Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.305
Filtrar
Mais filtros










Intervalo de ano de publicação
1.
Molecules ; 24(16)2019 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-31434234

RESUMO

The effect of the counteranion of hexadecyltrimethylammonium salts on the physico-chemical properties of organoclays was investigated, using a selected natural clay mineral with a cation exchange capacity of 95 meq/100 g. The uptake amount of C16 cations was dependent on the hexadecyltrimethylammonium (C16) salt solution used, the organoclay prepared from C16Br salt solution exhibited a value of 1. 05 mmole/g higher than those prepared from C16Cl and C16OH salt solutions. The basal spacing of these organoclays was in the range of 1.81 nm to 2.10 nm, indicating a similar orientation of the intercalated surfactants, and could indicated that the excess amount of surfactants, above the cation exchange capacity of 0.95 meq/g could be adsorbed on the external surface of the clay mineral sheets. These organoclays were found to be stable in neutral, acidic, and basic media. The thermal stability of these organoclays was carried out using thermogravimetric analysis and in-situ X-ray diffraction (XRD) techniques. The decomposition of the surfactant occurred at a maximum temperature of 240 °C, accompanied with a decrease of the basal spacing value close to 1.42 nm. The application of these organoclays was investigated to remove an acidic dye, eosin. The removal amount was related to the initial used concentrations, the amount of the surfactants contents, and to the preheated temperatures of the organoclays. The removal was found to be endothermic process with a maximum amount of 55 mg of eosin/g of organoclay. The value decreased to 25 mg/g, when the intercalated surfactants were decomposed. The reuse of these organoclays was limited to four regeneration recycles with a reduction of 20 to 30%. However, noticeable reduction between 35% to 50% of the initial efficiency, was achieved after the fifth cycle, depending of the used organoclays.


Assuntos
Compostos de Cetrimônio/química , Amarelo de Eosina-(YS)/isolamento & purificação , Tensoativos/química , Carbono/análise , Argila/química , Amarelo de Eosina-(YS)/química , Corantes Fluorescentes/química , Corantes Fluorescentes/isolamento & purificação , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Nitrogênio/análise , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Termogravimetria , Difração de Raios X
2.
Anal Bioanal Chem ; 410(27): 6977-6984, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30194453

RESUMO

Applications of asymmetrical flow field-flow fractionation (AF4) continue to expand rapidly in the fields of nanotechnology and biotechnology. In particular, AF4 has proven valuable for the separation and analysis of particles, biomolecular species (e.g., proteins, bacteria) and polymers (natural and synthetic), ranging in size from a few nanometers to several micrometers. The separation of non-spheroidal structures (e.g., rods, tubes, etc.) with primary dimensions in the nanometer regime, is a particularly challenging application deserving of greater study and consideration. The goal of the present study was to advance current understanding of the mechanism of separation of rod-like nano-objects in the AF4 channel. To achieve this, we have systematically investigated a series of commercially available cetyltrimethylammonium bromide stabilized gold nanorods (AuNRs), with aspect ratios from 1.7 to 10. Results show clearly that the retention time is principally dependent on the translational diffusion coefficient of the AuNRs. Equations used to calculate translational and rotational diffusion coefficients (cylinder and prolate ellipsoid models) yield similarly good fits to experimental data. Well characterized gold nanorods (length and diameter by transmission electron microscopy) can be used as calibrants for AF4 measurements allowing one to determine the aspect ratio of nanorod samples based on their retention times. Graphical abstract ᅟ.


