Cetyltrimethylammonium Bromide Complex Research Articles

Counteraction of the cetyltrimethylammonium bromide-induced protein aggregation by heparin: Potential impact on protein aggregation and neurodegenerative diseases using biophysical approaches

Heparin, a member of the glycosaminoglycan (GAG) family, is an extremely acidic sulfur-containing polysaccharide which has been suggested to be coupled with protein aggregation-related diseases including Alzheimer's, Parkinson's and Prion diseases. Here, we study the effect of heparin on the cetyltrimethylammonium bromide (CTAB)-induced aggregation of bovine serum albumin (BSA) exploiting biophysical approaches. Kinetic measurements indicated that heparin caused complete inhibition of CTAB-induced aggregation of protein with a significant decrease in the apparent rate constant. Far- and near-UV CD measurements depicted that CTAB behaves as a protein-aggregating agent. However, the perturbation of secondary and tertiary structure-induced by CTAB and the CTAB-induced amyloid formation of protein were prevented by heparin. ITC measurements revealed that enhancement of aggregation induced by CTAB was as a result of sequential binding in which CTAB binds with the protein and accompanied by exothermic heat of interaction. ITC measurements also showed that CTAB and heparin form complex while the complex does not bind with protein. Thus, we hypothesize that CTAB-Heparin complex is engaged in the inhibition of protein aggregation. Therefore, the mechanism of action of CTAB-heparin complex in inhibition of protein aggregation may be used as a basis of the development of therapeutic strategies of various neurodegenerative complications.

Hyperbranched polyglycerols derivatives as cetyltrimethylammonium bromide nanocarriers on enhanced oil recovery processes

AbstractIn this work, the efficiency of partially hydrophobized hyperbranched polyglycerols (HPG11 and HPG12) as cetyltrimethylammonium bromide (CTAB) carriers was evaluated to prevent surfactant losses by adsorption on reservoir rocks surface during enhanced oil recovery (EOR) processes. Interactions between surfactant and polymers were studied by conductivity, zeta potential, and particle size measurements showing that complexes were formed between the components. The ability of PG, HPG11, HPG12 and those complexes to reduce the interfacial tension (IFT) was verified and one of the complexes was able to reduce the IFT to values under 1.0 mN/m, suggesting the occurrence of a synergy between the components. Molecular dynamics simulations indicated the preferential sites of interaction between surfactants and HPGs. HPG11:CTAB and HPG12:CTAB complexes' ability to permeate an unconsolidated porous medium and deliver the surfactant at the water–oil interface, increasing oil production, was evaluated through transport and oil displacement tests, and the results showed that the HPG12:CTAB complex led to almost 90% of oil recovery.

Gold-Modified Micellar Composites as Colorimetric Probes for the Determination of Low Molecular Weight Thiols in Biological Fluids Using Consumer Electronic Devices

This work describes a new, low-cost and simple-to-use method for the determination of free biothiols in biological fluids. The developed method utilizes the interaction of biothiols with gold ions, previously anchored on micellar assemblies through electrostatic interactions with the hydrophilic headgroup of cationic surfactant micelles. Specifically, the reaction of AuCl4− with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB) produces an intense orange coloration, due to the ligand substitution reaction of the Br− for Cl− anions, followed by the coordination of the AuBr4− anions on the micelle surface through electrostatic interactions. When biothiols are added to the solution, they complex with the gold ions and disrupt the AuBr4−–CTAB complex, quenching the initial coloration and inducing a decrease in the light absorbance of the solution. Biothiols are assessed by monitoring their color quenching in an RGB color model, using a flatbed scanner operating in transmittance mode as an inexpensive microtiter plate photometer. The method was applied to determine the biothiol content in urine and blood plasma samples, with satisfactory recoveries (i.e., >67.3–123% using external calibration and 103.8–115% using standard addition calibration) and good reproducibility (RSD < 8.4%, n = 3).

