The physicochemical properties of CTAB solutions in the presence of α-tocopherol

Structural studies on the interaction of CTAB with alginate: Possibility of surfactant therapy with chemo sensitization effect

The present study reports the preparation of sodium alginate-cetyltrimethylammonium bromide (CTAB) nanoparticles (SANPs) through the interaction of a fixed concentration of alginate (0.2% w/v in water) with two different concentrations of CTAB i.e., below (0.4 mM) and above (1.2 mM) critical micelle concentration (CMC) and the elucidation of its structure on the basis of dynamic light scattering, transmission electron microscopy, small angle neutron scattering and zeta potential measurements. The results indicated that the concentration of CTAB dictated the hydrodynamic shape and size of SANPs. While both the micellized (> CMC) and monomeric forms (< CMC) of CTAB resulted in the formation of negatively charged near spherical particles, the SANPs containing micellized form of CTAB exhibited smaller and more compact hydrodynamic structure compared to those containing monomeric form of CTAB. The cytotoxicity studies involving cancerous cell lines (A549 and L132) indicated that the anticancer activity of CTAB was retained in the SANPs. Subsequently, encapsulation of doxorubicin (DOX), a potent anticancer drug in to SANPs enhanced the efficacy of the overall nano-formulation for effectively killing A549 and L132 cells. Additionally, the DOX loaded SANPs also exhibited the sustained and pH dependent drug release under reservoir-sink model. Together, polyelectrolyte complexation between alginate and CTAB appears as a novel strategy to design nano formulation exhibiting anticancer activity perse as well as for sensitizing the efficacy of chemotherapeutic drugs.

Manipulating Toughness and Microstructure in Polyelectrolyte Complex Hydrogels with Competitive Surfactant Micelles

Polyelectrolyte complex (PEC) hydrogels provide a promising strategy to develop a class of physically cross-linked networks characterized by exceptional toughness and self-healing properties. However, the precise control of the microstructure and the enhancement of mechanical properties still pose challenges in the field of PEC hydrogels. Herein, we propose a strategy to manipulate the structure of PEC with competitively charged surfactant micelles, leveraging the spatially confined surface charge and excluded volume effects to overcome coacervation issues associated with the PEC, thus achieving a simple one-step preparation of macroscopically uniform and tough PEC hydrogels. Specifically, polyelectrolyte complex/surfactant micelle (PEC-SM) hybrid hydrogels were prepared by one-step copolymerization of chitosan (CS)/acrylic acid/cetyltrimethylammonium bromide (CTAB) micelles. The content of CTAB micelles was found to continuously modulate both the structure and the mechanical properties of the resulting PEC-SM hydrogel network. On one hand, reversible deformation-recovery behavior exhibited by CTAB cavity micelles through hydrophobic interactions efficiently dissipates energy; on the other hand, competition between CS chains and CTAB micelles for electrostatic binding sites with poly(acrylic acid), along with excluded volume effects of CTAB micelles, imparts a hierarchical structure upon the PEC-SM hydrogel. Rheology provided detailed insights into the viscoelastic behaviors of PEC-SM hydrogels at varying CTAB concentrations. The intermolecular interaction and heterogeneous network structure of physically cross-linked PEC-SM hydrogels with CTAB micelles were elucidated by solid-state nuclear magnetic resonance (NMR) spectroscopy. On the basis of rheology and NMR results, complemented by other characterization analyses, the physical illustration of the PEC-SM hybrid hydrogel network structure regulated by competitive surfactant micelles is presented. This work offers valuable in-depth insight into polyelectrolyte complexation and provides a foundation for the development of robust PEC hydrogel materials.

