Two-faced behavior of amidated single-walled carbon nanotubes in terms of platelet function

János Fent, Péter Bihari, Susan Lakatos

Department of Pathophysiology, Laboratory Institute for Health Protection, Medical Centre of Hungarian Defense Forces
H-1134, Róbert Károly krt. 44, Budapest, Hungary

Previously we demonstrated that single-walled carbon nanotubes pristine or surface modified induce surface expression of the platelet activation marker (p-selectin, CD62P). Furthermore pristine, pegylated, carboxylated but not amidated single-walled carbon nanotubes induce platelet aggregation.
In platelet aggregates, platelets are cross-linked with fibrinogen. Prerequisite of formation of platelet aggregates is the activation of fibrinogen receptor (CD41). The activated form of fibrinogen receptor can be detected by PAC-1 antibody. We measured the PAC-1 binding of platelets in the presence of pristine, pegylated, carboxylated and amidated single-walled carbon nanotubes. All these samples induce PAC-1 binding on platelets indicating activation of fibrinogen receptor. To explain the lack of aggregation in the presence of amidated single-walled carbon nanotubes in spite of the activation of fibrinogen receptor, we assume that amidated SWCNTs in contrast to the other single-walled carbon nanotubes derivatives activate the fibrinogen receptor (CD41) only partially resulting in a “metastable” conformation with perfect epitopes for PAC-1 antibody binding with no fibrinogen binding ability. This “metastable” conformation of the fibrinogen receptor can be converted by collagen into its completely active form with perfect fibrinogen binding ability.  Further experiments are needed to clarify the mechanism of various single-walled carbon nanotubes induced platelet aggregation.

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