A Systematic Study of Mixed Surfactant Solutions of a Cationic Ester-Bonded Dimeric Surfactant with Cationic, Anionic and Nonionic Monomeric Surfactants in Aqueous Media

Viscoelastic and smart swelling disposition of Carboxymethylcellulose based hydrogels substantiated by Gemini surfactant and in-vitro encapsulation and controlled release of Quercetin

CMC-SA-12-E2-12 hydrogels were prepared from Carboxymethylcellulose (CMC), succinic acid (SA) (biocompatible cross-linker) and Ethane-1,2-diyl-bis(N, N-dimethyl-N-dodecylammoniumacetoxy) (referred as 12-E2-12) (0.0006, 0.0015, 0.003, 0.0045 mMoles) by thermal treatment with economical and easy solution polymerization strategy. The CMC-SA-12E2-12 hydrogels were characterized for mechanical and viscoelastic properties like self-healing, viscosity and modulus using rheological analysis. Further the structural, morphological and thermal properties were investigated by FTIR, SEM and TGA analysis. The investigation revealed significant modulation in mechanical, viscoelastic, self-healing and drug release behavior with the addition of 12-E2-12. The CMC-SA-12-E2-12 hydrogels were investigated for drug release studies in PBS 7.4 for 48 h using Quercetin dihydrate. The results showed sustained release behavior at optimised concentration values of surfactant. Release data fitted nicely to the Higuchi model and hence the release could be seen to be diffusion controlled phenomenon or Fickian diffusion. The biocompatibility of cross-linker and surfactant may potentially make the hydrogels suitable for drug delivery applications.

DPD Simulation on the Transformation and Stability of O/W and W/O Microemulsions

The dissipative particle dynamics simulation method is adopted to investigate the microemulsion systems prepared with surfactant (H1T1), oil (O) and water (W), which are expressed by coarse-grained models. Two topologies of O/W and W/O microemulsions are simulated with various oil and water ratios. Inverse W/O microemulsion transform to O/W microemulsion by decreasing the ratio of oil-water from 3:1 to 1:3. The stability of O/W and W/O microemulsion is controlled by shear rate, inorganic salt and the temperature, and the corresponding results are analyzed by the translucent three-dimensional structure, the mean interfacial tension and end-to-end distance of H1T1. The results show that W/O microemulsion is more stable than O/W microemulsion to resist higher inorganic salt concentration, shear rate and temperature. This investigation provides a powerful tool to predict the structure and the stability of various microemulsion systems, which is of great importance to developing new multifunctional microemulsions for multiple applications.

Alkyl-carbon chain length of two distinct compounds and derivatives are key determinants of their anti-Acanthamoeba activities

The opportunistic pathogen, Acanthamoeba castellanii is the causative agent for the sight threatening infection Acanthamoeba keratitis (AK). It is commonly associated with contact lens wearers, and prevalence is increasing at an alarming rate due to an inadequate preventive strategy to protect the lens from this protist. This problem is compounded by the lack of an effective acanthamoebocide, particularly with cysticidal activity in the contact lens solutions. We have used cytotoxicity assays and a variety of biophysical approaches to show that two molecules with tails made of alkyl carbon, alkylphosphocholines (APCs) and quaternary ammonium compounds (QACs) had significant chain-length dependent efficacy against A. castellanii trophozoites, the latter producing death via permeabilization, and DNA complexing. QACs were more effective than APCs and had activity against cysts. Conversely, the QAC with 12 alkyl carbon chain, was non toxic, its presence increased A. castellanii trophozoites biomass and delayed encystation by 96 h. Interestingly, it was unable to induce excystation and increased trophozoite sensitivity to APC16. These results present a mono- and multi-inhibitor management strategy effective against trophozoites and cysts that may be useful for formulating into contact lense cleaning solutions and reducing AK incidence.

