designed a portable device that contained arrays of reagent chambers and detection chambers. In the portable device, colorimetric reagents such as HAuCl4 and Na3Ct were contained in the reagent chambers; these reagents were subsequently transferred to the detection chambers where LAMP amplicons were present and thus allowed convenient sample delivery and multiplex detection. Owing to the high sensitivity of the in situ AuNPs, simplicity of portable device fabrication, and rapid colorimetric detection, we strongly believe that the fabricated portable device could serve as a kit for rapid POCT for instantaneous detection of infectious diseases, and could be readily usable at the bedside.


Asunto(s)
/métodos , Enterococcus faecium/aislamiento & purificación , Oro/química , Infecciones por Bacterias Grampositivas/diagnóstico , Nanopartículas del Metal/química , /aislamiento & purificación , Técnicas Biosensibles/métodos , Colorimetría , Humanos , Técnicas de Diagnóstico Molecular , Técnicas de Amplificación de Ácido Nucleico , Pruebas en el Punto de Atención , Rayos Ultravioleta
14.
Anal Chem ; 93(8): 4126-4133, 2021 03 02.
Artículo en Inglés | MEDLINE | ID: mdl-33570401

RESUMEN

The outbreak of the pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) calls for an urgent unmet need for developing a facial and cost-effective detection method. The requirement of well-trained personnel and sophisticated instrument of current primary mean (reverse transcription polymerase chain reaction, RT-PCR) may hinder the practical application worldwide. In this regard, a reverse transcription recombinase polymerase amplification (RT-RPA) coupled with CRISPR-Cas12a colorimetric assay is proposed for the SARS-CoV-2 detection. The methodology we have described herein utilizes DNA-modified gold nanoparticles (AuNPs) as a universal colorimetric readout and can specifically target ORF1ab and N regions of the SARS-CoV-2 genome. After the virus genome is amplified through RT-RPA, the resulting abundant dsDNA will bind and activate Cas12a. Under trans-cleavage degradation, the capped DNA substrate will be hydrolyzed gradually from AuNPs, demonstrating a change in the surface plasmon resonance (SPR), which can be facially monitored by UV-vis absorbance spectroscopy and naked eye observation. The high amplification efficiency from RT-RPA and Cas12a trans-cleavage process bring the sensitivity of our method to 1 copy of viral genome sequence per test. Notably, under the dual variations inspecting from the isothermal amplification and Cas12a activation process, the false positive events from other beta coronavirus members can be effectively avoided and thus significantly improve the specificity. Furthermore, the reliability of this colorimetric assay is validated by standard clinical samples from the hospital laboratory department. Through integration of the inherently high sensitivity and specificity from an RPA-coupled Cas12a system with the intrinsic simplicity of AuNP-based colorimetric assay, our method increases the practical testing availability of SARS-CoV-2.


Asunto(s)
Sistemas CRISPR-Cas , Colorimetría/métodos , ADN/química , Técnicas de Amplificación de Ácido Nucleico/métodos , ARN Viral/análisis , /aislamiento & purificación , Proteínas Bacterianas , Secuencia de Bases , Proteínas Asociadas a CRISPR , ADN/genética , Endodesoxirribonucleasas , Oro/química , Humanos , Nanopartículas del Metal/química , Fosfoproteínas/genética , Poliproteínas/genética , ARN Viral/genética , Transcripción Reversa , Resonancia por Plasmón de Superficie , Proteínas Virales/genética
15.
Talanta ; 225: 121978, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33592726

RESUMEN

In modern times, viruses still threaten people's lives. Among them, norovirus was the main pathogenic factor in the cause of gastroenteritis and foodborne illness, of which the GII.4 and GII.17 genotypes are prevalent in China and most parts of the world. A simple and low-cost platform for rapid and accurate norovirus detection remains a major challenge. After the cell-free system and paper-based chromogenic system were optimized, a rapid and specific norovirus detection method was established based on norovirus-specific sequences in combination with toehold switch elements. The development of a visible color change during detection eliminates the need for any complicated instruments. We validated this strategy and its specificity in differentiating GII.4, GII.17, Zika virus, and human coronavirus HKU1. The results showed that the optimized detection system not only provided a simple and rapid detection method for the sufficient differentiation of the two norovirus genotypes but also showed high specificity and no cross-reactivity with other viruses. Using nucleic acid isothermal amplification, this assay showed a limit of detection of 0.5 pM for the GII.4 genotype and 2.6 fM for the GII.17 genotype in reactions that could be observed directly with the naked eye. Our results suggested that this paper-based colorimetric method could serve as a simple and low-cost visual detection method for pathogens in clinical samples, especially in remote or rural areas.


