Конденсированные среды и межфазные границы (Jun 2019)
STRUCTURAL AND SPECTRAL CHARACTERISTICS OF COMPOSITES BASED ON PROTEIN CONDITIONS WITH SINGLE-WALLED CARBON NANOTUBES
Abstract
Purpose. The aim of the work is to study nanocomposites created by laser evaporation of waterprotein dispersion of carbon nanotubes. The studies are aimed to determine the features of the interaction between the composite components, as well as to the analysis of the internal and surface structures of nanocomposites, depending on the type and concentration of the used nanotubes. Methods and methodology. For the manufacture of nanocomposites single-walled carbon nanotubes of two types were used. Nanotubes of the fi rst type (SWCNTs I) were synthesized by the electric arc method on a Ni/Y catalyst. The average diameter of nanotubes was 1.4–1.8 nm, length ~ 0.3–0.8 microns. Nanotubes of the second type (SWCNTII) were obtained by the method of gas-phase synthesis. The average diameter was ~ 2–3.5 nm, their length was more than 5 microns. To create nanocomposites, a laser method was used to evaporate the waterprotein dispersion of nanotubes. However, the water dispertion of bovine albumin (25 %) and collagen (2 %) was used as a protein matrix. The binding of protein molecules to carbon component was described by Raman spectroscopy. To carry out a comprehensive analysis of the structure and microporosity of nanocomposites, the X-ray microtomography method was used. The study of the specifi c surface and pore volume of the samples was carried out with the use of the method of low-temperature nitrogen porosimetry. Results. There was a local boiling up of the dispersion of single-walled carbon nanotubes, which was accompanied by the appearance of inhomogeneities in the form of an evolved gas and subsequently produced the production of solid nanocomposites by laser evaporation of the aqueous dispersion of carbon nanotubes with the protein matrix. At the same time, the protein component in nanocomposites undergoes irreversible denaturation. It can be as a biocompatible binding material, which is a source of amino acids for biological tissues during the implantation of nanocomposites in the body. While manufacturing of nanocomposites, carbon nanotubes actively absorb radiation, creating an additional thermal heating of the organic components of tissue-engineering structures. As the temperature rises, the number of damages of the weak bonds in the tertiary structure of the protein, what allows the molecule to modify its position in space, increases. It is assumed that the heating from laser radiation and the additional heating from nanotubes accelerate these processes and contribute to the adhesion of the organic part of the composite to the carbon matrix. The internal structure of the SWCNTI nanocomposites was the most homogeneous. With an increase in concentration from 0.01 to 0.1 %, the average size of micropores increased from 45 to 85 μm and the sample porosity in general from 46 to 58 %. The share of open pores for two types of SWCNTI concentrations was 2 % of the total volume of the composite. SWCNTII-based nanocomposites with both concentrations had a wide range of micropore sizes from 33 to 314 μm. These samples with a concentration of 0.1 % nanotubes had a porosity of up to 73 % with an open pore fraction of 8 %. The presence of mesopores with an average size of up to 46 and 49 nm was found in SWCNTI-based composites, respectively, for concentrations of nanotubes of 0.01 and 0.1 %. An increase in the concentration of nanotubes led to a decrease in the specifi c values of the surface and pore volume of the sample. Conclusions. In this work, nanocomposites were created by laser evaporation of the water-protein dispersion of carbon nanotubes. The features of the interaction between the components of the composite were identifi ed. The analysis of the internal and surface structures of nanocomposites was carried out depending on the type and concentration of the used nanotubes. The structural characteristics of nanoscale composites should positively infl uence on the adhesive characteristics of the lateral processes of cells in various biotissues. The porosity of nanocomposites for biomedical applications is important for triggering the processes of neovascularization and neoinnervation in the repair of defects of biotissues. Thus, the nanocomposites studied in this work can be used as tissue-engineering matrixes to repair bulk defects of biological tissues.
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