Blood compatibility of biomaterials made of recombinant spider silk

Abstract: Native spider silk is an attractive lightweight natural polymeric material with a unique combination of strength, extendibility and flexibility. Synthetic, recombinant spider silk is an attractive biomaterial with several possible fields of application. When a foreign material is introduced to blood, this can for example cause unwanted coagulation and complement activation. The aim of this study was to investigate if coatings of heparin or albumin could improve the blood compatibility of films of recombinant spider silk and to develop an initial method to do so. Hypothetically, objects like pacemakers, stents and dental implants could be covered with spider silk films of high blood compatibility to reduce potentially harmful foreign body reactions caused by the immune defense. Increased blood compatibility would likely lead to improvements for both the individual patients and the society thanks to reduced load on healthcare institutions. Our objective was to assess the blood compatibility of both functionalized and non-functionalized recombinant spider silk by evaluating coagulation and activation of the complement system of the immune defense. Coagulation was evaluated visually on glass slides and complement activation was analyzed by measuring the concentration of the complement system mediator C3a in blood samples that had been exposed to the different materials. This study introduces a non-toxic and easy performed method of improving the blood compatibility of recombinant spider silk films by adding a heparin coating. Heparin coated surfaces had statistically significantly higher blood compatibility than uncoated surfaces. The effects of albumin coating of films were less clear compared to the results of heparin coated films. Complement activation could not be evaluated because of high activation in all samples prior contact with the materials that were included in the study.