Microfluidic assay for precise measurements of mouse, rat, and human neutrophil chemotaxis in whole-blood droplets

Abstract

Animal models of human disease differ in innate immune responses to stress, pathogens, or injury. Precise neutrophil phenotype measurements could facilitate interspecies comparisons. However, such phenotype comparisons could not be performed accurately with the use of current assays, as they require the separation of neutrophils from blood using species-specific protocols, and they introduce distinct artifacts. Here, we report a microfluidic technology that enables robust characterization of neutrophil migratory phenotypes in a manner independent of the donor species and performed directly in a droplet of whole blood. The assay relies on the particular ability of neutrophils to deform actively during chemotaxis through microscale channels that block the advance of other blood cells. Neutrophil migration is measured directly in blood, in the presence of other blood cells and serum factors. Our measurements reveal important differences among migration counts, velocity, and directionality among neutrophils from 2 common mouse strains, rats, and humans.

Neutrophil chemotaxis and transcriptomics in term and preterm neonates

“…1) [5, 6]. In brief, the filters block the dispersion of erythrocytes and monocytes into the migration channel, whereas actively migrating neutrophils can migrate through without a decrease in speed.…”

“…Recent advances have provided a unique opportunity to study low birth weight preterm population using whole blood assays in the first few days of life. In the past, such studies would have been impossible to perform because of the required large blood volumes, which have now been overcome with the use of novel microfluidic approaches [5]. These approaches circumvent the need for neutrophil purification, thus allowing the investigation of neonatal neutrophils from a single 400 microliter unprocessed whole blood sample.…”

Microfluidic devices for neutrophil chemotaxis studies

“…To further simplify the experimental process and reduce the damage caused to the neutrophils by the purification process, some researchers aim to integrate separating units and chemotaxis study units in the same chip [26,27,48,[84][85][86][87][88][89][90][91][92][93][94]. Therefore, the integrated microfluidic devices for neutrophil chemotaxis analysis directly from whole blood have been becoming a growing trend.…”

Neutrophil Chemotaxis in One Droplet of Blood Using Microfluidic Assays

“…Microfluidic assays also enable precise mechanical confinement of the migrating cells, which resemble the interstitial spaces present in vivo in tissues [14]. Moreover, multifunctional microfluidic assays allow for seamless integration of sample preparation with downstream chemotaxis assay on a single chip [15–22]. A majority of these chips accomplish the on-chip blood purification first, and then probe neutrophil chemotaxis [15, 19–21].…”