T. S. Demina

New Surface-Enhanced Raman Scattering Platforms: Composite Calcium Carbonate Microspheres Coated with Astralen and Silver Nanoparticles

Surface-enhanced Raman scattering (SERS) microspectroscopy is a very promising label-free, noncontact, and nondestructive method for real-time monitoring of extracellular matrix (ECM) development and cell integration in scaffolds for tissue engineering. Here, we prepare a new type of micrometer-sized SERS substrate, core-shell microparticles composed of solid carbonate core coated with silver nanoparticles and polyhedral multishell fullerene-like structure, astralen. Astralen has been assembled with polyallylamine hydrochloride (PAH) by the layer-by-layer manner followed by Ag nanoparticle formation by means of a silver mirror reaction, giving the final structure of composite particles CaCO3(PAH/astralen)x/Ag, where x = 1-3. The components of the microparticle carry multiple functionalities: (i) an easy identification by Raman imaging (photostable astralen) and (ii) SERS due to a rough surface of Ag nanoparticles. A combination of Ag and astralen nanoparticles provides an enhancement of astralen Raman signal by more than 1 order of magnitude. Raman signals of commonly used scaffold components such as polylactide and polyvinyl alcohol as well as ECM component (hyaluronic acid) are significantly enhanced. Thus, we demonstrate that new mechanically robust and easily detectable (by astralen signal or optically) core-shell microspheres based on biocompatible CaCO3 can be used as SERS platform. Particle design opens many future perspectives for fabrication of SERS platforms with multiple functions for biomedical applications, for example, for theranostic.

Effect of direct-current discharge treatment on the surface properties of chitosan-poly(L,L-lactide)-gelatin composite films

The surface of films made from a chitosan-poly(L,L-lactide)-gelatin mixture stabilized with a grafted-copolymer fraction has been modified by dc discharge treatment, as well as that of films made of the individual components. The surface properties of the films (wettability, surface energy), the chemical structure of surface layers, and their morphology have been examined by goniometric measurement of contact angles, X-ray photoelectron spectroscopy, and scanning electron microscopy.

Production of Nanopowders with the Help of Fiber Laser

Development of an efficient technology to produce nanopowders for nanostructured materials with improved mechanical, novel electromagnetic and optical properties is still of current importance. Nanoparticles can be made by means of laser-assisted material evaporation and subsequent vapor condensation. The method provides high-purity weakly agglomerated nanopowders with narrow grain size distribution, and can be applied to various materials. However, up to these days this technique has not found wide recognition because of a low output rate and high energy consumption. This report deals with the production technology and characteristics of nanopowders produced with the help of Yb-doped fiber laser. Data for the nanopowders characteristics, as well as output rate and energy consumption are discussed in this paper. The evaporation of materials with the help of the fiber laser was proved to be an efficient method for commercial production of the fine nanopowders.

Compatibility of cells of the nervous system with structured biodegradable chitosan-based hydrogel matrices

Hydrogel matrices for cell cultivation have been generated by two-photon laser polymerization of unsaturated chitosan derivatives and methacrylated hyaluronic acid. The adhesive and toxic properties of the matrices have been assessed, and the matrices have been shown to have a good compatibility with primary hippocampal cell cultures. The formation of morphologically normal neural networks by cells of the nervous system cultured on the surface of hydrogel matrices has been observed. The metabolic status of dissociated hippocampal cells cultured on the matrices was similar to that of the control cultures, as shown by the results of MTT reductase activity assay. Thus, matrices based on unsaturated polysaccharide derivatives crosslinked by laser irradiation showed good compatibility with differentiated cells of the nervous system and considerable potential for use in neurotransplantation.

Solid state synthesis of chitosan and its unsaturated derivatives for laser microfabrication of 3D scaffolds

Chitosans with various degrees of deacetylation and molecular weights and their allyl substituted derivatives were obtained through a solvent-free reaction under shear deformation in an extruder. Structure and physical-chemical analysis of the samples were carried out using nuclear magnetic resonance (NMR), ultraviolet (UV) and infrared radiation (IR) spectroscopy. Photosensitive materials based on the synthesized polymers were successfully used for microfabrication of 3D well-defined architectonic structures by laser stereolithography. Study on the metabolic activity of NCTC L929 cultured in the presence of the cured chitosan extracts indicates that the engineered biomaterials could support adhesion, spreading and growth of adherent-dependent cells, and thus could be considered as biocompatible scaffolds.

Chitosan-g-lactide copolymers for fabrication of 3D scaffolds for tissue engineering

Chitosan-g-oligo (L, D-lactide) copolymers were synthesized and assessed to fabricate a number of 3D scaffolds using a variety of technologies such as oil/water emulsion evaporation technique, freeze-drying and two-photon photopolymerization. Solid-state copolymerization method allowed us to graft up to 160 wt-% of oligolactide onto chitosan backbone via chitosan amino group acetylation with substitution degree reaching up to 0.41. Grafting of hydrophobic oligolactide side chains with polymerization degree up to 10 results in chitosan amphiphilic properties. The synthesized chitosan-g-lactide copolymers were used to design 3D scaffolds for tissue engineering such as spherical microparticles and macroporous hydrogels.

Modification of the chitosan structure and properties using high-energy chemistry methods

Literature on the modification of the natural polymer chitosan using high-energy chemistry methods (treatment by a low-temperature plasma, with an electron beam, energetic ions, or γ-iradiation) has been surveyed. The basic chitosan treatment procedures and facilities used in the processes have been described. The instrumental techniques used to study changes in the chemical structure and properties of modified chitosan have been considered. Data showing the possibility of using modified chitosan in medicine and biotechnology have been presented.

Amphiphilic systems based on polysaccharides produced by solid-phase synthesis − A review

The results of research on polymer blends based on polysaccharides (chitin, chitosan, cellulose, starch, etc.) and variously hydrophilic synthetic polymers produced by reaction mixing in solid state under pressure and shear stresses are summarized. The mechanisms of the processes occurring under solidphase synthesis conditions, the properties of the multicomponent systems formed, and the feasibility of their application for creating new biocompatible and biodegradable materials are discussed.

A Novel Approach to Design Chitosan-Polyester Materials for Biomedical Applications

A novel approach to design chitosan-polyester materials is reported. The method is based on mechanical activation and effective intermixing of the substrates under high pressure and shear deformation in the course of solid-state reactive blending. The marked departure of this approach from previous practice resides on exploitation of a variety of chemical transformations of the solid polymers that become feasible under conditions of plastic flow. Low temperatures (above Tg but below the melting points of the crystalline polymers) are maintained throughout the process, minimizing mechanical and oxidative degradation of the polymers. Morphology as well as structural, mechanical, and relaxation properties of those prepared blends of chitosan with semicrystalline poly(L,L-lactide) and amorphous poly(D,L-lactide-co-glycolide) has been studied. Grafting of polyester moieties onto chitosan chains was found to occur under employed pressures and shear stresses. The prepared polymer blends have demonstrated an amphiphilic behavior with a propensity to disperse in organic solvents that widens possibilities to transform them into promising materials for various biomedical applications.

Nanocrystalline Cellulose from Flax Stalks: Preparation, Structure, and Use

Preparation of nanocrystalline cellulose by acid hydrolysis of flax cellulose is described. According to atomic-force microscopy, the obtained nanocrystals were needle-like with average diameter 85 ± 39 nm and length 158 ± 89 nm. The potential of using nanocrystalline flax cellulose as an adhesive for heat-protective porous ceramics and an anisotropic reinforcing filler of polymer films was investigated.