Airborne Cell Analysis

摘要

A miniaturized analysis system for the study of living cells- and biochemical reactions in microdroplets was devel-oped. The technique utilizes an in-house-developed pi-ezoelectric flow-through droplet dispenser for precise reagent supply and an ultrasonic levitator for contactless saniple handling. A few-cell study was performed with living primary adipocytes. Droplets (500 nL) containing 3—15 individual cells were acoustically levitated. The addition of fi-adrenergic agonists into the levitated droplet using the droplet dispenser stimulated adipocyte lipolysis, leading to free fatty acid release and a consequent pH decrease of the surrounding buffer. The addition of insulin antagonized lipolysis and hence also the decrease in pH. The changes in pH, i.e., the cell response in the droplet, were followed using a pH-dependent fluorophore continu-ously monitored by fluorescence imaging detection. An image analysis computer program was employed to cal-culate the droplet intensities. To counteract droplet evaporation, found to affect the fluorescence intensities, a separate dispenser was used to continually add water, thus keeping the droplet volume constant.