Surface modification of silicone tubes by functional carboxyl and amine, but not peroxide groups followed by collagen immobilization improves endothelial cell stability and functionality

Surface modification by functional groups promotes endothelialization in biohybrid artificial lungs, but whether it affects endothelial cell stability under fluid shear stress, and the release of anti-thrombotic factors, e.g. nitric oxide (NO), is unknown. We aimed to test whether surface-modified silicone tubes containing different functional groups, but similar wettability, improve collagen immobilization, endothelialization, cell stability and cell-mediated NO-release. Peroxide, carboxyl, and amine-groups increased collagen immobilization (41-76%). Only amine-groups increased ultimate tensile strength (2-fold). Peroxide and amine enhanced (1.5-2.5 fold), but carboxyl-groups decreased (2.9-fold) endothelial cell number after 6 d. After collagen immobilization, cell numbers were enhanced by all group-modifications (2.8-3.8 fold). Cells were stable under 1 h-fluid shear stress on amine, but not carboxyl or peroxide-group-modified silicone (>50% cell detachment), while cells were also stable on carboxyl-group-modified silicone with immobilized collagen. NO-release was increased by peroxide and amine (1.1-1.7 fold), but decreased by carboxyl-group-modification (9.8-fold), while it increased by all group-modifications after collagen immobilization (1.8-2.8 fold). Only the amine-group-modification changed silicone stiffness and transparency. In conclusion, silicone-surface modification of blood-contacting parts of artificial lungs with carboxyl and amine, but not peroxide-groups followed by collagen immobilization allows the formation of a stable functional endothelial cell layer. Amine-group-modification seems undesirable since it affected silicone's physical properties.