Respirometry measures oxygen consumption in the fluid medium surrounding cells or tissues. Comparison of oxygen consumption rates for different cells and tissues as well as for the same cells and tissues in the presence of different molecular species in the extracellular fluid or inside the cells permits making conclusions regarding the mechanism of cellular respiration, mitochondrial activity or pathology within cells and tissues and, more generally, regarding metabolic dysfunctions associated with many diseases including cancer and neurological diseases.

The fundamental limitation of the currently available technology is that it requires many thousands of cells in the cell culture or tissue to produce sufficient oxygen consumption signal. The resulting measurements provide information about cellular function averaged over relatively large cell populations. However, most cell populations display heterogeneity of cellular behaviors and functions, even within genetically identical populations. Cells of different phenotypes may respond differently to external stimuli and consume oxygen at dramatically different rates than others. Such heterogeneity is a very important property of many tissues and disease types; however, it goes undetected in such averaged signals.

To overcome these limitations Drexel University researchers have designed a respirometry analyzer that measures oxygen consumption of a single cell. It provides for respirometry measurements on individual cells, and can be used with either one or many cells at a time in order to characterize heterogeneity of cellular respiration as well as to obtain average respiration behavior in cell population.

The invention relies on the use of double-barrel pipettes to perfuse individual cells that may be attached to a substrate or naturally distributed on surfaces of tissue samples. The total diameter of the double-barrel pipette should ideally be about the same as the maximum size of an individual cell. Fluid in one barrel is forced out to flow toward the cell, while the fluid in other barrel is suctioned in and away from the cell at the same rate. This way, the double-barrel pipette supplies new oxygen and other molecules to the cell or tissue with one barrel and removes the byproducts of cell’s metabolism with the through the other barrel. By sensing oxygen and possibly other molecules or ions in the incoming and outgoing flows of the fluid, oxygen consumption of an individual cell or a group of cells can be quantified. The same approach can be used to monitor cell’s consumption or production of other molecules.