Reverse Micellar System Research Articles

Molecular-Level Insights into the Microstructure of a Hydrated and Nanoconfined Deep Eutectic Solvent.

Despite the recent advancements in the field of deep eutectic solvents (DESs), their high viscosity often prevents practical applications. A versatile strategy to overcome this problem is either to add a co-solvent or to confine the DES inside a nanoscaled self-organized system. This work assesses the microstructures of a hydrated and nanoconfined DES comprising benzyltripropylammonium chloride [BTPA]Cl and ethylene glycol (EG). They act as a hydrogen-bond acceptor and a donor, respectively. The hydrogen bonding between [BTPA]Cl and EG in the DES (i.e., BTEG) and the molecular states of water in the hydrated BTEG were studied by Raman spectroscopy. The results show different hydrogen-bonding associations between water-water and water-BTEG or EG molecules. In addition, we investigated the confinement effects of BTEG in a Polysorbate 80 (Tween-80)/cyclohexane reverse micellar (RM) system. The results are compared with those of an ionic liquid-encapsulated RM system. The formation, bonding characteristics, and thermal stability of the RM droplets were studied by solubilization, dynamic light scattering, rheology, and Raman spectroscopy experiments. Furthermore, it is shown that hydrogen bonding between the DES and the surfactant leads to a stable RM system. Interestingly, the viscosity of the RM system is significantly lower than that of the neat DES suggesting that DESs have a much wider practical applicability in the form of RMs.

Use of Span 80 reverse micellar system for the extraction of pectinesterase from lemon peel waste

ABSTRACTReverse micellar systems of nonionic surfactant Span 80/isooctane/n-hexane is used for the extraction of pectinesterase from crude aqueous extract of lemon peel waste. The effect of extraction process parameters on the extraction efficiency and activity recovery were studied in detail for the lemon peel extract. The optimum NaCl concentration (0.2 mol/L), Span 80 concentration (0.3 mol/L), the extraction phase pH (7.0), the temperature (60°C), and oscillation time (30 min) were found out and the optimized conditions for the extraction from lemon peel waste resulted in back extraction efficiencies of 52.4%. A fairly good activity recovery (83.7%) of pectinesterase is obtained under these conditions.

Fractional Factorial Analysis for Identifying Significant Factors in Extraction of Jacalin From Jackfruit Seeds Using Anionic Reverse Micellar System

Abstract Reverse micellar extraction is emerging as one of the most reliable method for extraction and purification of various proteins and enzymes. In this study, fractional factorial design was used to identify the significant factors having the largest effects on the forward extraction process of jacalin using reverse micelles formed by an anionic surfactant, sodium bis(2-ethylhexyl) sulfosuccinate (AOT). Effect of five different factors, namely the aqueous phase pH, surfactant (AOT) concentration, salt (NaCl) concentration, contact time and volume ratio of organic to aqueous phase on the forward extraction efficiency were investigated using the 25-1 fractional factorial design. The results showed that only the aqueous phase pH, NaCl concentration and concentration of AOT had significant effects on the forward extraction efficiency of jacalin into AOT reverse micelles. Results obtained indicated that the fractional factorial design was a useful method for screening many process factors with minimum number of experiments.

Dyeing cotton with reactive dyes: a comparison between conventional water-based and solvent-assisted PEG-based reverse micellar dyeing systems

Use of reactive dyes of red, blue and yellow colours for exhaustion dyeing of cotton conventional water-based dyeing method and PEG-based solvent-assisted reverse micelle dyeing method was investigated. Calibration curves of both dyeing approaches were established. The calibration results show that red dye can achieve higher absorbance value than yellow and blue dyes and the R-square of the curves can reach a value above 0.99 which indicates the curves are linear in structure and suitable for subsequent measurement. The values of substantivity factor (S), exhaustion factor (E), rate of fixation (R) and fixation factor (F) (SERF) are measured in percentage. The results reveal that using reverse micelle method can achieve higher dye absorption in both exhaustion and fixation processes, resulting in higher final exhaustion of dye in fibre than with the conventional water-based method. Therefore, the reverse micellar dyed samples generally can obtain higher dye absorption, lower reflectance percentage and darker shade in appearance than conventional water-based dyeing.

