Do Ionic Liquids Exhibit the Required Characteristics to Dissolve, Extract, Stabilize, and Purify Proteins? Past-Present-Future Assessment.

Proteins are highly labile molecules, thus requiring the presence of appropriate solvents and excipients in their liquid milieu to keep their stability and biological activity. In this field, ionic liquids (ILs) have gained momentum in the past years, with a relevant number of works reporting their successful use to dissolve, stabilize, extract, and purify proteins. Different approaches in protein-IL systems have been reported, namely, proteins dissolved in (i) neat ILs, (ii) ILs as co-solvents, (iii) ILs as adjuvants, (iv) ILs as surfactants, (v) ILs as phase-forming components of aqueous biphasic systems, and (vi) IL-polymer-protein/peptide conjugates. Herein, we critically analyze the works published to date and provide a comprehensive understanding of the IL-protein interactions affecting the stability, conformational alteration, unfolding, misfolding, and refolding of proteins while providing directions for future studies in view of imminent applications. Overall, it has been found that the stability or purification of proteins by ILs is bispecific and depends on the structure of both the IL and the protein. The most promising IL-protein systems are identified, which is valuable when foreseeing market applications of ILs, e.g., in "protein packaging" and "detergent applications". Future directions and other possibilities of IL-protein systems in light-harvesting and biotechnology/biomedical applications are discussed.

Self-assembly of choline-based surface-active ionic liquids and concentration-dependent enhancement in the enzymatic activity of cellulase in aqueous medium.

The micellization of choline-based anionic surface-active ionic liquids (SAILs) having lauroyl sarcosinate [Sar]-, dodecylsulfate [DS]-, and deoxycholate [Doc]- as counter-ions was investigated in an aqueous medium. Density functional theory (DFT) was employed to investigate the net interactional energy (Enet), extent of non-covalent interactions, and band gap of the choline-based SAILs. The critical micelle concentration (cmc) along with various parameters related to the surface adsorption, counter-ion binding (ß), and polarity of the cores of the micelles were deduced employing surface tension measurements, conductometric titrations and fluorescence spectroscopy, respectively. A dynamic light scattering (DLS) system equipped with zeta-potential measurement set-up and small-angle neutron scattering (SANS) were used to predict the size, zeta-potential, and morphology, respectively, of the formed micelles. Thermodynamic parameters such as standard Gibb's free energy and standard enthalpy change of micellization were calculated using isothermal titration calorimetry (ITC). Upon comparing with sodium salt analogues, it was established that the micellization was predominantly governed by the extent of hydration of [Cho]+, the head groups of the respective anions, and the degree of counter-ion binding (ß). Considering the concentration dependence of the enzyme-SAIL interactions, aqueous solutions of the synthesized SAILs at two different concentrations (below and above the cmc) were utilized as the medium for testing the enzymatic activity of cellulase. The activity of cellulase was found to be ∼7- to ∼13-fold higher compared to that observed in buffers in monomeric solutions of the SAILs and followed the order: [Cho][Sar] > [Cho][DS] > [Cho][Doc]. In the micellar solution, a ∼4- to 5-fold increase in enzymatic activity was observed.

Water Induced Alterations in Self-Assembly of a Bio-Surfactant in Deep Eutectic Solvent for Enhanced Enzyme Activity.

