Anionic Sodium Dodecyl Sulfate Research Articles

Comparison of three techniques for decellularization of porcine bone-tendon-bone grafts

ABSTRACT Anterior cruciate ligament injuries are frequent afflictions related to sports or physical trauma. Autograft reconstruction strategies cause secondary injury to the patient. One alternative, supported by clinical evidence, is porcine xenografts. For clinical use, xenografts must be conditioned to avoid immune rejection. The most widely accepted procedure is tissue decellularization. We analyzed three decellularization strategies: the application of the anionic detergent sodium dodecyl sulfate (SDS), sonication, and freezing and thawing cycles. The treated tissues were evaluated histologically using H&E, Masson’s trichrome, Verhoeff-van Gieson staining, and DAPI for fluorescent staining of nuclei. Finally, collagen fiber preservation was evaluated by quantifying this protein by colorimetry. The most efficient decellularization techniques were sonication and SDS. Collagen fibers were preserved in all experimental conditions.

Covalent vs. Non covalent chemical modification of multiwalled carbon nanotubes based-nanofluids: Stability and thermal conductivity steadiness over temperature

Thermal conductivity enhancement coupled to nanoparticle dispersion stability over time are the two main conflicting requirements to overcome to develop carbon nanomaterial-based nanofluids. Both covalent and non-covalent approaches, having their own advantages and disadvantages, are commonly used for carbon nanotube based nanofluids development. However, they are rarely compared regarding their impact on stability and thermal conductivity performances for the same kind of nanofluid. In this work, multiwalled carbon nanotubes have been chemically modified by both covalent and non-covalent functionalization. For the covalent functionalization, a simple oxidation method is applied. It consists of refluxing the powdered MWCNTs in H2SO4/HNO3 at 5 M concentration. For the non-covalent approach, both an anionic (sodium dodecyl sulfate) and a non-ionic (Pluronic P123, comprising poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) in an alternating linear fashion, PEO-PPO-PEO) surfactants were employed at a concentration of 1 wt%. Nanofluids were prepared with multiwalled carbon nanotubes at a fixed concentration of 0.2 wt% for both chemical modification approaches. The oxidation reaction occurs without significant structure damaging as shown by transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. UV–visible spectrophotometry analysis shows a remarkable stability with temperature in the 293.15–303.15 K range over one-week and for a longer period of 49 days for all the three types of nanofluids. Their thermal conductivity has been investigated in the same temperature range. For all the three nanofluid series prepared with a fixed concentration of carbon nanomaterials, a thermal conductivity enhancement compared to that of the base fluid has been observed. The thermal conductivity evolution with temperature is different for each type of nanofluid. The covalently oxidized multiwalled carbon nanotube based nanofluids showed the better thermal conductivity enhancement steadiness (around 7 %) with temperature. The discussion on the surfactant-based nanofluid behavior proposes the possible involved mechanisms as temperature increases for each surfactant.

Fluorescence lifetime of pyrene butyric acid as a versatile sensing tool for monitoring self-assembled systems and microenvironment

Sensing applicability of the fluorescence lifetime of pyrene butyric acid (PBA) to understand the aggregation behaviour and microheterogeneity of different charged self-assembled surfactants i.e., anionic (sodium dodecyl sulfate, ∼ 8.5 mM), cationic (Cetyltrimethylammonium bromide, ∼ 0.95 mM), and non-ionic (Triton X100, ∼ 0.27 mM) in aqueous solution is explored in this study. Time domain fluorescence decay of PBA is introduced for the first time as a sensitive tool for characterizing the molecular microenvironment and for predicting the aggregation behaviour of surfactants, including the monitoring low to higher-order aggregates. A non-extensive distribution analysis on the fluorescence decay profiles yields the fluorescence lifetime and Full Width at Half Maxima (FWHM), with the latter serving as an indicator of the heterogeneity of the molecular microenvironment of the 'fluoroprobe'.The analytical strength of the fluorescence lifetime of PBA as a sensing tool has been validated using biosurfactants sodium cholate (NaC) and sodium deoxycholate (NaDC) with high fidelity. Careful analysis of the non-extensive distribution of the lifetime of PBA displays a substantial sensitivity towards microheterogeneity in its immediate vicinity and hence monitors the higher-order aggregation behaviour of bile salts in aqueous medium.

