Platelet adhesion on collagen surface: Effect of tocopherols, CEHCs and leptin and studies in microfluidic chamber

Platelet thrombus formation plays an important role in the initiation of many adverse cardiovascular events. Oxidative stress due to the release of oxidants by dysfunctional endothelial cells, smooth muscle cells and macrophages is one of the major factors contributing to vascular injury. alpha-tocopherol (alphaT), potent form of vitamin E, has been shown to possess anti-oxidant, anti-inflammatory and anti-aggregatory properties which are known to reduce cardiovascular risk. However, recent clinical trials have shown otherwise leading to an increased focus on gamma-tocopherol (gammaT), a homologue of alphaT, which also possesses anti-oxidant and anti-inflammatory properties. We studied the direct effect of tocopherols and their metabolites (CEHCs) on platelet function in an in vitro thrombosis model, a parallel plate flow chamber with collagen as thrombogenic surface at arterial (1000 s-1) and venous (100 s-1) shear rates. Our study suggests that gammaT and CEHCs inhibit platelet function on collagen surface where as alphaT does not. This in vitro thrombosis model (parallel plate flow chamber - 6000 mum X 125 mum) requires large quantities of blood. Hence, to reduce the quantity of blood required for an experiment we fabricated a micro channel of dimensions (500 mum X 50 mum), characterized the velocity and shear rate profiles using analytical and experimental methods, assembled the microfluidic chamber and successfully demonstrated that the performance of micro fluidic flow chamber in studying platelet function on collagen surface is similar to that in a parallel plate flow chamber. Hence, further studies using gammaT as anti-platelet agent can be done in microfluidic flow chamber using blood from small animals (rats, mice and cats) in vitro which will not be possible otherwise.