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1.
Anal Bioanal Chem ; 412(2): 499-506, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31807805

RESUMO

Although a massive research has been devoted on the exploration of noble metal-based nanozyme, less progress has been made in the investigation of palladium (Pd) nanozyme and the interaction between ions and Pd nanozyme. In this study, a new type of Pd nanozyme was prepared by a facile one-pot approach by using carboxylated chitosan as the stabilizer. Owing to the synergistic effect of carboxylated chitosan stabilized Pd nanoparticles (CC-PdNPs) can effectively catalyze the H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine sulfate (TMB) accompanied by a blue color change (oxidized TMB), indicating the peroxidase-like activity of CC-PdNPs. Furthermore, the Michaelis-Menten constants and catalytic stability of CC-PdNPs render them suitable for environmental analysis and bio-detection. Here, we found that while introducing the iodine ions (I-) into the reaction medium, the peroxidase-like activity of CC-PdNPs has been rapidly and effectively inhibited through the formation of Pd-I bond; thus, the active sites of PdNPs can be blocked by I-. Based on this specific inhibition by I-, a facile colorimetric assay has been performed for the detection of I- with an extremely low limit of detection (0.19 nM). Furthermore, the practicality of the proposed sensor also has been demonstrated in tap water, and the satisfactory recoveries were obtained. Our study not only demonstrated a novel Pd-based nanozyme but also provided guidance for I- sensing for environmental analysis, food inspection, and bio-detection. Graphical abstract.


Assuntos
Ácidos Carboxílicos/química , Quitosana/química , Colorimetria/instrumentação , Enzimas/química , Iodo/análise , Nanoestruturas/química , Paládio/química , Ânions , Limite de Detecção , Abastecimento de Água
2.
J Sci Food Agric ; 100(2): 874-884, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31680264

RESUMO

BACKGROUND: The low cost of aminoglycoside (AMG) antibiotics facilitates their excessive use in animal husbandry and the agriculture sector. This scenario has led to the occurrence of residues in the food chain. After several years of AMG use in antibacterial therapy, resistance to streptomycin has begun to appear. Most of the detection methods developed for AMG antibiotics lacks specificity. A broad target specific nanoprobe would be ideal for detecting the entire class of AMGs. A rapid and sensitive method for the detection of AMGs is urgently needed. RESULTS: Gallic acid-coated silver nanoparticles (AgNPs) were demonstrated as a nanoprobe for the colorimetric detection of AMGs (yellow to orange / red). A linear dynamic range of 50-650 pmol L-1 was achieved readily by ratiometric spectrophotometry (A560 /A400 ) with a limit of detection (LOD) as low as 36 pmol L-1 . The amine-groups of the AMGs function as molecular linkers, so that electrostatic coupling interactions between neighboring particles drive the formation of AgNP aggregates. The assay can also be applied for the determination of streptomycin residues in serum and milk samples. CONCLUSION: This study revealed the potential of an AgNP probe for the rapid and cost-effective detection of low-molecular-weight target analytes, such as the AMGs. A ligand-induced aggregation of AgNPs coated with gallic acid was reported to be a rapid and sensitive assay for AMGs. Analysis of streptomycin was demonstrated with excellent picomolar-level sensitivity. Thus, the validated method can find practical applications in the ultrasensitive detection of AMGs in complex and diagnostic settings. © 2019 Society of Chemical Industry.


Assuntos
Antibacterianos/análise , Colorimetria/métodos , Resíduos de Drogas/análise , Leite/química , Soro/química , Estreptomicina/análise , Água/química , Animais , Antibacterianos/farmacologia , Bovinos , Colorimetria/instrumentação , Limite de Detecção , Nanopartículas Metálicas/química , Prata/química
3.
Crit Rev Food Sci Nutr ; 60(1): 157-170, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-30311773

