High Content Evaluation of Shear Dependent Platelet Function in a Microfluidic Flow Assay

The high blood volume requirements and low throughput of conventional flow assays for measuring platelet function are unsuitable for drug screening and clinical applications. In this study, we describe a microfluidic flow assay that uses 50 mu L of whole blood to measure platelet function on similar to 300 micropatterned spots of collagen over a range of physiologic shear rates (50-920 s(-1)). Patterning of collagen thin films (CTF) was achieved using a novel hydrated microcontact stamping method. CTF spots of 20, 50, and 100 mu m were defined on glass substrates and consisted of a dense mat of nanoscale collagen fibers (3.74 +/- A 0.75 nm). We found that a spot size of greater than 20 mu m was necessary to support platelet adhesion under flow, suggesting a threshold injury size is necessary for stable platelet adhesion. Integrating 50 mu m CTF microspots into a multishear microfluidic device yielded a high content assay from which we extracted platelet accumulation metrics (lag time, growth rate, total accumulation) on the spots using Hoffman modulation contrast microscopy. This method has potential broad application in identifying platelet function defects and screening, monitoring, and dosing antiplatelet agents.