In this study, sulphated polysaccharides were investigated in respect to their blood compatibility properties (hemocompatibility). Pure chitosan was treated with sulphating agents such as SO(3)/pyridine complex and chlorosulfonic acid (HClSO(3)) to obtain 3,6-O-sulfochitosan with low and high concentration of sulfur. These synthetically derived materials and the commercially available sulphated polysaccharides heparin and dextran sulfate, both with high concentrations of sulfur, were coated onto PET foils to act as surfaces with strong antithrombotic activity. This treatment should lead to better blood compatibility properties of PET materials for medical applications. To examine this, the optimized free hemoglobin method was applied to determine the antithrombotic activity of these surfaces. Glass as the standard thrombotic surface and a heparin-coated PET surface as a surface well-known for its strong antithrombotic activity were used as internal references. The experiments showed that dextran sulfate and sulphated chitosan with high concentrations of sulfur demonstrated the same antithrombotic activity as heparin over the whole period of measurement time. In addition, a relationship between the sulfur concentration in these sulphated polysaccharides and their blood compatibility properties can be demonstrated in this article.

Purpose: Internationally-accepted standards have been developed for a range of tests and parameters for characterising the in-vitro interactions of biomaterials with blood. However, there are, as yet, no standards concerning the size, design and type of such in-vitro testing systems (1). Since the development of hemocompatible biomaterials provides a very important challenge in material science, there is a need for further progress in finding reliable and standardized methods for hemocompatibility testing (2). The aim of this research was to introduce a method for analyzing the hemocompatibility of different chemically-modified surfaces. Polyethylene terephthalate (PET), with surface modifications using differentpolysaccharides and their derivatives, were chosen because of their promising biocompatible properties and numerous potential biomedical applications.Methods: A modified hemoglobin-free method was used to determine the antithrombogenicity of the modified PET surfaces (4). The method was optimized for shaking rate, the addition of buffer, and blood temperature to decrease measuring errors. Five differently-modified PET surfaces were analyzed: chemically pre-treated PET and PET treated with chitosan, fucoidan, sulphated chitosan and heparin. Glass was used as a standard thrombogenic surface.Results: The results showed that a lower shaking rate, the addition of buffer, and blood cooling prior to measurement significantly decreased the standard deviation of the measurement results by a total of about 89 %.Conclusions: We believe this optimized hemoglobinfree method is suitable for distinguishing between chemically and structurally-different surfaces, such as glass and PET. The differences between PET surfaces coated with different polysaccharides were, however, less pronounced.