RESUMO

As a representative colorimetic biosnesor, paper-based LFSA have emerged as a promising and robust tool that can easily and instansly detect the presence of target biological components in food sample. Recently, LFSAs have gained a considerable attention as an alternative method for rapid diagnosis of foodborne pathogens to the conventional culture-based assays such as plate counting and PCR. One major drawback of the current LFSAs for the detection of pathogenic bacteria is the low sensitivity, limiting its practical applications in POCT. Not like many other protein-based biomarkers that are present in nM or pM range, the number of pathogenic bacteria that cause disease can be as low as few CFU/ml. Here, we review current advances in LFSAs for the detection of pathogenic bacteria in terms of chromatic agents and analyte types. Furthermore, recent approaches for signal enhancement and modifications of the LFSA architecture for multiplex detection of pathogenic bacteria are included in this review, together with the advantages and limitations of each techniques. Finally, the technological challenges and future prospect of LFSA-based POCT for the detection of pathogenic bacteria are discussed.


Assuntos
Bactérias/isolamento & purificação , Técnicas Biossensoriais , Contaminação de Alimentos/análise , Microbiologia de Alimentos/métodos , Colorimetria/instrumentação , Papel
4.
Talanta ; 206: 120219, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31514888

RESUMO

A new method to determine the total titratable acidity of orange, lemon and passion fruit, based on a spot test obtained from digital images and using anthocyanins as the biodegradable indicator, is presented for the first time. The colorimetric reactions were carried out by acid-base titration on a microscale, employing anthocyanin with a microplate for spot test purposes, with detection by digital imaging. To obtain highly precise data, a chamber based on a diffuser was developed to control the illumination supplied by the light emitting diodes, and coupled to a smartphone to acquire adequate digital images. High precision was obtained with a relative standard deviation of 0.758% for n = 95. The RGB values were extracted from the digital images and used as analytical signals, the values being correlated with the micro-volume of the titrant and used to construct the titration curves and obtain the first and second derivatives, respectively. For comparative purposes, the official AOAC (Association of Official Analytical Chemists) and MAPA (Ministry of Agriculture, Livestock and Food Supply of Brazil) methods were used and the results compared by applying the paired t-test at the 95% confidence level (n = 3). No difference was found between the values and the relative errors were less than 2.8%. The micro-titrimetric method was fast, uses anthocyanins as the natural indicator, is practical, and permits a reduction of 922 times or 99.9% of the volume required in a conventional titration. It is therefore ideal for routine analyses leading to a reduction in the waste generated, according to the principles of green chemistry.


Assuntos
Citrus sinensis/química , Frutas/química , Passiflora/química , Antocianinas/química , Colorimetria/instrumentação , Colorimetria/métodos , Química Verde/métodos , Concentração de Íons de Hidrogênio , Indicadores e Reagentes/química , Phaseolus/química , Smartphone , Titulometria/instrumentação , Titulometria/métodos
5.
Talanta ; 207: 120278, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594612

RESUMO

Cyanide is potentially hazardous and quickly acting chemical used in many fields of industry. Therefore, detection of cyanide is of main health concern due to its serious impacts on living organisms. In this context, we have developed rapid, low-cost and on-site sensory two molecules for the colorimetric and fluorogenic sensing of cyanide ion in aqueous samples and food samples. The prepared probes undergo distinct visual color change and exhibits selective fluorogenic turn-on or turn-off response towards cyanide. Competing anions have little or negligible effect on the detection of cyanide. The limit of detection for cyanide ion was calculated as low as 0.45 µM. Free receptors could be successfully regenerated by treating them with Ag+ ion. Moreover, a new visual colorimetric strip based on paper was fabricated with the pale yellow-to-pink color change signal. The fabricated test strips also demonstrated excellent selectivity towards cyanide ion without interfering possible fluoride and acetate ions. The smartphone-based technique which could directly read out the color value using a smartphone revealed an excellent potential for the cyanide detection without additional device.