Distinctive spectroscopic properties and adsorption behaviors of p-sulfonatocalixarene-cetyltrimethylammonium bromide supra-amphiphilic systems

So far, the knowledge about the properties of the calixarene-based supra-amphiphiles remain very limited. In the present study, we investigated the properties of p-sulfonatocalix[n]arene (SC[n], n = 4, 6 and 8)-cetyltrimethylammonium bromide (CTAB) supra-amphiphiles by measuring their fluorescence, UV–vis absorption, 1H NMR spectra as well as surface tension, and found that the calixarene/surfactant mixed systems exhibited special spectroscopic properties and adsorption behaviors. Although SC[n] and CTAB were both non-fluorescent, the resulting SC[n]-CTAB complexes emitted fluorescence; the strongest fluorescence intensity was observed when the molar ratio of CTAB to SC[n] reached the stoichiometry. The SC[n]-CTAB complexes and/or CTAB monomers did not adsorb at the air/water surface until the CTAB content was higher than the stoichiometry. Once CTAB began to adsorb at the surface, the surface tension decreased sharply (much faster than in the absence of SC[n]). Among SC[4], SC[6] and SC[8], SC[4] not only induced the CTAB molecules to line up most tightly at the air/water surface, but also possessed the strongest ability to promote the aggregation of the CTAB molecules in solution. Moreover, proteins did not break the binding between SC[n] and CTAB; they interacted with the complex instead and their activities were closely related to the molar ratio of CTAB to SC[n]. The present study should suggest the potential application of SC[n]/CTAB systems in fields such as fluorescent inks, encryption coding, and regulation of protein activity.

Silver-Assisted Synthesis of Gold Nanorods: the Relation between Silver Additive and Iodide Impurities.

Seed-mediated methods employing cetyltrimethylammonium bromide (CTAB) as a surfactant, and silver salts as additives, are the most common synthetic strategies for high-yield productions of quality Au nanorods. However, the mechanism of these reactions is not yet fully understood and, importantly, significant lab-to-lab reproducibility issues still affect these protocols. In this study, the direct correlation between the hidden content of iodide impurities in CTAB reagents, which can drastically differ from different suppliers or batches, and the optimal concentration of silver required to maximize the nanorods yield is demonstrated. As a result, high-quality nanorods are obtained at different iodide contents. These results are interpreted based on the different concentrations of CTAB and cetyltrimethylammonium iodide (CTAI) complexes with Ag+ and Au+ metal ions in the growth solution, and their different binding affinity and reduction potential on distinct crystallographic planes. Notably, the exhaustive conversion of CTAI-Au+ to CTAI-Ag+ appears to be the key condition for maximizing the nanorod yield.

Controlled etching of gold nanorods by the Au(III)-CTAB complex, and its application to semi-quantitative visual determination of organophosphorus pesticides

The authors describe a semi-quantitative colorimetric method for visual detection of organophosphorus pesticides (OPs). It is based on the aspect ratio dependent absorbance of gold nanorods (AuNRs) which is due to the localized surface plasmon resonance. The aspect ratio can be tailored by the Au(III) complex formed with cetyltrimethylammonium bromide (CTAB) which is affected by acetylcholinesterase (AChE) based hydrolysis. OPs act as inhibitors of this reaction. In the absence of OPs, the product (thiocholine) of enzymatic hydrolysis consumes almost all the Au(III) species. In this case, the amount of residual Au(III)-CTAB complexes is small, and etching of the AuNRs does not occur. In the presence of OPs, however, the activity of AChE is inhibited. Hence, only small quantities of (or no) thiocholine is produced, and Au(III) is not consumed. Au(III) is capable of etching AuNRs and to change their aspect ratio. This leads to a color change from brownish to gray, cyan, green, blue, purple, red, and colorless that can be easily observed with bare eyes. The AuNRs were incorporated into cellulose paper to obtain a paper stripe for visual detection of OPs. Under optimal conditions, both methods (AuNRs in aqueous solutions and on paper) allowed various OPs to be determined. Applied to parathion, the method had a detection limit as low as 1.2 ppb and a linear range from 0.01 to 1.84 ppm. It was applied to the analysis of cabbage washing solutions and sea water samples, and acceptable accuracy and good resolution were found. In our preconception, the method represents a valuable tool for on-site detection of OPs in agriculture products and food.

