Platelet Adhesion and Aggregation Dynamics over Collagen- and VWF-coated Surfaces: Insights from Dissipative Particle Dynamics Simulations and Microfluidic Experiments.

Platelet adhesion and aggregation at sites of vascular injury play a critical role in both physiological hemostasis and pathological thrombosis. Platelets rely on their surface receptors to form bonds with von Willebrand factor (VWF) and exposed subendothelial collagen to initiate the clotting process. Clot formation is a complex, multistep phenomenon involving mechanical and biochemical signaling that activates key surface receptors and drives morphological changes to form aggregates. Here, we perform dissipative particle dynamics (DPD) simulations in combination with experiments using collagen- and VWF-coated microfluidic channels perfused with human blood to investigate platelet adhesion and aggregation mechanisms under physiological flow conditions. We use a viscoelastic spring-dashpot system to model platelet-platelet and platelet-coated surface interactions and introduce a probabilistic approach to capture platelet attachment or detachment on collagen- and VWF-coated surfaces. We quantitatively compare our numerical simulation with experimental results and explain the observed dynamics. Our simulation results show scattered multilayer clots over collagen-coated surfaces, and single-layer, isolated platelet adhesion on VWF-coated surfaces, corroborating experimental observations. The platelet-covered area over collagen-coated surfaces monotonically increases over time, whereas it reaches a plateau after a period of perfusion on VWF-coated surfaces.