Assuntos
Colorimetria/economia , Colorimetria/instrumentação , Custos e Análise de Custo , Cianetos/análise , Corantes Fluorescentes/química , Smartphone , Cianetos/química , Limite de Detecção , Modelos Moleculares , Conformação Molecular , Fitas Reagentes/química , Fatores de Tempo , Água/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.
Anal Chim Acta ; 1087: 104-112, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31585557

RESUMO

The current work describes the development of a "nanopaper-based analytical device (NAD)", through the embedding of curcumin in transparent bacterial cellulose (BC) nanopaper, as a colorimetric assay kit for monitoring of iron and deferoxamine (DFO) as iron-chelating drug in biological fluids such as serum blood, urine and saliva. The iron sensing strategy using the developed assay kit is based on the decrease of the absorbance/color intensity of curcumin-embedded in BC nanopaper (CEBC) in the presence of Fe(III), due to the formation of Fe(III)-curcumin complex. On the other hand, releasing of Fe(III) from Fe(III)-CEBC upon addition of DFO as an iron-chelating drug, due to the high affinity of this drug to Fe(III) in competition with curcumin, which leads to recovery of the decreased absorption/color intensity of Fe(III)-CEBC, is utilized for selective colorimetric monitoring of this drug. The absorption/color changes of the fabricated assay kit as output signal can be monitored by smartphone camera or by using a spectrophotometer. The results of our developed sensor agreed well with the results from a clinical reference method for determination of Fe(III) concentration in human serum blood samples, which revealed the clinical applicability of our developed assay kit. Taken together, regarding the advantageous features of the developed sensor as an easy-to-use, non-toxic, disposable, cost-effective and portable assay kit, along with those of smartphone-based sensing, it is anticipated that this sensing bioplatform, which we name lab-on-nanopaper, will find utility for sensitive, selective and easy diagnosis of iron-related diseases (iron deficiency and iron overload) and therapeutic drug monitoring (TDM) of iron-chelating drugs in clinical analysis as well.


Assuntos
Celulose/química , Desferroxamina/análise , Quelantes de Ferro/análise , Ferro/análise , Smartphone , Colorimetria/instrumentação , Colorimetria/métodos , Curcumina/química , Desferroxamina/sangue , Desferroxamina/urina , Humanos , Ferro/sangue , Ferro/urina , Nanoestruturas/química , Papel , Saliva/química
9.
Analyst ; 144(21): 6382-6390, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31576382

RESUMO

An accurate quantification method with a wide linearity range is paramount for the development of low-cost, portable and point-of-care sensors. This work reports a new approach to analyze the colorimetric assays on paper-based sensors using the quantification from a light transmission method. Compared to the commonly-developed color intensity measurement on scanned digital images, a portable transmission densitometer is capable of directly quantifying the optical density of colorimetric results. The detection of heavy metals in an aqueous system, including Fe(ii), Cu(ii), and Ni(ii), was carried out to demonstrate the good performance and reliability of this method. Our measurements show that the linear quantification range spans from 0.5-500 mg L-1 for the assays of Cu(ii) and Fe(ii) and from 2-500 mg L-1 for Ni(ii) based on the reading of transmitted light through the assay spot. As a comparison, the linear range is restricted to 0.5-50 mg L-1 for the same assays when analysed by the common reflection method, suggesting a significant improvement in the accuracy and sensitivity of high analyte concentrations from the light transmission method. By expanding the linearity range, this method further streamlines the sampling procedure during analysis and will greatly advance the future development of paper-based analytical sensors.


Assuntos
Colorimetria/instrumentação , Luz , Limite de Detecção , Metais Pesados/agonistas , Fenômenos Ópticos , Papel , Desenho de Equipamento , Reprodutibilidade dos Testes
10.
Anal Bioanal Chem ; 411(28): 7511-7518, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31641824

RESUMO

A label-free, rapid response colorimetric aptasensor for sensitive detection of chloramphenicol (CAP) was proposed, which was based on the strategy of ssDNA-modified gold nanoparticle (AuNP) aggregation assisted by lanthanum (La3+) ions. The AuNPs generated a color change that could be monitored in the red, green, and blue and analyzed by the smartphone imaging app. La3+, as a trigger agent, strongly combined with the phosphate groups of the surface of ssDNA-AuNPs probe, which helps create AuNP aggregation and the color change of AuNPs from red to blue. On the contrary, when mixing with CAP, the aptamer (Apt) bound to CAP to form a rigid structure of the Apt-CAP complex, and La3+ attached to the phosphate groups of the complex, which prevented the aptamer from binding to the surface of the AuNPs. As a result, the color of the AuNPs changed to violet-red. Finally, UV-vis absorption spectroscopy and the smartphone imaging app were employed to determine CAP with a lower detection limit of 7.65 nM and 5.88 nM, respectively. The proposed strategy featuring high selectivity and strong anti-interference ability for detection of CAP in practical samples was achieved. It is worth mentioning that the simple and portable colorimetric aptasensor will be used for facilitating on-site detection of food samples.