Dual charge metallo-catanionic formulation to fight acquired infections with antimicrobial photodynamic therapy using visible light

The rising incidence of hospital-acquired infections and the increasing antibiotic resistance in bacteria are among the foremost challenges in the field of public health. Antibacterial Photodynamic Therapy (aPDT) has emerged as a promising alternative method for eradicating bacterial biofilms. Nonetheless, the limited ability of photosensitizers (PS) to penetrate bacterial cell walls and bacterial biofilms reduces their effectiveness in combating microbial activity. To address these limitations, we suggest formulations that incorporate common dyes such as Rose Bengal (RB) and Toluidine Blue (TB) as photosensitizers within vesicles. The self-assembled structures are formed from an aqueous mixture of two oppositely charged surfactants, creating metallo-catanionic vesicles. The innovative aspect here lies in the inclusion of a double-chain copper based metallosurfactant (bishexadecyltrimethyl ammonium copper tetrachloride (CuC II)) as a cationic component with anionic sodium dodecyl sulphate (SDS). The formation, stability and aggregation behaviour of the synthesized metallo-catanionic vesicles were estimated in the presence of cationic and anionic photosensitizers i.e. TB and RB, respectively. The confocal fluorescence microscopy confirmed the PS encapsulation into selected fractions SDS:CuC II (30:70) and (70:30). Further, in-situ singlet oxygen quantification was done using chemical trapping method which supports enhanced singlet oxygen quantum yields in the presence of metallo-catanionic vesicles. PS-loaded metallo-catanionic vesicles were further used in antimicrobial Photodynamic Therapy against Gram-negative bacteria Escherichia coli (E. coli). A tremendous decrease in bacterial growth was observed after applying a dose of PS (TB and RB) loaded metallo-catanionic vesicles in the presence of laser light irradiation. The colony forming unit (CFU) value decreases from 5.84 × 106 CFU/mL to nil with metallo-catanionic vesicles (SDS:CuC II) encapsulated with both TB and RB PS (light dose 40 mins). Hence, our current research demonstrates that these dual-charge metallo-catanionic vesicles can serve as effective delivery vehicles for photosensitizers in photodynamic therapy to combat bacterial infections. Furthermore, these vesicles have potential applications in the field of photomedicine.

Relationship between polymer-surfactant interaction and micellar solubilization revealed by NMR spectroscopy

Micellar solubilization is considered as a key factor affecting the recovery efficiency in chemically enhanced oil recovery (cEOR). However, it is poorly understood how polymers in surfactant-polymer (SP) flooding influences the micellar solubilization. Guar gum (GG) and hydroxyethyl cellulose (HEC) are two important and widely used polysaccharide polymers. In this work, the effect of GG and HEC on the solubilization of a crude oil model compound methyl benzoate (MB) in anionic sodium dodecyl sulfate (SDS) micelles and the underlying mechanism were explored at the molecular scale by NMR spectroscopy. GG and HEC slightly increased the MB solubility in SDS micelles but did not change the solubilization capacity. No correlation peak was observed to demonstrate the attractive interaction between polymer and SDS. After examination, there is weak electrostatic repulsion between HEC/GG and SDS, which made the polymer independent from SDS micelles and was unable to participate in the formation of micelles to alter micellar structure and solubilization behavior. Although the solubility of MB was slightly increased, this increase should originate from weak molecular interactions between polymers, surfactants and hydrophobic molecules, including hydrogen bonding, van der Waals forces and hydrophobic interactions, etc. In summary, without strong electrostatic attraction between polymer and surfactant, the solubilization of polymers and the solubilization of micelles proceed independently, resulting in that the solubilization capacity of SDS micelles was not improved.

Impact of anthracite blending and SDS addition on slurryability and stability of Indian high ash coal water slurry

ABSTRACT The conventional modes of transporting coal frequently result in substantial fiscal challenges and environmental deterioration. Slurry-based hydraulic transportation of coal through pipelines has proven to be a feasible and efficient method, offering economic benefits, reliability and minimal ecological damage. Due to the limited and rapidly depleting reserves of high-rank coal, the scientific community is compelled to utilize high ash coal (HAC) to meet the growing demands of the population. The HAC slurry is characterized by poor slurryability, stability and low calorific value. This research presents a straightforward solution to enhance the slurryability and stability of Indian HAC while improving its calorific value. Anthracite and anionic additive sodium dodecyl sulfate (SDS) were added in Indian HAC to prepare a high solid loading blended slurry with improved stability. The rheological characteristics, stability and zeta potential of prepared slurry samples were assessed and analyzed to determine the optimum anthracite proportion and SDS concentration. The optimum anthracite proportion and SDS concentration for low apparent viscosity and maximum stability were 30% and 0.6%, respectively. The inclusion of anthracite and SDS at optimal proportion yielded a slurry with 66% solid concentration, indicating a surge of 14% in the maximum possible solid loading.

