Platelet repellent properties of hydrogel coatings on polyurethane coated glass surfaces

• Published in: The Thoracic and Cardiovascular Surgeon
• Main Authors: Baghai, M., Tamura, N., Heilmann, C., Henze, M., Prucker, O., Zieger, B., Rühe, J., Goto, S., Beyersdorf, F.
• Format: Conference Proceeding
• Language: English
• Published: 10.02.2014
• ISSN: 0171-6425; 1439-1902
• DOI: 10.1055/s-0034-1367369

Objectives: Thromboembolism is a severe complication in patients with ventricular assist devices (VAD). Interactions of platelets with the artificial surface and pathological blood flow conditions may contribute to thrombus formation. Previous studies postulated that strongly swellable polymers, called hydrogels, are protein and cell repellent. This bio-inert behavior makes hydrogel coatings promising candidates as blood-compatible materials. However, an analysis of these polymer layers under whole blood conditions and shear stress are rare. In our study we systematically tested structurally similar hydrogel coatings belonging to the poly(N-alkyl acrylamide) class under whole blood perfusion and shear stress. The structural variations of the polymers lead to differences in their hydrophilicity and swelling behavior. Methods: Glass slides were coated with medical grade polyurethane (PU). Subsequently, each of the PU-coated slides was coated with a different polymer. In a first experimental series, the depositied polymers differed in their swelling factor (1.0-5.5) for structural reasons. In a second series, one representative poly(N-alkylacrylamide) was further studied by varying its degree of crosslinking (1%-10%). The slides were perfused with human blood containing fluoresceinated platelets at a shear rate of 1500 s −1 for three minutes for all experiments. Non-coated and PU coated glass slides served as a reference for thrombogenic surfaces. To quantify platelet adhesion, the overall percentage of surface coverage was calculated and statistically compared to the surface coverage on PU coatings. Results: We detected severe platelet aggregation and thrombus formation on non-coated and PU coated glass slides. There was no visible platelet adhesion on polymers with a swelling factor of above about 1.5 to 2 (p < 0.001). However, a lower swelling factor resulted in severe platelet adhesion (p = 0.06). Neither very low (1%) nor medium (2.5%, 5%) or very high degrees of crosslinking (7.5%, 10%) seemed to reverse the platelet repellent properties of the chosen polymer (p < 0.001). Conclusion: A swelling factor down to 1.5-2.5 seems to be sufficient to effectively prevent platelet adhesion under the described conditions. Moreover, different degrees of crosslinking ranging from 1% to 10% do not reverse platelet repellent properties of one representative polymer.