L. I. Krotova

A route to diffusion embedding of CdSe/CdS quantum dots in fluoropolymer microparticles

A green and efficient synthetic approach has been developed using supercritical carbon dioxide as a transport medium for the diffusion embedding of core shell CdSe/CdS quantum dots (QD) into polytetrafluorethylene (PTFE) microparticles, leading to matrix immobilisation of QD in PTFE. Transmission electron microscopy and photoluminescence spectroscopy probes show that the products are fine dispersive photoluminescent nanocomposites with QD being homogeneously isolated throughout the polymer microparticle volume. Up to 3 × 105 QD can be embedded into a single ∼1 μm PTFE microparticle by this technique without degradation of the microparticulate structure. A further photoluminescence study of thermally heated and laser irradiated CdSe/CdS/PTFE microparticles reveals excellent optical performance and stability over the 20–80 °C temperature range.

3D printing of PLGA scaffolds for tissue engineering

We proposed a novel method of generation of bioresorbable polymeric scaffolds with specified architectonics for tissue engineering using extrusion three-dimensional (3D) printing with solutions of polylactoglycolide in tetraglycol with their subsequent solidifying in aqueous medium. On the basis of 3D computer models, we obtained the matrix structures with interconnected system of pores ranging in size from 0.5 to 500 µm. The results of in vitro studies using cultures of line NIH 3Т3 mouse fibroblasts, floating islet cultures of newborn rabbit pancreas, and mesenchymal stem cells of human adipose tissue demonstrated the absence of cytotoxicity and good adhesive properties of scaffolds in regard to the cell cultures chosen.

Supercritical fluid micronization of risperidone pharmaceutical substance

A comparative study of the supercritical fluid micronization of risperidone pharmaceutical substance with an initial particle size of 50 to 100 μm by the RESS and SAS methods aimed at increasing the bioavailability of risperidone as a drug was performed. Both methods makes it possible to prepare risperidone particle of various forms, 5–20 μm in size. However, the SAS method is preferable, because in contrast to RESS, it does not cause contamination of risperidone with organic solvents used in both processes or any other impurities and also makes it possible to vary the shape and size of particles. It is shown that, during SAS micronization, the polymorphic form of risperidone changes from triclinic to monoclinic.

Comparative Analysis of Proliferation and Viability of Multipotent Mesenchymal Stromal Cells in 3D Scaffolds with Different Architectonics.

3D biodegradable materials (scaffolds) containing bioactive hydroxyapatite molecules fabricated by foaming in supercritical carbon dioxide and by selective laser sintering were used for culturing of mesenchymal stromal cells from the human adipose tissue. Experiments showed that stromal cells from the human adipose tissue adhered and proliferated on all studied types of structures. Addition of hyproxyapatite to the scaffold stimulated proliferation of stromal adipose tissue cells.

Supercritical fluid encapsulation of acizol into aliphatic polyether microparticles

Encapsulation of pharmaceutical grade acizol (Acizol® pharmaceutical substance) into bioresorbable D,L-polylactide and polylactoglycolide microparticles using supercritical carbon dioxide has been studied. An effective way for formation of polymer fine powders (mean particle size of about 10–20 µm) containing up to 20 wt % of the bioactive component without any organic solvent used has been suggested. Raman spectroscopy with spatial resolution was employed to analyze the distribution of acizol throughout the volume of the individual polymer microparticles and to study the kinetics of its release into saline. The rapid release (40–80% of the total amount of the encapsulated substance) from the samples under study was observed during the first hour, and then it was followed by a gradual, almost linear release between the 4th and 14th days of the experiment, with the total release continuing up to 100%.

Micronization of levofloxacin by supercritical antisolvent precipitation

The process of micronization of levofloxacin (LF, an antibacterial agent of the fluoroquinolone group) by the supercritical antisolvent precipitation technique (SAS) was investigated. It was shown that LF particles of different sizes (from 1 to 10 μm) and of various morphologies (from thin plates to elongated parallelepipeds) can be produced depending on the type of solvent used for conducting micronization. Investigation of the micronized LF preparations using the methods of IR-Fourier spectroscopy, Raman scattering, and circular dichroism showed that the LF micronization caused neither changes in its chemical structure nor racemization. Micronization of LF significantly affects the rate of its dissolution in model systems exhibiting effects dependent on the type of the solvent used for micronization. For example, the highest rate of dissolution at pH 4 was observed for LF preparations micronized with the help of chlorohydrocarbons. It was shown that the rate of dissolution of all micronized LF preparations was higher by 15–30% in comparison with the initial LF, which likely was related to the changes in the degree of crystallinity/amorphousness, as well as of morphologies of microparticles formed in the SAS process.

Formation of bioactive highly porous polymer matrixes for tissue engineering

The processes of fabrication of highly porous (60–90 vol %) bioactive heparin-containing polylactic scaffolds in supercritical carbon dioxide followed by their hydrophilization by dielectric barrier discharge plasma treatment in the atmosphere were studied. A homogeneous distribution of heparin (HP) over the polymer volume was demonstrated by spatially resolved Raman scattering (RS) spectroscopy. The kinetics of heparin release from the scaffolds in distilled water was studied by spectrophotometry. A virtually linear increase in heparin concentration in a solution was shown from the second until the 15th day of experiments. Comparative in vitro study of cytotoxicity and matrix properties of pure polymer and heparin-containing scaffolds using NIH 3T3 mice fibroblast cultures demonstrated a positive effect of heparin distribution over the polylactic scaffolds on both cell adhesion and proliferation.

Effect of solvent type and concentration on size and morphology of arbidol microparticles obtained by supercritical antisolvent precipitation

The capability of arbidol microparticle preparation by supercritical antisolvent (SAS) precipitation was demonstrated. A nonmonotonic dependence of the average particle size on the concentration was found, while the position of the minimum is dependent on the type of solvent used. It is possible to prepare Arbidol particles of various morphology and size from several microns to several hundred microns depending on the conditions.

SCF micronization of poly-3-hydroxybutyrate using supercritical antisolvent

Micronization of poly-3-hydroxybutyrate (PHB) by the supercritical fluid antisolvent precipitation (SAS) technique using supercritical carbon dioxide as an antisolvent was studied experimentally. The possibility of preparing particles of varying morphology (including hollow spheres) and specified size from 100 nm to 20 μm was demonstrated. The influence of different mechanisms of solid phase formation during SAS micronization on the size and morphology of PHB microparticles under different experimental conditions was considered.

Preparation of fluorescent nanocomposites with CdSe/CdS quantum dots by dispersion polymerization in supercritical carbon dioxide

A new method for preparing fluorescent polymer nanocomposites based on dispersion copolymerization of methyl methacrylate and styrene in the presence of CdSe/CdS quantum dots in supercritical carbon dioxide medium is proposed. A one-step scheme of the formation of fine poly(methyl methacrylate)/polystyrene/CdSe/CdS nanocomposites is realized, and the factors influencing their photoluminescent characteristics and photochemical stability under prolonged exposure to natural conditions (sunlight) and intense UV irradiation in air are examined.