The most common method for measuring cell proliferation (see profile, page 27) monitors the metabolism of a yellow tetrazolium salt (MTT) to blue-colored formazan. Unfortunately this is a time-consuming endpoint assay, precluding kinetic studies. Bedford, Mass.-based BD Biosciences-Discovery Labware has developed a novel detection system that solves this problem. The BD Oxygen Biosensor uses an oxygen-sensitive fluorescent dye (tris-1,7-diphenyl-1, 10-phenanthroline ruthenium (II) chloride) embedded in a gas-permeable silicone polymer matrix affixed to a standard Falcon® multiwell plate. The fluorescence of the dye is quenched by oxygen. When cells grow, oxygen is depleted and fluorescence increases. Conversely, fluorescence decreases when cells die, making the assay fully reversible. Because the dye material is built into the plate, time-consuming addition steps are eliminated.

Katherine Tsaioun, a scientist at GPC-Biotech in Cambridge, Mass., has used the plates for antibacterial whole cell screening. According to Tsaioun, one of the strains of bacteria tested...

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