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1.
J Environ Sci Health B ; 55(1): 60-68, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31971076

RESUMO

This work reports the development of a very-simple-to-construct stir-bar extraction device so called "a dumbbell-shaped stainless steel stir-bar." The extraction device was assembled from a rolled up stainless steel net filled with an XAD-2 sorbent and a metal rod to allow the use of a magnetic stirrer during extraction. The dumbbell-shaped stainless steel stir-bar was used to extract diethyl phthalate (DEP), dibutyl phthalate (DBP), and di(2-ethylhexyl) phthalate (DEHP) before analysis by a gas chromatograph equipped with an electron capture detector (GD-ECD). Under the optimal conditions, the developed method provided a good linearity from 10.0 to 1,000.0 ng mL-1 for all three compounds. Limits of detection and limits of quantification were 9.37 ± 0.29 ng mL-1 and 31.22 ± 0.95 ng mL-1 for DEP, 5.73 ± 0.31 ng mL-1 and 19.1 ± 1.0 ng mL-1 for DBP and 3.30 ± 0.06 ng mL-1 and 11.0 ± 0.19 ng mL-1 for DEHP, respectively. Good recoveries in the range of 81.89 ± 0.17 to 109.5 ± 2.0% were achieved when the method was used to extract phthalate esters in five instant noodle and two rice soup samples.


Assuntos
Fracionamento Químico/instrumentação , Análise de Alimentos/instrumentação , Oryza , Ácidos Ftálicos/isolamento & purificação , Aço Inoxidável , Fracionamento Químico/métodos , Cromatografia Gasosa , Dibutilftalato/isolamento & purificação , Dietilexilftalato/isolamento & purificação , Desenho de Equipamento , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Limite de Detecção , Ácidos Ftálicos/química , Reprodutibilidade dos Testes
2.
Food Chem ; 309: 125685, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31693964

RESUMO

A doubly porous microcomposite polyaniline/graphene oxide/octadecyl-bonded silica magnetite (PANI/GOx/C18-SiO2-Fe3O4) alginate adsorbent was developed and employed to extract fluoroquinolones. The Fe3O4 facilitated rapid and convenient for the separation of the adsorbent from sample solutions. The double porosity of the alginate hydrogel enhanced the surface area of the polyaniline coating. The developed method exhibited good linearity of 0.0010-50 µg L-1 for danofloxacin; 0.0050-50 µg L-1 for norfloxacin, ciprofloxacin and enrofloxacin; and 0.010-50 µg L-1 for sarafloxacin and difloxacin. The limits of detection were between 0.001 and 0.010 µg L-1 with RSD below 9.0%. The PANI/GOx/C18-SiO2-Fe3O4 adsorbent was utilized to extract fluoroquinolones from honey, milk and egg samples and satisfactory extraction recoveries were achieved ranged from 80 to 98%. The developed adsorbent has good stability which can be reused up to 7 times, is simple to prepare and convenient to use for the extraction fluoroquinolones.


Assuntos
Fracionamento Químico/métodos , Fluoroquinolonas/isolamento & purificação , Análise de Alimentos , Compostos de Anilina/química , Animais , Ciprofloxacino/análogos & derivados , Ciprofloxacino/isolamento & purificação , Ovos/análise , Enrofloxacina/isolamento & purificação , Óxido Ferroso-Férrico/química , Grafite/química , Mel/análise , Limite de Detecção , Leite/química , Norfloxacino/isolamento & purificação , Porosidade , Dióxido de Silício/química
3.
Anal Chim Acta ; 1091: 30-39, 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31679572

