PLLA/Fibrin Tubular Scaffold: A New Way for Reliable Endothelial Cell Seeding

In the present work a simple and quick technique for cell seeding into tubular-shaped scaffolds, which allows a homogeneous cell distribution, was tested. The poly-L-lactide (PLLA) scaffolds, prepared via diffusion induced phase separation (DIPS), were filled with fibrin gel in order to obtain a hybrid scaffold for Vascular Tissue Engineering applications. The formation of immobilized fibrin networks on the inner surface of the tubular scaffolds was observed using confocal microscopy and SEM. Morphological analysis of the so-obtained scaffold revealed that the fibrin gel is uniformly distributed on the internal surface of the scaffold, leading to an organized structure. Moreover a penetration of the gel into the porous wall of the scaffold was observed. The in vitro endothelial cell cultures carried out in the scaffolds highlighted a faster cell proliferation inside the hybrid scaffold with respect to simple PLLA scaffold. Results show that the fibrin/PLLA hybrid scaffold may be favourably used for Vascular Tissue Engineering applications. 1. Introduction Cardiovascular disease remains the leading cause of mortality in western nations, with an estimated prevalence of almost 80 million in the USA alone. In particular, coronary artery disease is the leading cause of death, accounting for 53% of the total mortality related to cardiovascular disease [1]. Tissue engineering approaches are being investigated as potential solutions to these problems. Adhesion of tissue cells to biomaterials is a prerequisite of paramount importance for the successful incorporation of vascular implants or the colonization of scaffolds in tissue engineering applications [2]. As a matter of fact, cell adhesion plays a critical role in the normal function of mammalian cells by regulating proliferation, differentiation, and phenotypic behaviour. Initial efforts to design biomaterials have focused on achieving robust mechanical interactions between the biomaterial and adjacent cells (i.e., integration). However, evidence is emerging that cell/biomaterial interactions can affect cell/cell interactions and consequently impact tissue development and functions. Therefore, successful outcomes of tissue engineering efforts may require the development of materials that can promote and facilitate both cell/cell and cell/biomaterial adhesion [3]. Synthetic biomaterials in vascular applications, such as PLLA, poly-lactic-glycolic acid (PLGA), and -polycaprolattone (PCL), are easily modified, highly reproducible, and can be synthesized in bulk. However, synthetic polymers alone lack specific