Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.313
Filtrar
1.
Spectrochim Acta A Mol Biomol Spectrosc ; 309: 123770, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38157746

RESUMO

In this study, the complexation of potential chemo-therapeutic antibacterial drug, ciprofloxacin (CIP) with varying concentrations of surface active compounds (SACs) i.e., (N-(2-hydroxyethyl)-N,N-dimethyl-1-dodecanaminium bromide (12Cho.Br) and cetyltrimethylammonium bromide (CTAB) has been studied. Multispectroscopic techniques were exploited to carry out the study. The higher binding constant (Kb) value for CIP-CTAB than CIP-12Cho.Br obtained from fluorescence data revealed stronger binding of CTAB than 12Cho.Br, owing to the stronger hydrophobic-hydrophobic interaction betweeen CIP and CTAB compared to CIP and 12Cho.Br. The time resolve fluorescence decay shows changes in average lifetime (τavg) with the increasing concentration of 12Cho.Br and CTAB. The changes in τavg suggests that complex formation is taking place between CIP and 12Cho.Br / CTAB. Further, the formation of micelles by 12Cho.Br / CTAB and the effect of alkyl chain length was studied by dynamic light scattering (DLS) and zeta potential to confirm the drug complexation with 12Cho.Br and CTAB. The antibacterial activity has been performed for CIP and 12Cho.Br and CTAB. It was observed that in presence of lower concentrations of 12Cho.Br/ CTAB, the activity of the drug increased. The activity was also found cationic alkyl chain length dependent. Moreover, in-vitro cytotoxicity of CIP and its combinations with 12Cho.Br and CTAB was performed using MTT assay on HEK293 (Human embryonic kidney cells).


Assuntos
Ciprofloxacina , Líquidos Iônicos , Humanos , Cetrimônio , Ciprofloxacina/farmacologia , Líquidos Iônicos/química , Tensoativos/química , Colina , Células HEK293 , Compostos de Cetrimônio/farmacologia , Compostos de Cetrimônio/química , Micelas , Antibacterianos/farmacologia
2.
Environ Sci Pollut Res Int ; 30(41): 94474-94484, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37535279

RESUMO

Cocoa shell was modified whit sodium hydroxide (NaOH) and cationic surfactant cetyltrimethylammonium bromide (CTAB) to increase surface functionality, surface area, and positive charge density. The prepared adsorbent CC-OH-CTAB was used to remove indigo carmine (IC) and bromocresol green (BCG) dyes from water. The optimal pH for IC and BCG adsorption were 2 and 4, respectively. The equilibrium was attained after a contact time of 30 min for IC and 120 min for BCG. The maximum adsorption capacity (Qmax) of IC and BCG obtained was 85.1 mg g-1 and 192.7 mg g-1, respectively. The Liu isotherm model best described the equilibrium results. The adsorption kinetics model showed that IC and BCG adsorption onto CC-OH-CTAB followed the pseudo-first-order and pseudo-second-order model, respectively. The regeneration and reusability experiments indicated that CC-OH-CTAB had much stability and excellent performance meanwhile repeatedly used. Finally, the insertion of CTAB on the CC-OH surface proved to be an excellent way to improve the adsorption performance of this material concerning dyes.


Assuntos
Corantes , Poluentes Químicos da Água , Cetrimônio , Corantes/química , Adsorção , Compostos de Cetrimônio/química , Índigo Carmim , Cinética , Poluentes Químicos da Água/análise , Concentração de Íons de Hidrogênio
3.
J Colloid Interface Sci ; 631(Pt A): 202-211, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36375300

RESUMO

HYPOTHESIS: Quatsome nanovesicles, formed through the self-assembly of cholesterol (CHOL) and cetyltrimethylammonium bromide (CTAB) in water, have shown long-term stability in terms of size and morphology, while at the same time exhibiting high CHOL-CTAB intermolecular binding energies. We hypothesize that CHOL/CTAB quatsomes are indeed thermodynamically stable nanovesicles, and investigate the mechanism underlying their formation. EXPERIMENTS: A systematic study was performed to determine whether CHOL/CTAB quatsomes satisfy the experimental requisites of thermodynamically stable vesicles. Coarse-grain molecular dynamics simulations were used to investigate the molecular organization in the vesicle membrane, and the characteristics of the simulated vesicle were corroborated with experimental data obtained by cryo-electron microscopy, small- and wide-angle X-ray scattering, and multi-angle static light scattering. FINDINGS: CHOL/CTAB quatsomes fulfill the requisites of thermodynamically stable nanovesicles, but they do not exhibit the classical membrane curvature induced by a composition asymmetry between the bilayer leaflets, like catanionic nanovesicles. Instead, CHOL/CTAB quatsomes are formed through the association of intrinsically planar bilayers in a faceted vesicle with defects, indicating that distortions in the organization and orientation of molecules can play a major role in the formation of thermodynamically stable nanovesicles.