RESUMO

A screw-based portable and simple solid phase microextraction device was fabricated by a 3D printer and used in combination with the developed silver-incorporated porous polyaniline film pencil lead solid-phase microextraction fiber (Ag/PANI SPME). Scanning electron microscopy revealed a porous structure of the electrodeposited Ag/PANI film. The spectrum from energy dispersive x-ray spectroscopy (EDS) and the elemental map confirmed the presence of silver in the porous polymer film. It was used under stirring for the extraction of five phthalate esters: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP). The extracted solution was identified and quantified by gas chromatography using a flame ionization detector (GC-FID). Under the optimum conditions of the developed method, a good linearity was obtained in a concentration range of 5.0-1000 µg L-1 for all five phthalate esters with limits of detection (LODs) of 4.41 ±â€¯0.91 µg L-1, 3.98 ±â€¯0.92 µg L-1, 3.65 ±â€¯0.74 µg L-1, 4.91 ±â€¯0.52 µg L-1 and 4.25 ±â€¯0.66 µg L-1 for DMP, DEP, DBP, BBP and DEHP, respectively. The developed method provided good precision when tested with standard solutions (RSD < 5.5%, n = 6) and real samples (RSD < 3.4%, n = 6). Good fiber-to-fiber reproducibility was also confirmed by extraction with six newly prepared fibers; recoveries ranged from 81.09 ±â€¯0.54% to 92.92 ±â€¯0.46% with RSD <6.6%. The developed method was used to determine phthalate esters in 14 cosmeceutical samples. In rubbing alcohol samples, DEP and DEHP were detected at 7.03 ±â€¯0.76 µg L-1 and 5.89 ±â€¯0.53 µg L-1, respectively, while in contact lens cleaners, DEHP was found in a concentration range from 5.3 ±â€¯1.1 µg L-1 to 6.8 ±â€¯1.2 µg L-1. No phthalate esters contamination was detectable in saline solutions, eye cleaners and antibacterial disinfectant liquids. Recoveries in the range of 81.92 ±â€¯0.99% to 102.4 ±â€¯1.1% indicated the good accuracy of the developed method.


Assuntos
Compostos de Anilina/química , Cosmecêuticos/análise , Ésteres/análise , Grafite/química , Ácidos Ftálicos/análise , Prata/química , 2-Propanol/análise , Adsorção , Cromatografia Gasosa , Soluções para Lentes de Contato/análise , Desinfetantes/análise , Desenho de Equipamento , Limite de Detecção , Impressão Tridimensional , Solução Salina/análise , Microextração em Fase Sólida/instrumentação , Microextração em Fase Sólida/métodos
4.
Mikrochim Acta ; 186(12): 822, 2019 11 21.
Artigo em Inglês | MEDLINE | ID: mdl-31754802

RESUMO

A nanosorbent composed of magnetite nanoparticles, graphene oxide and a molecularly imprinted polymer (Fe3O4@SiO2-NH2/GOx/MIP) was synthesized and applied to simultaneous extraction of cephalexin, cefazolin and cefoperazone from milk. The use of magnetite nanoparticles enables fast extraction by using an external magnet. The use of graphene oxide increases extraction affinity, and the MIP improves selectivity. Extraction efficiency was optimized by investigating the effects of the template-to-monomer and cross-linker ratios, the desorption condition, extraction time, salting-out effect, stirring rate, sample volume and amount of adsorbent. The cephalosporins were quantified by using HPLC. Under optimum condition, the linear range of the method extends from 2.5 to 100 µg L-1 for cephalexin and cefazolin, and from 5.0 to 100 µg L-1 for cefoperazone. The limits of detection are 2.5 µg L-1 for cephalexin and cefazolin, and 5 µg L-1 for cefoperazone. The adsorbent was applied to the extraction of cephalosporins from milk, with recoveries in a range from 80.2 to 111.7% and with RSDs of <8.5%. Graphical abstractSchematic representation of a nanocomposite adsorbent consisting of magnetic molecularly imprinted polymer and graphene oxide (GOx). Integrating of magnetite nanoparticles, GOx and high specificity of MIP, the method exhibited a rapid, high extraction efficiency, good selectivity for multi-residue analysis of cephalosporins.


Assuntos
Cefalosporinas/análise , Grafite/química , Nanopartículas de Magnetita/química , Ácidos Polimetacrílicos/química , Adsorção , Animais , Técnicas Biossensoriais , Bovinos , Cromatografia Líquida de Alta Pressão , Limite de Detecção , Fenômenos Magnéticos , Leite/química , Impressão Molecular , Sensibilidade e Especificidade , Dióxido de Silício/química , Extração em Fase Sólida
5.
Mikrochim Acta ; 186(6): 338, 2019 05 09.
Artigo em Inglês | MEDLINE | ID: mdl-31073696

