Volume 60, Issue 4

CO 2 -switchable materials in general and CO 2 -switchable surfactants in particular are of great interest in environmental research. There is a great potential to make processes more environmentally friendly by enhancing reusability and circularity and thus reducing material costs and energy consumption by replacing common non-switchable surfactants with their switchable counterparts. Inspired by this, the present work deals with the surface and foaming properties of aqueous solutions of the novel anionic CO 2 -switchable tail surfactant sodium 4-(methyl(octyl)amino)butane-1-sulfonate. In the presence of N 2 , the unprotonated surfactant is able to stabilize foams. By switching, i.e. by protonating the CO 2 -responsive trialkyl amine group in the surfactants hydrocarbon chain, the amphiphilic nature of the surfactant is reduced which is indicated by an increase of the plateau surface tension and a higher CMC compared to the non-protonated surfactant. Furthermore, the ability of the protonated surfactant to stabilize foams is reduced.

Methyl ester sulfonate (MES) is considered as an efficient and novel surfactant used as main active ingredient in cleansing products. MES is often produced via sulfonation of methyl ester (ME) with sulfonating agent. In this study, ME was synthesized from used cooking oil (UCO) via transesterification and then sulfonated to produce MES using two different sulfonating agents (chlorosulfonic acid (CSA) and sodium bisulfite (NaHSO 3 )). The influence of various factors (temperature, sulfonating agent/ME molar ratio and time) on MES yield was investigated. Analysis of optimal MES samples was carried out using different techniques (GC-FID, FTIR and 1 H NMR). The maximum MES yield of 88.2 % was achieved with CSA/ME molar ratio of 1.2:1 at 70 °C for 3 h while the highest MES yield of 79.4 % was obtained with NaHSO 3 /ME molar ratio of 1.2:1 at 90 °C for 3 h. FTIR and 1 H NMR analyses revealed the presence of methyl (CH 2 − asymmetric and CH 2 − symmetric stretching vibrations), esters (C=O, C–O, and O–CH 3 ), and sulfonate (S=O) groups in MES CSA and MES NaHSO3 samples, thereby affirming the desired product. Surface tension analysis showed that the MES CSA and MES NaHSO3 have low critical micelle concentrations of 0.079 g/L and 0.14 g/L, respectively while the corresponding surface tensions were 51.9 mN/m and 30.94 mN/m for MES CSA and MES NaHSO3 respectively.

Polyhydroxyalkanoates (PHAs) are emerging biodegradable bioplastics, and rhamnolipids are sustainable biosurfactants; both are considered as alternatives to synthetic petroleum-based plastics and surfactants, respectively. Herein, the effects of three distinct nitrogen sources on PHAs and rhamnolipid yields during the fermentation process have been undertaken. The study focuses on the optimum co-production of PHAs and rhamnolipid using a Pseudomonas aeruginosa strain grown on wasted soybean oil (WSO) with different nitrogen sources in the minimal salts’ media under salinity stress with shake flask conditions. The yields of PHAs and rhamnolipids were observed to be 2.20 g L −1 and 1.02 g L −1 , respectively, with carbamide as the sole nitrogen and WSO (2 %, w/v) as the sole carbon source. The fermentative yields of both PHAs (2.37 g L −1 ) and rhamnolipids (1.24 g L −1 ) roughly increased up to 8 % under salinity stress. The products were characterized using advanced analytical techniques. The chemical structure of rhamnolipid with this strain had previously been elucidated, whereas the PHA produced was identified as a poly(hydroxybutyrate).

Felodipine is a dihydropyridine calcium channel blocker commonly used for the treatment of mild to moderate hypertension and angina pectoris. Felodipine undergoes extensive hepatic first pass metabolism resulting in low oral bioavailability of 15 %. The aim of this study is to develop a formulation of nanovesicular Spanlastics to improve the transdermal delivery of felodipine and solve the problem of low bioavailability. The felodipine-loaded Spanlastics were prepared using the ethanol injection method with Span 60 as surfactant and Tween 80, which provides elasticity to the vesicles, according to the 2 3 factorial design using Design Expert ® Software version 13. The solution that had the highest desirability was optimized. The final five runs were incorporated into a gel base and evaluated for in vitro drug release, spreadability and viscosity. Stability studies were conducted over a period of 3 months. The formulated Spanlastics had a particle size in the range of (132–155) nm and an entrapment efficiency in the range of (80–94) %. The final five runs were found to have optimum characteristics. Differential scanning calorimetry, X-ray diffraction studies and Fourier transform infrared studies were performed to ensure the encapsulation of the drug in the nanovesicles. The developed hydrogel showed in vitro drug release in the range of (80–94) % and the formulation was found to be stable after a period of 3 months. The optimized formula comprised of Span 60 and Tween 80 in ratio of 8:2. Overall, the results confirmed that Spanlastics loaded with felodipine proved to be superior nanocarriers for transdermal delivery of felodipine.

