Experimental Evaluation of Biodegradable Film Compositions Based on Gelatin with Colchicine.

Biodegradable film compositions based on natural biopolymer gelatin with immobilized colchicine were prepared and their efficiency in prevention of the adhesion process in the pericardium was evaluated on rabbit model of postoperative pericarditis. The use of gelatin-based biodegradable film compositions significantly reduced the intensity of adhesion formation in the pericardial cavity, while immobilization of anti-inflammatory drug colchicine amplified their anti-adhesion activity.

[Biospecific properties of lysine-contained polyelectrolyte coatings for devices contacting blood].

Biospecific properties of thromboresistant bilayer and multilayer coatings based on polyelectrolyte complexes of modified copolymer of N-vinylpyrrolidone and maleic acid (VPMA) with chitosan, amphiphilic chitosan or albumin were investigated. VPMA contained affinity ligand towards plasminogen--alpha-amino coupled lysine residues. Polyethylene and polystyrene surfaces were investigated before and after their covering by protective polyelectrolyte coatings. The specific adsorption of plasminogen (precursor of the fibrinolytic enzyme plasmin) from its solutions and from human plasma was investigated using these model systems. It was found that all coatings with the outer contact lay of lysine-contained affinity polymer had affinity to plasminogen. But multilayer polyelectrolyte coatings were more efficient than bilayer coatings with single application of layers and the affinity polymer coatings without interlayer. The decrease in trombogenicity degree of the materials modified by polyelectrolyte coatings was shown in vitro and ex vivo. Emplyment of proposed modification of surfaces will improve hemocompatibility of medical devices.

In vitro and in situ intercellular adhesion molecule-1 (ICAM-1) expression by endothelial cells lining a polyester fabric.

In order to improve long-term patency of vascular grafts, the promising concept of endothelial cell seeding is actually under investigation. Our laboratory tested a polyester coated with albumin and chitosan which permits a rapid colonization by human umbilical vein endothelial cells (HUVEC) and it seems relevant to test in vitro the expression of adhesive molecules expressed by cells with regard to the inflammatory process. We studied intercellular adhesion molecule-1 (ICAM-1) expression and focused our work on the determination of ICAM-1 sites expressed per adherent cell lining the biomaterial, thus in situ, in comparison to control HUVEC on plastic wells: the results obtained by binding experiments were correlated to flow cytometry analyses and showed that the polyester does not induce a proinflammatory state and that HUVEC covering the structure are able to respond to a stimulus.

[The gas-exchange properties of membrane blood oxygenators with immobilized heparin]. / Gazoobmennye svoistva membrannykh oksigenatorov krovi s immobilizovannym geparinom.

Gas-exchange properties of membrane oxygenators (MO) "MOST-122" with immobilized heparin have been studied during 18 open heart surgeries. It has been shown that heparin immobilization on MO surfaces that are in contact with blood is accompanied by enhanced MO ability to oxygenate blood and remove CO2.

[10 years' experience of heart valve bioprostheses. Present status and future development]. / 10-letnii opyt bioprotezirovaniia klapanov serdtsa. Sovremennoe sostoianie i perespektivy razvitiia.

Long-term results of mitral valve replacement with bioprostheses of three original designs are overviewed. Refinement of the supporting framework design, and of modelling and conservation methodologies has made it possible to improve the survival rates and provided for the absence of specific complications in two groups of patients. Experimental evidence allows for anticipating an increase in the terms of bioprostheses performance.

[The use of immobilized heparin in perfusion systems with membrane oxygenation during heart surgery]. / Ispol'zovanie immobilizovannogo geparina v perfuzionnykh sistemakh s membrannoi oksigenatsiei pri kardiokhirurgicheskikh vmeshatel'stvakh.

The analysis of 65 cases of cardiopulmonary bypass surgery using systems distinct in the type of the oxygenator used (contact, membrane) and the degree of thromboresistance of blood-contacting surfaces has demonstrated that the use of heparin-covered membrane blood oxygenators and systems allows of a considerable reduction in blood trauma during perfusion and a 5-6-fold decrease of heparin doses employed for extracorporeal membrane blood oxygenation.

[A new approach to the creation of heart valve xenograft bioprostheses resistant to calcification]. / Novyi podkhod k sozdaniiu ksenobioprotezov klapanov serdtsa, rezistentnykh k kal'tsifikatsii.

The calcium binding activity of xenograft tissue in stages of modification with papain, diphosphonates, and heparin was studied on a model of accelerated calcification in subcutaneous implantation of cusps of pig's aortic bioprostheses to 42 rats. In immobilization of 3-amino-1-oxypropylidendiphosphonic acid and xydiphon the amount of calcium in the implants reduced 50 times as compared to the control. The first stage of ion-covalent heparin immobilization--treatment with albumin--increased the calcium-binding activity of the biomaterial, but subsequent heparinization reduced again the calcium content in the cusp tissue to the level attained in the stage of diphosphonate immobilization. The results of the chemical analysis correlated with the findings of morphological examination. Besides, the new method of treatment made it possible to increase the strength of the biological tissue by 20%. This method of storage of bioprostheses is promising for clinical approbation.

[Studies and clinical experiences in the use of domestic blood vessel prostheses with increased thromboresistance]. / Issledovaniia i klinicheskii opyt primeneniia novykh otechestvennykh sosudistykh protezov s povyshennoi tromborezistentnost'iu.

The experimental and clinical data on the use of new native grafts with increased thromboresistance--the Vitlan and heparinized ones are presented. In all the acute and chronic experiments, the increased thromboresistance of both types of the grafts versus the common Fluorlon-Lavsan ones, and well-formed neointima with sufficient vascularization by the year 1 and 5 of follow-up were revealed. Complete organization of the external and internal capsules of the grafts was noted 5 mos later, no tissue reaction to Vitlan and heparinized grafts was revealed. The Vitlan grafts were used in 19 patients. Good immediate and long-term results were obtained in reconstruction of the aorto-femoral, aorto-pulmonary and femoro-popliteal segments with the grafts of 10 and 8 mm in diameter. All the Vitlan shunts of the femoro-popliteal segment with 6 mm diameter were thrombosed 1-6 mos after the operation. The heparinized grafts with 8 mm diameter at the femoro-popliteal position were used in 28 patients, good long-term results were noted in 27.

Polyethylene/hydrophilic polymer blends for biomedical applications.

Polyethylene blends with poly(2-hydroxyethyl methacrylate) [poly(HEMA)] or poly(2,3-dihydroxypropyl methacrylate) [poly(DHPMA)] were prepared by swelling polyethylene with HEMA or 2,3-epoxypropyl methacrylate (EPMA) and by polymerization of the respective monomers. Poly(EPMA) in blends was hydrolysed to poly(DHPMA) with acetic acid. The blends had similar surface and bulk compositions. Swelling with water and surface wettability were proportional to the content of the hydrophilic component; at the same content the polyethylene/poly(DHPMA) blends appeared more hydrophilic than those of polyethylene/poly(HEMA). Thrombus formation in contact with blood examined ex vivo and in vivo was considerably slower on the blends than on unmodified polyethylene. The tests indicated optima in composition; the best biological response was achieved with the blends containing about 14% poly(HEMA) or 16% poly(DHPMA).