Deep eutectic solvents (DESs) meet important requirements for green solvent technology, including non-toxicity, biodegradability, sustainability, and affordability. Despite possessing low cohesive energy density than water, DESs have been found to support the self-assembly of amphiphiles. It is very much pertinent to examine the effect of water on self-assembly of surfactants in DESs as the presence of water alters the inherent structure of DES, which is expected to affect the characteristic properties of self-assembly. Following this, we have investigated the self-assembly of amino-acid based surfactant, Sodium N-lauroyl sarcosinate (SLS), in DES-water mixtures (10, 30 and 50 w/w% of water) and explored the catalytic activity of Cytochrome-c (Cyt-c) in the formed colloidal systems. Investigations using surface tension, fluorescence, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) have shown that DES-water mixtures promote the aggregation of SLS, resulting in the lower critical aggregation concentration (cac ∼1.5-6-fold) of the surfactant as compared to water. The nanoclustering of DES at low water content and it's complete de-structuring at high water content affects the self-assembly in a contrasting manner governed by different set of interactions. Further, Cyt-c dispersed in DES-water colloidal solutions demonstrated 5-fold higher peroxidase activity than that observed in phosphate buffer.

Mixed Aggregates of Surface-Active Ionic Liquids and 14-2-14 Gemini Surfactants in an Aqueous Medium as Fluid Scaffolds for Enzymology of Cytochrome-c.

The aggregation behavior of the surface-active ionic liquid (SAIL), 3-(2-(hexadecyloxy)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [C16Emim][Cl], and a gemini surfactant (GS) (14-2-14) in the whole mole fraction range has been investigated in an aqueous medium employing various techniques. Experimentally obtained values of critical aggregation concentration (cac) are in good agreement with the theoretical cac values obtained using Clint's equation. Rubingh's model has been employed to evaluate the extent of synergistic interactions between two components, which has been found to be dependent upon the composition of a mixture of surfactants. The polarity index, hydrodynamic diameter (Dh), zeta potential (ζ-Pot.), and morphology of the aggregates have been found to be dependent upon the extent of hydrophobic as well as dipolar interactions and the degree of counterion binding governed by the content of the GS in mixed aggregates. Thermodynamic parameters evaluated employing isothermal titration calorimetry have revealed the aggregation as an entropy-driven process. Density functional theory calculations provide a detailed account of the SAIL-GS interactions at the molecular level. The reduced density gradient (RDG) along with the calculated isosurfaces asserts that the dominant interactions are noncovalent interactions. Furthermore, the enzymology of cytochrome-c in the aqueous SAIL-GS aggregated systems has been investigated and a two-fold increase in the enzyme activity has been observed in the aggregates formed by the GS as compared to that in buffer.

Spontaneous Fibrillation of Bovine Serum Albumin at Physiological Temperatures Promoted by Hydrolysis-Prone Ionic Liquids.

This study highlights the role of time-dependent hydrolysis of ionic liquid anion, [BF4]-, of ionic liquid (IL), 1-ethyl-3-methylimidazolium tetrafluoroborate, [C2mim][BF4], which results in ever-changing pH conditions. Such pH changes along with the ionic interactions bring conformational changes in bovine serum albumin (BSA), leading to the formation of amyloid fibers at 37 °C without external control of pH or addition of electrolyte. The fibrillation of BSA occurs spontaneously with the addition of IL; however, the highest growth rate has been observed in aqueous solution of 10% IL (v/v %) among investigated systems. Thioflavin T (ThT) fluorescence emission has been employed to monitor the growth and development of ß-sheet content in amyloid fibrils. The structural alterations in BSA have also been investigated using intrinsic fluorescence measurements. Circular dichroism (CD) measurements confirmed the formation of amyloid fibrils. Transmission electron microscopy (TEM) has been explored to establish the morphologies of BSA fibrils at different intervals of time, whereas atomic force microscopy (AFM) has established the helically twisted nature of grown amyloid fibrils. The docking studies have been utilized to understand the insertion of IL ions in different domains of BSA, which along with decreased pH cause the unfolding and growth of BSA into amyloid fibrils. It is expected that the results obtained from this study would help to understand the impact of IL containing [BF4]- anion on protein stability and aggregation along with providing a new platform to control the formation of amyloid fibrils and other biomaterials driven via ionic interactions and alterations in pH.

Biamphiphilic ionic liquid based aqueous microemulsions as an efficient catalytic medium for cytochrome c.