Modulation of the Excited-State Proton Transfer Rate of d-luciferin in Mixed Reverse Micellar Systems.

The excited-state proton transfer (ESPT) rate of photo-acids in a confined medium depends on several physical parameters of the immediate environment. We introduce a new parameter in the form of charge type at the interface of reverse micellar (RM) systems to modulate the ESPT rate. We investigate the ESPT reaction of d-luciferin in mixed RM systems composed of nonionic polyoxyethylene(5)nonylphenylether (Igepal CO-520) with cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in cyclohexane (Cy) at different mole fractions of Ig (XIg) and fixed hydration. ESPT is feeble in AOT RM, whereas it is favorable in the other two RMs. Addition of Ig is observed to facilitate ESPT in AOT RM linearly, whereas in DDAB, it shows a synergistic effect. The various physical parameters of water in the mixed RM water pool have been investigated using dynamic light scattering, Fourier transform infrared, and time-resolved fluorescence spectroscopy measurements to underline the ESPT mechanism in these mixed RMs.

Novel Carbohydrate Based Non-Ionic Gemini Surfactants with Flexible Spacer as Reverse Micellar Systems for Encapsulation of D- and L-Enantiomers of Some Aromatic α-Amino Acids in n-Hexane

AbstractNovel non-ionic gemini surfactants derived from carbohydrate carrying two hydrophobic tails with varying tail length of C12, C14 and C16, two sugar moiety as head groups, and an α-(CH2)6-flexible spacer have been synthesized. The head group of these gemini surfactants consists of sugar moiety connected to C-6 of tertiary amines. These gemini amphiphiles were explored as reverse micellar systems for encapsulation of some D- and L-enantiomers of aromatic α-amino acids i.e. histidine (His), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp) in n-hexane in the absence of water. It is found that these amino acids are encapsulated in the order of His > Phe > Tyr > Trp, and it is also observed that in almost all cases the D-enantiomers were better encapsulated as compared to the L-enantiomers. In all cases, encapsulation of D- and L-enantiomers of aromatic α-amino acids increased with increase of the hydrophobic chain length of the gemini surfactants.

Effect of Hydrophilic-lipophilic Balance (HLB) Values of PEG-based Non-ionic Surfactant on Reverse Micellar Dyeing of Cotton Fibre with Reactive Dyes in Non-aqueous Medium

The effect of hydrophilic-lipophilic balance (HLB) of polyethylene glycol-based non-ionic surfactants of polyoxyethylene stearyl ether and polyoxyethylene tridecyl ether series of seven types on reverse micellar dyeing system of cotton was studied in non-aqueous heptane solvent medium. The relationships between HLB values of surfactants and reflectance, K/Ssum value and levelness of the dyed samples were investigated. The experimental results reveal that reflectance percentage increases and K/Ssum value decreases with increase of HLB value while good levelness and visual appearance of dyed samples can be achieved only with optimum HLB value. The most suitable HLB value for reverse micelle dyeing of cotton ranges from 12 to 14 since there is stable formation of reverse micelle under this range. Fastness to washing of dyed cotton samples was also evaluated. The results show that samples dyed by both non-ionic surfactant series can achieve excellent washing fastness supporting reproducibility of K/Ssum value, reflectance percentage and levelness of reverse micelle dyed samples with various surfactants.

A New Thermodynamic Approach for Protein Partitioning in Reverse Micellar Solution

Reverse micellar systems are nanofluids with unique properties that make them attractive in high selectivity separation processes, especially for biological compounds. Understanding the phase behavior and thermodynamic properties of these nanosystems is the first step in process design. Separation of components by these nanosystems is performed upon contact of aqueous and reverse micellar phases. Due to the complexities of components molecular interactions, phase behavior studies of these solutions are different from regular liquid-liquid systems, and few thermodynamic models have been developed to describe distribution of extract between phases. In this study, a thermodynamic model with φ-φ approach and use of equations of states (EOS) is developed for the first time to describe the protein phase equilibria in reverse micellar systems. The developed model assumes that some reverse micelles act as active surfaces which can adsorb protein molecules. Also, the non-ideal behavior of micellar solution was modeled by three EOS, i.e. vdW, PR, and SRK. Results showed that SRK EOS shows the best match with experimental data of Bovine Serum Albomin (BSA) extraction from aqueous solution using reverse micellar solution of CTAB, a cationic surfactant. In addition, results indicate that the proposed thermodynamic model can describe the changes in electrostatic forces and increase in active surfaces on equilibrium protein extraction. Also, the standard deviation shows an excellent match between experimental data and model predictions.