Use of liquid crystals for imaging different inclusion abilities of α-cyclodextrin and β-cyclodextrin toward cetyltrimethyl ammonium bromide

We herein report a method for the imaging of different inclusion abilities of α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) toward cetyltrimethyl ammonium bromide (CTAB) using liquid crystals (LCs). The optical transition from the dark to the bright state was caused by the inclusion interaction between CTAB and CDs. It was confirmed that α-CD formed more stable CTAB complexes than β-CD, leading to different optical responses of the LCs from the α-CD/CTAB and β-CD/CTAB systems. This method could be used to provide a visual method for selection of the correct CD molecules for interaction with surfactant molecules in recognition systems.

Paper-Based Device for Rapid Visualization of NADH Based on Dissolution of Gold Nanoparticles.

We describe a paper-based device that enables rapid and sensitive room-temperature detection of dihydronicotinamide adenine dinucleotide (NADH) via a colorimetric readout and demonstrate its value for monitoring NAD+-driven enzymatic reactions. Our system is based on NADH-mediated inhibition of gold nanoparticle (AuNPs) dissolution in a Au3+-cetyltrimethylammonium bromide (CTAB) solution. We fabricated a device consisting of a mixed cellulose ester paper featuring a wax-encircled, AuNP-coated film atop a cotton absorbent layer sandwiched between two plastic cover layers. In the absence of NADH, the Au3+-CTAB complex dissolves the AuNP layer completely, generating a white color in the test zone. In the presence of NADH, Au3+ is rapidly reduced to Au+, greatly decreasing the dissolution of AuNPs and yielding a red color that becomes stronger at increasing concentrations of NADH. This device exploits capillary force-assisted vertical diffusion, allowing us to apply a 25 μL sample to a surface-confined test zone to achieve a detection limit of 12.5 μM NADH. We used the enzyme glucose dehydrogenase as a model to demonstrate that our paper-based device can monitor NAD+-driven biochemical processes with and without selective dehydrogenase inhibitors by naked-eye observation within 4 min at room temperature in a small sample volume. We believe that our paper-based device could offer a valuable and low-cost analytical tool for monitoring NAD+-associated enzymatic reactions and screening for dehydrogenase inhibitors in a variety of testing contexts.

A resonance Rayleigh scattering detection of DNA hybridization based on interaction between DNA and surfactants

We developed a new method that used surfactants to detect DNA hybridization in aqueous media, this method is highly sensitive and based on a resonance Rayleigh scattering (RRS) technique. Cationic surfactants, cetyltrimethyl ammonium bromide (CTAB) and cetylpyridinebromide (CPB), anionic surfactants, sodium dodecylbenzene sulphonate (SDBS) and sodium dodecyl sulphonate (SDS), nonionic surfactants Triton-100 (TX-100) and Tween-80 (T-80), interacted with double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA), and were investigated respectively. The RRS signal was strongest in the case of the CTAB complex which therefore was selected as the probe. Based on the RRS data, a linear relation between RRS intensity and target DNA concentration was found. Mechanism investigations have shown that CTAB can bind to DNA by electrostatic and hydrophobic interactions and aggregate on the molecular surface of dsDNA at pH 7.2. By using CTAB as a probe, we detected and analyzed two kinds of characteristic sequences.