Considering the remarkable applicability of ionic liquids (ILs) in bio-catalysis involving enzymes, herein, we report new IL based aqueous microemulsions as a catalytic reactor for cytochrome c (Cyt-c). Microemulsions (µEs), comprising water as the polar component, imidazolium (cation) and dioctylsulfosuccinate (AOT) (anion) based biamphiphilic ionic liquid (BAIL) as the surfactant and a hydrophobic ionic liquid (HIL) as the non-polar component have been prepared and characterized. The use of BAIL has promoted the formation of µEs without any co-surfactant, owing to its higher surface activity. The effect of ester- or amide-functionalization of the alkyl chain of the imidazolium cation of BAILs on the phase behavior of µEs has been investigated. The prepared µEs have been characterized via conductivity, dynamic light scattering (DLS), UV-vis absorption and steady-state fluorescence (using external polarity probes) techniques. The prepared µEs have been employed as nano-reactors for exploring the catalytic activity of Cyt-c. The formed BAIL-water nano-interfaces in reverse µEs have exerted a positive effect on the catalytic activity of Cyt-c stored in a water pool of reverse µEs. A five-fold higher rate constant in µEs as compared to buffer establishes µEs as a better catalytic medium. Furthermore, the differing nature of nano-interfaces created by BAILs and water in reverse µEs, depending on the functionalization of the alkyl chain of the cationic part of BAIL, has exerted varying influence on the catalytic activity of Cyt-c. It is expected that the present work will result in providing a versatile platform for the creation of new IL and water based µEs for bio-catalytic applications.

Thermally Stable Ionic Liquid-Based Microemulsions for High-Temperature Stabilization of Lysozyme at Nanointerfaces.

The development of new strategies for thermal stability and storage of enzymes is very important, considering the nonretention of catalytic activity by enzymes under harsh conditions of temperature. Following this, herein, a new approach based on the interfacial adsorption of lysozyme (LYZ) at nanointerfaces of ionic liquid (IL)-based microemulsions, for enhanced thermal stability of LYZ, is reported. Microemulsions (MEs) composed of dialkyl imidazolium-based surface active ILs (SAILs) as surfactants, ILs as the nonpolar phase, and ethylene glycol (EG) as the polar phase, without any cosurfactants, have been prepared and characterized in detail. Various regions corresponding to polar-in-IL, bicontinuous, and IL-in-polar phases have been characterized using conductivity measurements. Dynamic light scattering (DLS) measurements have provided insights into the size distribution of microdroplets, whereas temperature-dependent DLS measurements established the thermal stability of the MEs. Nanointerfaces formed by SAILs with EG in thermally stable reverse MEs act as fluid scaffolds to adsorb and provide thermal stability, up to 120 °C, to LYZ. Thermally treated LYZ upon extraction into a buffer shows enzyme activity owing to negligible change in the active site of LYZ, as marked by retention of microenvironment of Trp residues present in the active site of LYZ. The present work is expected to establish a new platform for the development of novel nanointerfaces utilizing biobased components for other biomedical applications.

Effect of the Alkyl Chain Length of Amphiphilic Ionic Liquids on the Structure and Dynamics of Model Lipid Membranes.

We compare the biophysical and structural aspects of the interaction of amphiphilic ionic liquids containing 1-alkyl-3-methylimidazolium cation ([CnMIM]+, n = 8, 12, or 16) with membranes composed of zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol (POPG). Liposome affinity and permeabilization were determined using ζ-potential and fluorescence studies, correlated with the cytoxicity of [CnMIM]+Br- toward HeLa cell lines. Membrane affinity is strongest in the case of [C16MIM]+Br- followed by [C12MIM]+Br- and [C8MIM]+Br- for both membranes, and trends remained the same in the case of membrane permeability and cytotoxicity. Solid-state NMR spectroscopy was used to localize [CnMIM]+ inside the lipid bilayers and to study their impact on the head group and acyl chain structures and dynamics of the lipid molecules. The charged ring moiety of the [CnMIM]+ is localized in the lipid-water interface of the membranes irrespective of the chain length and membrane surface charge. While [C8MIM]+ binds the membrane most weakly, it induces the largest disorder in the lipid chain region. A lack of fast flip-flop motions of the amphiphiles in the case of long chain [C16MIM]+ is suggested to render the membrane unstable, which increases its permeability. Between the lipid molecules, the POPC membrane incurs larger disorder in lipid chain packing upon insertion of [CnMIM]+ molecules. The study provides structural details of the impact of increasing chain lengths in [CnMIM]+ on the structural properties of lipid bilayers.