Effect of surfactants on the interfacial viscoelasticity and stability of silk fibroin at different oil-water interfaces.

The biocompatible amphiphilic silk fibroin, extracted from domesticated silkworms, can adsorb at the oil-water interface and form elastic interfacial layers. In this study, three surfactants (cationic cetyltrimethylammonium bromide, the nonionic polyoxyethylene sorbitan monolaurate, and the anionic sodium dodecyl sulfate) were selected to investigate, through interfacial shear rheology, the influences of surfactants on the interfacial viscoelasticity and stability of silk fibroin at the interfaces between water and two different oils. The presence of surfactant prolongs the equilibration time and enhances the interfacial elastic modulus and toughness of the interfacial silk fibroin layers, especially at the nonpolar dodecane-water interface. However, when the surfactant exceeds a critical concentration, the shear modulus and stability of interfacial silk fibroin layers begin to decrease due to the competitive adsorption of surfactant molecules and the weakening of the protein network. Owing to electrostatic interactions, the ionic surfactants cetyltrimethylammonium bromide and sodium dodecyl sulfate can form more hydrophobic complexes with silk fibroin, which results in higher shear moduli than for silk fibroin and silk fibroin-polyoxyethylene sorbitan monolaurate mixture. Both the surfactant type and oil polarity play important roles in the adsorption, shear viscoelasticity, and stability of silk fibroin at the oil-water interface. Enhanced interactions between a silk fibroin-surfactant mixture and the oil phase delay the equilibration of the adsorption layers but strengthen the stability of interfacial layers. © 2023 Society of Chemical Industry.

Insights into the micellar catalysed efficient oxidation of 2- and 3-pentanol by cerium(iv) in a greener medium of SDS and STS

A green envelop of aqueous micellar media generated by anionic surfactants SDS and STS catalyzes the Ce(iv) based oxidation of isomeric pentanols.

Synthesis and Characterization of a Novel Nanosized Polyaniline.

Polyaniline (PANI) is a conductive polymer easily converted into a conducting state. However, its limited mechanical properties have generated interest in fabricating PANI composites with other polymeric materials. In this study, a PANI-prevulcanized latex composite film was synthesized and fabricated in two phases following chronological steps. The first phase determined the following optimum parameters for synthesizing nanosized PANI, which were as follows: an initial molar ratio of 1, a stirring speed of 600 rpm, a synthesis temperature of 25 °C, purification via filtration, and washing using dopant acid, acetone, and distilled water. The use of a nonionic surfactant, Triton X-100, at 0.1% concentration favored PANI formation in a smaller particle size of approximately 600 nm and good dispersibility over seven days of observation compared to the use of anionic sodium dodecyl sulfate. Ultraviolet-visible spectroscopy (UV-Vis) showed that the PANI synthesized using a surfactant was in the emeraldine base form, as the washing process tends to decrease the doping level in the PANI backbone. Our scanning electron microscopy analysis showed that the optimized synthesis parameters produced colloidal PANI with an average particle size of 695 nm. This higher aspect ratio explained the higher conductivity of nanosized PANI compared to micron-sized PANI. Following the chronological steps to determine the optimal parameters produced a nanosized PANI powder. The nanosized PANI had higher conductivity than the micron-sized PANI because of its higher aspect ratio. When PANI is synthesized in smaller particle sizes, it has higher conductivity. Atomic force microscopy analysis showed that the current flow is higher across a 5 µm2 scanned area of nanosized PANI because it has a larger surface area. Thus, more sites for the current to flow through were present on the nanosized PANI particles.