Assuntos
Fracionamento por Campo e Fluxo/métodos , Ouro/química , Nanotubos/química , Cetrimônio , Compostos de Cetrimônio/química , Difusão , Hidrodinâmica , Nanotubos/ultraestrutura , Tamanho da Partícula
3.
Nanotechnology ; 29(46): 465703, 2018 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-30168799

RESUMO

Recently, DNA molecules embedded with magnetite (Fe3O4) nanoparticles (MNPs) drew much attention for their wide range of potential usage. With specific intrinsic properties such as low optical loss, high transparency, large band gap, high dielectric constant, potential for molecular recognition, and their biodegradable nature, the DNA molecule can serve as an effective template or scaffold for various functionalized nanomaterials. With the aid of cetyltrimethylammonium (CTMA) surfactant, DNA can be used in organic-based applications as well as water-based ones. Here, DNA and CTMA-DNA thin films with various concentrations of MNPs fabricated by the drop-casting method have been characterized by optical absorption, refractive index, Raman, and cathodoluminescence measurements to understand the binding, dispersion, chemical identification/functional modes, and energy transfer mechanisms, respectively. In addition, magnetization was measured as a function of either applied magnetic field or temperature in field cooling and zero field cooling. Saturation magnetization and blocking temperature demonstrate the importance of MNPs in DNA and CTMA-DNA thin films. Finally, we examine the thermal stabilities of MNP-embedded DNA and CTMA-DNA thin films through thermogravimetric analysis, derivative thermogravimetry, and differential thermal analysis. The unique optical, magnetic, and thermal characteristics of MNP-embedded DNA and CTMA-DNA thin films will prove important to fields such as spintronics, biomedicine, and function-embedded sensors and devices.


Assuntos
Compostos de Cetrimônio/química , DNA/química , Nanopartículas de Magnetita/química , Cetrimônio , Medições Luminescentes , Campos Magnéticos , Nanopartículas de Magnetita/análise , Gases em Plasma/química , Refratometria , Espectrofotometria Ultravioleta , Análise Espectral Raman , Temperatura , Termogravimetria
4.
Molecules ; 23(9)2018 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-30223595

RESUMO

The organo-clays (OCs) were prepared by a cation exchange reaction between surfactant (cetyltrimethylammonium, C16TMA) from different counterions (Bromide, Chloride, and Hydroxide). The effect of the counterions was investigated on the physico-chemical properties of the prepared organo-clays. The highest uptake of organic cations (1.60 mmol/g) was achieved using cetyl trimethylammonium bromide solution and the lowest value (0.93 mmol/g) was obtained after modification with cetyl trimethylammonium hydroxide solution starting from the same initial ratio of mmol/g of clay greater than 2.40. The arrangement of C16TMA cations within the interlayer space was assumed to be perpendicular with a tilt angle of 32° to the plane of clay sheets instead of being parallel to the clay surface using C16TMAOH solution at the same ratio. Different techniques were used to characterize these materials. The thermal stability of these organ-clays was investigated using an in-situ X-ray diffraction (XRD) technique. The decomposition of the surfactant moiety occurred at temperatures higher than 215 °C and was accompanied with a shrinkage of the basal spacing value to 1.42 nm. These materials were applied in the removal of an acid dye "eosin." The removed amount of eosin depended on the initial concentrations and the content of surfactants in the organo-clays. The removal of eosin was found to be an endothermic process. The maximum amount of 90 mg/g was achieved. The preheated treatment temperature of two selected OCs did affect the removal properties of eosin. A progressive reduction was observed at temperatures higher than 200 °C. The regeneration of spent OCs was studied and acceptable removal efficiency was maintained after 4 to 6 cycles depending on the used initial concentrations.


Assuntos
Compostos de Cetrimônio/química , Argila/química , Amarelo de Eosina-(YS)/química , Cátions , Temperatura Alta , Estrutura Molecular , Propriedades de Superfície
5.
Opt Lett ; 43(16): 4021-4024, 2018 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-30106942

RESUMO

We experimentally demonstrated a green liquid laser at the wavelength of 570 nm, utilizing the optical gain of vitamin B2 in a highly polar organic solvent, and proposed an efficient method to enhance its lasing efficiency by adding DNA-lipid complex (DNA-CTMA) in the solution. Optical properties of vitamin B2 in the hexafluoro-2-propanol solvents were investigated by adding various amounts of DNA-CTMA in terms of the UV-visible absorbance, the visible emission, and the fluorescence lifetime. A Fabry-Perot cavity was built to obtain the laser oscillation at 570 nm using a pulsed pump source at the wavelength of 450 nm, 5 ns pulse duration, and 10 Hz repetition rate. By adding DNA-CTMA, both the output power and slope efficiency were enhanced along with a significant reduction of the lasing threshold pump power. The proposed scheme could open new potential for highly efficient biolasers.


