F.S. Senatov

Structure and properties of ultra-high molecular weight polyethylene filled with disperse hydroxyapatite

The possibility of preparing composite materials filled with hydroxyapatite on the basis of ultra-high molecular weight polyethylene for use in replacement arthroplasty was studied. The composites were prepared by the combined mechanoactivation of the starting components followed by compaction via thermal pressing. The structures of the resulting composite powder and monolithic composite were investigated by means of differential scanning calorimetry and X-ray diffraction analysis, and the effect of introduced hydroxyapatite on the degree of polymer crystallinity was elucidated. The composites were tested to determine the concentration dependences of their physicomechanical and tribological properties. On the basis of the experimental data, it was concluded that the mechanoactivation processing affords the high-quality polymeric composites, thereby providing the disperse distribution of the filler over the matrix. By a combination of physicomechanical and tribological characteristics, the materials developed can be suggested for the production of articulated joint liners of hip and knee endoprostheses.

Application of Microstructured Intermetallides in Turbine Manufacture. Part 1: Present State and Prospects (A Review)

The objective of the present work is the analysis of the present state and prospects of the development of competitive technologies for creating microstructured materials of the class of intermetallides and their application in turbine and engine manufacture. The present review examines the general strategy of the development of the industry of heat-resistant materials of the class of intermetallides. A comparative analysis of the specific properties, advantages, and disadvantages of titanium, nickel, and iron aluminides and transition metals (Nb, Mo, and Ti) silicides in view of their application in construction of aircraft engines and gas-burning power-generating turbines is performed. The state and prospects of the development of competitive pilot technologies of manufacture and application of the above materials are analyzed.

Preparation of porous ultrahigh-molecular-weight polyethylene using subcritical water

We developed a method of subcritical water extraction of NaCl from ultrahigh-molecular-weight polyethylene (UHMWPE) samples as a step in the preparation of a porous polymeric product, a promising material for implant production. Optimum process conditions were determined to be as follows: pressure 250 bar, temperature 120°C, and water flow rate 3 g/min. This method allows decreasing ten-fold (from 10 to 1 h) the time of salt extraction from the samples. The UHMWPE obtained was shown by scanning electron microscopy to have a porous structure with a main pore diameter from 80 to 700 μm.

Application of microstructured intermetallides in turbine manufacture. Part 2: Problems in development of heat-resistant alloys based on TiAl (a review)

The problems of formation of the necessary microstructure of intermetallic materials providing the required mechanical properties under extreme operating conditions are considered by the example of doped TiAl intermetallides. The problem of corrosion stability of intermetallides under extreme operating conditions is examined.

Long-Term Creep and Impact Strength of Biocompatible 3D-Printed PLA-Based Scaffolds

In the present work porous scaffolds for trabecular bone defects replacement were studied. PLA and PLA/HA сomposites were obtained by extrusion. Scaffolds were obtained by 3D-printing by fused filament fabrication method. Long-term creep and Charpy impact tests show that PLA/HA scaffolds with the maximum force for destruction at impact of 119 N can function under a load of up to 10 MPa without shape changing and loss of mechanical properties. In vivo tests were used to investigate biocompatibility of scaffolds. The scaffolds may be used as implants for unloaded small bone defects replacement

Physicomechanical properties of a composite material based on ultrahigh-molecular-weight polyethylene filled with ceramic particles

The effect of the shape of filler particles on the mechanical properties of a composite material based on ultrahigh-molecular-weight polyethylene produced by thermal compacting after preliminary mechanical activation of the initial materials is studied. As a filler, Al2O3 in the form of an ultradispersed powder with a particle size of 200 nm or as 1-μm microspheres is used. The effects of the fillers of both types on the mechanical properties of the composite material is found to be positive and comparable in the concentration range under study (1–10 wt %). The degree of matrix hardening depends on the shape of filler particles.