Aqueous systems of a surface active ionic liquid having an aromatic anion: phase behavior, exfoliation of graphene flakes and its hydrogelation.

Surface active ionic liquid (SAIL) induced hydrogelation, in the absence of additives, is important considering the properties of soft-hydrogels that can be utilized in different applications. The present study is concerned with the phase behavior and hydrogelation of a SAIL, 1-hexadecyl-3-methylimidazolium p-toluenesulfonate, [C16mim][PTS]. The obtained information about the phase behavior along with the surfactant like behavior of the SAIL was exploited for effective exfoliation of graphene-flakes from graphite in aqueous medium that remain stable for at least one month. Thus the obtained dispersion of graphene-flakes was subsequently hydrogelated exploiting the observations made from the phase behavior of the SAIL, via entanglement of long worm-like micelles of the SAIL formed at higher concentration. The obtained graphene-flake based hydrogels were found to be equally stable as compared to the blank hydrogel as well as against centrifugation. The low melting point of hydrogel facilitates the extraction of graphene-flakes from the hydrogel matrix by heating and diluting the gel and there is no sign of agglomeration in the extracted graphene-flakes even if the extraction is carried out after a period of three months. The present work is an exemplary study on exfoliation, hydrogelation and extraction of graphene-flakes from a hydrogel, when required, using a SAIL and is expected to provide a new platform for utilization of SAILs for efficient graphene exfoliation and subsequent preparation of functional materials.

Colloidal systems of surface active ionic liquids and sodium carboxymethyl cellulose: physicochemical investigations and preparation of magnetic nano-composites.

The complexation of three surface active ionic liquids (SAILs): 1-methyl-3-dodecylimidazolium chloride, [C12mim][Cl], and its amide, 3-(2-(dodecylamino)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [C12Amim][Cl], and ester, 3-methyl-1-dodecyloxycarbonylmethylimidazolium chloride, [C12Emim][Cl], functionalized counterparts with sodium carboxymethylcellulose (NaCMC), has been investigated. The behaviour of colloidal systems comprising SAILs and NaCMC at the air-solution interface has been investigated using tensiometry. The formed colloids in the bulk have been characterized for their mobility, surface charge, shape, size and morphology along with their relative hydrophobicity/hydrophilicity and other thermodynamic parameters of interest in different concentration regimes of the SAILs. For this, various techniques such as conductivity, turbidity, dynamic light scattering, ζ-potential, scanning electron microscopy (SEM) and fluorescence measurements have been employed. H-bonding prone SAILs, i.e. [C12Amim][Cl] and [C12Emim][Cl], are found to interact with NaCMC in a contrasting manner as compared to their non-functionalized counterpart. The formed complexes of SAILs and NaCMC have been explored for the one pot preparation of magnetic nano-composites by doping colloids of SAILs and NaCMC with zinc ferrite (ZnFe3O4) nano-particles. The prepared magnetic nano-composites are characterised using X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometry (VSM). It is expected that the present work would offer a new colloidal route for the preparation of SAILs and biopolymer assisted nano-composites along with providing physical insights into the complexation phenomenon.

Effect of alkyl chain functionalization of ionic liquid surfactants on the complexation and self-assembling behavior of polyampholyte gelatin in aqueous medium.

