Comprehensive NMR Investigation of Imidazolium-Based Ionic Liquids [BMIM][OSU] and [BMIM][Cl] Impact on Binding and Dynamics of the Anticancer Drug Doxorubicin Hydrochloride

For the design of an efficient drug delivery system utilizing an ionic liquid (IL) as a carrier, it is prudent to gain molecular/atomistic level insights of a drug with IL in terms of binding and dynamics. In this scenario, the influence of anionic counterpart of imidazolium-based ILs, namely, 1-butyl-3-methyl-imidazolium octyl sulfate [BMIM][OSU] and 1-butyl-3-methyl-imidazolium chloride [BMIM][Cl] in their submicellar region ([IL] = 20 mM) on the model water-soluble anticancer drug doxorubicin hydrochloride (DOX) was probed by employing an arsenal of nuclear magnetic resonance (NMR) approaches. The salient feature of the present study includes the significant interaction of DOX with [BMIM][OSU], whereas the lack of such an interaction with [BMIM][Cl] is gauged by 1H NMR translation self-diffusometry and is further corroborated by 13C chemical shift perturbation. The two-step model was utilized to estimate the bound fraction (pb) and equivalent partition coefficient (K) of DOX with [BMIM][OSU]. A combination of selective and nonselective spin-lattice relaxation rates (R1SEL and R1NS, respectively) enables to gauze the significant interaction of DOX with [BMIM][OSU] over [BMIM][Cl]. Furthermore, 1D transient and truncated driven nuclear Overhauser enhancement (NOE) data analyses in the initial rate limit permits the evaluation of the cross-relaxation efficacy of DOX with the investigated ILs. An Arrhenius-type temperature dependence of the drug's self-diffusion was observed for DOX, DOX-[BMIM][OSU], and DOX-[BMIM][Cl] aqueous mixtures and the corresponding activation energies were evaluated.

NMR Studies on the Interaction of Anticancer Drug Doxorubicin with Membrane Mimetic SDS

In the formulation of efficient drug delivery systems, it is essential to unravel the structural and dynamical aspects of the drug's interaction with biological membranes. This has been done for the anticancer drug-membrane system comprising doxorubicin hydrochloride (DOX), a water-soluble anticancer drug, and the micellar sodium dodecyl sulfate (SDS), the latter serving as a useful mimic for membrane proteins. Using a multimodal NMR approach involving ¹H, ²H, and ¹³C as probe nuclei and through the determination of chemical shifts, spin-relaxation, nuclear Overhauser enhancements (NOE), and translational self-diffusion (SD), the binding characteristics of the DOX with SDS have been determined. The perturbation to ¹³C chemical shifts of SDS indicate the penetration of DOX into the SDS micelle, which is further revealed by ¹H-¹H NOESY and SD measurements. ²H spin-relaxation measurements and their analysis using a two-step model show DOX induced SDS micellar volume changes, which determine the correlation times involved in the DOX-SDS mobility.

Interaction between sodium dodecylsulfate (SDS) and pluronic L61 in aqueous medium: assessment of the nature and morphology of the formed mixed aggregates by NMR, EPR, SANS and FF-TEM measurements

The interaction of copolymer L61 i.e., (EO)2(PO)32(EO)2 (where EO and PO are ethylene and propylene oxides, respectively) with surfactant SDS (sodium dodecylsulfate) in relation to their self-aggregation, dynamics and microstructures has been physicochemically studied in detail employing the Nuclear Magnetic Resonance (NMR), Electron Paramagnetic Resonance (EPR), Small-Angle Neutron Scattering (SANS), and Freeze-Fracture Transmission Electron Microscopy (FF-TEM) methods. The NMR self-diffusion study indicated a synergistic interaction between SDS and L61 forming L61-SDS mixed complex aggregates, and deuterium (2H) NMR pointed out the nonspherical nature of these aggregates with increasing [L61]. EPR spectral analysis of the motional parameters of 5-doxyl steraric acid (5-DSA) as a spin probe provided information on the microviscosity of the local environment of the L61-SDS complex aggregates. SANS probed the geometrical aspects of the SDS-L61 assemblies as a function of both [L61] and [SDS]. Progressive evolution of the mixed-aggregate geometries from globular to prolate ellipsoids with axial ratios ranging from 2 to 10 with increasing [L61] was found. Such morphological changes were further corroborated with the results of 2H NMR and FF-TEM measurements. The strategy of the measurements, and data analysis for a concerted conclusion have been presented.

Thermodynamically stable vesicle formation of biodegradable double mPEG-tailed amphiphiles with sulfonate head group

The development of efficient, biodegradable and biocompatible surfactants has become a pressing need because of adverse effects of surface-active compounds on the aquatic environment and human health. Cleavable surfactants containing a labile functional group have the ability to eliminate some of these problems. Consequently, PEGylated amphiphiles have found widespread applications in pharmaceutics, household purposes, and drug delivery. Herein we report synthesis and characterization of two novel amphiphiles which to our knowledge are the first examples of double PEG-tailed amphiphiles with an anionic head group. Considering their chemical structure, they are expected to be biodegradable, biocompatible, milder and less irritant than conventional surfactants. The solution behavior of these newly developed amphiphiles was thoroughly investigated in aqueous buffer (pH 7.0) at 25 °C. The surface activity of the compounds in aqueous buffer was studied by surface tension measurements. The self-assembly properties were investigated by various techniques such as fluorescence and NMR spectroscopy, dynamic light scattering, transmission electron microscopy, atomic force microscopy, and isothermal titration calorimetry. Both molecules were found to be surface active in water and exhibit spontaneous vesicle formation in the absence of any additives at room temperature. As in the cases of conventional surfactants, the self-assembly is driven by the hydrophobic effect. The vesicles produced in aqueous media were shown to encapsulate hydrophobic dyes and exhibit structural transitions upon addition of salts. The sensitivity of the vesicles to change in environments qualifies them for potential use in drug delivery.

