2.3.1. Cell Viability Assay

The scaffolds (discs with a diameter of 10 mm) were pre-incubated with the culture medium for 2 h to achieve complete moistening of the material. Human umbilical vein endothelial cells (HUVEC) were isolated from umbilical vein of newborn by collagenase IV. Culture medium was removed from the wells before seeding the HUVEC cells on the scaffolds (2000–8000 cells per well). The seeding density of cells was about 50–65% of the monolayer. Control cells were cultivated in parallel on tissue culture polystyrene. The viability of endothelial cells was assessed after 48-h cultivation on the surface of the matrices. The culture medium was removed and the cells were incubated with Alamar Blue^® (Invitrogen, Eugene, OR, USA), as earlier described [26]. Matrices without cells were used as a control for assessing the dye sorption on the tested materials.