| Abstract
| - A miniaturized analysis system for the study of living cellsand biochemical reactions in microdroplets was developed. The technique utilizes an in-house-developed piezoelectric flow-through droplet dispenser for precisereagent supply and an ultrasonic levitator for contactlesssample handling. A few-cell study was performed withliving primary adipocytes. Droplets (500 nL) containing3−15 individual cells were acoustically levitated. Theaddition of β-adrenergic agonists into the levitated dropletusing the droplet dispenser stimulated adipocyte lipolysis,leading to free fatty acid release and a consequent pHdecrease of the surrounding buffer. The addition of insulinantagonized 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 continuously monitored by fluorescence imaging detection. Animage analysis computer program was employed to calculate the droplet intensities. To counteract dropletevaporation, found to affect the fluorescence intensities,a separate dispenser was used to continually add water,thus keeping the droplet volume constant.
|