Spontaneous vesicle formation by biodegradable novel double mPEG-tailed amphiphiles.

Physicochemical Understanding of Self-Aggregation and Microstructure of a Surface-Active Ionic Liquid [C4mim] [C8OSO3] Mixed with a Reverse Pluronic 10R5 (PO8EO22PO8)

Physicochemical studies on aqueous mixtures of ionic liquids (ILs) and reverse pluronics are limited. Self-aggregation dynamics and microstructure of a surface-active IL (SAIL), 1-butyl-3-methylimidazolium octylsulfate [C₄mim] [C₈OSO₃], in the presence of a reverse pluronic, PO₈EO₂₂PO₈ (known as 10R5), were studied using isothermal titration calorimetry (ITC), high-resolution nuclear magnetic resonance (NMR), and small-angle neutron scattering (SANS) methods. Also, cryo-/freeze-fracture transmission electron microscopy was employed to determine the microstructures of SAIL/10R5 mixtures. The ITC and NMR results revealed facilitation of SAIL aggregation in the presence of 10R5 forming mixed aggregates as well as free SAIL micelles. ²H spin relaxation rate data pointed out the onset of slow dynamics of the aqueous SAIL/10R5 mixture with an increase in either the former or the latter. Globular morphologies of the mixed species as well as their individual components were corroborated from the measurements. The preferential location of interaction of the SAIL with the 10R5 was identified from ¹³C NMR chemical shift findings to be in the interfacial region of the assembled SAIL. The formed species were mixed interacted aggregates but not mixed micelles that arise from mixed surfactants. The physicochemical information acquired herein would enrich the literature on the 10R5/SAIL mixed microheterogeneous systems having importance in the making of useful green drug carrier systems and templates for the synthesis of nanomaterials.

Selective binding and dynamics of imidazole alkyl sulfate ionic liquids with human serum albumin and collagen – a detailed NMR investigation

STD NMR and selective spin-relaxation analysis evidenced the selective binding (anionic part) of imidazole alkyl sulfate ionic liquids with proteins (HSA and collagen). These studies also enabled the ionic liquids to be ranked based on their binding affinities with the proteins of study.

Vesicle to micelle transition in the ternary mixture of L121/SDS/D2O: NMR, EPR and SANS studies

Proposed model depicting vesicle to mixed micelle transformation in a ternary mixture of L121/SDS/D₂O.

Physicochemical perspectives (aggregation, structure and dynamics) of interaction between pluronic (L31) and surfactant (SDS)

The influence of the water soluble non-ionic tri-block copolymer L31 on the microstructure and self-aggregation dynamics of the anionic surfactant sodium dodecylsulfate (SDS) in aqueous solution was investigated.

Interactions between sodium polyacrylate and mixed surfactants of polyoxyethylene tert-octyl phenyl ether and dodecyltrimethylammonium bromide

Interactions between sodium polyacrylate and mixed surfactants of polyoxyethylene tert-octyl phenyl ether and dodecyltrimethylammonium bromide in 40 mM NaBr aqueous solutions were studied using isothermal titration calorimetry.

Micellization and related behavior of sodium dodecylsulfate in mixed binary solvent media of tetrahydrofuran (Tf) and formamide (Fa) with water: a detailed physicochemical investigation

The detailed aggregation behavior of sodiumdodecyl sulfate (SDS) in tetrahydrofuran (Tf)-water (W) and formamide (Fa)-water (W) media at varied volume percent compositions has been investigated. Surface tension (ST), conductance (Cond), viscosity (Visc), isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and small angle neutron scattering (SANS) were used in this study. The presence of nonaqueous solvents affected the critical micelle concentration (CMC) of SDS, the counter-ion binding of the micelle, the energetics of the air/water interfacial adsorption and micellization of the amphiphiles in the bulk, the ion-association (ion-pair, triple-ion, quadruple, etc. between Na(+) and DS(-) ions) as well as the weakly soluble (aggregation less) amphiphile solution. Tf has been observed to produce a "dead zone" or "non-micelle formation zone" in the mixed Tf-W domain of 10-40 vol%. Fa influenced the SDS aggregation up to 70 vol%, at higher proportions (below the Krafft temperature (K(T))), instead of the micelle, "randomly arranged globular assembly" (RAGA) was formed. The correlation of the standard free energy of micellization (ΔG(m)(0)) with different solvent parameters (1) dielectric constant (ε), (2) viscosity (η0), (3) Reichardt parameter (E(T)(30)), (4) Gordon parameter (G), and (5) Hansen-Hildebrand hydrogen bonding parameter (δ(h)) has been attempted. It has been found that δ(h) produced a master correlation between ΔG(m)(0) and δ(h) for different binary mixtures such as Tf-W, Fa-W, Ml-W and Dn-W.