Influence of the Degree of Deacetylation of Chitosan and BMP-2 Concentration on Biocompatibility and Osteogenic Properties of BMP-2/PLA Granule-Loaded Chitosan/β-Glycerophosphate Hydrogels

Compositions based on chitosan/β-glycerophosphate hydrogels with highly porous polylactide granules can be used to obtain moldable bone graft materials that have osteoinductive and osteoconductive properties. To eliminate the influence of such characteristics as chain length, degree of purification, and molecular weight on a designed material, the one-stock chitosan sample was reacetylated to degrees of deacetylation (DD%) of 19.5, 39, 49, 55, and 56. A study of the chitosan/β-glycerophosphate hydrogel with chitosan of a reduced DD% showed that a low degree of deacetylation increased the MSCs (multipotent stromal cells) viability rate in vitro and reduced the leukocyte infiltration in subcutaneous implantation to Wistar rats in vivo. The addition of 12 wt% polylactide granules resulted in optimal composite mechanical and moldable properties, and increased the modulus of elasticity of the hydrogel-based material by approximately 100 times. Excessive filling of the material with PLA (polylactide) granules (more than 20%) led to material destruction at a ~10% strain. Osteoinductive and osteoconductive properties of the chitosan hydrogel-based material with reacetylated chitosan (39 DD%) and highly porous polylactide granules impregnated with BMP-2 (bone morphogenetic protein-2) have been demonstrated in models of orthotopic and ectopic bone formation. When implanted into a critical-size calvarial defect in rats, the optimal concentration of BMP-2 was 10 μg/mL: bone tissue areas filled the entire material’s thickness. Implantation of the material with 50 μg/mL BMP-2 was accompanied with excessive growth of bone tissue and material displacement beyond the defect. Significant osteoinductive and osteoconductive properties of the material with 10 μg/mL of BMP-2 were also shown in subcutaneous implantation.     

Optical diagnostics of dispersing He plasma

An experimental study has been made of the characteristics of radiation from a dispersing helium plasma. From measurements of the space-time dependence of the line intensities of the helium 2³P — n³D series we obtained the distribution of the populations of the n³D levels for n=3–10. The study has shown that over a wide range of conditions the high-lying levels (n=5–10) are in equilibrium with electrons while a substantial deviation from equilibrium is observed for levels n=3, 4. From the energy distribution of the populations of the upper levels we determined the space-time dependence of the electron temperature, which reflects the process of effective electron cooling during dispersal of the plasma. The gas temperature was estimated from the populations of helium singlet and triplet levels with n=5. The time distribution of the electron density in the plasma was found from the Stark broadening of the spectral lines.Deceased.V. D. Kuznetsov Siberian Physicotechnical Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 15–19, November, 1992.     

Plasma radiation emitted by dense mixtures of rare gases excited by an electron beam and by a discharge

An experimental investigation was made of the radiation emitted from a plasma formed by rare gases (He, Ne, Ar, Kr, Xe) excited by a beam of electrons with different parameters and by discharge pulses (P= 0.1–0.5 atm, I=1 kA, U=10–15 kV, C=0.25 F). An investigation was made of the spectral composition and time characteristics of the radiation, and of their dependences on the excitation conditions. New molecular bands were observed in the near-ultraviolet and visible ranges. The uniquely large widths of these bands could be of interest in the amplification of light in a wide spectral range.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 56–73, January, 1992.     

Bromination of 6-Methyl-5-nitrouracil

Russian Journal of Organic Chemistry - At bromination of 6-methyl-5-nitrouracil with bromine in methanol a mixture formed of the initial compound with...     

Rheological properties of acrylonitrile—acrylamide—styrene copolymer solutions synthesized by classical and controlled radical polymerizations

Russian Chemical Bulletin - The results of a comparative study of the rheological properties of acrylonitrile copolymers solutions synthesized by classical and controlled radical polymerizations in...     

Study of “Racemic Compound-Like” Behavior of Diastereomeric Mixture of Pinanyl Sulfoxides by X-Ray Diffraction,IR Spectroscopy,and DFT Calculations

Abstract

The oxidation of a β-hydroxysulfide in the pinane series by use of m-chloroperbenzoic acid resulted in the formation of the corresponding β-hydroxysulfoxide as a mixture of two diastereomers in 4:5 ratio. According to single-crystal X-ray diffraction (XRD) results, it is established that the diastereomeric mixture of sulfoxides crystallizes in the “racemic compound-like” manner under formation of asymmetric dimers through S=O··H–O interactions. This asymmetric dimer formed from diastereomeric molecules is a structural unit in both crystal modifications, the triclinic and the monoclinic one. The behavior of the diastereomeric mixture of pinane derived sulfoxides in crystals, melts and in tetrachloromethane solutions was studied by IR spectroscopy. The density functional theory (DFT) method with 6-31G (d, p) basis set was used to calculate the optimized geometrical parameters and vibrational frequencies of different associates in solutions. The calculated vibrational frequencies are compared with experimental IR spectra.     

Acid-Base Properties of 6-Methyluracil-5-carbonitrile and Its N-Methyl Derivatives

Russian Journal of General Chemistry - The constants of acid-base equilibrium of 6-methyluracil-5-carbonitrile in water were determined spectrophotometrically. For the first time,...