RESUMO

A fluorometric method is described for the detection of ampicillin. A polypyrrole containing fluorescent CdTe quantum dots was incorporated into a silica-based molecularly imprinted polymer. The composite MIP displays good fluorescence (with excitation/emission maxima at 355/548 nm), and high selectivity and affinity for ampicillin due to the use of polypyrrole. Ampicillin is found to quench the fluorescence of composite much more strongly than the emission of a non-imprinted polymer. The imprinting factor of 7.5 implies that the nanocomposite probe contains specific binding sites. The MIP probe has two linear response ranges, one from 0.10 to 25 µg L-1 of ampicillin, and one from 25 to 100 µg L-1. The limit of detection is 0.05 µg L-1. The method was applied to the determination of ampicillin in (spiked) milk and meat samples and gave recoveries between 81.7 and 98.7%. The results agreed well with HPLC techniques. Graphical abstract Schematic presentation of nanocomposite fluorescence probe of polypyrrole and quantum dots incorporated in a molecularly imprinted polymer. Integrating of QDs, high specificity of MIPs and high affinity of polypyrrole, the method exhibited highly sensitive and selective for ampicillin detection.

6.
Talanta ; 197: 465-471, 2019 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-30771963

RESUMO

An environmentally friendly method of etching a stainless steel plunger wire, to replace the conventional hydrofluoric acid approach, was developed for plunger-in-needle liquid phase-microextraction (PIN-LPME). The one-step etching procedure was performed by immersing the plunger wire in a ferric chloride-hydrochloric acid (FeCl3-HCl) solution. The etched wire was then used for LPME as the organic solvent holder. After solvent coating, the wire was directly exposed to a water sample for extraction of polycyclic aromatic hydrocarbons (PAHs), which were then subjected to thermal desorption in the injector of a gas chromatograph for gas chromatography-mass spectrometric (GC-MS) analysis. The parameters affecting PIN-LPME efficiencies (i.e., extraction solvent, solvent coating mode and time, stirring rate, extraction time and salting effect) were also investigated. Under the most favourable conditions, PIN-LPME-GC-MS exhibited high enrichment factors of between 70 and 349 for the 9 PAHs, low detection limits (between 0.006 and 0.058 ng mL-1), and good precision (with relative standard deviations ranging from 4.4% to 9.7%). The developed method was successfully applied for the extraction and determination of PAHs in tap, river and drain water samples. Good relative recoveries of the PAHs over the range of 84.3-101.9% were obtained with spiked genuine water samples.

7.
Sensors (Basel) ; 18(10)2018 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-30347779

RESUMO

Simple, robust, and low-cost nitrate- and ammonium-selective electrodes were made using substrate prepared from household materials. We explored phosphonium-based ILs and poly (methyl methacrylate)/poly(decyl methacrylate)(MMA-DMA) copolymer as matrix materials alternative to classical PVC-based membranes. IL-based membranes showed suitability only for nitrate-selective electrode exhibiting linear concentration range between 5.0 × 10-6 and 2.5 × 10-3 M with a detection limit of 5.5 × 10-7 M. On the other hand, MMA-DMA-based membranes showed suitability for both ammonium- and nitrate-selective electrodes, and were successfully applied to detect NO3- and NH4⁺ in water and soil samples. The proposed ISEs exhibited near-Nernstian potentiometric responses to NO3- and NH4⁺ with the linear range concentration between 5.0 × 10-5 and 5.0 × 10-2 M (LOD = 11.3 µM) and 5.0 × 10-6 and 1.0 × 10-3 M (LOD = 1.2 µM), respectively. The power of ISEs to detect NO3- and NH4⁺ in water and soils was tested by comparison with traditional, portable colorimetric techniques. Procedures required for analysis by each technique from the perspective of a non-trained person (e.g., farmer) and the convenience of the use on the field are compared and contrasted.