Effect of biologically active amino acids based deep eutectic solvents on sodium dodecyl sulfate: A comparative spectroscopic study

Study the effects of three novel synthesized biologically deep eutectic solvents (DESs) on the micellar characteristics of anionic sodium dodecyl sulfate (SDS). The biologically active amino acids based three DESs synthesized have composed the 2:1 M of L-Aspartic acid (DES1), L-Tyrosine (DES2), L-Glutamine (DES3) and choline chloride, furthermore which characterized by FTIR. Surface tension, viscosity, UV–visible, fluorescence, and FTIR spectroscopy are a few of the techniques used to study the interactions of SDS within 5 and 10 wt% of three novel biological DESs in aqueous solutions. The presence and absence of 5 and 10 wt% of the three novel biological DESs in an aqueous solution is used to study the critical micelle concentration (CMC) and various interfacial characteristics including CMC, the efficiency of adsorption, the maximum surface excess concentration, the packing parameter, the minimum area per molecule, and the surface pressure at CMC, is assessed by the surface tension method. The calculated fluorescence data and those obtained using surface tension and UV–visible methods correspond well. The interactions that cause changes in the structure of the surfactant self-assemblies within aqueous DESs were investigated using FTIR technique. It is significant to highlight that the presence of unique biological DESs considerably facilitates the micellization process for SDS and the extent is more affinity for DES2 compared to DES1/DES3. The colloidal properties of DES and their combinations with water are anticipated to benefit from the current findings.

Binding and occupancy properties of gabapentin in mixed surfactant systems

AbstractThis research highlights the efficacy of mixed micellar systems as an innovative chemical formulation for improving the binding properties of active pharmaceutical drugs. The formulations based on the mole fraction were utilized for preparing mixed micelles with anionic sodium dioctyl sulfosuccinate (AOT) and sodium dodecyl sulphate (SDS). DLS measurements demonstrated the formation of small micelles and mixed micelles in SDS‐AOT combinations. A UV absorbance investigation demonstrated the effectiveness of the SDS‐AOT mixed micelles for determining the binding constant (Kb) and mean ion occupancy (i0) of the anticonvulsant gabapentin (GBP) drug. Kb values increased, but the occupancy (i) of GBP per micelle decreased by decreasing the mole fraction (α) of SDS from αSDS 0.9 to 0.1, predicting a shift in occupancy of drugs from the Palisade to the Stern layer. To get a better comprehension of micellization behavior and preferential interaction of the drugs under study, molecular docking studies were performed. According to the docking studies, the GBP displayed significant binding in the presence of SDS‐AOT when compared to pure SDS and AOT molecules. Ultimately, in pharmaceutical applications, mixed micelle played an important role in enhancing the binding and encapsulation efficiency of drugs.

In Vitro Cytocompatibility Assessment of Novel 3D Chitin/Glucan- and Cellulose-Based Decellularized Scaffolds for Skin Tissue Engineering

Background: Naturally derived sustainable biomaterials with high flexibility, mechanical properties, biocompatibility, and the ability to manipulate surface chemistry, providing a natural cellular environment, can be used for tissue engineering applications. However, only a few researchers have demonstrated the exploitation of natural architectures for constructing three-dimensional scaffolds. The chemical decellularization technique for fabricating natural scaffolds and their cytocompatibility assessment for tissue engineering applications need to be thoroughly explored and evaluated. Methods: Decellularization of natural scaffolds has been performed via a chemical method using anionic detergent sodium dodecyl sulfate (SDS) which was used for the in vitro culturing of murine embryonic NIH/3T3 fibroblasts. Techniques such as field-emission scanning electron microscopy (FE-SEM), compressive testing and swelling ratio, and biodegradation were performed to characterize the properties of fabricated decellularized natural scaffolds. Nucleic acid quantification, DAPI, and H&E staining were performed to confirm the removal of nuclear components. In vitro cytocompatibility and live/dead staining assays were performed to evaluate cultured fibroblasts’ metabolic activity and qualitative visualization. Results: 3D chitin/glucan- and cellulose-based scaffolds from edible mushroom (stem) (DMS) and unripe jujube fruit tissue (DUJF) were fabricated using the chemical decellularization technique. FE-SEM shows anisotropic microchannels of highly microporous structures for DMS and isotropic and uniformly arranged microporous structures with shallow cell cavities for DUJF. Both scaffolds exhibited good mechanical properties for skin tissue engineering and DUJF showed a higher compressive strength (200 kPa) than DMS (88.3 kPa). It was shown that the DUJF scaffold had a greater swelling capacity than the DMS scaffold under physiological conditions. At 28 days of incubation, DUJF and DMS displayed approximately 14.97 and 15.06% biodegradation, respectively. In addition, DUJF had greater compressive strength than DMS. Compared to DMS scaffolds, which had a compressive stress of 0.088 MPa at a 74.2% strain, the DUJF scaffolds had a greater compressive strength of 0.203 MPa at a 73.6% strain. The removal of nuclear DNA in the decellularized scaffolds was confirmed via nucleic acid quantification, DAPI, and H&E staining. Furthermore, both of these scaffolds showed good adherence, proliferation, and migration of fibroblasts. DMS showed better biocompatibility and high viability of cells than DUJF. Conclusions: This sustainable scaffold fabrication strategy is an alternative to conventional synthetic approaches for the in vitro 3D culture of mammalian cells for various tissue engineering and cultured meat applications.

