Biocompatibility of Titanium Oxynitride Coatings Deposited by Reactive Magnetron Sputtering.

Titanium oxynitride coatings deposited by reactive magnetron sputtering improve biocompatibility of vascular stents by increasing NO production, viability, and adhesion of EA.hy926 cells. Thus, the application of titanium oxynitride coatings is a promising strategy for increasing the biocompatibility of nitinol stents.

A New Look at Structural Changes in the Aortic Root in Aortic Valve Stenosis.

The aim of the study was to identify new anatomical landmarks of the aortic root and the relationship between the sizes of anatomical structures using the method of computed tomography angiography to improve models of heart valves and the methods for their selection in clinical practice. Materials and Methods: The dataset of computed tomography angiography prior to aortic valve replacement in 262 patients was analyzed. The mean age was 75.0±5.9 years. 99 (37.8±3.0%) men and 163 (62.2±3.0%) women took part in the study. The annulus fibrosus, sinotubular junction, and height of the sinuses of Valsalva were measured. Results: In the tricuspid aortic valve group (n=251), in more than 50% of the cases, the diameter of the annulus fibrosus ranged from 23 to 26 mm. No significant association between the diameter of the annulus fibrosus and patient height (r=0.35; p=0.01) or body surface area (r=0.25; p=0.01) and the height of the sinuses of Valsalva (r=0.34; p=0.01) were revealed. Based on the ratio of the height of the sinuses of Valsalva and the diameter of the annulus fibrosus, three variants of the structure of the aortic root were identified: type A - K>1.05; type B- 0.95≤K≤1.05; type C- K<0.95. Type C of the aortic root was found to predominate in most cases, namely, in 98.0±0.9% (n=246).In the bicuspid aortic valve group (n=11), 2 patients had a type A of the aortic root, 1 patient had a type B, and 8 patients had a type C. Conclusion: A classification of variants of the aortic root structure has been proposed, which will be useful not only for practitioners when choosing a treatment method, but also for researchers to understand the structural characteristics of the aortic root in patients with its pathology.

The Influence of Weaving Technologies on the Integral Characteristics of Synthetic Vascular Prostheses.

The aim of the study is to determine physical and structural properties of woven synthetic prostheses depending on the type of the weave. Materials and Methods: Ten vascular prostheses manufactured at the Science and Technology Park of the BNTU "Polytechnic" (Minsk, Republic of Belarus) have been analyzed. The prostheses differed in the type of weaving, duration and temperature of thermal fixation during crimping. Three samples had a single-layer structure and 7 samples had a double-layer structure. Tests for water permeability, resistance to radial bending, and porosity of the prostheses have been performed. Results: The single-layer woven prostheses have demonstrated a low level of water permeability: the best result was shown by sample No.1: 80 [77.1; 80.5] ml/min/cm2. A strong direct correlation was revealed for these prostheses: the larger the pore diameter, the greater permeability (r=0.778; p=0.05). The single-layer woven prostheses appeared to be most resistant to radial bending, samples No.1 and 3 had no deformations at the minimum radius of the cylinder (r<4 mm), sample No.2 showed deformation on the cylinder with r=5 mm. For the single-layer prostheses, a strong negative correlation was noted (r=‒0.97; p=0.04) between the density of the warp threads and the kinking radius.All double-layer prostheses have demonstrated higher water permeability and weak resistance to deformation during radial bending. Samples No.4 and 8 were found to have minimum and maximum water permeability of 276.5 [258.3; 288.4] and 538.8 [533.3; 564.3] ml/min/cm2, respectively. The minimum kinking radius (7 mm) was shown by samples No.9 and 10. The worst results were demonstrated by sample No.6, which was deformed with minimal bending. Conclusion: Samples with ordinary plain weave have a low level of water permeability and high resistance to radial deformation, which makes them look most promising for the application in vascular surgery.

Cytotoxicity of Xenogeneic Pericardium Preserved by Epoxy Cross-Linking Agents.