Assuntos
Técnicas Biossensoriais/métodos , Cloranfenicol/análise , Colorimetria/instrumentação , Ouro/química , Lantânio/química , Nanopartículas Metálicas/química , Smartphone , Animais , Galinhas , Inocuidade dos Alimentos , Leite/química , Produtos Avícolas/análise
11.
Anal Chim Acta ; 1083: 150-156, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31493805

RESUMO

Most of the on-site approaches for inferring of the post-mortem interval are still based on observative data from the direct body inspection, whereas, objective and quantitative analyses, such as potassium in the vitreous humor, are require laboratory instrumentation and skilled personnel. The present paper presents a simple and low cost analytical method suitable for use at the crime scene for inferring the time since death. The method uses a microfluidic paper-based device (µPAD) for the determination of ammonium in the vitreous humor (VH) based on the selective interaction between the ammonium and the Nessler's reagent. The color change was measured in terms of "RGB distance" by using a simple and free smartphone application. The optimized device showed a limit of detection of 0.4 mmol L-1, with between days precision less than 9.3% expressed as relative standard deviation, and accuracy between days from 94.5% to 104.5%. The selectivity of the Nessler's reaction was tested towards the main vitreous humor compounds, and no significant interferences were found. This paper-based analytical device was successfully used for the determination of ammonium ion in VH samples from forensic autopsies. The results obtained with the proposed method, although for a limited number of cases (n = 25), showed a close correlation with the data obtained with an instrumental analysis based on capillary electrophoresis. Moreover, in order to make the evaluation of results as simple as possible, a direct correlation between the color intensity, expressed as RGB distance, and the post-mortem interval was studied and a significant correlation was found (R2 > 0.78). In conclusion, the present preliminary study showes that the proposed device could be an additional tool to the traditional methods for a more accurate, although still presumptive, estimation of the time of death directly at the crime scene.


Assuntos
Compostos de Amônio/análise , Medicina Legal/métodos , Papel , Mudanças Depois da Morte , Corpo Vítreo/química , Adulto , Idoso , Colorimetria/instrumentação , Colorimetria/métodos , Medicina Legal/instrumentação , Humanos , Iodetos/química , Limite de Detecção , Compostos de Mercúrio/química , Técnicas Analíticas Microfluídicas/instrumentação , Técnicas Analíticas Microfluídicas/métodos , Pessoa de Meia-Idade , Estudo de Prova de Conceito , Reprodutibilidade dos Testes , Fatores de Tempo , Adulto Jovem
12.
Anal Chim Acta ; 1082: 152-164, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31472704

RESUMO

Development of simultaneous bacteria detection and eradication with simple, rapid, and reusable material is important in addressing bacterial contamination issues. In this study, we utilized the expression of alkaline phosphatase (ALP) from bacteria to design fluorescence ON/OFF system for bacteria detection, also using metal oxide nanoparticle for obtaining antibacterial activity and recyclability. The fluorescent-based biosensor with antibacterial activity was prepared by intercalating ALP-sensitive polymer dot (PD) containing ß-cyclodextrin (ß-CD) onto montmorillonite (MMT) as loading matrix via ionic exchange reaction, followed by immobilization of magnetic iron oxide (Fe3O4) and NIR-responsive cesium tungsten oxide (CsWO3). The PD-ßCD-MMT/Fe3O4-CsWO3 nanocomposite exhibited strong fluorescence intensity, which was quenched in the presence of bacterial ALP (0-1000 U/L) due to hydrolysis of p-nitrophenyl phosphate (NPP) into p-nitrophenol (NP) in the hydrophobic site of ß-CD. Furthermore, the nanocomposite could detect both gram-negative Escherichia coli and gram-positive Staphylococcus aureus in the range of 101-107 CFU/mL (LOD 5.09 and 4.62 CFU/mL, respectively), and showed high antibacterial activity against bacteria by generating photothermal heat under 5 min NIR irradiation, causing damage to bacterial cells. This material also demonstrated recyclability via magnetic field exposure due to the presence of Fe3O4. In addition, the fluorescence can be recovered following pH shock and re-conjugation of ß-CD molecules. After 4 cycles, nanocomposite still showed stable photothermal effects and fluorescence-based bacteria detection. Thus, this reusable material offers promising approach for simultaneous bacteria detection and killing, which is simple, rapid, and effective.