8.
Anal Bioanal Chem ; 410(27): 7185-7193, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30167743

RESUMO

A hierarchically porous structured composite monolith sorbent of polypyrrole-coated graphene oxide and octadecyl silica incorporated in chitosan cryogel (PPY/GOx/C18/chitosan) was synthesized and used as solid-phase extraction sorbent for the determination of carbamate pesticides. Various factors affecting the characteristics of the adsorbents (chemistry of the sorbent, polymerization time, concentrations of graphene oxide and octadecyl silica) and the extraction efficiency using the prepared sorbents, such as sample loading, desorption conditions, sample volume, sample flow rate, sample pH, and ionic strength, were investigated and optimized. Under the optimal conditions of sorbent preparation and extraction, the developed composite monolith sorbent provided wide linear responses from 1.0 to 500 µg L-1 for carbofuran and diethofencarb, from 0.5 to 500 µg L-1 for carbaryl, and from 2.0 to 500 µg L-1 for isoprocarb. The limits of detection using HPLC-UV at 203, 220, and 208 nm were in the range of 0.5-2.0 µg L-1. When the composite monolith sorbent was applied for the pre-concentration and determination of carbamate in fruit juices, good recoveries (84.1-99.5%) were achieved. The developed sorbents were porous and exhibited low back pressure enabling their use at high flow rates during sample loading. Extraction and clean-up were highly efficient, and the good physical and chemical stability of the sorbent enables reuse up to 13 times. Graphical abstract ᅟ.


Assuntos
Carbamatos/isolamento & purificação , Quitosana/química , Criogéis/química , Sucos de Frutas e Vegetais/análise , Grafite/química , Praguicidas/isolamento & purificação , Polímeros/química , Pirróis/química , Adsorção , Carbamatos/análise , Cromatografia Líquida de Alta Pressão/métodos , Análise de Alimentos/métodos , Limite de Detecção , Praguicidas/análise , Porosidade , Reprodutibilidade dos Testes , Extração em Fase Sólida/métodos
9.
J Sep Sci ; 41(20): 3892-3901, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30098128

RESUMO

A calix[4]arene-functionalized graphene oxide/polydopamine-coated cellulose acetate adsorbent was fabricated for the pre-concentration of aflatoxins. The highly porous developed adsorbent does not produce the high backpressure that normally occurs in particle-packed cartridges and its large surface area helps to improve adsorption. The highly efficient adsorption of aflatoxins by the hybrid adsorbent is facilitated via hydrogen bonding and hydrophobic and π-π interactions. Polymerization time, amount of calix[4]arene-functionalized graphene oxide, type and volume of desorption solvent, sample pH, sample volume, and sample flow rate were optimized. The linearity of aflatoxin B1 was in the range of 0.01-10.0 µg/kg, aflatoxin B2 was in the range of 0.02-10.0 µg/kg and aflatoxin G1 and aflatoxin G2 were in the range of 0.050-10.0 µg/kg. The limits of detection were 0.01 µg/kg for aflatoxin B1, 0.02 µg/kg for aflatoxin B2 and 0.05 µg/kg for aflatoxin G1 and aflatoxin G2. The developed calix[4]arene-functionalized graphene oxide/polydopamine-coated cellulose acetate adsorbent was successfully utilized for the analysis of aflatoxins from corn samples and the extraction efficiency was satisfactory with obtained recoveries from 83.0 to 106.7%. Moreover, fabricated adsorbent is easy to prepare, inexpensive, and can be reused.


Assuntos
Aflatoxinas/análise , Calixarenos/química , Celulose/análogos & derivados , Indóis/química , Fenóis/química , Polímeros/química , Extração em Fase Sólida , Zea mays/química , Adsorção , Celulose/química , Grafite/química , Concentração de Íons de Hidrogênio , Estrutura Molecular , Óxidos/química , Tamanho da Partícula , Propriedades de Superfície
10.
Opt Lett ; 43(15): 3730-3733, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30067666

RESUMO

In this Letter, we utilize one-dimensional wavelet analysis to improve the quality of morphology images and velocity profiles of optical coherence tomography simultaneously, by performing analysis on the complex time-frequency plane of raw interferograms, prior to image construction. The results indicate a robust signal improvement that also preserves accuracy for both morphology and velocity information and has been demonstrated on a variety of samples with diverse flow speeds and morphologies.

11.
Talanta ; 188: 658-664, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-30029427

RESUMO

This article reports the detection of Salmonella spp. based on M13 bacteriophage in a capacitive flow injection system. Salmonella-specific M13 bacteriophage was immobilized on a polytyramine/gold surface using glutaraldehyde as a crosslinker. The M13 bacteriophage modified electrode can specifically bind to Salmonella spp. via the amino acid groups on the filamentous phage. An alkaline solution was used to break the binding between the sensing surface and the analyte to allow renewable use up to 40 times. This capacitive system provided good reproducibility with a relative standard deviation (RSD) of 1.1%. A 75 µL min-1 flow rate and a 300 µL sample volume provided a wide linear range, from 2.0 × 102 to 1.0 × 107 cfu mL-1, with a detection limit of 200 cfu mL-1. Bacteria concentration can be analyzed within 40 min after the sample injection. When applied to test real samples (raw chicken meat) it provided good recoveries (100-111%). An enrichment process was also explored to increase the bacteria concentration, enabling a quantitative detection of Salmonella spp. This biosensor opens a new opportunity for the detection of pathogenic bacteria using bacteriophage.


