© 2003 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume IIA: Biocompatibility, Landes Bioscience, Georgetown, TX, 2003

15.5.5.2 Mechanical Interactions with Platelets

Platelets (aka. thrombocytes) are more fragile than red cells and can break more easily in a wound, physically bursting open and spilling out their contents into the local tissue (i.e., degranulation). The material within triggers a complex chain of biochemical events involving numerous proteins that results in soluble fibrinogen being converted into insoluble fibrin, which condenses out in the form of a fibrous scaffolding upon which a clot can be built (Section 15.2.5). The primary danger of unintended thrombocytolysis normally lies at the arterial wall, which may be layered with rough-textured cholesterol and lipid plaques, and where shear forces are highest. Fortunately, hundreds of platelets may break nearby without triggering a local thrombogenic event (Section 15.2.5). The human body normally has ~2.1 trillion platelets in circulation or pooled (Section 8.5.1), each with a ~10 day lifespan [4095], so the natural platelet destruction (and production) rate is ~2.4 x 10⁶ sec^-1, almost as many as for red blood cells.

Possible pathological mechanical interactions uniquely between medical nanorobots and platelets may include nanorobotic mechanical thrombocytolysis (Section 15.5.5.2.1) and the disruption of platelet aggregation (Section 15.5.5.2.2). Nanorobots might also interfere with phagocytosis by platelets [775, 868, 875, 881-883, 885], or with the motility of platelets [1969, 4096-4099] (e.g., 0.1-0.5 micron/sec across HEMA surfaces [1969]), two relatively minor functions of the platelet which will not be discussed further here.

Last updated on 30 April 2004