Understanding of the Charge Origin in Nonpolar Suspensions to Control the Formation of Platinum Nanoparticle Monolayers by Electrophoretic Deposition

One of the important questions about understanding the principle mechanisms of electrophoretic deposition in nonpolar systems is to identify the origin of electric charge carried by nanoparticles. We developed a simple model of nanoparticle charging and we explained how the amount of the charge carried by nanoparticles can affect the quality of deposited monolayers. We used the centrifugation of Pt nanoparticles in water-AOT-isooctane reverse micellar system for controlling the charge carried by Pt nanoparticles.

Photoinduced viscosity control of lecithin-based reverse wormlike micellar systems using azobenzene derivatives.

This report describes the controlled viscosity changes of photoresponsive reverse wormlike micellar systems formed by soybean lecithin (SoyPC), d-ribose, and azobenzene derivatives in decane. UV light irradiation produces a significant (150-fold) decrease in solution viscosity by triggering a structural transformation of the wormlike micelles. Subsequent visible light irradiation leads to recovery of the initial micellar structure and elevated solution viscoelasticity. This dramatic, reversible variation in solution viscosity by light irradiation can be applied to cosmetics, personal care products, and device components.

Octane-Assisted Reverse Micellar Dyeing of Cotton with Reactive Dyes.

In this study, we investigated the computer colour matching (CCM) of cotton fabrics dyed with reactive dye using the octane-assisted reverse micellar approach. The aim of this study is to evaluate the colour quality and compare the accuracy between CCM forecasting and simulated dyeing produced by conventional water-based dyeing and octane-assisted reverse micellar dyeing. First, the calibration of dyeing databases for both dyeing methods was established. Standard samples were dyed with known dye concentrations. Computer colour matching was conducted by using the colour difference formula of International Commission on Illumination (CIE) L*a*b*. Experimental results revealed that the predicted concentrations were nearly the same as the expected known concentrations for both dyeing methods. This indicates that octane-assisted reverse micellar dyeing system can achieve colour matching as good as the conventional water-based dyeing system. In addition, when comparing the colour produced by the conventional water-based dyeing system and the octane-assisted reverse micellar dyeing system, the colour difference (ΔE) is ≤1, which indicates that the reverse micellar dyeing system could be applied for industrial dyeing with CCM.

Purification of recombinant human interferon gamma from fermentation broth using reverse micellar extraction: A process optimization study

ABSTRACTIn the present investigation, we have shown a single step purification of IFN-γ from the fermentation broth of recombinant Kluyveromyces lactis (K. lactis) strain, using cationic surfactant based reverse micellar extraction (RME) system. The forward and back extraction processes were optimized in order to improve the overall extraction process. 78%, 93% and 98% forward extraction efficiencies (FEE) were obtained after the process by using aqueous phase pH 12, 150 mM CTAB and 0.2 M NaCl respectively. Afterwards, back extraction efficiency (BEE) was maximized by the optimization of stripping phase pH, isopropyl alcohol (IPA) and potassium chloride (KCl) concentration by employing Taguchi’s method of orthogonal array. Stripping phase pH 7, 15% IPA & 0.8 M KCl were found to be the best possible parameters producing 83% BEE. The usage of IPA has proven to reduce the effect of micellar-micellar based interaction, which was reflected as an improvement in BEE. This study demonstrates that the reverse micellar system is a highly promising and efficient tool for the direct extraction of recombinant proteins from fermentation broth. Moreover, this system holds a high potential to be an integral part of the downstream process used in biopharmaceutical industry.

