Which Gelatin and Antibiotic Should Be Chosen to Seal a Woven Vascular Graft?

Among the vascular prostheses used for aortic replacement, 95% are woven or knitted grafts from polyester fibers. Such grafts require sealing, for which gelatin (Gel) is most often used. Sometimes antibiotics are added to the sealant. We used gelatin type A (GelA) or type B (GelB), containing one of the three antibiotics (Rifampicin, Ceftriaxone, or Vancomycin) in the sealant films. Our goal was to study the effect of these combinations on the mechanical and antibacterial properties and the cytocompatibility of the grafts. The mechanical characteristics were evaluated using water permeability and kinking radius. Antibacterial properties were studied using the disk diffusion method. Cytocompatibility with EA.hy926 endothelial cells was assessed via indirect cytotoxicity, cell adhesion, and viability upon direct contact with the samples (3, 7, and 14 days). Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to visualize the cells in the deep layers of the graft wall. "GelA + Vancomycin" and "GelB + vancomycin" grafts showed similar good mechanical characteristics (permeability~10 mL/min/cm2, kinking radius 21 mm) and antibacterial properties (inhibition zones for Staphilococcus aureus~15 mm, for Enterococcus faecalis~12 mm). The other samples did not exhibit any antibacterial properties. The cytocompatibility was good in all the tested groups, but endothelial cells exhibited the ability to self-organize capillary-like structures only when interacting with the "GelB + antibiotics" coatings. Based on the results obtained, we consider "GelB + vancomycin" sealant to be the most promising.

Remote Outcomes with Poly-ε-Caprolactone Aortic Grafts in Rats.

Poly-ε-caprolactone ((1,7)-polyoxepan-2-one; PCL) is a biodegradable polymer widely used in various fields of bioengineering, but its behavior in long-term studies appears to depend on many conditions, such as application specificity, chemical structure, in vivo test systems, and even environmental conditions in which the construction is exploited in. In this study, we offer an observation of the remote outcomes of PCL tubular grafts for abdominal aorta replacement in an in vivo experiment on a rat model. Adult Wistar rats were implanted with PCL vascular matrices and observed for 180 days. The results of ultrasound diagnostics and X-ray tomography (CBCT) show that the grafts maintained patency for the entire follow-up period without thrombosis, leakage, or interruptions, but different types of tissue reactions were found at this time point. By the day of examination, all the implants revealed a confluent endothelial monolayer covering layers of hyperplastic neointima formed on the luminal surface of the grafts. Foreign body reactions were found in several explants including those without signs of stenosis. Most of the scaffolds showed a pronounced infiltration with fibroblastic cells. All the samples revealed subintimal calcium phosphate deposits. A correlation between chondroid metaplasia in profound cells of neointima and the process of mineralization was supported by immunohistochemical (IHC) staining for S100 proteins and EDS mapping. Microscopy showed that the scaffolds with an intensive inflammatory response or formed fibrotic capsules retain their fibrillar structure even on day 180 after implantation, but matrices infiltrated with viable cells partially save the original fibrillary network. This research highlights the advantages of PCL vascular scaffolds, such as graft permeability, revitalization, and good surgical outcomes. The disadvantages are low biodegradation rates and exceptionally high risks of mineralization and intimal hyperplasia.

Epoxy- versus Glutaraldehyde-Treated Bovine Jugular Vein Conduit for Pulmonary Valve Replacement: A Comparison of Morphological Changes in a Pig Model.