The complexation behaviour of an imidazolium based ionic liquid surfactant (ILS) 3-methyl-1-dodecylimidazolium chloride, [C12mim][Cl], and its amide and ester functionalized counterparts 3-(2-(dodecylamino)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [C12Amim][Cl], and 3-methyl-1-dodecyloxycarbonylmethylimidazolium chloride, [C12Emim][Cl], with a model protein gelatin (G) in aqueous solution has been investigated. Complexation of G with ILSs at the air-solution interface has been monitored by tensiometry, whereas complexation and ILS mediated self-assembly of G-ILS complexes in the bulk have been followed by dynamic light scattering (DLS), zeta-potential measurements, conductivity, and fluorescence techniques. The morphology of different self-assembled architectures has been monitored by scanning electron microscopy (SEM). Different transitions observed from various techniques in different concentration regimes of ILSs have been assigned to the varying extent of complexation and ILS mediated self-assembly of G-ILS complexes. The functionalization of the alkyl chain of the ILS [C12mim][Cl] with an amide ([C12Amim][Cl]) or ester ([C12Emim][Cl]) moiety owing to their additional hydrogen bonding (H-bonding) ability along with rigidity ([C12Amim][Cl]) or flexibility ([C12Emim][Cl]) near the imidazolium head group has been found to exert great influence on their complexation with G. This influence is fashioned as self-assembled structures of G-ILS complexes into discrete large hexagonal sheet-like or near spherical architectures, depending on the concentration and type of functionality of the alkyl chain of ILSs. The thermodynamic forces behind the complexation and self-assembly processes have been monitored by isothermal titration calorimetry (ITC) measurements and are discussed in detail. As both the nature of the ILS and protein (charge and structure) could affect their interactional behavior, the present results are expected to be very useful in deeply understanding the structure-property relationship between the nature of the ILS and proteins, which would be of great importance in the field of functional soft-materials.

Interactional behavior of the polyelectrolyte poly sodium 4-styrene sulphonate (NaPSS) with imidazolium based surface active ionic liquids in an aqueous medium.

The present study aims to develop an understanding of the interactions between an anionic polyelectrolyte, poly sodium 4-styrene sulphonate (NaPSS), and cationic surface active imidazolium based ionic liquids (SAILs), [Cnmim][Cl] (n = 10, 12, 14) using a multi-technique approach. Various physicochemical and electrochemical techniques such as surface tension, conductivity, fluorescence, isothermal titration calorimetry (ITC), dynamic light scattering (DLS), turbidity, potentiometry, cyclic voltammetry (CV), and differential pulse voltammetry (DPV) are employed to obtain comprehensive information about NaPSS-SAIL interactions. Different stages of interaction, corresponding to the critical aggregation concentration (cac), critical saturation concentration (Cs) and critical micelle concentration (cmc) have been observed owing to the strong electrostatic and hydrophobic interactions, and the results obtained from different techniques complement each other very well. The results extracted from DLS and turbidity measurements clearly indicated that the size of the micelle like aggregates first decreases and then increases in the presence of polyelectrolyte. The binding isotherms obtained using potentiometry show a concentration dependence and the highly co-operative nature of the interactions which is attributed to aggregation of the polyelectrolyte-SAIL complexes. The diffusion coefficients (Dm) of the electroactive probe in the pure and NaPSS-SAIL mixed systems were obtained, which were further used to obtain the values of the micellar self-diffusion coefficients (D) and inter-micellar interaction parameters (kd).

Self-assembly of azobenzene bilayer membranes in binary ionic liquid-water nanostructured media.