Asunto(s)
Infecciones por Caliciviridae/diagnóstico , Colorimetría/métodos , Gastroenteritis/diagnóstico , Infecciones por Caliciviridae/virología , Colorimetría/economía , Colorimetría/instrumentación , Análisis Costo-Beneficio , Gastroenteritis/virología , Genotipo , Humanos , Norovirus/genética , Norovirus/fisiología , Técnicas de Amplificación de Ácido Nucleico/métodos , Papel , ARN Viral/genética , Sensibilidad y Especificidad
16.
Sci Total Environ ; 766: 142579, 2021 Apr 20.
Artículo en Inglés | MEDLINE | ID: mdl-33601667

RESUMEN

A colorimetric sensor for detection of Hg2+ is developed via graphene oxide/gold nanoparticles (GO/AuNPs) nanocomposite as peroxidase mimic. In the absence of Hg2+, the adsorption of ss-DNA on GO/AuNPs resulted in the decrease of peroxidase-like activity of GO/AuNPs, which catalyzed the oxidation of 3, 3, 5, 5-tetramethylbenzidine (TMB) to be very light blue. In the presence of Hg2+, the oligonucleotides of T-Hg2+-T conformation formed by thymine-Hg(II)-thymine interaction could not be adsorbed or bonded on GO/AuNPs, and the GO/AuNPs resumed their original high activity of peroxidase mimic and catalyzed the oxidation of TMB into distinct blue product. Under optimized conditions, the absorbance value at the wavelength of 655 nm (A655) was linearly related with the concentration of Hg2+ in the range between 5.2 × 10-9 M and 1.2 × 10-7 M with a detection limit of 3.8 × 10-10 M. By visual observation with the naked eye, Hg2+ as low as 3.3 × 10-7 M could cause color change in solution. The specific T-Hg2+-T binding made it easy to selectively detect Hg2+. The results show that the colorimetric assay offers great potential for the detection of Hg2+ in real samples.


Asunto(s)
Mercurio , Nanopartículas del Metal , Colorimetría , Oro , Oligonucleótidos
17.
Food Chem ; 347: 128987, 2021 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-33461117

RESUMEN

The present study reports the effect of sorbitan monopalmitate (SM) as a crystallization modifier on the physicochemical properties of mango butter (MB). The concentration of SM was varied in the range of 1 and 5 wt%. The addition of SM promoted the aggregation of globular MB crystals. The FTIR patterns did not show any significant changes when SM was added. XRD and DSC analyses confirmed the crystallization of MB crystals in stable ß' and ß (V) polymorphic states. However, SM also introduced imperfections in the crystal lattices of MB. Among all formulations, M2 (SM; 1% w/w) possessed a mechanically stable network structure. The crystallization rate of MB was tailored by SM in a concentration-dependent manner. The solid content was highest in M4 (SM; 5% w/w) at 10 °C and 30 °C among all the oleogels. In gist, SM in manageable quantities can be utilized for preparing custom-tailored MB-based products.