Assuntos
Compostos de Cetrimônio , Simulação de Dinâmica Molecular , Cetrimônio , Microscopia Crioeletrônica , Compostos de Cetrimônio/química , Colesterol/química , Bicamadas Lipídicas/química
4.
Langmuir ; 38(48): 14768-14778, 2022 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-36437713

RESUMO

A catanionic surfactant system is an aqueous solution or dispersion of cationic and anionic surfactants that spontaneously self-assemble into structures such as micelles, vesicles, and coacervates. Their structural diversity varies depending on the ratios of cationic and anionic surfactants (compositions), the chemical structure of the constituent molecules, etc. Herein, two types of catanionic surfactant systems were systematically characterized: (i) cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), both typical ionic surfactants; and (ii) dodecylmethylimidazolium ammonium bromide ([C12mim]Br) and SDS, where the former is an ionic liquid. By observing the sample appearance, turbidity, and particle size, the phase state of each system was analyzed according to the total concentration of surfactants and the molar ratio of cationic surfactants to the total concentration. Especially, for specific compositions of catanionic surfactant vesicles (cataniosome), the closed structure of the vesicles was confirmed through calcein entrapment and release detected with a fluorescence assay. The polarities of the interface of the prepared self-assemblies were evaluated using a fluorescence probe, Laurdan. The packing state of the molecules in the formed self-assembly structure was estimated using Raman spectroscopy. The results clearly indicate consistent phase-transition behavior for the CTAB-SDS (i) and [C12mim]Br-SDS (ii) systems, depending on the total surfactant concentration and composition, while the membrane properties of the two systems differed. The cataniosome formed in the CTAB-SDS system was in a tightly packed membrane state and more hydrophobic than that formed in the [C12mim]Br-SDS system owing to the difference in the structure of the constituting molecule: [C12mim]Br has a larger head group and shorter acyl chain than CTAB. The self-assembly properties evaluated in this study were compared with those of typical lipid membranes, liposomes (lipid vesicles), to determine a possible application of the catanionic systems with various self-assembly formulations.


Assuntos
Surfactantes Pulmonares , Tensoativos , Tensoativos/química , Cetrimônio , Dodecilsulfato de Sódio/química , Compostos de Cetrimônio/química , Cátions/química , Excipientes
5.
Molecules ; 27(14)2022 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-35889205

RESUMO

In recent years, there has been increasing interest in daily-use chemical products providing a pleasant scent. The added fragrance molecules may induce microstructural transitions of surfactant aggregates, which further affect the physical and chemical properties of the products. Here, the effects of four types of aromatic alcohols (cinnamyl alcohol, phenyl ethanol, phenyl methanol and anisyl alcohol) on cetyltrimethylammonium bromide (CTAB)/KBr aggregates were studied. The combined results from rheology, dynamic light scattering, and transmission electron microscopy measurements showed that cinnamyl alcohol induced significant micellar growth, while increases in micellar growth were less obvious for the other aromatic alcohols. The changes in the interfacial molarities of water, aromatic alcohol, and bromide ions during such transitions were studied using the chemical trapping method. Transitions resulting from added cinnamyl alcohol were accompanied by significant declines in interfacial water and bromide ion molarities, and a rise in interfacial alcohol molarity. The marked decrease in interfacial water molarity was not observed in previous studies of the octanol induced formation of wormlike micelles and vesicles, indicating that a different mechanism was presented in the current system. Nuclear magnetic resonance investigation showed that π-π stacking between cinnamyl alcohols, but not cation-π interactions between alcohols and CTAB headgroups, facilitated the tight packing of alcohol molecules in CTAB aggregates and the repulsion of water from the interfacial region. The current study may provide a theoretical basis for the morphological regulation of surfactant aggregates in the presence of additives.