Assuntos
Fosfatase Alcalina/química , Antibacterianos/farmacologia , Escherichia coli/isolamento & purificação , Nanopartículas de Magnetita/química , Pontos Quânticos/química , Staphylococcus aureus/isolamento & purificação , Antibacterianos/química , Bentonita/química , Césio/química , Césio/efeitos da radiação , Colorimetria/instrumentação , Colorimetria/métodos , Reutilização de Equipamento , Escherichia coli/efeitos dos fármacos , Calefação , Raios Infravermelhos , Limite de Detecção , Nanopartículas de Magnetita/efeitos da radiação , Testes de Sensibilidade Microbiana/instrumentação , Testes de Sensibilidade Microbiana/métodos , Nanocompostos/química , Nitrofenóis/química , Compostos Organofosforados/química , Polímeros/química , Staphylococcus aureus/efeitos dos fármacos , Compostos de Tungstênio/química , Compostos de Tungstênio/efeitos da radiação , beta-Ciclodextrinas/química
13.
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
14.
Anal Chim Acta ; 1080: 146-152, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31409464

RESUMO

Field-amplified stacking (FAS) is a commonly used method for enhancing the sensitivity of charged species from low conductive media in capillary electrophoresis. FAS also showed significant sensitivity enhancement effect on a uniform paper fluidic channel by proper design of the electrolyte. In this paper, a novel method of introducing electric field gradient is proposed by geometry design of a 2D paper fluidic channel, and field amplification effect was successfully demonstrated with reduced requirement on the sample's conductivity. Sensitive colorimetric detection of microalbuminuria (MAU) from urine samples was demonstrated by mobile phone camera. Experimental results showed that, with active electric field motivation, up to 93.5% of the loaded protein probe could be effectively transferred and stacked into a narrow band on the newly designed paper fluidic channel. A limit of detection (LOD) of 6.5 mg‧L-1 HSA was achieved with a dynamic range of 10-300 mg‧L-1 (linear in the range of 10-100 mg‧L-1, R2 = 0.991). Combined with selective staining of albumin with bromophenol blue (BPB), the established method was applied to the detection of MAU from clinical urine samples, and consistent results with that of the clinical method were obtained. With this paper-based analytical device (PAD), MAU from highly conductive urine samples can be directly loaded and detected without any pretreatment. This method provides a way to develop highly sensitive point-of-care test (POCT) for rapid screening of some diseases.


Assuntos
Albuminúria/diagnóstico , Colorimetria/métodos , Eletroforese Capilar/métodos , Papel , Albumina Sérica Humana/urina , Azul de Bromofenol/química , Colorimetria/instrumentação , Corantes/química , Eletroforese Capilar/instrumentação , Humanos , Limite de Detecção
15.
Anal Chim Acta ; 1080: 162-169, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31409466

RESUMO

Driven by a bright prospect for rapid, portable and cost-effective point-of-care testing, an assembled Pasteur pipette device to integrate nucleic acid extraction, amplification and detection was developed to detect B. cereus in a sample-to-answer format. Denaturation Bubble-mediated Strand Exchange Amplification (SEA) was chosen to perform isothermal amplification because it requires only a pair of primers and one Bst DNA polymerase. The established SEA can detect as low as 1.0 × 10-13 M genomic DNA of B. cereus, which was comparable with the previously reported method for B. cereus detection. The assembled Pasteur pipette allows sample-to-answer diagnostic in a simple, low-cost, portable, and disposable format. The inherent function of Pasteur pipette enables direct liquid handling without the need of extra pipettes, syringes or pumps. Visual readout was achieved by using a pH sensitive dye, further simplifying result judgment process. The detection limit for B. cereus is 1.0 × 104 CFU/mL in pure cultures, while the detection limit in artificially contaminated milk is 1.0 × 105 CFU/mL without enrichment and 1.0 × 100 CFU/mL following 12 h enrichment. Considering that typical cell counts in food samples associated to food poisoning are 1.0 × 105 to 1.0 × 108 CFU per gram/milliliter B. cereus, our Pasteur pipette is enough sensitive for answer-to-sample diagnosis of B. cereus even directly from foods without enrichment. The whole diagnostic procedure could be completed within 50 min, dramatically decreasing the detection time. In a word, the assembled Pasteur pipette device, combined with a homemade metal bath, possesses great potential for sample-to-answer application in resource-limited settings.


