Figure 1: Autoregulation of heparin release from thrombin-sensitive starPEG-heparin hydrogels.

(a) Thrombin generation from prothrombin, as caused by various different activation schemes associated with the exposure of blood to foreign materials, carries the risk of subsequent thrombus formation. (b) As a selective protease, thrombin cleaves the peptide NH₂-Gly-Gly-(D)Phe-Pip-Arg-Ser-Trp-Gly-Cys-Gly-CONH₂ of the linker unit in the biohybrid starPEG-heparin materials between arginine and serine. Through this, heparin becomes released with kinetics that depend on the degree of crosslinking. (c) Released heparin catalyses the complexation of thrombin with its plasma-based inhibitor, antithrombin, resulting in the inactivation of thrombin. (d) Removal of thrombin from the system according to (c) terminates gel degradation and further heparin release.