Design and evaluation of novel blood incubation systems for in vitro hemocompatibility assessment of planar solid surfaces

Abstract

Success in the development of hemocompatible biomaterials depends on adequate equipment and procedures for standardized analysis of blood-materials interactions in vitro. In view of the limited standard of knowledge on that important aspect, two novel incubation systems were designed, built, and evaluated for the in vitro assessment of the hemocompatibility of planar solid surfaces: A screening setup was introduced for the comparison of up to 12 different samples. A perfusion setup was developed to model the directed blood flow in the vascular system during incubation by a recirculation circuit, allowing the variation of the wall shear rate at the sample surface. The incubation procedures utilized freshly drawn, heparinized whole human blood. Hemocompatibility in terms of selected aspects of coagulation, thrombogenicity, and immune responses was quantified through plasma levels of characteristic molecules (immunoassays), cell counting, and analysis of adherent cells and fibrin formation (scanning electron microscopy), respectively. Prevention of blood-air contact and mechanical stress, constant temperature and blood pH during incubation, and the suitable choice of reference materials were found to be crucial for reliable testing. Considering those requirements, screening and perfusion system both provided sensitive discrimination between a given set of planar solid surfaces. In conclusion, the suggested methods for an in vitro hemocompatibility assessment permit versatile, sensitive, and efficient analysis of important blood-material interactions despite the unavoidable variability of blood characteristics in different experiments.