Assuntos
Carga Bacteriana/métodos , Bacteriófago M13/fisiologia , Técnicas Biossensoriais/métodos , Salmonella/isolamento & purificação , Sequência de Aminoácidos , Animais , Bacteriófago M13/química , Galinhas/microbiologia , Técnicas Eletroquímicas/métodos , Eletrodos , Contaminação de Alimentos/análise , Microbiologia de Alimentos , Ouro/química , Limite de Detecção , Peptídeos/química , Reprodutibilidade dos Testes , Salmonella/química , Ligação Viral
12.
Spectrochim Acta A Mol Biomol Spectrosc ; 201: 382-391, 2018 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-29775931

RESUMO

A nanocomposite optosensor consisting of carboxylic acid functionalized multiwall carbon nanotubes and CdTe quantum dots embedded inside a molecularly imprinted polymer (COOH@MWCNT-MIP-QDs) was developed for trace ciprofloxacin detection. The COOH@MWCNT-MIP-QDs were synthesized through a facile sol-gel process using ciprofloxacin as a template molecule, 3-aminopropylethoxysilane as a functional monomer and tetraethoxysilane as a cross-linker at a molar ratio of 1:8:20. The synthesized nanocomposite optosensor had high sensitivity, excellent specificity and high binding affinity to ciprofloxacin. Under optimal conditions, the fluorescence intensity of the optosensor decreased in a linear fashion with the concentration of ciprofloxacin and two linear dynamic ranges were obtained, 0.10-1.0 µg L-1 and 1.0-100.0 µg L-1 with a very low limit of detection of 0.066 µg L-1. The imprinting factors of the two linear range were 17.67 and 4.28, respectively. The developed nanocomposite fluorescence probe was applied towards the determination of ciprofloxacin levels in chicken muscle and milk samples with satisfactory recoveries being obtained in the range of 82.6 to 98.4%. The results were also in good agreement with a HPLC method which indicates that the optosensor can be used as a sensitive, selective and rapid method to detect ciprofloxacin in chicken and milk samples.


Assuntos
Ciprofloxacino/sangue , Impressão Molecular/métodos , Nanocompostos/química , Nanotubos de Carbono/química , Pontos Quânticos , Humanos , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes
13.
Talanta ; 184: 429-436, 2018 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-29674065

RESUMO

A portable and simple microextractor device was constructed by aligning six miniaturized multi-stir-rod microextractors. Each microextractor was prepared from rod-like multiwalled carbon nanotubes functionalized with a carboxylic group (MWCNTs-COOH) in composite monoliths that were bundled together and connected to a small DC motor. Using six of these microextractors, the device could extract six samples at the same time. A scanning electron microscope (SEM) showed the MWCNTs-COOH well distributed throughout the highly porous structure of the monolith-MWCNTs-COOH-stir-rod. This miniaturized multi-stir-rod microextractor device was used for the extraction of four parabens, methylparaben (MP), ethylparaben (EP), propylparaben (PP) and butylparaben (BP). Under optimized conditions, good linearities were obtained in the concentration range of 1.0 ng mL-1 to 1.0 µg mL-1 for MP and EP and 2.0 ng mL-1 to 1.0 µg mL-1 for PP and BP. The limits of detection were low, 636.2 ±â€¯7.6 pg mL-1 for MP, 675.5 ±â€¯6.0 pg mL-1 for EP, 676.6 ±â€¯8.6 pg mL-1 for PP and 803.4 ±â€¯9.6 pg mL-1 for BP. The developed microextractor could be used up to 15 times (%RSDs from 1.5 to 5.2) and also provided good preparation reproducibility (%RSD from 1.3 to 5.8, n = 6). The % RSDs of intra-day (n = 6) and inter-day (n = 6) precisions were obtained from 1.10-7.79 and 1.96-7.55, respectively. This developed device coupled with high performance liquid chromatography-diode array detector (HPLC-DAD) was applied for the extraction and preconcentration of four parabens in personal care products and cosmetics. The recoveries were studied by spiking the standard solution of parabens in real samples. Good recoveries were obtained in the range of 89.0 ±â€¯2.7 to 102.7 ±â€¯1.8% for MP, 88.09 ±â€¯6.4 to 102.5 ±â€¯1.0% for EP, 83.4 ±â€¯6.4 to 102.9 ±â€¯1.5% for PP and 83.5 ±â€¯3.6 to 102.3 ±â€¯2.0% for BP. This developed device might be easily applied for the extraction and preconcentration of other trace organic compounds in sample matrices.