Asunto(s)
Mantequilla/análisis , Hexosas/análisis , Mangifera/metabolismo , Colorimetría , Cristalización , Elasticidad , Mangifera/química , Espectroscopía Infrarroja por Transformada de Fourier , Temperatura , Viscosidad , Difracción de Rayos X
18.
Food Chem ; 347: 128988, 2021 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-33465686

RESUMEN

A label-free colorimetric method based on exonuclease I (Exo I)-assisted signal amplification with protamine as a medium was developed for analysis of kanamycin. In this study, a double-stranded DNA (dsDNA) probe was tailored by manipulating an aptamer and its complementary DNA (cDNA) ensuring detection of target with high selectivity and excellent sensitivity. Herein, protamine could not only combine with negatively charged gold nanoparticles but also interaction with polyanion DNA. Upon addition of target kanamycin, the target-aptamer complex was formed and the cDNA was released. Thus, both aptamer and cDNA could be digested by Exo I, and the captured kanamycin was liberated for triggering target recycling and signal amplification. Under optimized conditions, the proposed colorimetric method realized a low detection limit of 2.8 × 10-14 M along with a wide linear range plus excellent selectivity. Our strategy exhibited enormous potentials for fabricate various kinds of biosensors based on target-induced aptamer configuration changes.


Asunto(s)
Colorimetría/métodos , Exodesoxirribonucleasas/metabolismo , Kanamicina/análisis , Animales , Aptámeros de Nucleótidos/química , Aptámeros de Nucleótidos/metabolismo , Sondas de ADN/química , Sondas de ADN/metabolismo , ADN Complementario/química , ADN Complementario/metabolismo , Oro/química , Límite de Detección , Nanopartículas del Metal/química , Leche/química , Técnicas de Amplificación de Ácido Nucleico
19.
Food Chem ; 348: 129128, 2021 Jun 30.
Artículo en Inglés | MEDLINE | ID: mdl-33516992

RESUMEN

A novel colorimetric aptasensor based on unmodified gold nanoparticle (AuNPs) and single-strand DNA (ssDNA) aptamer was developed for the rapid and sensitive detection of T-2 toxin. In the absence of T-2, the AuNPs were wrapped by the aptamer to avoid the salt-induced aggregation and the solution remains red. In the presence of T-2, the aptamer was bound with T-2 and released from the surface of AuNPs, resulting in the aggregation of AuNPs under proper salt solution and the color change from red to purple-blue. The aptasensor exhibited a high sensitivity and selectivity for the detection of T-2. The range of linearity and detection limit were 0.1 ng/mL-5000 ng/mL (0.21435 nM-10717.5 nM) and 57.8 pg/mL (0.124 nM), respectively. The aptasensor developed here was applicable to assay T-2 in wheat and corn samples. These results implied that the colorimetric aptasensor was potentially useful in food detection.


Asunto(s)
Aptámeros de Nucleótidos/química , Colorimetría/métodos , ADN de Cadena Simple/química , Oro/química , Nanopartículas del Metal/química , Toxina T-2/análisis , Aptámeros de Nucleótidos/metabolismo , Límite de Detección , Triticum/metabolismo , Zea mays/metabolismo
20.
Biosensors (Basel) ; 11(2)2021 Jan 21.
Artículo en Inglés | MEDLINE | ID: mdl-33494276

RESUMEN

Antibiotics are classes of antimicrobial substances that are administered widely in the field of veterinary science to promote animal health and feed efficiency. Cattle-administered antibiotics hold a risk of passing active residues to milk, during the milking process. This becomes a public health concern as these residues can cause severe allergic reactions to sensitive groups and considerable economic losses to the farmer. Hence, to ensure that the produced milk is safe to consume and adheres to permissible limits, an on-farm quick and reliable test is essential. This study illustrates the design and development of a microfluidic paper biosensor as a proof-of-concept detection system for gentamicin in milk. Localized surface plasmon resonance (LSPR) properties of gold nanoparticles have been explored to provide the user a visual feedback on the test, which was also corroborated by RGB analysis performed using Image J. The assay involves the use of a short stretch of single stranded DNA, called aptamer, which is very specific to the gentamicin present in the milk sample. The camera-based LOD for the fabricated paper device for milk samples spiked with gentamicin was calculated to be 300 nM, with a reaction time of 2 min.


Asunto(s)
Gentamicinas/análisis , Técnicas Analíticas Microfluídicas , Leche/química , Animales , Aptámeros de Nucleótidos , Técnicas Biosensibles , Colorimetría/métodos , Resonancia por Plasmón de Superficie
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...