Due to their elastomeric behavior, polyurethane-based scaffolds can find various applications in soft-tissue engineering. However, their relatively inert surface has to be modified in order to improve cell colonization and control cell fate. The present study focuses on porous biodegradable scaffolds based on poly(ester-urea-urethane), functionalized concomitantly to the scaffold elaboration with low-molecular-weight (LMW) fucoidan; and their bio-activation with platelet rich plasma (PRP) formulations with the aim to promote cell response. The LMW fucoidan-functionalization was obtained in a very homogeneous way, and was stable after the scaffold sterilization and incubation in phosphate-buffered saline. Biomolecules from PRP readily penetrated into the functionalized scaffold, leading to a biological frame on the pore walls. Preliminary in vitro assays were assessed to demonstrate the improvement of scaffold behavior towards cell response. The scaffold bio-activation drastically improved cell migration. Moreover, cells interacted with all pore sides into the bio-activated scaffold forming cell bridges across pores. Our work brought out an easy and versatile way of developing functionalized and bio-activated elastomeric poly(ester-urea-urethane) scaffolds with a better cell response.

Предлагается расширение модели коэффициента интенсивности напряжений на длинные трещины полуэллиптической формы с учетом обобщения Мураками, ограниченного короткими трещинами. Методика позволяет с приемлемой эффективностью рассчитать коэффициент интенсивности напряжений путем использования новой поверхности, возникшей в результате распространения трещины. Предлагаемое расширение модели учитывает два фактора, которые непосредственно влияют на характер распространения указанного типа трещин, - преждевременное закрытие и воздействие нагрузок. Валидация новой модели проведена с использованием результатов усталостного поведения толстых пластин при трехточечном изгибе с тремя коэффициентами нагрузки. Расчет скорости распространения фронта трещины и количества циклов перехода от одного фронта к другому возможен путем адаптации формулы Пэриса к разработанной модели ΔK, которая является репрезентативной для всего фронта трещины, а не только для нескольких выбранных точек. Предложенная методика может рассматриваться как упрощенный метод оценки опасности полуэллиптических трещин, особенно для сосудов под давлением, и открывает новые перспективы использования поверхности трещины в исследованиях усталости материала. In this work, an extension of the stress-intensity factor model to long semi-elliptic shaped cracks is proposed considering the generalizing of Murakami limited to short cracks. The latter allows the calculation of the stress intensity factor by using the new surfaces of the crack created by propagation with an acceptable efficiency. The extension we propose to take into account the effect of two factors which are directly influencing the propagation behaviour of this cracks type, the premature closure, and the load ratio. The validation of the new model was carried out using the fatigue results reported in literature on thick plates by three-point bending with three load ratios. The calculation of the propagation velocity of the crack front and the number of cycles of the transition from one front to another is possible by adapting the Paris law to the new model of ΔK, that is representative of the entire crack front and not only a few points generally chosen on the front and is considered as a characteristic. This methodology can provide engineers with a simplified method to evaluate the harmfulness of this type of cracks, especially in the case of pressure vessels. It can also open new perspectives on the use of a crack surface in fatigue studies.