Mechanism of Coomassie Brilliant Blue G-250 binding to cetyltrimethylammonium bromide: An interference with the Bradford assay

The Bradford protein assay is a popular method because of its rapidity, sensitivity, and relative specificity. This method is subject to some interference by nonprotein compounds. In this study, we describe the interference of cetyltrimethylammonium bromide (CTAB) with the Bradford assay. This interference is based on the interaction of Coomassie Brilliant Blue G-250 (CBB) with this cationic detergent. This study suggests that both electrostatic and hydrophobic interactions are involved in the interaction of CTAB and CBB. The anionic and neutral forms of CBB bind to CTAB by electrostatic attraction, which accelerates hydrophobic interactions of these CBB forms and the hydrophobic tail of CTAB. Consequently, the hydrophobic regions of the dominant free cationic form of CBB dye compete for the tail of CTAB with two other forms of the dye and gradually displace the primary hydrophobic interactions and rearrange the primary CBB–CTAB complex. This interaction of CTAB and CBB dye produces a primary 650-nm-absorbing complex that then gradually rearranges to a complex that shows an absorbance shoulder at 800–950nm. This study conclusively shows a strong response of CBB to CTAB that causes a time-dependent and nearly additive interference with the Bradford assay. This study also may promote an application of CBB for CTAB quantification.

Use of cetyltrimethylammonium bromide as a simple probe for rapid determination of emodin by resonance light scattering technique

A new resonance light scattering (RLS) method for emodin determination with cationic surfactant cetyltrimethylammonium bromide (CTAB) as probe has been developed. In Britton–Robinson buffer (pH 6.5) medium, emodin reacted with cationic surfactant CTAB and formed the emodin–CTAB complex. The complex aggregated together through hydrophobic forces and causing great enhancement of RLS signals with the maximum peak located at about 350nm. The enhanced RLS intensities were found to be proportional to the concentration of emodin in the range of 0.54–9.72μgml−1 with the detection limit (3σ) of 10.3ngml−1. In this work, the characteristics of RLS, absorption, fluorescence spectra of the system were studied. The optimum reaction condition and the influencing factors on the RLS signal were investigated in detail. The proposed method was applied to the analysis of emodin in synthetic samples and human urine with satisfactory results. Furthermore, the forms of the substances under the experimental condition and the mechanism of the reaction were discussed in detail.

Catalytic-adsorptive stripping voltammetric determination of ultra-trace iridium(III). Application to fresh- and sea-water

An extremely sensitive stripping voltammetric procedure for ultra-trace determination of iridium(III) is reported. The method is based on the interfacial accumulation of the iridium(III)–CTAB complex onto the glassy carbon electrode, followed by the catalytic reduction of the adsorbed complex in the presence of bromate. 0.3molL−1 acetate buffer pH 4.7+6.9×10−2molL−1 NaBrO3+2.7×10−5molL−1 cetyltrimethylammonium bromide (CTAB)+0.2molL−1 KCl was employed as the supporting electrolyte.The analytical procedure was verified by the analysis of the standard reference materials: Sea Water BCR-CRM 403 and Fresh Water NIST-SRM 1643d.The accuracy, expressed as relative error e%, was satisfactory, being lower than 6%, while precision as repeatability, expressed as relative standard deviation sr%, was generally lower than 5%. The limit of detection was of the order of 2–3ngL−1.Once set up on the standard reference materials, the analytical procedure was transferred and applied to superficial water sampled in proximity to superhighway and in the Po river mouth area.

Refolding and purification of histidine-tagged protein by artificial chaperone-assisted metal affinity chromatography

This article has proposed an artificial chaperone-assisted immobilized metal affinity chromatography (AC-IMAC) for on-column refolding and purification of histidine-tagged proteins. Hexahistidine-tagged enhanced green fluorescent protein (EGFP) was overexpressed in Escherichia coli, and refolded and purified from urea-solubilized inclusion bodies by the strategy. The artificial chaperone system was composed of cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD). In the refolding process, denatured protein was mixed with CTAB to form a protein–CTAB complex. The mixture was then loaded to IMAC column and the complex was bound via metal chelating to the histidine tag. This was followed by washing with a refolding buffer containing β-CD that removed CTAB from the bound protein and initiated on-column refolding. The effect of the washing time (i.e., on-column refolding time) on mass and fluorescence recoveries was examined. Extensive studies by comparison with other related refolding techniques have proved the advantages of AC-IMAC. In the on-column refolding, the artificial chaperone system suppressed protein interactions and facilitated protein folding to its native structure. So, the on-column refolding by AC-IMAC led to 99% pure EGFP with a fluorescence recovery of 80%. By comparison at a similar final EGFP concentration (0.6–0.8 mg/mL), this fluorescence recovery value was not only much higher than direct dilution (14%) and AC-assisted refolding (26%) in bulk solutions, but also superior to its partner, IMAC (60%). The operating conditions would be further optimized to improve the refolding efficiency.

