Abstract
Covalent cross-linking is a common strategy to improve the mechanical properties of biological polymers. The most prominent field of application of such materials is in medicine, for example, in the form of bioprinting, drug delivery, and wound sealants. One biological polymer of particular interest is the blood clotting protein fibrinogen. In the natural process, fibrinogen polymerizes to fibrous hydrogel fibrin. Although the material shows great potential, its costs are very high due to the required enzyme thrombin. Recently, we introduced several approaches to trigger a thrombin-free fibrillogenesis of fibrinogen to a fibrin-like material. Inspired by the natural pathway of blood clotting in which covalent cross-linking stabilizes the clot, this "pseudofibrin" is now developed even further by covalently cross-linking the fibers. In particular, the effect of inexpensive glutaraldehyde on fiber morphology, rheological properties, and irreversible gel dissolution is investigated. Additionally, new insights into the reaction kinetics between fibrinogen and glutaraldehyde are gained. It could be shown that the fibrous structure of pseudofibrin can be retained during cross-linking and that glutaraldehyde significantly improves rheological properties of the hydrogels. Even more important, cross-linking with glutaraldehyde can prevent dissolution of the gels at elevated temperatures.