Tuning the network charge of biohybrid hydrogel matrices to modulate the release of SDF-1

The delivery of chemotactic signaling molecules via customized biomaterials can effectively guide the migration of cells to improve the regeneration of damaged or diseased tissues. Here, we present a novel biohybrid hydrogel system containing two different sulfated glycosaminoglycans (sGAG)/sGAG derivatives, namely either a mixture of short heparin polymers (Hep-Mal) or structurally defined nona-sulfated tetrahyaluronans (9s-HA4-SH), to precisely control the release of charged signaling molecules. The polymer networks are described in terms of their negative charge, i.e. the anionic sulfate groups on the saccharides, using two parameters, the integral density of negative charge and the local charge distribution (clustering) within the network. The modulation of both parameters was shown to govern the release characteristics of the chemotactic signaling molecule SDF-1 and allows for seamless transitions between burst and sustained release conditions as well as the precise control over the total amount of delivered protein. The obtained hydrogels with well-adjusted release profiles effectively promote MSC migration in vitro and emerge as promising candidates for new treatment modalities in the context of bone repair and wound healing.

Analysis of raster imprints parameters on the basis of models and experimental research

Structural scheme of models for determining the integral density of raster scale of an imprint, raster tone in percentage, optical density of scales on the basis of the measured optical density of the solid area and other characteristics have been worked out. The results of imitation design in the form of characteristics for different parameters have been provided. Optical density of raster scales obtained on the models has been found out to be quite similar to the results of experimental studies.

INFLUENCE OF ULTRASONIC ACTION ON THE RATE OF CHARGE FORMATION OF THE INVERSION LAYER IN METAL-GLASS-SEMICONDUCTOR STRUCTURES

Исследовано влияние ультразвукового воздействия на плотность электронных состояний, локализованных на межфазной границе раздела Si-стекло. Предложена методика определения величин скорости поверхностной и объемной генерации носителей заряда, на основе расчета временной зависимости ширины области пространственного заряда (ОПЗ) и сравнении её с экспериментальной зависимостью. Ультразвуковая обработка структур Al-n-Si стекло Al, частотой 2.5 мГц мощностью 0.5 Вт, в течение 40 минут приводит к уменьшению скорости формирования заряда инверсионного слоя. Это обусловлено уменьшением интегральной плотности электронных состояний, локализованных на межфазной границе раздела полупроводник-стекло, при этом энергетический спектр объемных электронных состояний в полупроводнике не меняется. The effect of ultrasonic action on the density of electronic states localized at the Si-glass interface is studied. A method is proposed for determining the surface and volume generation rates of charge carriers using the calculated time dependence of the space charge region width (SCR) when comparing it with the experimental dependence. Ultrasonic treatment of Al-n-Si glass Al structures with a frequency of 2.5 MHz and a power of 0.5 W for 40 minutes leads to a decrease in the rate of charge formation of the inversion layer. This is due to a decrease in the integral density of electronic states localized at the semiconductorglass interface and does not affect the energy spectrum of bulk electronic states in asemiconductor.

APPROXIMATE INTEGRATION OF HIGHLY OSCILLATING FUNCTIONS

Elementary approximate formulae for numerical integration of functions containing oscillating factors of a special form with a parameter have been proposed in the paper. In this case general quadrature formulae can be used only at sufficiently small values of the parameter. Therefore, it is necessary to consider in advance presence of strongly oscillating factors in order to obtain formulae for numerical integration which are suitable in the case when the parameter is changing within wide limits. This can be done by taking into account such factors as weighting functions. Moreover, since the parameter can take values which cannot always be predicted in advance, approximate formulae for calculation of such integrals should be constructed in such a way that they contain this parameter in a letter format and they are suitable for calculation at any and particularly large values of the parameter. Computational rules with such properties are generally obtained by dividing an interval of integration into elementary while making successive approximation of the integral density at each elementary interval with polynomials of the first, second and third degrees and taking the oscillating factors as weighting functions. The paper considers the variant when density of the integrals at each elementary interval is approximated by a polynomial of zero degree that is a constant which is equal to the value of density in the middle of the interval. At the same time one approximate formula for calculation of an improper integral with infinite interval of the function with oscillating factor of a special type has been constructed in the paper. In this case it has been assumed that density of the improper integral rather quickly goes to zero when an argument module is increasing indefinitely. In other words it is considered as small to negligible outside some finite interval. Uniforms in parameter used for evaluation of errors in approximate formulae have been obtained in the paper and they make it possible to calculate integrals with the required accuracy.

COMPARATIVE ANALYSIS OF THREE-DIMENSIONAL NANOSTRUCTURE OF POROUS BIOCOMPATIBLE SCAFFOLDS MADE OF RECOMBINANT SPIDROIN AND SILK FIBROIN FOR REGENERATIVE MEDICINE

Aim.To perform a comparison of three-dimensional nanostructure of porous biocompatible scaffolds made of fibroinBombix moriand recombinant spidroin rS1/9.Materials and methods.Three-dimensional porous scaffolds were produced by salt leaching technique. The comparison of biological characteristics of the scaffolds shows that adhesion and proliferation of mouse fibroblastsin vitroon these two types of scaffolds do not differ significantly. Comparative experimentsin vivoshow that regeneration of bone tissue of rats is faster with implantation of recombinant spidroin scaffolds. Three-dimensional nanostructure of scaffolds and interconnectivity of nanopores were studied with scanning probe nanotomography (SPNT) to explain higher regenerative activity of spidroin-based scaffolds.Results.Significant differences were detected in the integral density and volume of pores: the integral density of nanopores detected on 2D AFM images is 46 μm–2 and calculated volume porosity is 24% in rS1/9-based scaffolds; in fibroin-based three-dimensional structures density of nanopores and calculated volume porosity were 2.4 μm–2 and 0.5%, respectively. Three-dimensional reconstruction system of nanopores and clusters of interconnected nanopores in rS1/9-based scaffolds showed that volume fraction of pores interconnected in percolation clusters is 35.3% of the total pore volume or 8.4% of the total scaffold volume.Conclusion.Scanning probe nanotomography method allows obtaining unique information about topology of micro – and nanopore systems of artificial biostructures. High regenerative activity of rS1/9-based scaffolds can be explained by higher nanoporosity of the scaffolds.