Shape control synthesis of multi-branched gold nanoparticles

Multi-branched gold nanoparticles (MBGNs) were prepared by a seed-mediated growth method using assistance of AgNO 3 and cetyltrimethylammonium bromide (CTAB) acting as the surface modifiers of the particle. The size of MBGNs was changed from 150 to 1500 nm, in which the branches with length up to 100 nm were formed. The formation of the branches was discussed as the selective growth of surfaces restricted by the Ag +–CTAB complex. The surface plasmon resonance properties were strongly affected by the morphology of MBGNs and tuned over the wide wavelengths.

Influencing Factors on the Properties of Complex Systems Consisting of Hydrolyzed Polyacrylamide/Triton X-100/Cetyl Trimethylammonium Bromide: Viscosity and Dynamic Interfacial Tension Studies

A complex system that consists of cetyltrimethylammonium bromide (CTAB), Triton X-100 (TX-100), and hydrolyzed polyacrylamide (HPAM), differing from the old-time conceptions of the displacement system, has been studied. It is indicated that the complex system is capable of satisfying requirements of high viscosity and low interfacial tension under conditions of higher temperature and mineralized water. The dynamic interfacial tension of the complex system depends upon multifarious factors, such as the ratio of TX-100/CTAB, concentrations of HPAM and surfactants, temperature, and the mineralized degree, etc. Especially, it is interesting that the dynamic interfacial tension of the complex system cannot reach an ultralow value (<1 × 10−2 mN·m−1) when one component is lacking among the HPAM/TX-100/CTAB complex system. From the results of the adsorption on quartz sands and on the core flooding tests, it can be concluded that the HPAM/TX-100/CTAB complex system is suitable for use as a displacement system in an oil field after polymer flooding.

A LB film morphological study with reference to biopolymer–surfactant interaction taking gelatin–CTAB system as a model

The interaction of gelatin with cetyltrimethylammonium bromide (CTAB) studied at pH 9 and an ionic strength of 0.005, produces an interfacial surface active gelatin–CTAB (monomer) complex (GS n I), a surface inactive gelatin–CTAB (micelle) complex in bulk (GS m B), followed by coacervation, and its solubilization in micellar solution of CTAB. We have herein attempted to probe the interfacial morphological changes of gelatin and its CTAB complexes, and not the bulk properties like coacervation and/or micellar solubilization. The morphologies of pure gelatin and CTAB films and that of gelatin–CTAB interacted complex at the interface have been investigated using LB, SEM, AFM and ellipsometric techniques. The stability of the gelatin monolayer at varied concentrations with and without CTAB has been examined. The SEM images of stabilized films of gelatin and gelatin–CTAB complex have witnessed compact smooth as well as rough surfaces with formation of distinct domains. Drastic morphological change in the film before the critical aggregational concentration of CTAB (T 2) has been in line with an initial abrupt decrease in surface tension. This has been corroborated by AFM measurements, which along with morphology demonstration has provided information on the diameter of the ensembles formed and roughness of the LB films constituted of pure components and their complexes. Thickness of the film was at its maximum in the domain region, as corroborated by ellipsometric technique. Such an elaborate interfacial monolayer and film morphology study of biopolymer-amphiphile system has been rarely documented in literature.