Assuntos
Compostos de Cetrimônio/química , DNA/química , Lasers , Riboflavina/química , Solventes/química , Animais , Desenho de Equipamento
6.
Int J Pharm ; 548(1): 474-479, 2018 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-29990535

RESUMO

The limited stability of catanionic vesicles has discouraged their wide use for encapsulation and controlled release of active substances. Their structure can easily break down to form lamellar phases, micelles or rearrange into multilamellar vesicles, as a consequence of small changes in their composition. However, despite the limited stability, catanionic vesicles possess an attractive architecture, which is able to efficiently encapsulate both hydrophobic and hydrophilic molecules. Therefore, improving the stability of the vesicles, as well as the control on unilamellar structures, are prerequisites for their wider application range. This study focuses on the impact of ß-cyclodextrins for the stabilization of SDS/CTAB catanionic vesicles. Molar ratio and sample preparation procedures have been investigated to evaluate the temperature stability of catanionic vesicles. Diffusion and spectroscopic techniques evidenced that when ß-cyclodextrins are added, unilamellar structures are stabilized above the multilamellar-unilamellar vesicles critical temperature. The results evidence encouraging perspectives for the use of vesicular nanoreservoirs for drug depot applications.


Assuntos
Compostos de Cetrimônio/química , Sistemas de Liberação de Medicamentos , Dodecilsulfato de Sódio/química , Tensoativos/química , Lipossomas Unilamelares/química , beta-Ciclodextrinas/química , Cetrimônio , Temperatura
7.
Colloids Surf B Biointerfaces ; 170: 144-151, 2018 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-29894835

RESUMO

Due to the enforcement of regulatory restrictions to prevent risk to human health from Bisphenol A (BPA), its structural analogue Bisphenol F (BPF) has been introduced into the market as an alternative. But however recent studies describe BPF as an effectual endocrine disruptor. Hence, there is an indispensible need for research concerning BPF human and environmental exposure level. In this work, we have elicited the development of an economical electrochemical sensor, to quantify and investigate in detail the electrochemical behavior of BPF using carbon paste electrode (CPE) modified with zinc oxide reduced graphene nanocomposite (ZnO/G) and cetyltrimethylammonium bromide (CTAB). The ZnO/G was synthesized using Hummers method and characterized by spectroscopic techniques. Under optimal conditions, conductive and biocompatible ZnO/G/CTAB/MCPE offered ultra sensitivity for BPF recognition by Differential Pulse Voltammetry (DPV), with a detection limit of 0.06 µM. Lowering of activation energy for electro-oxidation of BPF and absence of peak for interfering molecule Ascorbic acid (AA) makes it an unique sensor for the detection of BPF with significant analytical advantage over other electrodes reported in literature. Versatility of the electrode was demonstrated by applying it to real time analysis of human body fluids, canned beverage and different water samples fortified with BPF. The satisfactory recoveries obtained, consequently authenticates the practicality of the proposed sensor.


Assuntos
Compostos Benzidrílicos/análise , Carbono/química , Compostos de Cetrimônio/química , Técnicas Eletroquímicas , Nanocompostos/química , Fenóis/análise , Óxido de Zinco/química , Cetrimônio , Eletrodos , Estrutura Molecular , Tamanho da Partícula , Propriedades de Superfície
8.
Artigo em Inglês | MEDLINE | ID: mdl-29935478