Surfactants interaction with sulfathiazole: Spectroscopic, conductometric, and thermodynamic approach

Taking into the account the advantages of surfactant micelles as drug carrier, the interaction of sulfathiazole (STZ) with three types of surfactants, namely, cationic cetyltrimethylammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and non-ionic t-octylphenoxypolyethoxyethanol (TX-100) has been studied by using UV–visible spectroscope and conductivity measurements. The critical micelle concentration (CMC), degree of ionization (α), counter ion binding constant (β), free energy change of micellization (ΔG0m), relative solubility (St/S0), STZ-surfactant interaction constant (θ), approximate number (n) of STZ molecules incorporated per micelle, heat capacity (ΔC0m), and transfer of thermodynamic parameters were calculated and discussed for both the systems. The CMC values of CTAB and SDS were found to decrease in presence of increasing STZ concentrations. The values of counter ions dissociation were also found to be dependent of temperature. The ΔG0m values are obtained to be negative of both systems. A comparison of the binding constants (KC) calculated from the Kawamura equation indicated that the solubilization tendency of STZ with CTAB is much higher than that with SDS micelles. However, this interaction was weak since no significant change in the micellization phenomenon was observed with TX-100 under our experimental conditions.

A novel pH-responsive wormlike micelles combinated sodium dodecyl sulfate (SDS) and diethylenetriamine (DETA) based on noncovalent electrostatic interaction

pH-Responsive wormlike micelles (WLMs) have attracted lots of attention due to their abundant advantages, for example, ease of adjustment and strong reversibility. We have learned that the degree of protonation of diethylenetriamine (DETA) varies with pH, and the anionic sodium dodecyl sulfate (SDS) can connect with cationic groups. Inspired by this, a novel pH-responsive WLMs was prepared based on noncovalent electrostatic interaction with sodium dodecyl sulfate (SDS) and DETA at a molar ratio of 3:1. Properties of the SDS/DETA system were assessed from the aspects of rheology, macro-morphology, aggregates diameter, and micro-morphology. When the pH decreased from 9.98 to 6.80, the SDS/DETA system represented as a weak gel with the viscosity increasing from 7.6 mPa s to 1.4 × 103 mPa·s and the average hydrodynamic radius increasing from 5.6 to 91.3 nm. The phenomenon is attributed to the protonation of DETA when reducing the pH and the formation of WLMs based on electrostatic interaction between DETA and SDS. However, when pH was further reduced by adding HCl, the SDS/DETA system would reach its isoelectric point, thus the solution became turbid with low viscosity. The SDS/DETA solution represents excellent reversibility (at least three cycles) in viscoelasticity by adjusting the pH value, and such pH-responsive WLM holds significant potential for broader applications in biomedical, oilfield chemistry, and other fields.

Synergism in mixtures of nano benzimidazolium Gemini ionic liquid and sodium dodecyl sulfate surfactants in tuning interfacial properties of crude oil−water system

The high price of newly explored surfactants is a concern in applications, but their mixture with conventional surfactants can bring about desired outcomes. Gemini surface active ionic liquids (GSAILs) have emerged as unique materials in tuning interface properties. Surfactants like sodium dodecyl sulfate (SDS), on the other hand, are known effective and commercially available. This study investigates the simultaneous effects of a benzimidazolium cationic GSAIL, [C4benzim-C6-benzimC4][Br2], and SDS surfactants on the interfacial tension (IFT), emulsification, and wettability alteration of the crude oil−water system. The results demonstrate amazing synergies up to 97.6 % in the IFT reduction. An ultra-low IFT of 0.16 mN·m−1 was achieved with an optimum GSAIL mole fraction of 0.4, attributed to the attractive interaction between the cationic GSAIL and the anionic SDS. Mixtures also give 54.3 and 72.8 % synergies in emulsification and wettability alteration, respectively. The adsorption of individual and mixture of surfactants were theoretically analyzed using the Frumkin adsorption isotherm and the non-ideal interactions of the binary mixtures (NIBM) theory. The corresponding determined parameters were consistent. To have a more comprehensive analysis, the results were compared with those obtained with an analogous structure imidazolium GSAIL.