Assuntos
Bacillus cereus/isolamento & purificação , Carga Bacteriana/métodos , Colorimetria/métodos , DNA Bacteriano/análise , Animais , Carga Bacteriana/instrumentação , Proteínas de Bactérias/química , Colorimetria/instrumentação , Corantes/química , DNA Polimerase Dirigida por DNA/química , Contaminação de Alimentos/análise , Geobacillus stearothermophilus/enzimologia , Limite de Detecção , Leite/microbiologia , Técnicas de Amplificação de Ácido Nucleico/métodos , Papel
17.
Food Chem ; 300: 125177, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31323607

RESUMO

A point-of-care testing chip was developed for the colorimetric detection of inorganic mercury ion (Hg2+). The disposable chip fabricated by three-dimensional printing technology contains DNAzymes produced by rolling circle amplification (RCA); a color change caused by the enzymatic reaction between DNAzymes and the peroxidase substrate 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) is measured using a portable spectrophotometer. In the "turn-off"-type RCA reaction, the annealing of the T(12) primer that initiates the RCA reaction is blocked by the interaction of thymine with Hg2+; thus, the amount of amplified DNAzymes causing a color change is decreased depending on Hg2+ concentration. The colorimetric signal is enhanced by amplifying double-repeat DNAzymes from a circular DNA template. The chip detected Hg2+ in tap drinking water samples with high sensitivity (lowest validated value: 3.6 µg/L) and showed better selectivity, precision, and reproducibility than conventional analysis instruments. This low-cost easy-to-use platform can reduce the risk of accidental Hg2+ poisoning.


Assuntos
Colorimetria/instrumentação , Água Potável/análise , Mercúrio/análise , Impressão Tridimensional , Poluentes Químicos da Água/análise , Colorimetria/métodos , DNA Catalítico/química , Desenho de Equipamento , Mercúrio/química , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrofotometria/métodos
18.
Talanta ; 204: 525-532, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357329

RESUMO

In this work, we present a smartphone-based multiplexed enzymatic biosensor utilizing the unique colorimetric properties of the poly(aniline-co-anthranilic acid) (ANI-co-AA) composite film coupled with horseradish peroxidase (HRP), glucose oxidase (GOx), horseradish peroxidase-glucose oxidase (GOx-HRP) and tyrosinase (Tyr) enzymes. The enzymes are immobilized on the composite polymer film by adsorption and they catalyze a reversible redox color change of the host polymer from green to blue in the presence of their substrate. A smartphone was applied as color detector, for image acquisition and data handling. A ColorLab® android application, free of charge software application, was used to enable easy and clear display of the sensors' response indicating remarkable changes in the optical features. The results were confirmed by the spectrophotometric measurements. The developed colorimetric enzymatic biosensors were studied and optimized in relation to different experimental parameters. Moreover, the colorimetric enzymatic biosensors were applied to food and pharmaceutical analysis. It has been shown by these studies that the colorimetric biosensors are promising as quick and simple tests for handheld analysis in various fields.


