Application of small-angle X-ray scattering to the characterization and quantification of the drug transport nanosystem based on the soybean phosphatidylcholine

Study of Physico-Chemical Properties and Morphology of Phospholipid Composition of Indomethacin

Nonsteroidal anti-inflammatory drugs (NSAIDs), inhibitors of cyclooxygenase-2, an enzyme involved in the formation of anti-inflammatory prostaglandin PGE2, are the most common treatment for chronic inflammatory diseases, such as, for example, arthritis. One of the most commonly used drugs of this class is indomethacin, a derivative of indolylacetic acid. In this work, we studied the physicochemical properties of the phospholipid composition of indomethacin obtained earlier (codenamed “Indolip”) and the effect of freeze drying on its parameters. It was shown that the properties such as particle size, light transmission, phospholipid oxidation index did not change significantly, which indicated the stability of the drug after lyophilization. Measurement of the spectra of small-angle neutron scattering has shown that morphologically, Indolip is a vesicle whose radius is five times greater than the value of the bilayer thickness.

Restoring structural parameters of lipid mixtures from small-angle X-ray scattering data

Small-angle X-ray scattering (SAXS) is widely utilized to study soluble macromolecules, including those embedded into lipid carriers and delivery systems such as surfactant micelles, phospho-lipid vesicles and bilayered nanodiscs. To adequately describe the scattering from such systems, one needs to account for both the form factor (overall structure) and long-range-order Bragg reflections emerging from the organization of bilayers, which is a non-trivial task. Presently existing methods separate the analysis of lipid mixtures into distinct procedures using form-factor fitting and the fitting of the Bragg peak regions. This article describes a general approach for the computation and analysis of SAXS data from lipid mixtures over the entire angular range of an experiment. The approach allows one to restore the electron density of a lipid bilayer and simultaneously recover the corresponding size distribution and multilamellar organization of the vesicles. The method is implemented in a computer program, LIPMIX, and its performance is demonstrated on an aqueous solution of layered lipid vesicles undergoing an extrusion process. The approach is expected to be useful for the analysis of various types of lipid-based systems, e.g. for the characterization of interactions between target drug molecules and potential carrier/delivery systems.

Determination of the Vesicular Systems Parameters: Parallel Implementation and Analysis of the PTNS Vesicle Structure

Parameters of the phospholipid vesicular systems are determined by means of minimization of the discrepancy between experimental data on the small angle scattering intensity and the numerical results within the frame of the separated form factors method. Effectiveness of parallel implementation is tested at the cluster HybriLIT. Results of numerical analysis of small angle neutron scattering data on polydispersed population of unilamellar vesicles of phospholipid transport nanosystem are presented.