Surfactant integrated nanoarchitectonics for controlled morphology and enhanced functionality of tungsten oxide thin films in electrochromic supercapacitors

This research focuses on tungsten oxide (WO3) as a promising material, and the study investigates the electrodeposition of WO3 thin films on fluorine-doped tin oxide (FTO) coated glass substrates using three different surfactants: cationic hexamethylenetetramine (HMTA), anionic sodium dodecyl sulfate (SDS), and non-ionic polyethylene glycol (PEG). The X-ray diffraction analysis confirms that the resulting thin films exhibit amorphous structures. Raman analysis supports the identification of the pure WO3 phase based on the stretching and vibrational modes observed in the colored and bleached states. The X-ray photoelectron spectroscopic study examines the influence of cathodic and anodic potentials on the formation of oxidized and reduced tungsten species in surfactant-aided WO3 thin films. Field emission scanning electron microscopy is utilized to investigate the impact of different surfactants on the morphology of WO3 thin films, revealing the formation of porous, clumped, and dense nanogranules on the film surface. Electrochromic energy storage investigations highlight the superior performance of the W-PEG (polyethylene glycol assisted WO3) thin film, which exhibits efficient lithium-ion accommodation and desirable bifunctional characteristics. The optimized W-PEG sample demonstrates excellent electrochromic performance, including high optical modulation (84.39 %), good reversibility (98 %), and high coloration efficiency (117.95 cm2/C). Supercapacitive measurements reveal a high areal capacitance of 44.1 mF/cm2 at a current density of 0.1 mA/cm2, as well as an energy density of 0.024 mWh/cm2 at a power density of 0.1 mW/cm2, with 85 % capacitive retention over 8000 consecutive galvanostatic charge-discharge cycles. Furthermore, the application potential of nanogranular WO3 for electrochromic energy storage is demonstrated through the successful illumination of a red and green light-emitting diode (LED) using fully colored electrochromic supercapacitor devices (4 × 3 cm2), highlighting their energy storage capability.

Exploring the pH-Responsive Interaction of β-Blocker Drug Propranolol with Biomimetic Micellar Media: Fluorescence and Electronic Absorption Studies.

Interaction of neutral and charged lipophilic beta-blocker drug, propranolol (PPL) with biomimicking nanocavities formed by micelles bearing same and opposite charges namely, cationic cetyltrimethylammonium bromide (CTAB), a surface-active ionic liquid 1-hexadecyl-3-methylimidazolium chloride (HDMIC) and anionic sodium dodecyl sulphate (SDS) have been investigated using fluorescence and absorption spectroscopic techniques. Binding of PPL to SDS at pH < pKa is characterised by biphasic interactions with decrease in fluorescence intensity at lower concentrations and subsequent increase post micellization. All the surfactants show significant interactions with the neutral drug molecule at pH > pKa, which is evident from the strongest binding constant ( ) values at pH 10.4. Results of quenching studies indicate that the location of drug molecule is determined by its charge, which is influenced by both pH and charge on micelle surface. For PPL-CTAB and PPL-HDMIC systems, quenching was strongest at pH 10.4, moderate at pH 7.4 and was absent at pH 3.5. However, the PPL-SDS system displayed similar values at all pH conditions, suggesting that the probe is at the same position regardless of pH. Non-covalent interactions, which play crucial role in biological systems, are similarly the primary driving force governing the interaction between PPL and surfactant micelles.