Anionic azobenzene-containing amphiphile 1 (sodium 4-[4-(N-methyl-N-dodecylamino)phenylazo]benzenesulfonate) forms ordered bilayer membranes in binary ionic liquid (1-ethyl-3-methylimidazolium ethyl sulfate, [C2mim][C2OSO3])-water mixtures. The binary [C2mim][C2OSO3]-water mixture is macroscopically homogeneous at any mixing ratio; however, it possesses fluctuating nanodomains of [C2mim][C2OSO3] molecules as observed by dynamic light scattering (DLS). These nanodomains show reversible heat-induced mixing behavior with water. Although the amphiphile 1 is substantially insoluble in pure water, it is dispersible in the [C2mim][C2OSO3]-water mixtures. The concentration of [C2mim][C2OSO3] and temperature exert significant influences on the self-assembling characteristics of 1 in the binary media, as shown by DLS, transmission electron microscopy (TEM), UV-vis spectroscopy, and zeta-potential measurements. Bilayer membranes with rod- or dotlike nanostructures were formed at a lower content of [C2mim][C2OSO3] (2-30 v/v %), in which azobenzene chromophores adopt parallel molecular orientation regardless of temperature. In contrast, when the content of [C2mim][C2OSO3] is increased above 60 v/v %, azobenzene bilayers showed thermally reversible gel-to-liquid crystalline phase transition. The self-assembly of azobenzene amphiphiles is tunable depending on the volume fraction of [C2mim][C2OSO3] and temperature, which are associated with the solvation by nanoclusters in the binary [C2mim][C2OSO3]-water media. These observations clearly indicate that mixtures of water-soluble ionic liquids and water provide unique and valiant environments for ordered molecular self-assembly.

Micellization behavior of morpholinium-based amide-functionalized ionic liquids in aqueous media.

Morpholinium-based amide-functionalized ionic liquids (ILs) [C(n)AMorph][Br], where n = 8, 12, and 16, have been synthesized and characterized for their micellization behavior in aqueous medium using a variety of state of the art techniques. The adsorption and micellization behavior of [CnAMorph][Br] ILs at the air-solution interface and in the bulk, respectively, has been found to be much better compared to that observed for nonfunctionalized homologous ILs and conventional cationic surfactants, as shown by the comparatively higher adsorption efficiency, lower surface tension at the critical micelle concentraiton (γ(cmc)), and much lower critical micelle concentration (cmc) for [C(n)AMorph][Br] ILs. Conductivity measurements have been performed to obtain the cmc, degree of counterion binding (ß), and standard free energy of micellization (ΔG(m)°). Isothermal titration calorimetry has provided information specifically about the thermodynamics of micellization, whereas steady-state fluorescence has been used to obtain the cmc, micropolarity of the cybotactic region, and aggregation number (N(agg)) of the micelles. Both dynamic light scattering and atomic force microscopy have provided insights into the size and shape of the micelles. 2D (1)H-(1)H nuclear Overhauser effect spectroscopy experiments have provided insights into the structure of the micelle, where [C16AMorph][Br] has shown distinct micellization behavior as compared to [C8AMorph][Br] and [C12AMorph][Br] in corroboration with observations made from other techniques.

Complexation, dimerisation and solubilisation of methylene blue in the presence of biamphiphilic ionic liquids: a detailed spectroscopic and electrochemical study.

The interactions of methylene blue (MB), a redox active dye with surface active biamphiphilic ionic liquids (BAILs): 1-butyl-3-methylimidazolium dodecylsulfate, [C4mim][C12OSO3] and 1-hexyl-3-methylimidazolium dodecylsulfate [C6mim][C12OSO3] have been investigated in aqueous medium to explore the candidature of surface active ionic liquids (ILs) in the field of dye-surfactant chemistry. Various thermodynamic, spectroscopic and electrochemical techniques such as conductivity, steady-state fluorescence, UV-visible absorption, and cyclic voltammetry (CV) have been used to obtain comprehensive information about MB-BAIL interactions. The presence of MB is seen to enhance the critical micellar concentration (cmc) of BAILs. The extent of interaction between the MB and BAILs varies with the concentration as well as the nature of BAILs. Different interactional phenomena such as the formation of ion-pair complexes, dimers, and solubilisation of monomers of MB have been observed in different concentration regimes of BAILs. A quantitative evaluation of the process of interaction between MB and BAILs has been made in terms of various micellar and binding parameters exploiting UV-visible absorption and CV measurements. Comparatively more hydrophobic [C6mim][C12OSO3] interacts strongly with MB as compared to [C4mim][C12OSO3] via hydrophobic and electrostatic interactions.