RESUMO

A simple micellar electrokinetic chromatography (MEKC), using cetyltrimethyl ammonium bromide (CTAB) as micelles, for the determination of ciprofloxacin (CIP), enrofloxacin (ENR), norfloxacin (NOR) and ofloxacin (OFL) residues in surface water was developed. Peak Master was used for predicting amounts of analyte ionic forms to reduce numbers of tedious experiments in optimizing the analyte capacity factors. A baseline separation (Rs > 2.8) of the analytes was achieved in 7 min using 15 mM sodium dihydrogen phosphate (pH 6.0) containing 3 mM CTAB and a capillary with an effective length of 56.0 cm. A negative polarity voltage of 20 kV was used to enable the migration of the cationic micelles toward the detection site. The method shows good linearity in a range of 5 and 20 µg mL-1 and precision (%RSD < 6.45). Percent recoveries of the method were in a range of 65.1-88.7%. The limits of detection and quantitation were in the ranges of 1-2 and 3-5 µg mL-1, respectively. Two steps sample clean-up and preconcentration of surface water samples by hydrophilic-lipophilic balance and fluoroquinolone-molecularly imprinted polymer were advantageous for removal of humic acids and enabling the detection of fluoroquinolone residues in the samples. Finally, the method was applied for fluoroquinolone residues analysis of surface water in Thailand.


Assuntos
Compostos de Cetrimônio/química , Cromatografia Capilar Eletrocinética Micelar/métodos , Fluoroquinolonas/análise , Rios/química , Poluentes Químicos da Água/análise , Cetrimônio , Fluoroquinolonas/química , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Poluentes Químicos da Água/química
9.
J Colloid Interface Sci ; 529: 547-555, 2018 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-29957579

RESUMO

Core-shell nanostructured materials, which are of great interest for fundamental research and industrial applications, have properties that can be enhanced by combining component superstructures. Here, we report the new construction of magnetic core-shell gold nanostars (AuNSs) for controlled release of drug. The AuNSs were successfully embedded intact between an inner silica layer and outside mesoporous silica layer to create magnetic core/shell hybrid nanoparticles by using a base cationic templating surfactant, cetyltrimethylammonium hydroxide (CTAOH). The core-shell nano-composites containing AuNSs exhibit the characteristics including high magnetization, mesoporous nanostructure, photothermal properties and low in vitro toxicity, showing the potential applications for drug delivery and controlled release.


Assuntos
Preparações de Ação Retardada/química , Ouro/química , Nanopartículas de Magnetita/química , Tensoativos/química , Compostos de Cetrimônio/química , Hidróxidos/química , Porosidade , Dióxido de Silício/química
10.
Int J Mol Sci ; 19(5)2018 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-29747462

RESUMO

A hierarchical mesoporous zeolitic imidazolate framework (ZIF-8) was processed based on cetyltrimethylammonium bromide (CTAB) as a morphological regulating agent and amino acid (l-histidine) as assisting template agent. Burkholderia cepacia lipase (BCL) was successfully immobilized by ZIF-8 as the carrier via an adsorption method (BCL-ZIF-8). The immobilized lipase (BCL) showed utmost activity recovery up to 1279%, a 12-fold boost in its free counterpart. BCL-ZIF-8 was used as a biocatalyst in the transesterification reaction for the production of biodiesel with 93.4% yield. There was no significant lowering of conversion yield relative to original activity for BCL-ZIF-8 when continuously reused for eight cycles. This work provides a new outlook for biotechnological importance by immobilizing lipase on the hybrid catalyst (ZIF-8) and opens the door for its uses in the industrial field.


Assuntos
Biocombustíveis , Compostos de Cetrimônio/química , Enzimas Imobilizadas/química , Lipase/química , Burkholderia cepacia/enzimologia , Catálise , Cetrimônio , Esterificação , Histidina/química , Zeolitas/química
11.
Spectrochim Acta A Mol Biomol Spectrosc ; 201: 223-228, 2018 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-29753967

RESUMO

We report on a chemiluminescence (CL) system based on simultaneous enhancing effect of Si-doped carbon dots (Si-CDs) and cetyltrimethylammonium bromide (CTAB) on HCO3--H2O2 reaction. The possible CL mechanism is investigated and discussed. Excited-state Si-CDs was found to be the final emitting species, which are probably produced via electron and hole injection by oxy-radicals. The effect of several other heteroatom-doped CDs and undoped CDs was also investigated and compared with Si-CDs. Furthermore, it was found that catecholamines such as dopamine, adrenaline and noradrenaline remarkably diminish the CL intensity of Si-CD-HCO3--H2O2-CTAB system. By taking advantage of this fact, a sensitive probe was designed for determination of dopamine, adrenaline and noradrenaline with a limit of detection of 0.07, 0.60 and 0.01 µM, respectively. The method was applied to the determination of catecholamines in human plasma samples.