Tensiometry-based sensing of aggregation and of evaporation behavior of a volatile amphiphile in mixed solutions with ionic and nonionic surfactants

Mixed surfactants solutions containing volatile amphiphiles, e.g. fragrances, are envisaged to exhibit correlations between aggregation behavior, molecular interactions, composition of the mixed adsorbed layers and the concentration of the volatile component in the vapors. These issues are addressed with tensiometric methods by considering dynamic and steady-state interfacial adsorption-evaporation behavior at both sides of air-liquid interface in mixed solutions of geraniol and micelle-forming ionic and non-ionic surfactants. Pendant drop tensiometry proved to be a sensitive method in assessing the concentration of geraniol in the vapors above mixed solutions. Differences in the release of the fragrance from the mixed interfacial layers are explained by competitive contributions of specific barrier mechanisms and concentration-dependent aggregation in bulk solutions. Synergetic effect in reducing surface tension was evident for mixtures of geraniol with anionic sodium dodecyl sulfate (SDS) and cationic dodecyltrimethylammonium bromide (DTAB) surfactants. Dynamic anti-synergetic effect in SDS-geraniol mixtures is attributed to strong aggregation behavior, which was found to hinder the evaporation of geraniol. Measurements of the headspace concentration indicated weak interactions between geraniol and micelles of non-ionic highly surface active Brij-35 surfactant. The presented results extend the traditional analytical toolbox for evaluating factors which affect the mass transfer of volatile organic amphiphiles between aqueous and gas phases.

Thermodynamics of modulation of interaction of α-helix inducer 2, 2, 2-trifluoroethanol with lysozyme in presence of cationic, anionic and non-ionic surfactants

The interactions of anionic sodium dodecyl sulphate (SDS), cationic cetyltrimethylammonium bromide (CTAB) and nonionic triton X-100 (TX-100) surfactants with lysozyme at pH = 2.4 have been studied individually as well as in combination with 2,2,2-trifluoroetanol (TFE). Urea has also been used in combination with surfactants. By using these combinations, efforts have been made to obtain partially folded conformations of the protein in the presence of surfactants and effect of α-helix inducer 2,2,2-trifluoroethanol on these intermediate states. Thermodynamic analysis of all these interactions has been done employing a combination of UV-visible, fluorescence and circular dichroism spectroscopies. The results have been correlated with each other and characterized qualitatively as well as quantitatively. At lower concentration of surfactant, the thermodynamic parameters indicated the destabilizing effect of SDS, stabilizing effect of CTAB and unappreciable destabilizing impact of TX-100 on lysozyme. The enhancement in destabilization effect or reduction in stabilization effect of surfactants on lysozyme in the presence of TFE and urea has also been indicated. Communicated by Ramaswamy H. Sarma

Rheology, viscoelasticity and microstructural properties of OAPB-SDS mixtures at different temperature and pH conditions

Viscoelastic surfactant (VES) fluids are widely used in the hydraulic fracturing process to increase oil and gas productivity. Zwitterionic (carbon-18) surfactant solution, which is commonly used in VES fluids, has high critical micelle concentration, resulting in high used concentration and lack of economy. Furthermore, it is not applicable to high-temperature conditions. The oleylamidopropyl betaine (OAPB, carbon-25) with longer carbon chain has lower critical micelle concentration (CMC) and better high temperature resistance. In addition, it behaves better viscosity increasing capacity combining with anionic sodium dodecyl sulfate (SDS) surfactant. In this study, the viscoelasticity and microstructural properties of OAPB-SDS (OADS) mixtures at different temperature and pH conditions were investigated deeply. Rheology and structural morphology properties of the OADS mixed fluids were investigated by rheometer, and transmission electron cryo-microscopy. The results showed that OADS solution demonstrated elastic gel-like fluid behavior with zero shear viscosity of 3.5 × 106 mPa.s at neutral pH and room temperature, while OAPB solution demonstrated viscous fluid behavior with zero shear viscosity (ηo) of 62 mPa.s. The viscoelasticity and microstructural properties of OADS solution were influenced by concentration, pH and temperature. It was gel-like fluid at 25–40 °C, viscoelastic fluid at 60–80 °C and totally viscous fluid at 90 °C. The OADS was viscous at 0.5 wt% concentration, viscoelastic at 0.6 wt% concentration and elastic at 0.75 wt% concentration. The OADS solution showed viscous, viscoelastic and elastic behaviors at pH value of 3, 4, and 7 respectively. The fluid exhibited viscosity switch ability by reversibly altering pH values. The Cryo-TEM images confirmed that the OADS micelle experience microstructural transformed from long wormlike micelles (WLMs) to spherical micelles as the pH changes. The mixture fluid improved viscoelastic and aggregation properties than that of individual surfactant component, possessing lower used surfactant concentration. This study is useful in understanding the properties of mixed zwitterionic-anionic fluids, which is thermo-pH responsive, valuable in the fracturing.