The aim of the study was to assess the cytotoxic effect of xenopericardial biomaterial treated with di- and pentaepoxides on the cell cultures in vitro. MATERIALS AND METHODS: Samples of bovine and porcine pericardium were used in the work. Three different modes were employed for preservation: 1) 0.625% solution of glutaraldehyde (GA) and a two-fold change on days 2 and 7; 2) 5% solution of ethylene glycol diglycidyl ether (EGDE) changed on day 2; 3) 5% EGDE solution for 10 days, then 2% pentaepoxide solution also for 10 days. The cytotoxicity of the biomaterial was assessed by the extraction method. To determine the cytotoxicity of the biomaterial, EA.hy926 cells, multipotent mesenchymal stem cells (MMSCs), and fibroblasts were used. Cell viability was determined by the MTT test. The level of apoptosis and necrosis in the cell cultures was assessed by staining with acridine orange and ethidium bromide after cultivation with xenopericardial extracts employing different modes of preservation. RESULTS: Extracts of bovine and porcine pericardium preserved with GA have been found to have the greatest toxic effect on the cell cultures showing 20-33% reduction of cell viability. Extracts from bovine and porcine pericardium preserved with di- and pentaepoxy compounds do not have a toxic effect on endothelial cells, MMSCs, and fibroblasts since cell viability reduction is by no more than 15%. The lowest level of apoptosis and necrosis is observed in the cell cultures under the influence of extracts from the pericardium, preserved with diepoxide and pentaepoxide compounds. CONCLUSION: According to the MTT test for cytotoxicity and determination of the level of apoptosis and necrosis in cell cultures, bovine and porcine pericardia treated with di- and pentaepoxides have been established to have no cytotoxic effect on the culture of endothelial EA.hy926 cells, MMSCs, fibroblasts in vitro, whereas GA, in comparison with di- and pentaepoxides, has a toxic impact on the cells.

Ab ovo: Factors Affecting the Radial Stiffness of Thoracic Aorta Stent-Grafts.

The aim of the investigation was to study the factors influencing the radial stiffness of the thoracic aorta stent-grafts with the stent elements made of nitinol tubes by laser cutting and thermal shape setting. Materials and Methods: The work used stent elements made by different technologies by two different manufacturers from a nitinol tube with a wall thickness of 0.5 mm (E1) and 0.4 mm (E2), with a final diameter of 20 mm. Height of cells E1 - 15 mm, E2 - 12.5 mm. The stents were manually attached to a tubular woven non-crimped base (PTGO Sever, Russia) with a 6/0 suture, resulting in either single or continuous stitches. In the RLU124 radial force tester (Blockwise Engineering LLC, USA), each of the four stent-grafts, as well as their individual stent elements, were compressed by 10 mm from the initial diameter. The dependence of the radial forces on deformation under loading and unloading was graphically presented. The temperature and enthalpy of phase transitions of nitinols into the austenite (Af) and martensitic (Mf) phases were studied using differential scanning calorimetry (DSC-3; Mettler Toledo, USA). All indicators were compared with the characteristics of two commercial models - Cronus (China) and E-vita Open Plus (Germany). Results: Four prototypes of SibHybrid stent-grafts were tested; those differed in their stent elements, distances between them, and the type of sutures (single or continuous). The stent elements of the models studied differed in the values of Af, Mf, and the enthalpy of phase transitions of nitinols. The hardest stent was the E2 prototype. The fixation of stent elements to the woven fabric in the graft increased the radial force by 4.0-5.5 times. During compression by 50 and 20% of the original diameter, the SibHybrid models developed radial force 4.5-6.0 times greater compared with the E-vita Оpen Plus model. The radial force values of SibHybrid models were almost the same as for the Cronus and models at 20% compression. Using continuous twining round suturing increased the radial force by about 10 N; accordingly, SibHybrid E2 had the highest radial force because it was fixed by a continuous suture. The density of the stent elements fixed on the fabric did not affect the radial force of the stent-graft as a whole. Conclusion: In the manufacture of stent elements from nitinol tubes, the main factor determining the radial stiffness is the technology of nitinol shape setting. With the standard technology of thermal shape setting, radial force can be changed by varying the height of the structure cell element and the cross-sectional area of the cell bars, as well as the suturing technique.