Prediction of CO2 mass transfer parameters to light oil in presence of surfactants and silica nanoparticles synthesized in cationic reverse micellar system

CO2 miscible injection method combined with surfactants and silica nanoparticles was studied to investigate the effect of these additives on CO2 mass transfer parameters to the light oil, including diffusion coefficient, mass transfer coefficient and solubility. Silica nanoparticles with controlled size distribution were synthesized in isooctane/1-hexanol/CTAB/ammonium hydroxide, a highly-stable reverse micellar system with w o =5. The presence of Si-O-Si and Si-O-H bonds in FTIR spectra of the system revealed that silica nanoparticles are formed by partial hydrolysis of TEOS. Results of DLS indicated that the average size and size distribution of the synthesized nanoparticles were 27.6 nm and 13-76 nm, respectively. Diffusion tests were carried out using CO2 gas and three liquid systems: isooctane/1-hexanol, isooctane/1-hexanol/CTAB reverse micellar system without nanoparticles, and isooctane/1-hexanol/CTAB reverse micellar system with nanoparticles. Results of modeling and optimization of the gas-liquid systems under nonequilibrium interface condition, using pressure decay data show that the presence of surfactants and nanoparticles leads to decreased gas diffusion coefficient; while increased interface mass transfer resistance due to presence of aqueous droplets and nanoparticles as well as lower solubility of CO2 in the light oil are the results of applying these additives, which limits their application. The obtained CO2 diffusion coefficients for isooctane/1-hexanol, reverse micellar system without nanoparticles, and reverse micellar system with nanoparticles are 8.5550×10−8, 8.2216×10−8, and 8.1114×10−8 m2/s, respectively.

Ascorbyl radical disproportionation in reverse micellar systems

Ascorbyl radical was generated by the pulse radiolysis method and observed with the fast kinetic spectrophotometry within reverse micelles stabilized by AOT in n-heptane or by Igepal CO-520 in cyclohexane at different water to surfactant molar ratio, w0. Rate constants for the disproportionation of the ascorbyl radicals were smaller than those for intermicellar exchange for both type of reverse micelles and slower than those in homogeneous aqueous solutions. However, they increased with increasing w0 for AOT/n-heptane system, while they decreased for Igepal CO-520 system. The absorption spectra of ascorbic acid AOT/n-heptane reverse micellar system showed that the “pH” sensed by this molecule is lower than that in respective homogeneous aqueous solutions. The obtained results were rationalized taking into account three main factors (i) preferential location of ascorbic acid molecules in the interfacial region of the both types of reverse micelles; (ii) postulate that the pH of the interface is lower than that of the water pool of reverse micelles and (iii) different structure of the interface of the reverse micelles made by AOT in n-heptane and those formed by Igepal CO-520 I cyclohexane. Some possible consequences of these findings are discussed.

Reverse micellar partitioning of Bovine Serum Albumin with novel system

To overcome the difficulties associated with the conventional extraction process like poor selective extrac- tion of biomolecule and scale up of the process, the reverse micellar system consist of AOT/n-heptanol was considered to extract Bovine Serum Albumin (BSA) as a model biomolecule. The maximum forward extraction of BSA from aqueous phase to micelle phase was observed at AOT concentration 160 mM, aque- ous phase pH value of 4, NaCl concentration 0.8 M and 95% back extraction of BSA from micelle phase to stripping phase was obtained at 1 M NaCl concentration with the pH of 7.5. HPLC analysis confirmed the stability of BSA during extraction. The size and water content of the reverse micelle was also reported. The obtained results emphasize the application of the AOT/n-heptanol reverse micellar system for the extraction of BSA and may be utilized for the selective extraction of similar hydrophilic proteins from the complex sources.

Reverse micellar extraction of lactoferrin from its synthetic solution using CTAB/n-heptanol system.

The partitioning of Lactoferrin (LF) into the reverse micellar phase formed by a cationic surfactant, cetyltrimethylammonium bromide (CTAB) in n-heptanol from the synthetic solution of LF was studied. The solubilization behaviour of LF into the reverse micellar phase and back extraction using a fresh stripping phase were improved by studying the effect of processing parameters, including surfactant concentration, solution pH, electrolyte salt concentration and addition of alcohol as co-solvent. Forward extraction of 100% was achieved at CTAB concentration of 50mM in n-heptanol solvent, pH of 10 and 1M NaCl. The electrostatic force and hydrophobic interaction have major influence on LF extraction during forward and back extraction respectively. The size of the reverse micelles and their corresponding water content were measured at different operating conditions to assess their role on the LF extraction. The present reverse micellar system has potential to solubilise almost all the LF into the reverse micelles during forward extraction and could able to allow back extraction from the reverse micellar phase with addition of small amount of co-solvent.

