Measurement of lipolysis products secreted by 3T3-L1 adipocytes using microfluidics.

Glass microfluidic devices have been fabricated to monitor the secretion of glycerol or fatty acids from cultured murine 3T3-L1 adipocytes. In the current studies, adipocytes are perfused in a reversibly sealed cell chamber, and secreted products are analyzed by enzyme assay on either a single- or dual-chip device. The analysis of glycerol employed the use of a dual-chip system, which used separate chips for cell perfusion and sample analysis. An improved single-chip device integrated the cell perfusion chamber and analysis component on one platform. The performance of this device was demonstrated by the analysis of fatty acids but could also be applied to analysis of glycerol or other chemicals. The single-chip system required fewer cells and lower flow rates and provided improved temporal response. In both systems, cells were perfused with buffer to monitor basal response followed by lipolysis stimulation with the β-adrenergic agonist isoproterenol. Measured basal glycerol concentration from 50,000 cells was 28 μM, and when stimulated, a spike threefold higher than basal concentration was detected followed by a continuous release 40% above basal levels. Fatty acid basal concentration was 24 μM, measured from 6200 cells, and isoproterenol stimulation resulted in a constant elevated concentration sevenfold higher than basal levels.