14.
Mikrochim Acta ; 185(2): 148, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-29594556

RESUMO

A stir foam composed of graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) was prepared for use in micro-solid phase extraction sorbent of preservative agents and antioxidants from cosmetic products. The extracted analytes were quantified by GC-MS. Under the optimized conditions, the calibration plots are linear in the concentration ranges between 5.0 µg·L-1 to 1.0 mg·L-1 for benzoic acid, of 10.0 µg·L-1 to 1.0 mg·L-1 for 2-methyl-3-isothiazolinone (MI), and between 1.0 µg·L-1 and 1.0 mg·L-1 for both 3-tert-butyl-4-hydroxyanisole (BHA) and 2,6-di-tert-butyl-p-hydroxytoluene (BHT). The LODs are 1.0 µg·L-1 for benzoic acid, 5.0 µg·L-1 for MI and 0.5 µg·L-1 for both BHA and BHT. The stir-foam can be easily prepared, is inexpensive and well reproducible (RSDs <3%, for n = 6). It can be re-used for up to 12 times after which extraction efficiency has dropped to 90%. The method was successfully applied to the determination of preservatives and antioxidants in cosmetic samples. Recoveries from spiked samples ranged between 94.5 ± 2.1% and 99.8 ± 1.8%. Graphical abstract A stir foam was prepared from graphene oxide, poly(ethylene glycol) and natural latex (GO-PEG-NL) and is shown to be a most viable sorbent for the microextraction of trace amounts of preservative agents and antioxidants from cosmetic products.


Assuntos
Antioxidantes/isolamento & purificação , Conservantes Farmacêuticos/isolamento & purificação , Microextração em Fase Sólida/métodos , Hidroxianisol Butilado/análise , Hidroxitolueno Butilado/análise , Cosméticos/análise , Cromatografia Gasosa-Espectrometria de Massas , Grafite/química , Látex/química , Limite de Detecção , Polietilenoglicóis/química
15.
Biosens Bioelectron ; 102: 217-225, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29149687

RESUMO

A label-free electrochemical miRNA biosensor was developed based on a pyrrolidinyl peptide nucleic acid (acpcPNA)/polypyrrole (PPy)/silver nanofoam (AgNF) modified electrode. The AgNF was electrodeposited as redox indicator on a gold electrode, which was then functionalized with an electropolymerized layer of PPy, a conducting polymer, to immobilize the PNA probes. The fabrication process was investigated by electrochemical impedance spectroscopy. The biosensor was used to detect miRNA-21, a biomarker abnormally expressed in most cancers. The signal was monitored by the change in current of the AgNF redox reaction before and after hybridization using cyclic voltammetry. Two PNA probe lengths were investigated and the longer probe exhibited a better performance. Nucleotide overhangs on the electrode side affected the signal more than overhangs on the solution side due to the greater insulation of the sensing surface. Under optimal conditions, the electrochemical signal was proportional to miRNA-21 concentrations between 0.20fM and 1.0nM, with a very low detection limit of 0.20fM. The biosensor showed a high specificity which could discriminate between complementary, single-, doubled-base mismatched, and non-complementary targets. Three out of the seven tested plasma samples provided detectable concentrations (63 ± 4, 111 ± 4 and 164 ± 7fM). The sensor also showed good recoveries (81-119%). The results indicated the possibilities of this biosensor for analysis without RNA extraction and/or amplification, making the sensor potentially useful for both the prognosis and diagnosis of cancer in clinical application.