Ionic liquids (IL) have attained immense interest as substitutes for conventionally available surfactants because of their exceptionally favorable physicochemical properties. Most synthesized IL surfactants are not environmentally benign, and even utilizing high concentration, they form unstable micelles. In this regard, we have synthesized biocompatible and halogen free choline based ionic liquids by varying anions (choline oleate and cholinium bis(2-ethylhexyl) sulfosuccinate) and further investigated their micellization behavior in presence of the drug Cetrizine dihydrochloride. Characterizations of these synthesized ionic liquids were performed utilizing 1 HNMR spectroscopy. The thermodynamic investigation and determination of various surface-active parameters were based on tensiometry and conductometric titrations. The CMC value of choline oleate ([CHO][Ole]) was found to be lower than that of [Cho][AOT] and thus it has a better surface activity. The thermodynamic parameters (ΔGm0${{\Delta}G}_{m}^{0}$, ΔHm0${{\Delta}H}_{m}^{0}$, and ΔSm0${{\Delta}S}_{m}^{0}$) signifies spontaneous, stable, exothermic and entropy driven nature of micellization process. The various interfacial and surface parameters have been evaluated employing tensiometry. These environmentally friendly ionic liquids have been utilized as substitute for conventional surfactants including their applications in biology and pharmaceutical industries.

In order to improve the solubility and bioavailability of poorly water-soluble drugs, the synthesis of cost-effective nonionic surfactants has been the subject of greater scientific interest. The present study focuses on the synthesis of sulfonyl chloride derivatives as nonionic surfactants (surfactant 1 and surfactant 2 ) and their evaluation for the preparation of a clarithromycin-loaded niosomal drug delivery system. Surfactants 1 and 2 were characterised by EI-MS and 1 H NMR spectroscopy. The shape and size of the drug-loaded niosomal vesicles from the synthesised surfactants were examined by atomic force microscopy (AFM) and revealed a round morphology with an average size of (230.8 ± 2.35) nm and (248.1 ± 2.54) nm for the vesicles of surfactant 1 and surfactant 2 , respectively. The zeta potential of surfactant 1 -based niosomal vesicles was (– 7.70 ± 1.00) mV and that of surfactant 2 was (−14.6 ± 1.08) mV. The lower zeta potential values for surfactant 1 and surfactant 2 -based niosomal vesicles showed that these vesicles were neutral and relatively stable. The vesicles of surfactant 1 and 2 have a capacity to entrap the drug of about (62 ± 2.26) % and (69.67 ± 3.23) %, respectively. The vesicles of surfactant 1 released the largest amount of drug, i.e. (70.00 ± 2.45) % at pH 1.2. Biocompatibility in human blood and toxic effects on various cell lines were also studied for surfactants 1 and 2 , and they were found to be biocompatible and non-cytotoxic.

The study aims to scrutinize the mixed micellization and interfacial behavior of two 1-alkyl-3-butylimidazolium based surface-active ionic liquids (SAILs) i.e., 1-decyl-3-butylimidazolium bromide [C 10 bim][Br] and 1-tetradecyl-3-butylimidazolium bromide [C 14 bim][Br] under the influence of streptomycin sulphate (SS) drug in 5 mM concentration in aqueous media. Imidazolium-based SAILs have unique physicochemical properties and greater surface activity than conventional surfactants, which allows them to increase drug permeability, making them better drug carriers than currently available formulations. To fully utilize [C 14 bim][Br] and [C 10 bim][Br] in drug delivery applications, deep insight into the interactions occurring in the mixed micellar [C 10 bim][Br]/[C 14 bim][Br] systems in the drug’s presence are necessary to be examined. Thus, the study is conducted using conductivity and surface tension measurement techniques to fully exploit the self-assembly, micellization behavior and interactions occurring in the pure and mixed micellar system of [C 10 bim][Br]/[C 14 bim][Br] in water and 5 mM of SS solution in aqueous media. For this, various thermodynamic, surface-active and mixed micellar parameters of micellization have been calculated and analyzed with respect to change in mole fraction, temperature and addition of SS in solution.

The impact of different concentrations of sodium carboxymethyl cellulose (NaCMC) on the micellization process in cationic, ester-functionalized, ethyl-substituted imidazolium-based surface-active ionic liquids (SAILs) ([C n Eeim]Br where, n = 12, 14, 16) were investigated using specific conductivity and surface tension measurements at 298 K. The study focused on determining the critical micelle concentration (CMC) of the three pure SAILs and their mixtures with NaCMC to evaluate various thermodynamic and interfacial parameters. The results showed that the CMC values decreased significantly with increasing hydrophobicity of the SAILs, while the CMC increased with a gradual increase in the NaCMC mole fraction in the SAIL–NaCMC mixed systems. It was observed that the excess free energy of micellization ( ∆ G e x m ${{\increment}G}_{ex}^{m}$ ) and the minimum free energy of surface at equilibrium ( ∆ G min s ${{\increment}G}_{\mathrm{min}}^{s}$ ) exhibited an opposite behaviour, indicating that the formed mixed micelles were stable while the formed surface was unstable. The results of this study are useful for evaluating the properties of SAIL–NaCMC mixed systems to improve and better understand their applications in the food, medical and cosmetic industries.