Effect of cationic head group on micellization behavior of new amide-functionalized surface active ionic liquids.

Amide-functionalized surface active ionic liquids (SAILs), 1-methyl-1-dodecyl piperidinium chloride, [C12APip][Cl]; 1-methyl-1-dodecyl pyrrolidinium chloride, [C12APyrr][Cl]; 1-methyl-3-dodecyl imidazolium chloride, [C12Amim][Cl], and 1-methyl-1-dodecyl morpholinium chloride, [C12AMorph][Cl], have been synthesized, characterized and investigated for thermal stability, and micellization behavior in aqueous medium. The introduction of an amide moiety in the alkyl chain decreased the thermal stability of the functionalized SAILs compared to non-functionalized SAILs bearing a simple alkyl chain. A variety of state of the art techniques, viz. tensiometry, conductometry, steady-state fluorescence, isothermal titration calorimetry (ITC), dynamic light scattering (DLS) and atomic force microscopy (AFM), have been employed to investigate the micellization behavior. Amide-functionalized SAILs have shown much lower critical micelle concentration, cmc, and better surface active properties as compared to homologous non-functionalized SAILs. Steady-state fluorescence has provided information about cmc, aggregation number (Nagg) and polarity of the cybotactic region of the micelles, whereas ITC has provided insights into the thermodynamics of micellization. Furthermore, the size and shape of the micelles have been investigated using DLS and AFM techniques.

Water-pluronic-ionic liquid based microemulsions: Preparation, characterization and application as micro-reactor for enhanced catalytic activity of Cytochrome-c.

Microemulsions (µEs), comprising water as polar component, pluronic (normal, L35 and reverse, 10R5) as surfactant and a hydrophobic ionic liquid (HIL) as non-polar component have been prepared and characterized. Owing to higher surface activity, pluronics have promoted the formation of µEs without the use of co-surfactant. Thus prepared µEs have been utilized as nano-reactors for the oxidation of guaiacol in the presence of Cytochrome-c (Cyt-c) at 15, 20, and 25 °C. A 3.2- and 1.3-fold increase in the rate of formation of product of enzymatic catalysis in direct µE (HIL-in-water) with reverse pluronic (10R5) is observed at 15 and 20 °C as compared to that in buffer. However, negligible enzymatic activity is observed in the direct µE formed by normal pluronic (L35). The catalytic activity of Cyt-c decreases in reverse µEs (water-in-HIL) as compared to direct µEs irrespective of the nature of pluronic used. The contrasting nature of nano-interfaces formed by pluronics in µEs and the extent of hydration of these nano-interfaces controlled by temperature exerts varying influence on the catalytic activity of Cyt-c. It is expected that the present work would result in providing a versatile platform for the creation of new IL and pluronic-based µEs for bio-catalytic applications, which have never been reported.

Polymeric Precipitation Inhibitor Based Supersaturable Self-microemulsifying Drug Delivery System of Canagliflozin: Optimization and Evaluation.

