Enhancing decellularized vascular scaffolds with PVDF and PCL reinforcement: a fused deposition modeling approach

BackgroundDecellularized xenogenic scaffolds represent a promising substrate for tissue-engineered vascular prostheses, particularly those with smaller diameters (<6 mm). Despite their benefits, a notable limitation presents itself during decellularization, namely, the diminished mechanical strength that introduces the risk of aneurysmal dilations in the early post-implantation period. This study introduces a strategy for modification the mechanical properties of these biological scaffolds through the forming of an external polymeric reinforcement via thermal extrusion.MethodsThe study utilized scaffolds fabricated from bovine internal mammary arteries through decellularization and preservation. The scaffolds were divided into subgroups and reinforced with polymeric helices made of Polyvinylidene fluoride (PVDF) and Polycaprolactone (PCL), n = 5 for each. An experimental setup for external reinforcement coating was designed. Computed microtomography was employed to obtain accurate 3D models of the scaffolds. Mechanical properties were evaluated through in vitro uniaxial tension tests (Z50, Zwick/Roell, Germany), compliance evaluation and numerical simulations (Abaqus/CAE, Dassault Systemes, France) to investigate the effect of external reinforcement on aneurysm growth.ResultsUsing a double-layer helix for the reinforcement significantly enhanced the radial tensile strength of the scaffolds, increasing it up to 2.26 times. Yet, the comparison of vessel's compliance between two reinforced and the Control scaffolds within the physiological pressures range did not reveal any significant differences. Numerical simulation of aneurysm growth showed that thin-walled regions of the Control scaffold developed aneurysmal-type protrusions, bulging up to 0.7 mm, with a substantial degradation of mechanical properties. In contrast, both PVDF and PCL reinforced scaffolds did not exhibit significant property degradation, with deformations ranging 0.1–0.13 mm depending on the model, and a maximum decrease in the modulus of elasticity of 23%.ConclusionThe results of the study demonstrated that the external polymer helical reinforcement of decellularized scaffolds via thermal extrusion enables a controlled modification of mechanical properties, notably enhancing radial strength while maintaining sufficient compliance within the physiological pressure range. A series of in vitro tests demonstrated the consistency and potential of this approach for decellularized xenogenic scaffolds, a concept that had not been explored before

ПРЕИМУЩЕСТВА И НЕДОСТАТКИ ПРОТЕЗА КЛАПАНА СЕРДЦА С ДИНАМИЧЕСКИМ АДАПТИВНЫМ КАРКАСОМ В СРАВНЕНИИ С КЛАССИЧЕСКИМ КАРКАСНЫМ: ОЦЕНКА ГИДРОДИНАМИЧЕСКИХ ПОКАЗАТЕЛЕЙ БИОПРОТЕЗОВ «ТИАРА» И «ЮНИЛАЙН»