Assuntos
Catecolaminas/sangue , Medições Luminescentes/métodos , Nanoestruturas/química , Carbono/química , Cetrimônio , Compostos de Cetrimônio/química , Humanos , Limite de Detecção , Modelos Lineares , Reprodutibilidade dos Testes , Silício/química , Tensoativos/química
12.
Food Chem ; 259: 213-218, 2018 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-29680046

RESUMO

An Electrochemical nonenzymatic sensor was fabricated based on cetyltrimethylammonium bromide (CTAB), chitosan (Chit) and carbon nanotube (CNT) nanocomposite modified glassy carbon electrode. Scanning electron microscopy morphology showed that CNT well dispersed in Chit, while CTAB micelles assembled on the surface of the CNT. Due to the synergetic effect of the three components, excellent electrocatalytic activity towards the oxidation of hydroxymethanesulfinate (HMS) in the presence of both fixed and varying concentrations of sulfite was achieved. An enhanced peak current and expanded peak-to-peak separation between HMS and sulfite was observed. Differential pulse voltammetry was applied to quantify HMS and the calibration curve was linear in the range of 30-800 µM with a detection limit of 9.6 µM. The method was applied in the determination of HMS in food samples collected from local markets, and the results have no remarkable difference with the reference HPLC method.


Assuntos
Compostos de Cetrimônio/química , Quitosana/química , Técnicas Eletroquímicas , Mesilatos/análise , Nanotubos de Carbono/química , Sulfitos/química , Carbono/química , Cetrimônio , Eletrodos , Análise de Alimentos , Concentração de Íons de Hidrogênio , Limite de Detecção , Microscopia Eletrônica de Varredura
13.
Spectrochim Acta A Mol Biomol Spectrosc ; 198: 278-282, 2018 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-29554518

RESUMO

The interactions of a protein cytochrome c with some selected conventional and ionic liquid surfactants have been investigated at pH7.4 using ultraviolet-visible and fluorescence spectroscopic techniques. We used four conventional surfactants - cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), sodium N-dodecanoylsarcosinate (SDDS), and N-decanoyl-N-methylglucamine (Mega 10), and a surface active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (C16MeImCl). All the investigated surfactants were found to induce an unfolding of the protein cytochrome c. In presence of CTAB, SDDS and C16MeImCl, the heme iron atom was found to loose methionine from its axial position. Differential binding of the surfactant monomers and their micelles to the protein molecules was inferred. The ionic surfactants were found to be more effective than the nonionic one in unfolding the investigated protein. However, the extent of binding of CTAB/C16MeImCl to cytochrome c reaches a plateau past the critical micellization concentration (cmc) of the surfactant. For each of the cytochrome c-DTAB, cytochrome c-SDDS and cytochrome c-Mega 10 system, although there exists an inflection in the surfactant-binding, saturation point could not be detected. It has been demonstrated from the ultraviolet-visible spectral studies that the oxidation state of iron in cytochrome c does not change when the protein binds with the investigated surfactants.


Assuntos
Citocromos c/química , Líquidos Iônicos/química , Tensoativos/química , Animais , Cetrimônio , Compostos de Cetrimônio/química , Ácidos Graxos/química , Glucosamina/análogos & derivados , Glucosamina/química , Cavalos , Imidazóis/química , Ferro/química , Ferro/metabolismo , Miocárdio/enzimologia , Conformação Proteica , Compostos de Amônio Quaternário/química , Sarcosina/análogos & derivados , Sarcosina/química , Espectrometria de Fluorescência , Espectrofotometria Ultravioleta
14.
Chemistry ; 24(28): 7200-7209, 2018 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-29572993