Interaction between Silicates and Ionic Surfactants in Dilute Solution

Understanding the interaction between silicate ions and surfactants is critical for the design and development of mesoporous siliceous materials. We examined the interaction between sodium silicate ions and three different cationic surfactants [namely, cetyltrimethylammonium bromide (CTAB), tetradecyltrimethylammonium bromide (TTAB), and dodecyltrimethylammonium bromide (DTAB)] and an anionic surfactant [sodium dodecyl sulfate (SDS)] in dilute solution at room temperature. From the combination of several techniques, such as conductometric and potentiometric titrations, dynamic light scattering, and isothermal titration calorimetry, the phase behavior of the sodium silicate and CTAB system was determined. We observed that the aggregation behavior of the silicate-CTAB system is similar to that of a polymer-surfactant system. The formation of the silicate-CTAB complex is induced by the adsorption of SiOH and SiO- groups, aided by CTAB unimers. The electrostatic attraction and hydrophobic interaction are the dominant forces controlling the formation of silicate-CTAB complexes. When these complexes are saturated with CTAB unimers, free CTAB micelles are then produced. TEM micrographs revealed that a stable Si-O-Si network is absent within the silicate-CTAB complexes, and surprisingly, stable silicate-CTAB complexes with ordered structure were observed. The present finding is important for understanding the interaction between silicate and surfactant in the synthesis of mesoporous structure in the dilute solution regime.

Spatially-Directed Oxidation of Gold Nanoparticles by Au(III)−CTAB Complexes

Gold nanoparticles are readily oxidized by Au(III) in the presence of cetyl-trimethylammonium bromide (CTAB). Oxidation occurs preferentially at surface sites with higher curvature. Conversely, oxidation with cyanide ions in the absence of CTAB leads to uniform oxidation over the whole surface. Examples of the spatially directed oxidation are provided using large, irregular spheres, nanocubes, and nanorods. We conclude that the mechanism of oxidation depends on whether the oxidant is attached to CTAB micelles. It is postulated that the CTAB micelles approach the nanoparticles preferentially at the tips, leading to spatially directed oxidation.

DNA Compaction at Hydrophobic Surfaces Induced by a Cationic Amphiphile

Cetyltrimethylammonium bromide (CTAB) induces partially irreversible compaction of DNA-adsorbed layers on hydrophobic silica. Additionally, there is a synergistic increase in the adsorbed amount when both CTAB and DNA are present as compared to the surface excess concentration of either of the individual components. In this study of the DNA adsorption and DNA−CTAB coadsorption by ellipsometry, emphasis has been placed on the DNA molecular weight as well as its conformation (single and double stranded). The DNA molecular weight and conformation have a large effect on the surfactant-free DNA adsorption behavior but not on the mixed DNA−CTAB adsorption behavior. Comparison between interfacial and bulk complexation has been made where possible. The DNA−CTAB complexes at the interface are neutral despite the large excess of DNA in the bulk. The final structure of the adsorbed layer was found to be dependent on the history of complex formation and DNA size.

Fluorescence and X-ray diffraction studies on binding and complexes of surfactants and dansylated polyelectrolytes with sulfonate groups

Binding of cationic surfactant cetyltrimethylammonium bromide (CTAB) on polyelectrolytes ADDan containing different amounts of sulfonate groups was studied by fluorescence spectrum of dansyl labels in aqueous solution. With increasing concentration of CTAB, there was an abrupt drop in the emission maximum wavelength λem and a sharp increase in the relative intensity RF defined as the ratio of emission in the presence of CTAB to that without CTAB. The critical aggregation concentration (cac) determined from the former was about 3×10−5mol/l without obvious dependence on polymer charge density. Solid complex films of polyelectrolyte–surfactant of CTAB or dodecyltrimethylammonium chloride (DTAC) were obtained by precipitation and their fluorescence anisotropy r indicated a high mobility of the dansyl chromophore. The r-value for ADDan–CTAB complexes obviously decreased as the charge density of the polyelectrolyte increased while the r for ADDan–DTAC complexes was slight decline, suggesting the contribution of alkyl tails of the surfactant to local mobility. It was the first time to find that the higher the charge density of the polyelectrolyte, the less polar the micellar aggregation of polyelectrolyte–surfactant complex becomes in dilute aqueous solution, which remains in the solid complex. SAXS of the solid complexes illustrated a long-range ordered lamella structure with the long period d of 3.87 and 3.04nm for CTAB and DTAC complexes, respectively.