Aggregation and interfacial phenomenon of amphiphilic drug under the influence of pharmaceutical excipients (green/biocompatible gemini surfactant)

In the current study, we have examined the interaction amongst an antidepressant drug amitriptyline hydrochloride (AMH) and ethane-1, 2-diyl bis(N,N-dimethyl-N-cetylammoniumacetoxy) dichloride (16-E2-16, a green gemini surfactant) through tensiometric and fluorimetric techniques in aqueous/electrolyte/urea solutions. Significant variations are observed in the various evaluated parameters in the present study. Gemini 16-E2-16 has outstanding surface properties along with a much lower cmc value, demonstrating very little toxicity as well as considerable antimicrobial activity. The cmc values of mixtures decrease through increase in mole fraction (α₁) of 16-E2-16, which specifies the nonideality of the solution mixtures, along with demonstrating the occurrence of mixed micellization too. Negative β^Rub values signify on the whole attractive force of interaction between constituents of mixed micelles. Owing to the incidence of electrolyte NaCl (50 mmol.kg^–1), lowering of the micelles’ surface charge happens, resulting in aggregation taking place at lower concentration while the presence of urea (NH₂CONH₂) halts micellization taking place, which means the cmc value increases in the attendance of urea. The ΔGmo values for all systems were negative along with the presence of electrolyte/urea. The excess free energy (G_ex) of studied mixed systems was also estimated and found to be negative for all the systems. Using the fluorescence quenching method, the micelle aggregation number (N_agg) was evaluated and it was found that the contribution of gemini surfactant was always more than that of the AMH and their value enhances in the existence of electrolyte while decreasing in the attendance of NH₂CONH₂ in the system. In addition, other fluorescence parameters such as micropolarity (I₁/I₃), dielectric constant (D_exp) as well as Stern–Volmer binding constants (K_sv) of mixed systems were evaluated and the results showed the synergistic performance of the AMH + 16-E2-16 mixtures. Along with tensiometric and fluorimetric techniques, FT-IR spectroscopy was also engaged to reveal the interaction among constituents.

Formation of Mixed Micelles of the Environmentally Acceptable Oxy-Diester-Linked Gemini Surfactants with Brij 58

Three oxy-diester-linked cationic gemini surfactants (2,2′-[(oxybis(ethane-1,2-diyl))bis(oxy)]bis(N-alkyl-N,N-dimethyl-2-oxoethanaminium) dichloride, Cm-DEG-Cm (m = 12, 14, 16), were synthesized. The physicochemical properties of the gemini surfactants and their mixtures with Brij 58 were studied by surface tension measurements at various mole fractions and 30°C. The critical micelle concentration (CMC) of the gemini surfactants are smaller than that of their corresponding single-chain counterparts having the same number of carbon atoms in the hydrophobic tail versus polar head. At all investigated compositions, the experimentally obtained CMC values of the surfactant mixtures are smaller than the CMCideal (ideal CMC – CMC of the solution at ideal state); the lower CMC of the mixed systems compared to those the individual surfactants and the negative β values (for both the mixed micelles and monolayers) indicate a synergistic interaction among both the surfactant components. The interaction parameters (βm and βσ) of the mixed surfactant systems were evaluated by using theoretical models. Negative values of β imply an overall attractive force in the mixed state. Also, the free excess energy of mixing was found to be negative for all the systems.

Solubility Enhancement of Polycyclic Aromatic Hydrocarbons by an Eco-Friendly Ester-Linked Gemini Surfactant and its Mixtures with Conventional Surfactants

The present study deals with the solubility enhancement of the two polycyclic aromatic hydrocarbons (PAHs) anthracene and pyrene in the aqueous micellar system of the cationic ester-containing cleavable gemini surfactant ethane-1,2-diyl-bis(N,N-dimethyl-N-tetradecylammoniumacetoxy) dichloride (14-E2-14 = C14H29(CH3)2N+(CH2COOCH2)2N+(CH3)2C14H29 · 2Cl−)), and its equimolar binary mixtures with some typical conventional cationic, anionic and non-ionic surfactants. The surface tension and conductivity measurements were used to evaluate the physicochemical parameters such as the critical micelle concentration (CMC), the interaction parameter (βm) and Gibbs excess free energy of micellization (ΔGexm) of the systems. The extent of solubilization of the micellar systems towards PAHs has been quantified in terms of molar solublization ratio (MSR), micellar/water partition coefficient (ln Km) and the standard Gibbs free energy of solubilization (ΔGs0). Above the CMC, all studied single as well as binary gemini-conventional surfactant systems show an increase in solubilization of the PAHs. For pure systems, the MSR value of Brij 58 was found to be significantly higher than that of the other amphiphiles. Amongst the mixed surfactant systems, the solubility enhancement of anthracene is found to be maximum in the 14-E2-14 + SDS/SDBS system whereas the system14-E2-14 + Brij 58 shows a higher solubility for pyrene.

