title: A simple method for activating the platelets used in microfluidic platelet aggregation tests: Stirring-induced platelet activation.
abstract: High-shear stimulation is well known as one of the key factors affecting platelet activation and aggregation, which can lead to the formation of a thrombus. In one of our previous studies, we introduced migration distance-based platelet function analysis in a microfluidic system. In this study, we set out to examine the effects of stirring on shear-induced platelet activation and aggregation in a chamber system by using a rotating stirrer. We found that the rotating stirrer caused not only rotational shear flow but also a strong radial secondary flow. The latter flow led to efficient mixing in the chamber. Moreover, the rotational flow led to the generation of shear stress, the magnitude of which can be controlled to activate the platelets. Activated platelets tend to aggregate themselves. The maximum platelet aggregation was observed at a critical shear rate of 3100 s-1, regardless of the stirrer shape. Furthermore, the time taken to attain maximum aggregation was significantly shortened when using a wide stirrer (30 s) instead of a narrow one (180 s). When using a flat stirrer, the non-uniform shear field in the chamber system was resolved with the radial secondary flow-induced mixing; thus, most of the platelets were homogenously activated. The stirring-induced platelet activation mechanism was experimentally confirmed in a microfluidic system for a platelet aggregation test while monitoring the migration distance until the microfluidic channel is occluded. Our findings indicate that the present system, consisting of a rotating stirrer and a confined chamber, provides effective shear stimulation for activating platelets and inducing platelet aggregates.
authors.affiliation: School of Mechanical Engineering, Korea University , Seoul 136-701, South Korea.
authors.forename: Hoyoon
authors.initials: H
authors.lastname: Lee
authors.affiliation: School of Mechanical Engineering, Korea University , Seoul 136-701, South Korea.
authors.forename: Gyehyu
authors.initials: G
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, College of Medicine, Korea University Guro Hospital , Seoul 152-703, South Korea.
authors.forename: Chaeseung
authors.initials: C
authors.lastname: Lim
authors.affiliation: Department of Internal Medicine, College of Medicine, Yonsei University Gangnam Severance Hospital , Seoul 135-720, South Korea.
authors.forename: ByoungKwon
authors.initials: B
authors.lastname: Lee
authors.affiliation: School of Mechanical Engineering, Korea University , Seoul 136-701, South Korea.
authors.forename: Sehyun
authors.initials: S
authors.lastname: Shin