The quest to globally scan cellular functions started in the 1970s with the invention of 2-D gel electrophoresis, which allowed researchers to measure levels of most proteins in the cell and track how these levels change under different growth conditions. More modern proteomic tools extend the concept. The next step came with DNA microarrays that measure thousands of genes that are turned on or off.
The newest tools for global cell scanning are Phenotypic MicroArrays (PMs) that simultaneously evaluate thousands of biological properties, such as pathways in living cells. Proteomics, DNA microarrays, and PMs all complement each other and give a panoramic view of what is going on in a cell, says Barry Bochner, Ph.D., founder and CSO of Biolog (www.biolog. com) in Hayward, CA.
PMs bridge the gap between molecular changes and actual biological outcomes. Just as DNA microarrays measure the levels of thousands of genes at once, PMs test 2,000 physiological responses simultaneously.
While a graduate student at the University of Michigan in the 1970s, Dr. Bochner discovered that some redox chemical reactions measure cellular respiration with simple color changes. Those reactions launched Biologs patented technology platform.
Dr. Bochner reasoned that when people are ill, a physician obtains a blood sample and runs a battery of tests to scan the health of vital organs. I wanted to run a cell through a battery of tests and scan its physiology quickly, explains Dr. Bochner, who founded the company in 1984.
Many cellular pathways are linked to cell respiration, which forms the basis of the PM technology. Cellular respiration is detected quantitatively by redox measurements. A color forms when a dye in the assay is reduced. The dye chemistry is simple, and the color change is nonreversible.
The PM assays are dried on the bottom of microwell plates. Each well contains a different assay designed to test a unique cell function, including cell surface binding and transport functions, biosynthesis of small molecules or macromolecules, formation of cellular structures, stress and repair processes, cellular respiratory functions, and the metabolism of carbon, nitrogen, phosphorus, and sulfur.
A researcher adds a cell suspension into each microwell, which solubilizes the chemicals and sets off the redox reactions. Cellular responses representing hundreds of cellular properties are measured, continuously monitored, and recorded.
Biologs PMs are unlike anything else out there, states Dr. Bochner. The technology falls into the broad category of cell-based assays. However, typical cell-based assays measure only one trait, whereas we measure 400 to 2,000 traits of cells, Dr. Bochner claims.