RESUMO

A new class of hierarchically structured mesoporous silica core-shell nanoparticles (HSMSCSNs) with a periodic mesoporous organosilica (PMO) core and a mesoporous silica (MS) shell is reported. The applied one-pot, two-step strategy allows rational control over the core/shell chemical composition, topology, and pore/particle size, simply by adjusting the reaction conditions in the presence of cetyltrimethylammonium bromide (CTAB) as structure-directing agent under basic conditions. The spherical, ethylene- or methylene-bridged PMO cores feature hexagonal (p6mm) or cage-like cubic symmetry (Pm3‾ n) depending on the organosilica precursor. The hexagonal MS shell was obtained by n-hexane-induced controlled hydrolysis of TEOS followed by directional co-assembly/condensation of silicate/CTAB composites at the PMO cores. The HSMSCSNs feature a hierarchical pore structure with pore diameters of about 2.7 and 5.6 nm in the core and shell domains, respectively. The core sizes and shell thicknesses are adjustable in the ranges of 90-275 and 15-50 nm, respectively, and the surface areas (max. 1300 m2 g-1 ) and pore volumes (max. 1.83 cm3 g-1 ) are among the highest reported for core-shell nanoparticles. The adsorption and controlled release of the fungicide propiconazole by the HSMSCSNs showed a three-stage release profile.


Assuntos
Compostos de Cetrimônio/química , Fungicidas Industriais/química , Nanopartículas/química , Compostos de Organossilício/química , Dióxido de Silício/química , Adsorção , Cetrimônio , Hidrólise , Tamanho da Partícula
15.
Talanta ; 182: 247-252, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29501148

RESUMO

Electrokinetic stacking (ES) is effective for improving sensitivity of paper-based analytical device (PAD) for charged analytes. In this paper, we successfully demonstrated ES of electrically neutral analytes on PAD, and the performance was characterized by smartphone-based colorimetry and fluorescence. Firstly, SDS from cathode reservoir stacked as a micelle band on an open paper fluidic channel by ES, and the target analyte was swept by the micelle. Meanwhile, the probes at the other side were carried by electroosmotic flow (EOF). Eventually, neutral components preloaded on the channel were concentrated as the narrow stacking band. Taking the rhodamine B as a probe, the effects of EOF, background electrolyte concentration and anionic surfactant concentration were investigated. Fluorescence detection of rhodamine B and colorimetric analysis of Sudan III demonstrated the sensitivity enhanced and its potential for the semi-quantitative test. Under the optimized conditions, fluorescence detection limit of 50 nM of rhodamine B was achieved with a linear range of 1.0-10 µM (R2 = 0.99). The colorimetric detection limit for Sudan III was 5.2 µM and the linear range was 5-40 µM (R2= 0.99). Compared with direct analysis without stacking, the signal levels of rhodamine B and Sudan III were increased by 30-fold and 6-fold, respectively. This study showed that with ES, sensitive and rapid PAD detection of electrically neutral analytes could be achieved.


Assuntos
Compostos Azo/isolamento & purificação , Cromatografia Capilar Eletrocinética Micelar/métodos , Colorimetria/métodos , Eletroforese Capilar/métodos , Rodaminas/isolamento & purificação , Celulose/análogos & derivados , Celulose/química , Cetrimônio , Compostos de Cetrimônio/química , Eletricidade , Eletro-Osmose , Limite de Detecção , Micelas , Reprodutibilidade dos Testes , Dodecilsulfato de Sódio/química
16.
Talanta ; 182: 405-413, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29501171