Polymer-Amphiphile Interactions: An Overview

Interactions between the polymers and amphiphiles in aqueous solutions have generated considerable interest among researchers because of the widespread applications, relatively complex behavior and improved physicochemical properties of the mixtures. Numerous studies on the surfactant-polymer systems have been carried out in recent years and the number of scientific reports has considerably increased. Various applications of polymers in different areas and many works concerning the amphiphiles are being published every year. Usually, the mixed systems containing polymers and amphiphiles show solution properties different from those of individual solutions due to interaction between the components. The present review article mainly focuses on the behaviour of polymers in aqueous solutions, in the absence or presence of amphiphiles, such as surfactants, drugs, etc. It also summarizes effect of the nature of amphiphiles on aggregation properties of polymers in aqueous solution, and interaction of conventional as well as gemini surfactants with polymers.

Surfactants in aquatic and terrestrial environment: occurrence, behavior, and treatment processes

Surfactants belong to a group of chemicals that are well known for their cleaning properties. Their excessive use as ingredients in care products (e.g., shampoos, body wash) and in household cleaning products (e.g., dishwashing detergents, laundry detergents, hard-surface cleaners) has led to the discharge of highly contaminated wastewaters in aquatic and terrestrial environment. Once reached in the different environmental compartments (rivers, lakes, soils, and sediments), surfactants can undergo aerobic or anaerobic degradation. The most studied surfactants so far are linear alkylbenzene sulfonate (LAS), quaternary ammonium compounds (QACs), alkylphenol ethoxylate (APEOs), and alcohol ethoxylate (AEOs). Concentrations of surfactants in wastewaters can range between few micrograms to hundreds of milligrams in some cases, while it reaches several grams in sludge used for soil amendments in agricultural areas. Above the legislation standards, surfactants can be toxic to aquatic and terrestrial organisms which make treatment processes necessary before their discharge into the environment. Given this fact, biological and chemical processes should be considered for better surfactants removal. In this review, we investigate several issues with regard to: (1) the toxicity of surfactants in the environment, (2) their behavior in different ecological systems, (3) and the different treatment processes used in wastewater treatment plants in order to reduce the effects of surfactants on living organisms.

Conformational alterations induced by novel green 16-E2-16 gemini surfactant in xanthine oxidase: Biophysical insights from tensiometry, spectroscopy, microscopy and molecular modeling

Herein we report the interaction of a biodegradable gemini surfactant, ethane-1,2-diyl bis(N,N-dimethyl-N-hexadecylammoniumacetoxy) dichloride (16-E2-16) with bovine milk xanthine oxidase (XO), employing tensiometry, fluorescence spectroscopy, UV spectroscopy, far-UV circular dichroism spectroscopy (CD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and computational molecular modeling. Surface tension results depict substantial changes in the micellar as well as interfacial parameters (CMC, ΠCMC, γCMC, Γmax, Amin, ΔGmic° and ΔGads°) of 16-E2-16 gemini surfactant upon XO combination, deciphering the interaction of XO with the gemini surfactant. Fluorescence measurements reveal that 16-E2-16 gemini surfactant causes quenching in the xanthine oxidase (XO) fluorescence spectra via static procedure and the values of various evaluated binding parameters (KSV, Kb, kq, ΔGb° and n) describe that 16-E2-16 effectively binds to XO. Three dimensional fluorescence, 8-anilino-1-naphthalene sulfonic acid (ANS) binding, F1F3 ratio, UV, CD, FTIR, SEM and TEM results delineate changes in the secondary structure of xanthine oxidase. Molecular docking results provide complement to the steady-state fluorescence findings and support the view that quenching occurs due to non-polar environment experienced by aromatic residues of the enzyme. The results of this study can help scientists to tune the conformation of an enzyme (XO) with biocompatible amphiphilic microstructures, which will help to unfold further understanding in the treatment modes of various diseases like gout, hyperuricemia, liver and brain necrosis.