Electrokinetic transport of CTAB induces multiphasic behavior during capillary adsorption and desorption

Cationic surfactant coatings (e.g., CTAB) are commonly used in CE to control EOF and thereby improve separation efficiencies. However, our understanding of surfactant adsorption and desorption dynamics under EOF conditions is limited. Here, we apply automated zeta potential analysis to study the adsorption and desorption kinetics of CTAB in a capillary under different transport conditions: diameter, length, voltage alternation pattern and frequency, and applied pressure. In contrast to other studies, we observe slower kinetics at distinct capillary wall zeta potential ranges. Within these ranges, which we call "stagnant regimes," the EOF mobility significantly counteracts the electrophoretic (EP) mobility of CTA+ and hinders the net transport. By constructing a numerical model to compare with our experiments and recasting our experimental data in terms of the net CTA+ transport volume normalized by surface area, we reveal that the EP mobility of CTA+ and the capillary surface-area-to-volume ratio dictate the zeta potential range and the duration of the stagnant regime and thereby govern the overall reaction kinetics. Our results indicate that further transport-oriented studies can significantly aid in the understanding and design of electrokinetic systems utilizing CTAB and other charged surfactants.

Lipid oxidation in emulsions and bulk oils: a review of the importance of micelles

Lipid oxidation is a major cause of quality deterioration in food products. In these foods, lipids are often present in a bulk or in emulsified forms. In both systems, the rate, extent and pathway of oxidation are highly dependent on the presence of colloidal structures and interfaces because these are the locations where oxidation normally occurs. In bulk oils, reverse micelles (association colloids) are present and are believed to play a crucial role on lipid oxidation. Conversely, in emulsions, surfactant micelles are present that also play a major role in lipid oxidation pathways. After a brief description of lipid oxidation and antioxidants mechanisms, this review discusses the current understanding of the influence of micellar structures on lipid oxidation. In particular, is discussed the major impact of the presence of micelles in emulsions, or reverse micelles (association colloids) in bulk oil on the oxidative stability of both systems. Indeed, both micelles in emulsions and associate colloids in bulk oils are discussed in this review as nanoscale structures that can serve as reservoirs of antioxidants and pro-oxidants and are involved in their transport within the concerned system. Their role as nanoreactors where lipid oxidation reactions occur is also commented.

Experimental Study on the Partial Discharge Characteristics of Palm Oil and Coconut Oil Based Al2O3 Nanofluids in the Presence of Sodium Dodecyl Sulfate

This experimental study aims to examine the partial discharge (PD) properties of palm oil and coconut oil (CO) based aluminum oxide (Al₂O₃) nanofluids with and without surfactants. The type of surfactant used in this study was sodium dodecyl sulfate (SDS). The volume concentrations range of Al₂O₃ dispersed in oil samples was varied from 0.001% to 0.05%. The ratio of surfactants to nanoparticles was set to 1:2. In total, two different types of refined, bleached and deodorized palm oil (RBDPO) and one type of CO were measured for PD. Mineral oil (MO) was also examined for comparison purpose. PDIV measurements for all samples were carried out based on rising voltage method whereby a needle-sphere electrode configuration with a gap distance of 50 mm was chosen in this study. Al₂O₃ improves the PDIVs of RBDPO, CO and MO whereby the highest improvements of PDIVs are 34%, 39.3% and 27%. The PD amplitude and repetition rate of RBDPO improve by 38% and 81% while for CO, it can increase up to 65% and 80% respectively. The improvement of PD amplitude and repetition rate for MO are 18% and 95%, regardless with and without SDS. Without SDS, the presence of Al₂O₃ could cause 26%, 75% and 65% reductions of the average emission of light signals for RBDPOA, RBDPOB and CO with the improvement of PD characteristics but both events do not correlate at the same volume concentration of Al₂O₃. On the other hand, the average emission of light signal levels of the oils increases with the introduction of SDS. The emission of light signal in MO does not correlate with the PD characteristics improvement either with or without SDS.