HighlightsThe «TiAra» bioprosthetic heart valves have better hemodynamic characteristics, such as higher effective orifice area and a lower mean pressure gradient.The «UniLine» bioprosthetic heart valve demonstrated better closing dynamic, expressed in a smaller regurgitation volume. Aim. To assess hydrodynamic characteristics of the «TiAra» bioprosthetic heart valve with flexible supporting frame compared with the classic stented «UniLine» bioprosthetic aortic valve.Methods. Using the Vivitro Pulse Duplicator (Vivitro Labs, Canada), we simulated the function of the heart via generating pulsatile flow to analyze bioprosthetic heart valves. To comprehensively assess the bioprosthesis function, three valves of each standard size (21, 23, 25 mm) were submitted to hydrodynamic testing, thus making a sample of nine bioprostheses of each model. The article provides the analysis of  the effective orifice area, mean pressure gradient, regurgitation volume, and assessment of the statistical sensitivity of the parameters between groups at p = 0.05.Results. The assessment revealed that the «TiAra» bioprosthesis has bigger effective orifice area (p = 0.006) and lower mean pressure gradient (p = 0.02): 1.6–2.2 cm2 and 3.6–6.3 mmHg versus 1.08–1.73 cm2 and 4.8–12.1 mmHg, respectively. The regurgitation volume, however, was lower in the «UniLine» bioprostheses 0.8–4.1 mL/cycle versus 6.2–9.0 mL/cycle (p = 0.0004).Conclusion. Despite the fact that both studied models showed good hydrodynamic performance, the prosthesis with the flexible supporting frame («TiAra») showed better results regarding its effectiveness in vitro via presenting with bigger effective orifice area and lower mean pressure gradient. At the same time, the «UniLine» stented bioprosthesis had lower regurgitation volume, i.e. better closing dynamics.Основные положенияБиопротезы клапанов сердца «ТиАра» обладают лучшими гемодинамическими характеристиками: более высокой эффективной площадью отверстия и меньшим средним транспротезным градиентом.Биопротез «ЮниЛайн» продемонстрировал более качественную запирательную функцию, выраженную в меньшем объеме регургитации. Цель. Оценка гидродинамических характеристик биопротеза клапана сердца «ТиАра» с динамическим адаптивным опорным каркасом в сравнении с классическим каркасным биопротезом «ЮниЛайн».Материалы и методы. Исследование проводили с помощью имитации физиологического гидродинамического потока в стендовых условиях на установке Vivitro Pulse Duplicator (Vivitro Labs, Канада). Для комплексной оценки работы биопротезов тестированию подвергали по три экземпляра каждого типоразмера (21, 23, 25 мм), формируя таким образом выборки из девяти биопротезов каждой модели. В работе анализировали эффективную площадь отверстия, средний транспротезный градиент и объем регургитации, оценивая статистическую значимость различий между группами при p = 0,05.Результаты. Показано, что модель биопротеза с динамическим адаптивным опорным каркасом «ТиАра» обладает достоверно лучшими показателями эффективной площади отверстия (p = 0,006) и меньшим средним транспротезным градиентом (p = 0,02): 1,6–2,2 см2 и 3,6–6,3 мм рт. ст. против 1,08–1,71 см2 и 4,8–12,1 мм рт. ст. у биопротеза «ЮниЛайн». Объем регургитации при этом был ниже у биопротезов «ЮниЛайн», составив 0,8–4,1 против 6,2–9,0 мл/цикл соответственно (p = 0,0004).Заключение. Несмотря на то что обе исследованные модели изделий обладают хорошими гидродинамическими характеристиками, протез с динамическим адаптивным опорным каркасом («ТиАра») демонстрирует статистически достоверно лучшие результаты in vitro с позиции эффективной площади отверстия и среднего транспротезного градиента. При этом каркасный биопротез «ЮниЛайн» имеет более низкий объем регургитации, т. е. лучшую запирательную функцию

ML-driven segmentation of microvascular features during histological examination of tissue-engineered vascular grafts

IntroductionThe development of next-generation tissue-engineered medical devices such as tissue-engineered vascular grafts (TEVGs) is a leading trend in translational medicine. Microscopic examination is an indispensable part of animal experimentation, and histopathological analysis of regenerated tissue is crucial for assessing the outcomes of implanted medical devices. However, the objective quantification of regenerated tissues can be challenging due to their unusual and complex architecture. To address these challenges, research and development of advanced ML-driven tools for performing adequate histological analysis appears to be an extremely promising direction.MethodsWe compiled a dataset of 104 representative whole slide images (WSIs) of TEVGs which were collected after a 6-month implantation into the sheep carotid artery. The histological examination aimed to analyze the patterns of vascular tissue regeneration in TEVGs in situ. Having performed an automated slicing of these WSIs by the Entropy Masker algorithm, we filtered and then manually annotated 1,401 patches to identify 9 histological features: arteriole lumen, arteriole media, arteriole adventitia, venule lumen, venule wall, capillary lumen, capillary wall, immune cells, and nerve trunks. To segment and quantify these features, we rigorously tuned and evaluated the performance of six deep learning models (U-Net, LinkNet, FPN, PSPNet, DeepLabV3, and MA-Net).ResultsAfter rigorous hyperparameter optimization, all six deep learning models achieved mean Dice Similarity Coefficients (DSC) exceeding 0.823. Notably, FPN and PSPNet exhibited the fastest convergence rates. MA-Net stood out with the highest mean DSC of 0.875, demonstrating superior performance in arteriole segmentation. DeepLabV3 performed well in segmenting venous and capillary structures, while FPN exhibited proficiency in identifying immune cells and nerve trunks. An ensemble of these three models attained an average DSC of 0.889, surpassing their individual performances.ConclusionThis study showcases the potential of ML-driven segmentation in the analysis of histological images of tissue-engineered vascular grafts. Through the creation of a unique dataset and the optimization of deep neural network hyperparameters, we developed and validated an ensemble model, establishing an effective tool for detecting key histological features essential for understanding vascular tissue regeneration. These advances herald a significant improvement in ML-assisted workflows for tissue engineering research and development