Assuntos
Surfactantes Pulmonares , Tensoativos , Brometos , Cetrimônio , Compostos de Cetrimônio/química , Excipientes , Micelas , Odorantes , Tensoativos/química , Água/química
6.
Langmuir ; 38(8): 2486-2494, 2022 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-35164504

RESUMO

Although worm-like micelles were invented 35 years ago, its formation pathway remains unclear. Inspired by the fact that a single molecular level experiment could provide meaningful and additional information, especially in a heterogeneous subpopulation, herein, we present a single molecular level study on the formation of wormlike micelles by cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) in water. Our results indicated a coexistence of normal spherical micelles along with a big wormlike micelle in its formation path. More interestingly, we have two unique insights into the formation mechanism, which are inaccessible in ensemble averaged experiments: (i) at extremely low concentrations of the surfactant, [CTAB]/[NaSal] ∼ 0.06, the wormlike micelle attains the highest size; and (ii) the relative concentration of wormlike micelles is highest when [CTAB]/[NaSal] ∼ 2.


Assuntos
Compostos de Cetrimônio , Micelas , Cetrimônio , Compostos de Cetrimônio/química , Espectrometria de Fluorescência , Tensoativos/química
7.
Int J Mol Sci ; 21(18)2020 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-32948026

RESUMO

Catanionic vesicles are emerging interesting structures for bioapplications. They self-generate by a pairing of oppositely charged ionic surfactants that assemble into hollow structures. Specifically, the anionic-cationic surfactant pair assumes a double-tailed zwitterionic behavior. In this work, the multilamellar-to-unilamellar thermal transition of several mixed aqueous systems, with a slight excess of the anionic one, were investigated. Interestingly, it was found that the anionic counterion underwent a dissociation as a consequence of a temperature increase, leading to the mentioned thermal transition. The present work proposed the spectroscopic techniques, specifically multinuclear NMR and PGSTE (pulsed gradient stimulated echo), as a key tool to study such systems, with high accuracy and effectiveness, while requiring a small amount of the sample. The results presented herein evidence encouraging perspectives, forecasting the application of the studied vesicular nanoreservoirs, for e.g., drug delivery.


Assuntos
Nanotubos de Carbono/química , Ressonância Magnética Nuclear Biomolecular/métodos , Ânions/química , Cátions/química , Compostos de Cetrimônio/química , Micelas , Microscopia Confocal , Transição de Fase , Dodecilsulfato de Sódio/química , Tensoativos/química , Temperatura
8.
Bioconjug Chem ; 30(11): 2917-2930, 2019 11 20.
Artigo em Inglês | MEDLINE | ID: mdl-31621309

RESUMO

Nanoparticles in ionic solutions are usually surrounded by stabilizing molecules that avoid aggregation and determine their surface properties, which strongly influence their behavior. The present work aims to shed light on the static vs dynamic nature of the cetyltrimethylammonium bromide (CTAB) bilayer on gold nanoparticles and to understand its effects on nanoparticle evolution in biological systems. A systematic study of the CTAB bilayer of Au nanorods and nanospheres was carried out, exploring the role of excess free surfactant in solution on the surface properties of nanoparticles and their colloidal stability. The results indicated the presence of a CTAB bilayer in which the external layer was in rapid dynamic equilibrium with the free surfactant in solution. The internal surfactant layer of the gold nanospheres was also found to be in dynamic equilibrium. Conversely, the gold nanorods had a permanent internal layer. Consequently, the CTAB-nanoparticle dispersions always contained free CTAB in excess to maintain the colloidal stability of the NPs. In contrast, decreasing the free CTAB concentration resulted in nanoparticle aggregation. The impact of the dynamic equilibrium on the exposure of particles to biological fluids and on the formation of the nanoparticle protein corona was studied, revealing the different fates of the nanoparticles, which depended on the amount of free CTAB in solution.


Assuntos
Compostos de Cetrimônio/química , Ouro/química , Nanopartículas Metálicas/química , Nanotubos/química , Coroa de Proteína/metabolismo , Tensoativos/metabolismo , Humanos , Coroa de Proteína/química , Propriedades de Superfície , Tensoativos/química
9.
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
10.
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
11.
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
12.
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
13.
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
14.
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
15.
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
16.
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
17.
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
18.
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
19.
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
20.
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
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...