Effect of surfactants on the lightning breakdown voltage of palm oil and coconut oil based Al2O3 nanofluids

In this paper, the effect of different types of surfactants on the lightning breakdown voltages of palm oil (PO) and coconut oil (CO) based aluminium oxide (Al2O3) nanofluids is investigated. Three different types of surfactants were used in this study known as cationic (cetyl trimethyl ammonium bromide (CTAB)), anionic (sodium dodecyl sulfate (SDS)) and non-ionic (oleic acid (OA)). The volume percentage concentrations of Al2O3 dispersed into PO and CO were varied from 0.001% to 0.05%. The ratio of surfactant to the nanoparticles was set to 50% from the volume concentration of nanoparticles which equivalent to 1:2. In total, two types of refined, bleached and deodorized palm oil (RBDPO) and one type of CO were examined for lightning breakdown voltage. The test was carried out based on needle-sphere electrodes configuration with 25 mm gap distance. The presence of Al2O3 improves both positive and negative lightning breakdown voltages of RBDPO and CO. Under the positive and negative polarities, the CTAB does provide further improvements on the lightning breakdown voltages of RBDPOA (1st type of samples) and CO at most of the volume of concentration of Al2O3. SDS and OA could also further improve the lightning breakdown voltage of CO at certain volume concentration of Al2O3. On the other hand, the lightning breakdown voltage of RBDPOB based Al2O3 nanofluid (2nd type of samples) does not further improve with the introduction of surfactants. At most of the volume concentration of Al2O3, the introduction of CTAB further increases the times to breakdown and decrease the average streamer velocities of RBDPOA under both polarities. The same finding is observed for CO under positive polarity with CTAB and SDS as well as under negative polarity in the presence of all surfactants. The streamer velocities and times to breakdown patterns of RBDPOB based Al2O3 nanofluid are inconsistent in the presence of all surfactants. It is found that RBDPO and CO based Al2O3 nanofluids have second mode of streamer whereby the streamer velocities are from 1 km s-1 to 1.63 km s-1 regardless with or without surfactants.

Curcumin-loaded PLA-PEG copolymer nanoparticles for treatment of liver inflammation in streptozotocin-induced diabetic rats

This report focused on loading curcumin (CUR) drug into biodegradable Polylactide-poly(ethylene glycol) (PLA-PEG) copolymer nanoparticles as an effective anti-inflammatory agent in vivo to overcome the limitations resulted from the free CUR. By a simple nano-emulsification technique, hydrophobic CUR was loaded into hydrophobic polymer's segments and stabilized by cationic surfactant. They were then characterized by DLS, TEM, and SEM techniques providing monodispersed and spherical nanoparticles with an average diameter of 117 nm and high surface charge of +35 mV. Thereafter, they were orally administrated into five groups of rats, typically, control (healthy rats), streptozotocin (STZ)-induced diabetic rats, diabetics treated with free CUR, diabetics treated with PLA-PEG NPs, and diabetics treated with CUR-encapsulated PLA-PEG NPs. Next, complete blood analyses were assessed including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and nuclear factor kappa B (NF-ҡB), reduced glutathione (GSH), malondialdehyde (MDA), nitric oxide (NO), cyclooxygenase (COX-2), Peroxisome proliferator-activated receptors (PPAR-γ) and transforming growth factor-β1 (TGF-β1). The obtained results demonstrated that diabetes initially produced liver inflammation in rats manifested by leveraging the mean levels of serum AST, ALT inducing oxidative stress resulting in a clear increase in the levels of hepatic MDA and NO concomitant with a remarkable decrease in GSH. Moreover, diabetes significantly increased serum NF-ҡB, hepatic COX-2 and TGF-β1, while highly reduced hepatic PPAR-γ. In contrast, both CUR free and CUR-encapsulated NPs ameliorated the negative changes in diabetes but CUR-encapsulated NPs showed more pronounced treated effect than free CUR. In addition, histopathological investigations were performed on the liver tissues of all groups, showing a mitigation in inflammation while treating with CUR-NPs.