The cytosensor microphysiometer: biological applications of silicon technology

Abstract

A silicon-based device, dubbed a microphysiometer, can be used to detect and monitor the response of cells to a variety of chemical substances, especially ligands for specific plasma membrane receptors. The microphysiometer measures the rate of proton excretion from 10(4) to 10(6) cells. This article gives an overview of experiments currently being carried out with this instrument with emphasis on receptors with seven transmembrane helices and tyrosine kinase receptors. As a scientific instrument, the microphysiometer can be thought of as serving two distinct functions. In terms of detecting specific molecules, selected biological cells in this instrument serve as detectors and amplifiers. The microphysiometer can also investigate cell function and biochemistry. A major application of this instrument may prove to be screening for new receptor ligands. In this respect, the microphysiometer appears to offer significant advantages over other techniques.

Mouse β3a‐ and β3b‐adrenoceptors expressed in Chinese hamster ovary cells display identical pharmacology but utilize distinct signalling pathways

“…Energy production and intracellular metabolic processes lead to the production and excretion of protons. The EAR is detected as a change in potential across a silicon light-addressable sensor during periods of cessation of¯ow of medium (McConnell et al, 1992). Cells were seeded into 12 mm transwell inserts (3 mm pore size) (Costar) at 5610 5 cells per cup in media lacking FBS, and left to adhere overnight.…”

Antimalarial drugs disrupt ion homeostasis in malarial parasites

“…This instrument continuously monitors the extracellular pH surrounding cells in culture, and reports cell activation by measuring the increases in extracellular acidification rate occurring in response to agonist stimulation (McConnell et al 1992). The isolated parasites was resuspended in DMEM (GIBCO) plus 30% agarose to improve parasites adherence onto the polycarbonate membrane of the transwell capsules (3 µm pore size) at a density of 2.5 × 10 5 cells.…”

A New Action of Parathyroid Hormone

“…Cells acidify the environment via ion exchangers and pumps such as the Na ϩ /H ϩ antiporter and the H ϩ -ATPase and by transporting metabolites such as lactic acid across the plasma membrane (19). Several seven-transmembrane G protein-coupled receptors such as adrenergic, dopamine, and muscarinic receptors elicit concentration-dependent increases in ECAR in response to agonist binding (17,18,20); however, the physiological significance of receptor-mediated stimulation of extracellular acidification in these cell systems is not clear. In contrast, acidification of the bone microenvironment is known to be functionally important in skeletal metabolism and Ca 2ϩ /P i homeostasis (13).…”

“…Microphysiometry is a novel method for monitoring cellular metabolism (16) and has been effectively adapted to monitor acid secretion and metabolic rates in small populations of cultured cells in real time (17,18). Because local pH homeostasis is physiologically important in mineral ion metabolism, and PTH-stimulated bone resorption has been linked to acid production by osteoclasts (13), we utilized microphysiometry to monitor the effect of PTH on extracellular acidification in osteoblasts, the primary target cell for PTH in bone.…”