Pluronic P123/DMSO Lyotropic Liquid Crystal for Incorporating Bioactive Substances for Topical Application.

Lyotropic liquid crystals (LLCs) have attracted considerably growing interest in drug delivery applications over the last years. The structure of LLC matrices is complementary to cell membranes and provides an efficient, controlled, and selective release of drugs. In this work, a complex of experimental methods was used to characterize binary LLCs Pluronic P123/DMSO and triple LLC systems Pluronic P123/DMSO/Ibuprofen, which are interesting as transdermal drug delivery systems. Liquid crystalline, thermal, and rheological properties of LLCs were studied. Concentration and temperature areas of the lyomesophase existence were found, and phase transition enthalpies were evaluated. Intermolecular interactions among the components were studied by infrared (IR) spectroscopy. In vitro studies of Ibuprofen (Ibu) release from various LLCs allow differentiation of its release depending on the polymer content. Atomic force microscopy and contact angle methods were used to characterize the surface morphology of the hydrophobic membrane, which was used as a stratum corneum model, and also evaluate the adhesion work of the LLCs. A complex analysis of the results provided by these experimental methods allowed revealing correlations between the phase behavior and rheological characteristics of the LLCs and release kinetics of ibuprofen. The proposed biocompatible systems have considerable potential for a transdermal delivery of bioactive substances.

Chitosan/Lactic Acid Systems: Liquid Crystalline Behavior, Rheological Properties, and Riboflavin Release In Vitro.

Chitosan or its derivatives exhibit lyotropic liquid crystalline mesophases under certain conditions due to its semi-rigid structures. This work describes the development of chitosan-based biocompatible systems that include new components: lactic acid and non-ionic surfactants. Polarized optical microscopy studies revealed that these systems are capable of forming gels or lyotropic liquid crystals (LLCs) in a certain range of chitosan and lactic acid concentrations. According to the viscosity studies, the rheological flow of the LLCs can be accurately described by the Casson flow model. The intermolecular interactions of the LLC components were studied by FTIR spectroscopy. According to the FTIR data, hydrogen bonding is supposed to be responsible for the formation of the LLCs. In the studied systems, this LLC complex exists as the [ChitH+·CH3-CH(OH)-COO-] ion pair. The studied gel and LLCs were shown to possess the most prolonged release capabilities for riboflavin among similar binary LLC systems. The supramolecular organization and rheological characteristics of the studied chitosan-based systems were found to affect the release of riboflavin.

Incorporating a Tetrapeptide into Lyotropic Direct Hexagonal Mesophase.

An approach to incorporate a bioactive hydrophobic substance, C22H32N4O7 tetrapeptide (TP), into the structure of the hexagonal mesophases C12EO10/H2O and C12EO10/La(III)/H2O was proposed. Concentration and temperature ranges of mesophases in the C12EO10/H2O/TP and C12EO10/La(III)/H2O/TP systems were established. The analysis of the X-ray diffraction data revealed a change in the structural characteristics of mesophases in the presence of tetrapeptide. Formation of a denser packing of molecules in the mesophases with TP was detected. Based on the FTIR spectroscopy data, intermolecular changes in the systems were examined. Pulsed-gradient spin-echo NMR self-diffusion experiments were performed to characterize the structure of lyomesophases depending on system composition and temperature. The degree of hydration of water molecules in lyomesophases was analyzed. The data confirmed successful incorporation of tetrapeptide into the structure of lyomesophase and, therefore, the possibility of using hexagonal mesophases for both incapsulation and delivery of biomolecules.

N,N-dimethyldodecylamine oxide self-organization in the presence of lanthanide ions in aqueous and aqueous-decanol solutions.

The article represents the results of research in self-organization of new lanthanide systems in water-decanol medium. The systems are based on N,N-dimethyldodecylamine oxide, a zwitterionic surfactant. The study covers the complex formation of lanthanide ions with C12DMAO molecules and the influence of Ln(III) ions and medium composition on surfactant association in diluted solutions. The analysis of adsorption isotherms was carried out on the basis of the combination of Gibbs and Langmuir adsorption equations. The results were used to determine physicochemical properties and parameters of a monomolecular adsorption layer. The research objects were various lanthanide ions with identical coordination centers. A number of spectroscopic methods (UV, NMR self-diffusion, EPR, dynamic light scattering (DLS), and fluorescent analysis) were involved in the research for comparative estimations of molecular dynamics, critical micellization concentration, geometry, sizes, and aggregation numbers of micellar aggregates. Micelle structure simulation revealed good agreement between experimental data and quantum chemical calculations.

Mesogenic and luminescent properties of lyotropic liquid crystals containing Eu(III) and Tb(III) ions.

Lyotropic metallomesogens containing trivalent rare-earth metal ions have unique attractive behavior due to the combination of some specific properties of the lanthanide ions with anisotropic supramolecular organization liquid crystal and provide new promises in biochemistry and materials science. In this article, we have studied the liquid crystal and luminescence properties of lyotropic systems containing Eu(III) and Tb(III) ions based on nonionic surfactants. The type, the structural parameters of the mesophases, and the structure of a liquid crystal complex have been investigated using polarized optical microscopy (POM), X-ray diffraction, and Fourier transform infrared. In addition, on the basis of the luminescence lifetime, the structure of the first coordination sphere was determined. The results obtained based on time-resolved spectroscopy data are discussed in the light of the influence ligand environment, ion type, and the type of supramolecular organization on the luminescence efficiency of lyotropic lanthanide containing systems. The first time was reported for Eu(III) complexes increasing the luminescence efficiency in the hexagonal phase compared to the lamellar mesophase.