Thrombin inactivation on surfaces with covalently bonded heparin

Area of Science:

• Biomaterials Science
• Biochemistry
• Hematology

Background:

• Heparin's anticoagulant properties are crucial in biomedical applications.
• Understanding heparin-surface interactions with coagulation factors is essential for device development.

Purpose of the Study:

• To investigate the interaction between immobilized heparin fragments, thrombin, and antithrombin III (AT).
• To determine the thrombin binding capacity and inhibitory potential of heparin-coated surfaces.
• To elucidate the mechanism of thrombin inhibition on heparinized surfaces.

Main Methods:

• Covalent end-point attachment of porcine heparin fragments (8000 Daltons) to polyethylene.
• Adsorption of heparin surfaces with albumin, AT, or plasma.
• Exposure to thrombin and subsequent analysis of solution and surface-bound thrombin activity.
• Investigation of thrombin inhibition by AT and plasma on loaded surfaces.

Main Results:

• Heparin surfaces demonstrated a high capacity for binding thrombin.
• The thrombin inhibitory capacity of high-affinity heparin fragments was found to be limited.
• Surface-bound thrombin was rapidly inhibited by antithrombin III (AT) or plasma.
• Dilutions of AT or plasma affected the inhibition rate but not the overall inhibition capacity.

Conclusions:

• Immobilized heparin effectively binds thrombin, but AT is required for its inhibition.
• Antithrombin III binds to high-affinity heparin sites, facilitating thrombin migration and inhibition.
• The heparin surface facilitates a catalytic-like inhibition process, allowing for repeated thrombin inactivation.