Development of an Acoustofluidic Platform for Rapid Basophil Enrichment

Basophils have been implicated as key cells in allergic disease, but their study has been hampered by prolonged and complex procedures for purification from whole blood. In seeking to develop an acoustofluidic platform for the diagnosis of allergic reactions, we have developed a microfluidic method and compared it to the most commonly used experimental procedures for the efficient enrichment of basophil populations while retaining their functional characteristics. Blood was drawn from the median cubital vein of healthy donors and subjected to ammonium chloride or saponin treatment or hypotonic shock for red blood cell lysis. Basophils were purified either by acoustofluidic separation or by magnetic activated cell sorting (MACS). A multi-layered acoustofluidic device was manufactured by micromilling, and used to enrich basophils by acoustic radiation forces under continuous flow conditions. Flow rate was controlled by a syringe pump, and varied between 30 - 60 ml/h. Relative numbers of basophils were assessed by measuring histamine concentration by specific immunoassay in cell lysates diluted in distilled water. Basophil activation was investigated by measuring histamine release. Saponin treatment impaired basophil function and resulted in high spontaneous release of mediators. Basophil function was better preserved when erythrocytes were removed by hypotonic shock or ammonium chloride cell lysis. Preliminary data using the acoustofluidic platform indicates methods to isolate basophils in as little as 10 minutes, which is much faster and efficient than with currently available methods. Improved procedures for basophil purification should facilitate their application in in vitro diagnostics.