N-ГЛИКОЛИЛНЕЙРАМИНОВАЯ КИСЛОТА КАК ВОЗМОЖНЫЙ ТРИГГЕР ИММУННОГО ОТТОРЖЕНИЯ ЭПОКСИОБРАБОТАННЫХ КСЕНОПЕРИКАРДИАЛЬНЫХ БИОПРОТЕЗОВ КЛАПАНОВ СЕРДЦА

HighlightsStabilization of bovine pericardial tissue by ethylene glycol diglycidyl ether does not remove the N-glycolylneuraminic acid contained in its structure, which is one of the most immunoreactive glycan xenoantigens;N-glycolylneuraminic acid can potentially cause early immune rejection of epoxy-treated bioprosthetic heart valves. Aim. To assess the presence of N-glycolylneuraminic acid (Neu5Gc) in an intact bovine pericardial tissue stabilized by ethylene glycol diglycidyl ether and in the leaflets of epoxy-treated bioprosthetic heart valves (BHV) explanted due to dysfunction.Methods. By means of immunochemistry (using anti-Neu5Gc antibodies), we studied the fragments of 5 samples of intact epoxy-treated bovine pericardium commonly used in cardiac surgery. Similarly, we examined the fragments of the leaflets of 8 epoxy-treated BHVs that lasted for different time periods (1 day to 68 months) and excised during reoperation. The native bovine pericardium and the leaflets of 3 human aortic valves (AV) removed during reoperation in patients with aortic stenosis were used as positive and negative controls, respectively.Results. Positive reaction for Neu5Gc was observed in intact epoxy-treated xenopericardium and BHVs excised 1, 2, 20 and 42 days after implantation. The tissue of BHV that had lasted 30 months was characterized by the faint presence of Neu5Gc. In the leaflets of AV and in BHVs, explanted after 34, 63 and 68 months, Neu5Gc was not detected. Conclusion. Stabilization of xenobiomaterial with ethylene glycol diglycidyl ether does not remove the Neu5Gc. This saccharide remains in the biological tissue of epoxy-treated BHV for about 2.5 years after implantation. Основные положенияСтабилизация бычьего перикарда диглицидиловым эфиром этиленгликоля не экранирует содержащуюся в его структуре N-гликолилнейраминовую кислоту – один из наиболее иммунореактивных гликановых ксеноантигенов.N-гликолилнейраминовая кислота может являться потенциальным триггером раннего иммунного отторжения эпоксиобработанных ксенобиопротезов клапанов сердца. Цель. Оценить присутствие N-гликолилнейраминовой кислоты (ГНК) в интактном бычьем перикарде, стабилизированном диглицидиловым эфиром этиленгликоля, а также в створках эпоксиобработанных ксеноперикардиальных биопротезов клапанов сердца (БП), эксплантированных по причине дисфункций.Материалы и методы. Посредством иммуногистохимического окрашивания антителом к ГНК изучены фрагменты пяти лоскутов интактного эпоксиобработанного бычьего перикарда, применяемого в производстве БП. Аналогичным образом исследованы фрагменты створок восьми эпоксиобработанных БП со сроками функционирования от 1 дня до 68 мес. и иссеченных при репротезировании. В качестве положительного и отрицательного контролей использовали нативный бычий перикард и створки трех аортальных клапанов, удаленных при протезировании у пациентов с аортальным стенозом, соответственно.Результаты. Положительное окрашивание ГНК отмечено в интактном эпоксиобработанном ксеноперикарде и створках БП, иссеченных через 1, 2, 20 и 42 дня после имплантации. Ткани БП, функционировавшего 30 мес., характеризовались следовым присутствием ГНК. В створках аортальных клапанов и БП, эксплантированных через 34, 63 и 68 мес., ГНК не выявлена. Заключение. Стабилизация ксенобиоматериала диглицидиловым эфиром этиленгликоля не экранирует ГНК. Данный сахарид сохраняется в структуре биоматериала функционирующих эпоксиобработанных БП около 2,5 лет после имплантации.

