Unstimulated and Thrombin-Stimulated Platelets Binding to Immobilized Fibrinogen and Fibrin on Polystyrene Supports

Abstract

The binding of unstimulated and thrombin-stimulated platelets was studied with immobilized fibrinogen and fibrin on polystyrene. The amount of fibrinogen bound to the polystyrene support was 2 μg/tube, which represents 2.35 μg/cm². Immobilized fibrin was obtained by adding thrombin (5 nM) to immobilized fibrinogen. The number of unstimulated ¹¹¹ln-platelets bound to immobilized fibrinogen and fibrin was similar (3.2 ± 0.3 × 10⁶ and 3.1 ± 0.4 × 10⁶ platelets/μg fibrin-(ogen), respectively). The platelet binding steadily increased. In the first 2 min, the binding rate was 0.23 × 10⁶ platelets/μg fibrinogen/min. The binding rate then increased rapidly and saturation was reached at 10 min. The extent of the adhesion of resting platelets to immobilized fibrinogen is about one half that of the same platelets stimulated with thrombin. In thrombin-stimulated ¹¹¹In-platelets, the binding to immobilized fibrinogen and fibrin is time dependent, and saturation is reached at 5 min. The early rate of thrombin-stimulated platelet binding to fibrinogen is about twice that of binding to fibrin (1.25 and 0.74 × 10⁶ platelets/μg fibrin(ogen)/min, respectively). In saturation conditions, 1 μg fibrinogen binds 5.7 ± 0.6 × 10⁶ thrombin-stimulated platelets and 1 μg fibrin binds 4.6 ± 0.5 × 10⁶ thrombin-stimulated platelets. Our results indicate that the rate of platelet aggregation is faster than fibrin formation, and the rate of fibrinogen-platelet binding is faster than that of fibrin-platelet binding. Therefore, after thrombin stimulation, the binding of platelets to fibrin must be secondary to the binding of platelets to fibrinogen.

Targeted drug delivery to circulating tumor cells via platelet membrane-functionalized particles

“…To investigate the capability of PMDV-coated Si particles to target fibrin in a microvessel under flow conditions, a previous protocol for preparing fibrin-immobilized polystyrene beads was adopted to prepare an in vitro thrombosis model in microtubes [28]. Briefly, after immobilizing 1mg/ml fibrinogen on the microtube surface, thrombin was added to form fibrin.…”

“…Then, ultracentrifugation with a discontinuous sucrose gradient (5%, 40%, 55%) was performed to separate membrane vesicles from free proteins, intact platelets, and high-density granules. Previous studies have examined the electrostatically mediated deposition and fusion of negatively charged liposomes on cationic particle supports [27, 28]. In light of the negative surface charge of PMDVs, Si particles with diameters close to platelet size were functionalized with (3-Aminopropyl) triethoxysilane (APTES) to produce a positive charge on the surface.…”

The effect of thrombin on the dynamic exchange between intraplatelet and extraplatelet fibrinogen

“…125 I-labelled fibrinogen preparation. The recently obtained fibrinogen was 125 I-radiolabelled by the modified lactoperoxidase method (Martínez-Sales et al, 1995). 2-4 mg of fibrinogen in 0 .…”

The Platelet Integrin αIIbβ3 Differentially Interacts with Fibrin Versus Fibrinogen

“…Thus, much less is known about the former interaction. However, differences in the ability of ␣IIb␤3 antagonists to inhibit clot contraction versus platelet aggregation suggest that the interactions of ␣IIb␤3 with fibrinogen and fibrin are different (13)(14)(15)(16)(17)(18). The sites at which ␣IIb␤3 interacts with fibrin and fibrinogen also appear to be substantially different.…”