Assuntos
Técnicas Biossensoriais , Técnicas Eletroquímicas , MicroRNAs/isolamento & purificação , Hibridização de Ácido Nucleico/genética , Espectroscopia Dielétrica , Ouro/química , Humanos , Limite de Detecção , MicroRNAs/genética , Neoplasias/diagnóstico , Neoplasias/genética , Polímeros/química , Pirróis/química , Pirrolidinas/química , Prata
16.
Anal Chim Acta ; 985: 69-78, 2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28864196

RESUMO

Phthalate esters (PAEs), especially dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), di-2-ethylhexyl phthalate (DEHP) are widely used as plasticizers in plastics and polymers. They are not chemically bound and can easily migrate into food and human tissue that comes into contact with these materials. The method developed in this work was applied for the preconcentration and determination of these four phthalate esters that might leach from contact lenses and baby teethers. A novel stir-bead micro-solid phase extractor of chitosan cryogel composited with polypyrrole with a steel wire core was evaluated for the extraction of DMP, DEP, DBP and DEHP before analysis by high performance liquid chromatography (HPLC). Scanning electron micrographs of the polypyrrole-chitosan cryogel beads revealed a high porosity with large surface area. Under the optimum conditions, the developed method provided a good linearity in a concentration range from 10 to 750 ng mL-1 for DMP and from 5.0 to 750 ng mL-1 for DEP, DBP and DEHP. The limits of detection (LOD) were 6.07 ± 0.22 ng mL-1, 4.358 ± 0.097 ng mL-1, 4.408 ± 0.099 ng mL-1 and 3.916 ± 0.053 ng mL-1 for DMP, DEP, DBP and DEHP, respectively, and the method reproducibility was good (n = 6, % RSD < 6.0). DBP and DEHP were detected in two original storage solutions of contact lenses from 13.2 ± 1.1 ng mL-1 to 15.4 ± 1.9 ng mL-1 and from 21.3 ± 1.6 ng mL-1 to 23.5 ± 1.5 ng mL-1, respectively. In the artificial saliva in contact with baby teether samples only DEHP was found, from 4.91 ± 0.31 ng mL-1 to 6.78 ± 0.23 ng mL-1, with good recoveries ranging from 81.3 ± 8.4% to 106.3 ± 5.2%.


Assuntos
Quitosana , Soluções para Lentes de Contato/análise , Criogéis , Ácidos Ftálicos/análise , Polímeros , Pirróis , Saliva Artificial/análise , Ésteres , Reprodutibilidade dos Testes
17.
ACS Appl Mater Interfaces ; 9(38): 33368-33376, 2017 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-28846378

RESUMO

Printable organic bioelectronics provide a fast and cost-effective approach for the fabrication of novel biodevices, while the general challenge is to achieve optimized reaction kinetics at multiphase boundaries between biomolecules and electrodes. Here, we present an entirely new concept based on a modular approach for the construction of heterostructured bioelectronic interfaces by using tailored functional "biological microparticles" combined with "transducer microparticles" as modular building blocks. This approach offers high versatility for the design and fabrication of bioelectrodes with a variety of forms of interparticle spatial organization, from layered-structures to more advance bulk heterostructured architectures. The heterostructured biocatalytic electrodes delivered twice the reaction rate and a six-fold increase in the effective diffusion kinetics in response to a catalytic model using glucose as the substrate, together with the advantage of shortened diffusion paths for reactants between multiple interparticle junctions and large active particle surface. The consequent benefits of this improved performance combined with the simple means of mass production are of major significance for the emerging printed electronics industry.


Assuntos
Eletrodos , Biocatálise , Glucose , Cinética , Impressão
18.
Anal Bioanal Chem ; 409(20): 4697-4707, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28685175

RESUMO

A hybrid molecularly imprinted polymer (MIP)-coated quantum dot (QD) nanocomposite was synthesized and applied as a fluorescence probe for the highly sensitive and selective determination of salbutamol. The hybrid MIP-coated QD nanocomposite was synthesized via a copolymerization process in the presence of thioglycolic acid capped CdTe QDs with salbutamol as a template, 3-aminopropyltriethoxysilane as the functional monomer, and tetraethyl orthosilicate as a cross-linker. The optimum molar ratio of template, monomer, and cross-linker was 1:6:20. The fluorescence intensity of the hybrid MIP-coated QDs was efficiently quenched after salbutamol rebound to the recognition sites, as a result of charge transfer from QDs to salbutamol. The synthesized hybrid MIP-coated QD nanocomposite showed high sensitivity and good selectivity toward salbutamol. Under the optimal recognition conditions, the fluorescence intensity was quenched linearly with increasing concentration of salbutamol in the range from 0.10 to 25.0 µg L-1, with a detection limit of 0.034 µg L-1. The hybrid optosensor developed was successfully applied in the determination of salbutamol in animal feeds and meat samples. Satisfactory recoveries were obtained in the range from 85% to 98%, with a standard deviation of less than 8%. Furthermore, the accuracy of the hybrid MIP-coated QD nanocomposite was investigated by comparison with a conventional high-performance liquid chromatography method, with the results obtained with two methods agreeing well with each other. The advantages of this sensing method are simplicity, rapidity, cost-effectiveness, high sensitivity, and good selectivity. Graphical Abstract The synthesis of hybrid MIP-coated QDs nanocomposite.