Reverse micellar partitioning of Bovine Serum Albumin with novel system

Abstract To overcome the difficulties associated with the conventional extraction process like poor selective extraction of biomolecule and scale up of the process, the reverse micellar system consist of AOT/n-heptanol was considered to extract Bovine Serum Albumin (BSA) as a model biomolecule. The maximum forward extraction of BSA from aqueous phase to micelle phase was observed at AOT concentration 160 mM, aqueous phase pH value of 4, NaCl concentration 0.8 M and 95% back extraction of BSA from micelle phase to stripping phase was obtained at 1 M NaCl concentration with the pH of 7.5. HPLC analysis confirmed the stability of BSA during extraction. The size and water content of the reverse micelle was also reported. The obtained results emphasize the application of the AOT/n-heptanol reverse micellar system for the extraction of BSA and may be utilized for the selective extraction of similar hydrophilic proteins from the complex sources.

Computer Color Matching and Levelness of PEG-Based Reverse Micellar Decamethyl cyclopentasiloxane (D5) Solvent-Assisted Reactive Dyeing on Cotton Fiber

The color matching and levelness of cotton fabrics dyed with reactive dye, in a non-aqueous environmentally-friendly medium of decamethylcyclopentasiloxane (D5), was investigated using the non-ionic surfactant reverse-micellar approach comprised of poly(ethylene glycol)-based surfactant. The calibration dyeing databases for both conventional water-based dyeing and D5-assisted reverse micellar dyeing were established, along with the dyeing of standard samples with predetermined concentrations. Computer color matching (CCM) was conducted by using different color difference formulae for both dyeing methods. Experimental results reveal that the measured concentrations were nearly the same as the expected concentrations for both methods. This indicates that the D5-assisted non-ionic reverse micellar dyeing approach can achieve color matching as good as the conventional dyeing system. The levelness of the dyed samples was measured according to the relative unlevelness indices (RUI), and the results reveal that the samples dyed by the D5 reverse micellar dyeing system can achieve good to excellent levelness comparable to that of the conventional dyeing system.

Formation dynamics of reverse micelles and nanosized effects that accompany chemical reduction of silver nanoparticles in them

Dynamic light scattering has been employed to study the time evolution of a sodium bis(2-ethylhexyl) sulfosuccinate/isooctane/water/quercetin/AgNO3 system during the formation of reverse micelles (RMs), as well as water solubilization and formation of Ag nanoparticles (NPs) in them. It has been shown that physicochemical processes occurring in the reverse micellar system lead to the formation of light-scattering elements with average sizes of 0.67−2 nm (individual molecules of the surfactant and reductant), 2.5−4.5 nm (“dry” RMs) and 16−20 nm (RMs containing Ag NPs). The synthesis is accompanied by the formation of silver NPs with other sizes in an amount of less than 5%.

Acquisition of Water Solubility Diagrams in Ternary Systems (AOT/Organic Solvent/Alcohol) and Extraction of α‐Lactalbumin Using Reverse Micellar Systems

AbstractIn this study water solubility curves were constructed and calorimetric measurements obtained for reverse micellar systems consisting of an alcohol (isopropanol or butanol), surfactant (AOT) and organic solvent (isooctane or hexane). Also evaluated were the effects of alcohol and solvent type and surfactant concentration on the extraction of the α‐lactalbumin (α–la). From the obtained solubility diagrams for ternary systems, it was concluded that isooctane presented the highest water solubility capacity in the center of the micelle systems with hexane, since isooctane has greater molecular volume and greater effect of the surfactant aggregation number. With respect to the alcohols, it was observed that isopropanol and butanol act in the system as a co‐surfactant, since they prefer to adsorb at the water/solvent interface. It was also verified that butanol improved water solubility inside the reverse micellar due to its contribution to increase the critical packing parameter. The amount of α‐la extracted increased proportionally with the AOT concentration for systems with isooctane and hexane. However, for systems with the latter solvent, the concentration of extracted protein first increases and then decreases. The extraction power of reverse micellar systems with isooctane was influenced by the type of alcohol with butanol showing better results. For systems containing hexane there was no effect of the alcohol added to the system on extraction power of α‐lactalbumin.