BACKGROUND: The present investigation attempts to optimize Supersaturable lipid based formulation (SS SMEDDS) of Biopharmaceutical Classification System (BCS) class IV drug canagliflozin (CFZ) and evaluating the oral bioavailability of the formulation. METHODS: Preliminary screening revealed Poloxamer 188 to most effectively inhibit precipitation of CFZ after dispersion during in vitro supersaturation studies. Box Behnken Design was employed for designing different formulations, and various statistical analyses were done to select an appropriate mathematical model. The optimized formulation (OSS 1) was evaluated for in vitro drug release and ex vivo permeation studies to evaluate drug release and permeation rate. Pharmacokinetic studies have been carried out according to standard methodologies. RESULTS: The optimized formulation (OSS 1) containing 781.1 mg SS SMEDDS and 2.24% w/w Poloxamer 188 was developed at a temperature of 60°C, which revealed nano-globule size with negligible aggregation. Isothermal titration calorimetry revealed the thermodynamic state of formed microemulsion with negative ΔG. The optimized formulation was observed to possess physical stability under different stress conditions and acceptable drug content. In vitro dissolution of optimized SS SMEDDS revealed a higher dissolution rate of CFZ as compared to native forms of CFZ. The permeability of CFZ from optimized SS SMEDDS across various excised segments of rat intestine was observed to be multifold higher as manifested by 2.05-fold higher Cmax and 5.64- fold higher AUC0-36h following oral administration to Wistar rats. CONCLUSION: The results could be attributed to substantial lymphatic uptake and P-glycoprotein substrate affinity of CFZ in SS SMEDDS investigated through chylomicron and P-glycoprotein inhibition approach, respectively.

Aqueous colloidal systems of bovine serum albumin and functionalized surface active ionic liquids for material transport.

Detailed physicochemical and computational investigation are made to explore different aspects of complexation between bovine serum albumin (BSA) and three structurally different surface active ionic liquids (SAILs), 1-dodecyl-3-methylimidazolium chloride, [C12mim][Cl]; 3-(2-(dodecylamino)-2-oxoethyl)-1-methyl-1H-imidazol-3-ium chloride, [C12Amim][Cl] and 3-methyl-1-dodecyloxy carbonyl methylimidazolium chloride, [C12Emim][Cl]. The interfacial and bulk complexation behavior has been monitored using tensiometry, conductivity, steady-state fluorescence and turbidity measurements. Thermodynamic insights about complexation have been obtained using isothermal titration calorimetry (ITC) measurements whereas molecular docking studies were used to predict the possible binding sites of SAILs on BSA. The information obtained from these studies helped in establishing the formed BSA-SAIL complex as a pH dependent colloidal transport system for controlled transport of a lipophilic dye, Rhodamine 6G (R6G), in aqueous phase, which is supported by confocal laser scanning microscopy (CLSM). In the present work, the effect of functionalization over the alkyl chain of SAILs, modulating the colloidal properties of SAIL-BSA systems, has been explored along with the utilization of these complexes as a pH dependent reversible carrier of lipophilic molecules. It is expected that besides providing basic understanding of colloidal complexes of BSA with SAILs, the present work is expected to be helpful in extending the applications of such colloidal systems for material transport.

One-pot sustainable preparation of sunlight active ZnS@graphene nano-composites using a Zn containing surface active ionic liquid.

Herein we report a facile and sustainable method for the preparation of ZnS@graphene nano-composites (NCs). An appreciable amount of graphene is obtained by liquid-phase exfoliation using a zinc-containing surface active ionic liquid (SAIL). It is followed by in situ preparation of ZnS quantum dot (QD) decorated graphene sheets at room temperature for the first time. The employed method is distinct from all previous reports, as we have employed graphene instead of graphene oxide (GO) or reduced graphene oxide (rGO) and used relatively fewer chemicals. Further, a SAIL is employed as a precursor of Zn2+ as well as a template for the preparation of ZnS QDs onto graphene. The prepared ZnS@graphene NCs show enhanced photocatalytic performance for the degradation of Rhodamine B dye under sunlight and ciprofloxacin antibiotic under visible light as compared to bare ZnS QDs. The better photocatalytic activity of the NCs under visible light compared to that reported in the literature along with the ease of preparation is advantageous for scaling-up the process.