Biocompatible Nanocomposites Based on Poly(styrene-block-isobutylene-block-styrene) and Carbon Nanotubes for Biomedical Application

In this study, we incorporated carbon nanotubes (CNTs) into poly(styrene-block-isobutylene-block-styrene) (SIBS) to investigate the physical characteristics of the resulting nanocomposite and its cytotoxicity to endothelial cells. CNTs were dispersed in chloroform using sonication following the addition of a SIBS solution at different ratios. The resultant nanocomposite films were analyzed by X-ray microtomography, optical and scanning electron microscopy; tensile strength was examined by uniaxial tension testing; hydrophobicity was evaluated using a sessile drop technique; for cytotoxicity analysis, human umbilical vein endothelial cells were cultured on SIBS–CNTs for 3 days. We observed an uneven distribution of CNTs in the polymer matrix with sporadic bundles of interwoven nanotubes. Increasing the CNT content from 0 wt% to 8 wt% led to an increase in the tensile strength of SIBS films from 4.69 to 16.48 MPa. The engineering normal strain significantly decreased in 1 wt% SIBS–CNT films in comparison with the unmodified samples, whereas a further increase in the CNT content did not significantly affect this parameter. The incorporation of CNT into the SIBS matrix resulted in increased hydrophilicity, whereas no cytotoxicity towards endothelial cells was noted. We suggest that SIBS–CNT may become a promising material for the manufacture of implantable devices, such as cardiovascular patches or cusps of the polymer heart valve

Biomaterials Based on Carbon Nanotube Nanocomposites of Poly(styrene-b-isobutylene-b-styrene): The Effect of Nanotube Content on the Mechanical Properties, Biocompatibility and Hemocompatibility

Nanocomposites based on poly(styrene-block-isobutylene-block-styrene) (SIBS) and single-walled carbon nanotubes (CNTs) were prepared and characterized in terms of tensile strength as well as bio- and hemocompatibility. It was shown that modification of CNTs using dodecylamine (DDA), featured by a long non-polar alkane chain, provided much better dispersion of nanotubes in SIBS as compared to unmodified CNTs. As a result of such modification, the tensile strength of the nanocomposite based on SIBS with low molecular weight (Mn = 40,000 g mol–1) containing 4% of functionalized CNTs was increased up to 5.51 ± 0.50 MPa in comparison with composites with unmodified CNTs (3.81 ± 0.11 MPa). However, the addition of CNTs had no significant effect on SIBS with high molecular weight (Mn~70,000 g mol−1) with ultimate tensile stress of pure polymer of 11.62 MPa and 14.45 MPa in case of its modification with 1 wt% of CNT-DDA. Enhanced biocompatibility of nanocomposites as compared to neat SIBS has been demonstrated in experiment with EA.hy 926 cells. However, the platelet aggregation observed at high CNT concentrations can cause thrombosis. Therefore, SIBS with higher molecular weight (Mn~70,000 g mol−1) reinforced by 1–2 wt% of CNTs is the most promising material for the development of cardiovascular implants such as heart valve prostheses