A microfluidic platform for chemical stimulation and real time analysis of catecholamine secretion from neuroendocrine cells.

Release of neurotransmitters and hormones by calcium-regulated exocytosis is a fundamental cellular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. As such, there is significant interest in targeting neurosecretion for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistic insight coupled with increased experimental throughput. Here, we report a simple, inexpensive, reusable, microfluidic device designed to analyze catecholamine secretion from small populations of adrenal chromaffin cells in real time, an important neuroendocrine component of the sympathetic nervous system and versatile neurosecretory model.

Electrochemical detection of catecholamine release using planar iridium oxide electrodes in nanoliter microfluidic cell culture volumes.

Release of neurotransmitters and hormones by calcium regulated exocytosis is a fundamental cellular/molecular process that is disrupted in a variety of psychiatric, neurological, and endocrine disorders. Therefore, this area represents a relevant target for drug and therapeutic development, efforts that will be aided by novel analytical tools and devices that provide mechanistically rich data with increased throughput. Toward this goal, we have electrochemically deposited iridium oxide (IrOx) films onto planar thin film platinum electrodes (20 μm×300 μm) and utilized these for quantitative detection of catecholamine release from adrenal chromaffin cells trapped in a microfluidic network.

Enzyme-coated microelectrodes to monitor lactate production in a nanoliter microfluidic cell culture device.

Monitoring the degree of anaerobic respiration of cells in high density microscale culture systems is an enabling key technology and essential for cell-based biosensors. We have fabricated and incorporated miniature amperometric lactate sensing electrodes with working areas from 3 to 5×10(-2) mm2 into a microfluidic-based microscale cell culture system to measure the lactate production rate of fibroblasts in nanoliter volumes. Planar thin film platinum electrode arrays on glass substrates were spin coated with lactate oxidase and a protective Nafion layer.

Enzyme electrodes to monitor glucose consumption of single cardiac myocytes in sub-nanoliter volumes.

Monitoring the metabolic activity of cells in automated culture systems is one of the key features of micro-total-analysis-systems. We have developed a microfluidic device that allows us to trap single cardiac myocytes (SCMs) in sub-nanoliter volumes and incorporate amperometric glucose-sensing electrodes with working areas of 0.002 mm(2) to measure the glucose consumption of SCM.

On-chip acidification rate measurements from single cardiac cells confined in sub-nanoliter volumes.

The metabolic activity of cells can be monitored by measuring the pH in the extracellular environment. Microfabrication and microfluidic technologies allow the sensor size and the extracellular volumes to be comparable to single cells. A glass substrate with thin film pH sensitive IrO( x ) electrodes was sealed to a replica-molded polydimethylsiloxane (PDMS) microfluidic network with integrated valves.

Differential pH measurements of metabolic cellular activity in nl culture volumes using microfabricated iridium oxide electrodes.

In this paper we describe a new approach to measure pH differences in microfluidic devices and demonstrated acidification rate measurements in on-chip cell culture systems with nl wells. We use two miniaturized identical iridium oxide (IrOx) thin film electrodes (20 micromx400 microm), one as a quasi-reference electrode, the other as a sensing electrode, placed in two confluent compartments on chip. The IrOx electrodes were deposited onto microfabricated platinum (Pt) electrodes simultaneously using electrodeposition.

Thin-film IrOx pH microelectrode for microfluidic-based microsystems.

Microsensors are valuable tools to monitor cell metabolism in cell culture volumes. The present research describes the fabrication and characterization of on-chip thin-film iridium oxide pH microsensors with dimensions of 20 microm x 20 microm and 20 microm x 40 microm suitable to be incorporated into nl volumes. IrOx thin films were formed on platinum microelectrodes by electrochemical deposition in galvanostatic mode.