Development of Multianalyte Microphysiometry for the Study of Islets and Toxins

Abstract

Multianalyte microphysiometry is a real-time method for evaluating cellular metabolism using the multianalyte microphysiometer (MAMP), an instrument capable of measuring extracellular changes in the flux rates of oxygen, glucose, lactate, and acid. The MAMP has been utilized to study two different systems: the evaluation of islet metabolism and the effects of toxins on neuronal metabolism. A multichamber multipotentiostat was developed to enable measurement of multiple analytes in up to eight chambers of cells simultaneously. The MAMP was also modified with the addition of a MWCNT/DHP composite sensor to allow real-time electrochemical detection of insulin, as well as lactate, oxygen, and extracellular acidification. The MAMP was used to study the metabolic response of islets to stimulation with glucose and with potassium. Increases in insulin concentration as large as 100 µM were seen when islets were stimulated with 16.7 mM glucose, with increases also seen in lactate production. This sensitivity was much greater than that measured using perifusion methodology and a similar number of islets. This improvement was due to accumulation of secreted insulin during the stop-flow period and to the confined microfluidic volume of the MAMP. In toxin studies, PC-12 pheochromacytoma cells were treated with cholera toxin, which increases cAMP production. After a single two-minute exposure to 100 nM cholera toxin, there were large increases seen in lactate and extracellular acid production. Oxygen consumption decreased, and no measurable changes were seen in glucose consumption. Treatment of PC-23 cells with H-89, a small molecule that inhibits protein kinase A (PKA) response, lowered the metabolic response to cholera toxin, suggesting that PKA plays a role in the downstream metabolic response to cholera toxin.