Assuntos
Catecóis/análise , Glucose/análise , Peróxido de Hidrogênio/análise , Agaricales/enzimologia , Armoracia/enzimologia , Técnicas Biossensoriais/métodos , Colorimetria/instrumentação , Colorimetria/métodos , Enzimas Imobilizadas/química , Sucos de Frutas e Vegetais/análise , Glucose Oxidase/química , Peroxidase do Rábano Silvestre/química , Limite de Detecção , Monofenol Mono-Oxigenase/química , Polímeros/química , Pyrus/química , Reprodutibilidade dos Testes , Smartphone , Vinho/análise
19.
Talanta ; 204: 586-591, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357338

RESUMO

A simple, small and inexpensive photometer that uses a pair of light-emitting diodes (LEDs) and a simple operational amplifier was developed for investigating thiocyanate levels in saliva obtained from smokers and non-smokers. The photometer is based on paired emitter-detector diodes (PEDDs), and the entire system can be purchased for less than a hundred US dollars. The PEDD-based photometer can measure the transmittance of a solution in a 1-cm disposable polystyrene cuvette using only rechargeable dry-cell batteries, which makes it suitable for analysis outside of equipped laboratories. The metal complex formation between Fe (III) and thiocyanate ions in an acidic condition permits colorimetric detection of thiocyanate ions using LEDs emitting at 465 nm, because the complex shows maximum absorption at 457 nm. The developed photometer exhibits excellent performance with linearity ranging from 0.05 mmol L-1 to 0.75 mmol L-1 and a correlation coefficient (r2) > 0.999. The limits of detection and quantification were 0.01 mmol L-1 and 0.05 mmol L-1, respectively. Both intra- and inter-day precision were obtained with relative standard deviations (RSD) of less than 1% in the determination of thiocyanate. The proposed method is simple, facile, and sensitive enough to investigate the levels of thiocyanate in the saliva samples of smokers and non-smokers with centrifugation being the only special treatment for samples. The results showed that the concentrations of thiocyanate were approximately 5-fold higher in smokers than in non-smokers.


Assuntos
Saliva/química , Tiocianatos/análise , Colorimetria/instrumentação , Colorimetria/métodos , Humanos , Ferro/análise , Iluminação/instrumentação , Limite de Detecção , não Fumantes , Fotometria/instrumentação , Fotometria/métodos , Reprodutibilidade dos Testes , Fumantes
20.
Molecules ; 24(14)2019 Jul 23.
Artigo em Inglês | MEDLINE | ID: mdl-31340442

RESUMO

In recent years, there has been an increase in pesticide use to improve crop production due to the growth of agricultural activities. Consequently, various pesticides have been present in the environment for an extended period of time. This review presents a general description of recent advances in the development of methods for the quantification of pesticides used in agricultural activities. Current advances focus on improving sensitivity and selectivity through the use of nanomaterials in both sensor assemblies and new biosensors. In this study, we summarize the electrochemical, optical, nano-colorimetric, piezoelectric, chemo-luminescent and fluorescent techniques related to the determination of agricultural pesticides. A brief description of each method and its applications, detection limit, purpose-which is to efficiently determine pesticides-cost and precision are considered. The main crops that are assessed in this study are bananas, although other fruits and vegetables contaminated with pesticides are also mentioned. While many studies have assessed biosensors for the determination of pesticides, the research in this area needs to be expanded to allow for a balance between agricultural activities and environmental protection.


Assuntos
Técnicas Biossensoriais/métodos , Colorimetria/métodos , Técnicas Eletroquímicas/métodos , Medições Luminescentes/métodos , Praguicidas/isolamento & purificação , Espectrometria de Fluorescência/métodos , Agricultura , Técnicas Biossensoriais/economia , Técnicas Biossensoriais/instrumentação , Colorimetria/economia , Colorimetria/instrumentação , Conservação dos Recursos Naturais/métodos , Produtos Agrícolas/efeitos dos fármacos , Produtos Agrícolas/microbiologia , Produtos Agrícolas/parasitologia , Produtos Agrícolas/virologia , Técnicas Eletroquímicas/economia , Técnicas Eletroquímicas/instrumentação , Monitoramento Ambiental/instrumentação , Monitoramento Ambiental/métodos , Humanos , Limite de Detecção , Medições Luminescentes/economia , Medições Luminescentes/instrumentação , Musa/efeitos dos fármacos , Musa/microbiologia , Musa/parasitologia , Musa/virologia , Espectrometria de Fluorescência/economia , Espectrometria de Fluorescência/instrumentação
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