Benzene and 1-dodecene are often alkylated to produce linear alkylbenzene (LAB). LAB is the raw material for the production of linear alkylbenzene sulfonate (LAS), a very important anionic surfactant used in both industrial cleaning and commercial laundry processes, as well as in household laundry detergents. In the present study, we investigated the use of [Et 3 NH]Cl–2AlCl 3 modified with CuCl 2 as a catalyst for the alkylation of benzene with 1-dodecene, specifically looking at the effect of reaction conditions on product activity. The results showed that a conversion of 1-dodecene of 100.0 % and a selectivity of LAB of 93.79 % could be obtained when the following ideal reaction conditions were present: molar ratio of benzene/1-dodecene = 6, reaction temperature = 25 °C, reaction time = 10 min, stirring speed of 1000 rpm and addition of 5.0 mol % CuCl 2 ). The catalyst concentration was 7.0 mol %. FTIR and 31 P-TMPO-NMR measurements were performed to characterise the ionic liquid before and after the addition of CuCl 2 . After the addition of CuCl 2 , it was found that the acidity of the ionic liquid had decreased. The regeneration of the catalyst was also investigated and the cause of inactivation of the catalyst was determined. The results showed that CuCl 2 modified the ionic liquids and decreased the benzene/1-dodecene ratio, but the high product selectivity was maintained.

The kinetic investigation of Ru(III) promoted oxidation of L-phenylalanine (L-PheAla) by [Fe(CN) 6 ] 3− has been performed in anionic sodium dodecyl sulfate (SDS) micellar medium by recording the decrease in absorbance at 420 nm corresponding to [Fe(CN) 6 ] 3− using an UV–visible spectrophotometer. Using the pseudo-first-order condition, the course of the reaction was studied as a function of [Fe(CN) 6 3− ], ionic strength, [OH − ], [SDS], [Ru 3+ ], [L-PheAla] and temperature by changing one variable at a time. The results exhibit that [OH − ], [SDS], and [L-PheAla] are the crucial parameters that have an appreciable influence on the reaction rate. The reaction exhibits first-order kinetics in concentration ranges of Ru(III), [Fe(CN) 6 ] 3− and at low [L-PheAla] and [OH − ] concentrations. The incremental trend observed in the reaction rate with electrolyte concentration shows a positive salt effect. The reaction rate is almost 10 times faster in SDS micellar medium than in aqueous medium. [Fe(CN) 6 ] 3− has no appreciable effect on the CMC of SDS, since the polar head of SDS and [Fe(CN) 6 ] 3− are both negatively charged. The K + obtained from K 3 [Fe(CN) 6 ] and KNO 3 decreases the repulsion between the negatively charged heads of the surfactant molecules, which decreases the CMC of SDS. The activation parameters also support the outer-sphere electron transfer mechanism.

A simple and direct determination method for protein on fabric by measuring the surface reflectance of the bicinchoninic acid (BCA) reaction color has been reported. This study investigated the effects of four synthetic surfactants, six sodium fatty acids and one enzyme, as the coexisting substance on the direct determination of protein in cotton fabrics. The influence of the coexisting substance to the BCA reagent was examined. Then, seven coexisting substances present in detergents were selected, and the reflectance of reacted test swatch by protein and each coexisting substances were also measured, and then compared to the values obtained for protein alone. With the exception of sodium dodecyl sulfate and lauric acid, the concentration of the surfactants used in this study had little effect on protein determination. At low protease concentration there were no significant effects on the BCA method and determination.

A heterogeneous transesterification over a Zn-doped CaO catalyst was developed as a new alternative route to conventional homogeneous catalysis for the production of N-methyldiethanolamine-based esterquats. In this study, the optimum heterogeneous transesterification conditions for the production of N-methyldiethanolamine di-ester, a precursor of esterquats, in high yield were determined. At a temperature of 143 °C, a vacuum of 288 mbar, a molar ratio of 2:1 (methyl ester:N-methyldiethanolamine) and a catalyst dosage of 6 %, a maximum N-methyldiethanolamine di-ester yield of 83 % was obtained. The reused catalyst showed consistent activity in three consecutive runs, demonstrating the robustness of the Zn-doped CaO catalyst in the transesterification process. This route can reduce production costs due to the reusability of the catalyst and the elimination of water consumption in the neutralisation process for catalyst removal.