Shear-induced platelet aggregation: 3D-grayscale microfluidics for repeatable and localized occlusive thrombosis.

Atherothrombosis leads to complications of myocardial infarction and stroke as a result of shear-induced platelet aggregation (SIPA). Clinicians and researchers may benefit from diagnostic and benchtop microfluidic assays that assess the thrombotic activity of an individual. Currently, there are several different proposed point-of-care diagnostics and microfluidic thrombosis assays with different design parameters and end points. The microfluidic geometry, surface coatings, and anticoagulation may strongly influence the precision of these assays. Variability in selected end points also persists, leading to ambiguous results. This study aims to assess the effects of three physiologically relevant extrinsic design factors on the variability of a single end point to provide a quantified rationale for design parameter and end-point standardization. Using a design of experiments approach, we show that the methods of channel fabrication and collagen surface coating significantly impact the variability of occlusion time from porcine whole blood, while anticoagulant selection between heparin and citrate did not significantly impact the variability. No factor was determined to significantly impact the mean occlusion time within the assay. Occlusive thrombus was found to consistently form in the first third (333 μm) of the high shear zone and not in the shear gradient regions. The selection of these factors in the design of point-of-care diagnostics and experimental SIPA assays may lead to increased precision and specificity in high shear thrombosis studies.