RESUMO

In this work, magnetic graphene/mesoporous silica composites with carbon-functionalized pore-walls (denoted as MG@mSiO2-C composites) were synthesized and applied as restricted access matrix solid phase extraction (RAM-SPE) adsorbents for the determination of miglitol and voglibose in rat plasma by LC-MS/MS. The MG@mSiO2-C composites were synthesized by using the template (Cetyltrimethyl Ammonium Bromide, CTAB) as carbon source with sulfuric acid pretreated. The obtained nano-composites were proven to have many unique properties such as large specific surface area of 277.1 cm2 g-1, uniform mesopores with average pore size of 3.35 nm, and carbon-functionalized pore-walls. Taking advantage of the hydrophilic interaction between carbon and glycans, α-glucosidase inhibitors (miglitol and voglibose) could be directly extracted from rat plasma with no need of other pre-treatment procedures. The SPE conditions such as the adsorbent amount, elution solvent type, adsorption time and elution time were optimized. For both miglitol and voglibose, good linearities of 10-2000 ng mL-1 were obtained with determination coefficients (R2) > 0.99. The intra-day and inter-day RSDs were 3.3-6.9% (n = 6) and 6.0-8.0% (n = 6), respectively. The recoveries were in the range of 99.9-100.4% and the sensitivities were as low as 2-2.5 ng mL-1 (LOD). This MG@mSiO2-C composites-based RAM-SPE method offers high extraction efficiency for the determination of α-glucosidase inhibitor in plasma.


Assuntos
1-Desoxinojirimicina/análogos & derivados , Inibidores Enzimáticos/isolamento & purificação , Inositol/análogos & derivados , Nanocompostos/química , Dióxido de Silício/química , Extração em Fase Sólida/métodos , 1-Desoxinojirimicina/sangue , 1-Desoxinojirimicina/isolamento & purificação , Adsorção , Animais , Cetrimônio , Compostos de Cetrimônio/química , Inibidores Enzimáticos/sangue , Inositol/sangue , Inositol/isolamento & purificação , Limite de Detecção , Nanopartículas de Magnetita/química , Nanopartículas de Magnetita/ultraestrutura , Masculino , Nanocompostos/ultraestrutura , Porosidade , Ratos , Ratos Sprague-Dawley , alfa-Glucosidases/sangue , alfa-Glucosidases/química
17.
J Environ Manage ; 214: 86-93, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29518599

RESUMO

This study presents the results of the electrochemical degradation of the emulsifier cetrimonium chloride (CTAC) on a boron-doped diamond (BDD) anode under different current densities and flow rates. Higher values of these parameters result in a more rapid removal. Nevertheless, operation at low current reduces the required applied charge and increases the chemical oxygen demand (COD) removal efficiency, as there is less development of ineffective parasitic reactions. On the other hand, high flow rates reduce the required volumetric applied charge and increase the COD removal current efficiency. In order to assist and enrich the study, an economic analysis has been performed. For short expected plant lifespans, operation at low current is advantageous due to the lower investment required, whereas for longer expected lifespans, the operational costs make the lower current densities less costly. High flow rates are always advantageous from a financial point of view.


Assuntos
Compostos de Cetrimônio/química , Diamante , Poluentes Químicos da Água , Boro , Cetrimônio , Eletroquímica , Eletrodos , Oxirredução , Purificação da Água
18.
J Phys Chem B ; 122(8): 2355-2367, 2018 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-29406731

RESUMO

The surface property of the cationic micelles of cetyltrimethylammonium bromide (CTAB) in an aqueous medium is highly modified in the presence of tyrosineoctyl ester (TYOE) and tyrosinedodecyl ester (TYDE), the models for aromatic amino acid side chains of transmembrane proteins. While the synergistic interaction between the quaternary ammonium head group of CTAB and the π-electron cloud of aromatic amino acid ester is influenced by the relative orientation and the unusual molecular geometry of the latter, this eventually triggers a morphology transition of the spherical micelle to cylindrical/wormlike micelles and imparts a strong viscoelasticity in the medium. Physical characteristics of the elongated micelles have been investigated by high resolution transmission electron microscopy (HRTEM) and the small angle neutron scattering (SANS) technique; the complex fluidic nature of the system is investigated by a dynamic rheological measurement. The intermolecular interactions have been recognized via 1H NMR and 2D nuclear Overhauser effect spectroscopy (NOESY), and the unambiguous geometry of the end-caps of the rods has been ascertained for the first time. While the interplay between lipids and transmembrane proteins is thought to be crucial in controlling the membrane shape of the cells during many vital events such as cellular fission, fusion, and virus entry, the observed tuning of the micellar surface curvature via the cation-π interaction involving tyrosine analogues is thought provoking and opens up an avenue for new physical chemistry research on a vital biological phenomena.


