A Technology for Anti-Thrombogenic Drug Coating of Small-Diameter Biodegradable Vascular Prostheses.

The aim of the study was to develop a technology for anti-thrombogenic drug coating of biodegradable porous scaffolds and to evaluate the physicomechanical and hemocompatible properties of functionally active vascular prostheses with and without a drug coating. MATERIALS AND METHODS: Vascular prostheses from polyhydroxybutyrate/valerate and polycaprolactone with the incorporated vascular endothelial growth factor, the main fibroblast growth factor, and the chemoattractant SDF-1α were made by emulsion electrospinning. Additional surface modification of the prostheses was carried out by forming a hydrogel coating of polyvinylpyrrolidone capable of binding drugs as a result of complexation. Unfractionated heparin and iloprost were used as anti-thrombogenic drugs. RESULTS: We show that after the modification of vascular prostheses with heparin and iloprost, a 5.8-fold increase in the Young's modulus value was noted, which indicated a greater stiffness of these grafts compared to the unmodified controls. Platelet aggregation on the surface of heparin + iloprost coated vascular prostheses was 3.3 times less than that with the unmodified controls, and 1.8 times less compared to intact platelet-rich plasma. The surface of vascular prostheses with heparin and iloprost was resistant to adhesion of platelets and blood proteins. CONCLUSION: Drug (unfractionated heparin and iloprost) coating of the surface of biodegradable prostheses significantly improved the anti-thrombogenic properties of these grafts but contributed to the increased stiffness of the prostheses.

[Influence of unmodified and modified sutures on experimental abdominal adhesive process]. / Éksperimental'naia otsenka spaechnogo protsessa v briushnoi polosti pri ispol'zovanii nemodifitsirovannogo shovnogo materiala i modifitsirovannogo geparinom.

OBJECTIVE: Experimental assessment of the effect of modified and unmodified surgical suture material on abdominal adhesive process. MATERIAL AND METHODS: The study was performed on male rats of the Wistar subpopulation. There were 5 animals in each group. In all animals, midline abdominal incision was followed by suturing the parietal peritoneum with modified and unmodified suture material. All animals were euthanized with carbon dioxide vapors in 14 days after surgery. Macro- and microscopic assessment of severity of abdominal adhesive process was carried out. Two types of preparation of excised complexes 'peritoneum-suture material-adhesion' were applied for histological examination: paraffin sections and embedding in epoxy resin. Specimens were stained by Van Gieson and with methylene blue solution. Histological specimens were examined using Axio Imager A1 light microscope (Zeiss, Germany). RESULTS: Polypropylene filaments result extensive adhesions occupying about 75% of the area. Adhesions have a dense structure with signs of vascularization. Modification of suture material with solution of polyhydroxybutyrate/hydroxyvalerate and heparin reduce severity of adhesions. The use of modified suture material was followed by adhesions with more loose structure, no signs of vascularization. Adhesions occupied less than 25% of the area. Histological examination of excised complexes 'peritoneum-suture material-adhesion' revealed accumulation of inflammatory cells around the unmodified suture material, while there were no signs of tissue inflammatory process around the modified sutures. CONCLUSION: Application of polyhydroxybutyrate/hydroxyvalerate and heparin on the surface of surgical sutures is an effective method for prevention of abdominal adhesions.

First Experience of Sutureless Redo on Mitral Valve Using Valve-in-Valve Technique: Two-Stage Implantation on a Large Animal.

Sutureless implantation of the mitral valve bioprosthesis using the valve-in-valve method was performed on a large animal (sheep). According to the results of a two-stage implantation (primary implantation of a xenopericardial 26-mm framed bioprosthesis and reimplantation of the developed 23-mm bioprosthesis), minor changes in quantitative indicators were revealed: an increase in the transprosthetic gradient by 1.3 mm Hg and a decrease in the area of the mitral orifice by 21.6%. Considerable reduction in the intervention time by 18 min was achieved (by 40% in comparison with the primary prosthesis). The absence of adverse events in the animal and complications in the post-operative period, as well as physiological hemodynamic indicators indicate the safety of the developed medical device.

[Influence of suture material on the development of postoperative complications in vascular surgery and their prevention]. / Vliianie shovnogo materiala na razvitie posleoperatsionnykh oslozhnenii v sosudistoi khirurgii i puti ikh profilaktiki.

Postoperative complications in vascular surgery may be partly provoked by suture material. Analysis of the mechanisms of these complications may be useful for their prevention. Mechanisms of suture-induced thrombosis and neointimal hyperplasia, possible strategies for prevention of postoperative complications including those allowing drug deliveries directly to the vascular anastomosis area are discussed in the article. According to the literature data, heparin is the most optimal drug for modifying suture material and prevention of thrombosis and neointimal hyperplasia. Heparin delivery to the vascular anastomosis site will reduce the risk of thrombosis by inhibiting the activity of thrombin. Complex of heparin and antithrombin III increases inhibitory effect of antithrombin against thrombin. In addition, heparin is able to reduce proliferation of vascular smooth muscle cells through inhibition of the synthesis of extracellular matrix proteases involved in migration and proliferation of cells. Thus, heparin delivery to the vascular injury site may be used to prevent thrombosis and myoproliferative response. Moreover, this strategy prevents complications associated with systemic administration of anticoagulants.

Surface modification of electrospun poly-(l-lactic) acid scaffolds by reactive magnetron sputtering.

In this study, we modified the surface of bioresorbable electrospun poly-(l-lactic) acid (PLLA) scaffolds by reactive magnetron sputtering of a titanium target under a nitrogen atmosphere. We examined the influence of the plasma treatment time on the structure and properties of electrospun PLLA scaffolds using SEM, XRF, FTIR, XRD, optical goniometry, and mechanical testing. It was observed that the coating formed did not change physicomechanical properties of electrospun PLLA scaffolds and simultaneously, increased their hydrophilicity. No adverse tissue reaction up to 3 months after subcutaneous implantation of the modified scaffolds was detected in in-vivo rat model. The rate of scaffold replacement by the recipient tissue in-vivo was observed to depend on the plasma treatment time.

Biocompatibility and Structural Features of Biodegradable Polymer Scaffolds.

We performed a comparative analysis of physicochemical properties and biocompatibility of scaffolds of different composition on the basis of biodegradable polymers fabricated by casting and electrospinning methods. For production of polyhydroxyalkanoate-based scaffolds by electrospinning method, the optimal concentration of the polymer was 8-10%. Fiber diameter and properties of the scaffold produced by electrospinning method depended on polymer composition. Addition of polycaprolactone increased elasticity of the scaffolds. Bio- and hemocompatibility of the scaffolds largely depended on the composition formulation and method of scaffold fabrication. Polylactide introduced into the composition of polyhydroxybutyrate-oxyvalerate scaffolds accelerated degradation and increased adhesive properties of the scaffolds.