Prospects for the application of biporous sorbents based on hypercrosslinked styrene polymers for the prevention and treatment of systemic purulent-septic complications

The purpose of this study was to evaluate the capability of two sorbents based on hypercrosslinked styrene polymers (Styrosorb 514 and the magnetic material MMN200 based thereon) to adsorb bacteria and single-cell fungi and compare it with the granular activated carbon (GAC) used in the hemoperfusion column Adsorba 300 (Gambro Co., Sweden). The sorbents under investigation based on polystyrene are distinguished by the presence of a large number of open micropores with diameters of 1.5–3 nm and macropores with diameters of up to 100 nm, resulting in a high specific surface area (806 m2/g for Styrosorb 514 and 580 m2/g for MMN200). The sorbents have been packed into miniature models of columns for perfusion through which suspensions of microorganisms B. subtilis, L. acidophilus, and S. cerevisiae in physiological saline were filtered. Perfusion through the columns depressed the colony formation of B. subtilis and L. acidophilus by 95% and 90% for Styrosorb 514 and 84% and 91% for the carbon, respectively. After perfusion through MMN200, the index of colony-formation inhibition for both tested cultures was 21% (B. subtilis) and 25% (L. acidophilus). In addition, the investigated sorbents were found to exert a pronounced influence on S. cerevisiae yeast cells by reducing their amount in the suspension and decreasing the proportion of live cells in the remaining fraction when compared to intact controls (by 82% and 26% for Styrosorb 514, 74% and 27% for carbon, and 76% and 12% for MMN200, respectively). Thus, the results indicate that the biporous sorbents based on hypercrosslinked styrene polymers are distinguished by hemocompatibility and capable of eliminating different microorganisms, along with endogenous inflammation mediators and trigger factors provoking the development of organ and multiple-organ failure. Therefore, the investigated sorbents can be effectively used for the treatment of patients with bacteriaemia, sepsis, and septic shock of different origins.

Polyhydroxybutyrate/Hydroxyapatite Highly Porous Scaffold for Small Bone Defects Replacement in the Nonload-bearing Parts

In the present work, Polyhydroxybutyrate (PHB)/Hydroxyapatite (HA) porous composites (10%, 20%, 30 %, 40%, 50% weight HA) were obtained by sintering. PHB/20% HA optimally combines satisfactory mechanical properties with a high content of the bioactive component (HA). Porous PHB/20% HA scaffolds have shown high mechanical properties (compressive strength of 106 MPa and Young’s modulus of 901 MPa). A high volume fraction of interconnected pores (> 50 vol.%) was achieved with pore size of 50 μm - 500 μm. Biocompatibility of porous pure PHB and PHB/20%HA, as its osseointegration were assessed in vitro and after implantation in laboratory animals. PHB/20% HA (−5% ± 0.9%) and pure PHB (−3% ± 1.4%) samples after 24 hours of incubation with human leucocytes showed no significant level of cytotoxicity when p = 0.648 (p-value). In vitro massive adhesion of mouse Multipotent Mesenchymal Stromal Cells (MMSC) to the surface of both porous samples was shown. PHB/20% HA induced more intensive MMSC proliferation compared to pure PHB, which are 31% ± 6.1% and 20% ± 5.7 % respectively when p = 0.039. We observed the resorption (implant surface area was reduced by 49 %) and integration of the porous PHB/20% HA samples into surrounding tissues after 30 days of implantation. The signs of osteoclasts accumulation, neo-angigenesis and new bone formation were observed, which make PHB/20% HA promising for bone tissue engineering.

Development of biomimetic in vitro fatigue assessment for UHMWPE implant materials

An important research goal in the field of biomaterials lies in the progressive amendment of in vivo tests with suitable in vitro experiments. Such approaches are gaining more significance nowadays because of an increasing demand on life sciences and the ethical issues bound to the sacrifice of animals for the sake of scientific research. Another advantage of transferring the experiments to the in vitro field is the possibility of accurately control the boundary conditions and experimental parameters in order to reduce the need of validation tests involving animals. With the aim to reduce the amount of needed in vivo studies for this cause, a short-time in vitro test procedure using instrumented load increase tests with superimposed environmental loading has been developed at TUD to assess the mechanical long-term durability of ultra-high molecular weight polyethylene (UHMWPE) under fatigue loading in a biological environment.

Impregnation of Ultrahigh-Molecular-Weight Polyethylene with Amoxicillin in Subcritical Freon R22 Media

The method of impregnation of ultrahigh-molecular-weight polyethylene (UHMWPE) with amoxicillin in subcritical Freon R22 media is developed. For the first time, the possibility of polymer impregnation with a polar substance (a standard antibiotic amoxicillin) in the absence of cosolvents is shown. Cosolvents increase the polarity of the medium and removal of them from the polymer matrix is usually a serious problem. Amoxicillin desorption curves from the impregnated UHMWPE samples are obtained by high-performance liquid chromatography (HPLC). Polymeric samples impregnated with amoxicillin are active against gram-positive and gram-negative microorganisms S. aureus, S. epidermidis, E. faecalis, B. subtilis, and E. coli, allowing them to be considered as real implant models for replacement of bone tissue.