Valved conduits are often required to replace pulmonary arteries (PA). A widely used Contegra device is made of bovine jugular vein (BJV), preserved with glutaraldehyde (GA) and iso-propanol. However, it has several drawbacks that may be attributed to its chemical treatment. We hypothesized that the use of an alternative preservation compound may significantly improve BJV conduit performance. This study aimed to compare the macroscopic and microscopic properties of the BJV treated with diepoxide (DE) and GA in a porcine model. Twelve DE-BJVs and four Contegra conduits were used for PA replacement in minipigs. To assess the isolated influence of GA, we included an additional control group-BJV treated with 0.625% GA (n = 4). The animals were withdrawn after 6 months of follow-up and the conduits were examined. Explanted DE-BJV had a soft elastic wall with no signs of thrombosis or calcification and good conduit integration, including myofibroblast germination, an ingrowth of soft connective tissue formations and remarkable neoangiogenesis. The inner surface of DE-BJVs was covered by a thin neointimal layer with a solid endothelium. Contegra grafts had a stiffer wall with thrombosis on the leaflets. Calcified foci, chondroid metaplasia, and hyalinosis were observed within the wall. The distal anastomotic sites had hyperplastic neointima, partially covered with the endothelium. The wall of GA-BJV was stiff and rigid with degenerative changes, a substantial amount of calcium deposits and dense fibrotic formations in adventitia. An irregular neointimal layer was presented in the anastomotic sites without endothelial cover in the GA BJV wall. These results demonstrate that DE treatment improves conduit integration and the endothelialization of the inner surface while preventing the mineralization of the BJV, which may reduce the risk of early conduit dysfunction.

Influence of Single-Wall Carbon Nanotube Suspension on the Mechanical Properties of Polymeric Films and Electrospun Scaffolds.

Carbon nanotubes (CNTs) are used in applications ranging from electrical engineering to medical device manufacturing. It is well known that the addition of nanotubes can influence the mechanical properties of various industrial materials, including plastics. Electrospinning is a popular method for fabricating nanomaterials, widely suggested for polymer scaffold manufacturing. In this study, we aimed to describe the influence of single-walled carbon nanotube (SWCNT) suspensions on polymeric poured films and electrospun scaffolds and to investigate their structural and mechanical properties obtained from various compositions. To obtain films and electrospun scaffolds of 8 mm diameter, we used poly-ε-caprolactone (PCL) and poly(cyclohexene carbonate) (PCHC) solutions containing several mass fractions of SWCNT. The samples were characterized using tensile tests, atomic force and scanning electronic microscopy (AFM and SEM). All the studied SWCNT concentrations were shown to decrease the extensibility and strength of electrospun scaffolds, so SWCNT use was considered unsuitable for this technique. The 0.01% mass fraction of SWCNT in PCL films increased the polymer strength, while fractions of 0.03% and more significantly decreased the polymer strength and extensibility compared to the undoped polymer. The PHCH polymeric films showed a similar behavior with an extremum at 0.02% concentration for strength at break.

Effect of the Nanorough Surface of TiO2 Thin Films on the Compatibility with Endothelial Cells.

The cytocompatibility of titanium oxides (TiO2) and oxynitrides (N-TiO2, TiOxNy) thin films depends heavily on the surface topography. Considering that the initial relief of the substrate and the coating are summed up in the final topography of the surface, it can be expected that the same sputtering modes result in different surface topography if the substrate differs. Here, we investigated the problem by examining 16 groups of samples differing in surface topography; 8 of them were hand-abraded and 8 were machine-polished. Magnetron sputtering was performed in a reaction gas medium with various N2:O2 ratios and bias voltages. Abraded and polished uncoated samples served as controls. The surfaces were studied using atomic force microscopy (AFM). The cytocompatibility of coatings was evaluated in terms of cytotoxicity, adhesion, viability, and NO production. It has been shown that the cytocompatibility of thin films largely depends on the surface nanostructure. Both excessively low and excessively high density of peaks, high and low kurtosis of height distribution (Sku), and low rates of mean summit curvature (Ssc) have a negative effect. Optimal cytocompatibility was demonstrated by abraded surface with a TiOxNy thin film sputtered at N2:O2 = 1:1 and Ub = 0 V. The nanopeaks of this surface had a maximum height, a density of about 0.5 per 1 µm2, Sku from 4 to 5, and an Ssc greater than 0.6. We believe that the excessive sharpness of surface nanostructures formed during magnetron sputtering of TiO2 and N-TiO2 films, especially at a high density of these structures, prevents both adhesion of endothelial cells, and their further proliferation and functioning. This effect is apparently due to damage to the cell membrane. At low height, kurtosis, and peak density, the main factor affecting the cell/surface interface is inefficient cell adhesion.