Assuntos
Agonistas de Receptores Adrenérgicos beta 2/análise , Albuterol/análise , Ração Animal/análise , Carne/análise , Impressão Molecular/métodos , Nanocompostos , Polímeros/química , Pontos Quânticos , Animais , Concentração de Íons de Hidrogênio , Limite de Detecção , Microscopia Eletrônica de Varredura , Reprodutibilidade dos Testes , Espectroscopia de Infravermelho com Transformada de Fourier , Termogravimetria
19.
Biosens Bioelectron ; 96: 84-88, 2017 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-28463740

RESUMO

A simple renewable surface for a rapid antibacterial susceptibility test has been demonstrated. The 3-aminophenylboronic acid (3-APBA) modified electrode bind with cis-diol groups on the cell wall of both gram positive and gram negative bacteria. The detection of antibacterial susceptibility response by a capacitive system can be done within a short time, 2.5h for the whole process, with good repeatability of the electrode's preparation. An acid solution, could break the bonding between 3-APBA and the bacteria, which were then easily removed by the fluid flow, renewing the sensing surface for the next test. This modified electrode can be reused up to 35 times. This sensor is useful for testing the susceptibility of bacteria to antibacterial agents that affect their cell wall. Results from the capacitive sensor corresponded well with the antimicrobial information in the literature and to the morphology of the treated bacteria revealed by scanning electron microscopy. Antimicrobial susceptibility to natural products could also be easily tested.


Assuntos
Antibacterianos/farmacologia , Ampicilina/farmacologia , Técnicas Biossensoriais , Ácidos Borônicos/farmacologia , Ceftriaxona/farmacologia , Técnicas Eletroquímicas , Eletrodos , Bactérias Gram-Negativas/efeitos dos fármacos , Bactérias Gram-Positivas/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Microscopia Eletrônica de Varredura/métodos , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície , Tetraciclina/farmacologia , Vancomicina/farmacologia , Xantonas/farmacologia
20.
Talanta ; 167: 573-582, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28340763

RESUMO

A novel preconcentrator-separator two-in-one online system has been developed for the online analysis of trace amounts of four polycyclic aromatic hydrocarbons (PAHs) in tea samples. A micro-preconcentrator unit of zeolite imidazolate framework-8-poly(vinyl alcohol) cryogel (ZIF-8-PVA cryogel) and a micro-separation unit of multiwalled carbon nanotubes-poly(vinyl alcohol) cryogel (MWCNTs-PVA cryogel) were fabricated onto an acrylic plate. The eluent from this two-in-one system flowed directly to an on-column UV-visible detector. Under optimum conditions, the system provided a wide linear range from 0.10µgL-1 to 2.00mgL-1 for benzo(a)anthracene (BaA) and chrysene (Chry), 0.15µgL-1 to 3.00mgL-1 for benzo(a)pyrene (BaP) and 0.20µgL-1 to 5.00mgL-1 for benzo(b)fluoranthene (BbF). The limits of detection were 0.05µgL-1 of both BaA and Chry, 0.10µgL-1 of BaP and 0.20µgL-1 of BbF. This two-in-one system was cost-effective, easy to prepare, had excellent stability for up to 417 consecutive injection cycles and provided a good system-to-system reproducibility (n=6) with a relative standard deviation of less than 4%. The system was successfully applied to detect PAHs in tea samples. The concentrations of BaA, Chry, BaP and BbF in seven tea samples were found in the range of non-detectable 2.73±0.07mgL-1 with good recoveries of 83±6 to 108±4%. In addition, it can be easily applied for the detection of other aromatic compounds in contaminated water samples.

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