Characterization of the mechanisms governing heparin-bovine serum albumin complex interactions and associated anticoagulant activity

Heparin's interactions with body proteins affect its bioavailability and anticoagulant efficacy, resulting in variable clinical outcomes. This study focused on enhancing the specificity of heparin-BSA (bovine serum albumin) interactions to stabilize anticoagulant effects. We examined the impact of heparin-BSA complexes on coagulation indices such as activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and activated clotting time (ACT). The enoxaparin sodium-BSA complex demonstrated enhanced anticoagulant activity at an optimized 1 × 10^-3 mol/L concentration. Fluorescence spectroscopy revealed a single binding site between heparin and BSA, with binding affinities ranging from 3.9 × 10³ to 7.2 × 10⁴ L/mol, where enoxaparin sodium showed the highest affinity. The interactions were predominantly non-covalent, driven by van der Waals forces and hydrogen bonding, as indicated by negative ΔH° and ΔS° values. Advanced imaging techniques suggested structural changes in BSA and its microenvironment post-binding. Scanning electron microscopy confirmed tighter encapsulation of enoxaparin within BSA. Molecular docking identified the primary heparin disaccharide unit, △UA,2S-GlcNS,6S (IS), binding at Sudlow sites I and II, enhancing understanding of the interaction mechanisms. These findings provide insights into designing more effective anticoagulant therapies. This study elucidates the interaction mechanism between heparin and BSA, thereby providing a theoretical foundation for efforts to devise new anticoagulant drugs.