Assuntos
Compostos de Amônio Quaternário/química , Tirosina/química , Água/química , Cetrimônio , Compostos de Cetrimônio/química , Interações Hidrofóbicas e Hidrofílicas , Espectroscopia de Ressonância Magnética , Micelas , Microscopia Eletrônica de Transmissão , Difração de Nêutrons , Espalhamento a Baixo Ângulo , Tirosina/análogos & derivados
19.
Colloids Surf B Biointerfaces ; 163: 140-145, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29291499

RESUMO

A common capping agent for gold nanorods, Cetyl trimethylammonium bromide (CTAB), is particularly problematic for biological studies because of its cytotoxicity. Several procedures have been developed to remove the CTAB from the surface of the gold nanorods, but most are lengthy, involving many steps, and use expensive reagents. Here, we present a simple, one-pot method for the complete removal of CTAB from the surface of gold nanorods, so that particles can be more effectively utilized in biological in vivo studies. The procedure involves first adding sodium borohydride to remove the CTAB, quickly followed by a replacement ligand, such as mercaptoundecanoic acid (MUA). Both the CTAB removal and MUA replacement were monitored by FTIR, surface enhanced Raman spectroscopy (SERS) and X-Ray Photoelectron Spectroscopy (XPS) and compared to commercially available citrate-capped gold nanorods. The procedure presented herein is shown to be as effective at removing CTAB and replacing it with MUA as commercially available gold nanorod samples.


Assuntos
Boroidretos/química , Compostos de Cetrimônio/isolamento & purificação , Ácidos Graxos/química , Ouro/química , Nanopartículas Metálicas/química , Nanotubos/química , Compostos de Sulfidrila/química , Cetrimônio , Compostos de Cetrimônio/química , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Ressonância de Plasmônio de Superfície , Propriedades de Superfície , Termodinâmica
20.
Cutan Ocul Toxicol ; 37(1): 1-8, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28372461

RESUMO

Radioactive skin contamination is one of the most likely risks which occurs after accidental or occupational radiological accidents apart from internal contamination. In such cases where the radioactive contamination has occurred, the person who is contaminated should be decontaminated as early as possible to reduce the damaging health effects of radiation. In the present study, the decontamination efficiency of a developed skin decontamination kit "dermadecon" has been evaluated in animal models and human subjects using gamma scintigraphy. Decontamination efficiency (percentage of the radioactive contaminant removed) was calculated for each radioactive isotope of the study and compared with control where general washing procedure was followed using liquid and soap. The effectiveness of the kit was calculated in animal model with respect to 99mTc-sodium-pertechnetate (99mTcO4-), 201TlCl and 131I and was found 92.84 ± 4.9%, 91.18 ± 3.23% and 94.67 ± 2.92%, respectively. Whereas, in case of human skin, the decontamination efficiency for 99mTcO4- was observed to be 95.00 ± 3.21%. On the basis of findings from the study, it can be concluded that the decontamination agents of the used skin decontamination kit are effective for removal of localized radioactive contaminants from skin, as compared with normal decontamination using soap and water.


Assuntos
Descontaminação/métodos , Radioisótopos do Iodo/análise , Tecnécio/análise , Radioisótopos de Tálio/análise , Ácido Acético/química , Adulto , Animais , Cetrimônio , Compostos de Cetrimônio/química , Quelantes/química , Ácido Edético/química , Humanos , Ácido Hipocloroso/química , Radioisótopos do Iodo/química , Masculino , Pessoa de Meia-Idade , Oxidantes/química , Cintilografia , Ratos Sprague-Dawley , Substâncias Redutoras/química , Pele , Bicarbonato de Sódio/química , Tecnécio/química , Radioisótopos de Tálio/química , Tiossulfatos/química , Adulto Jovem
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA