Yeast-based assays chemical methods

Historically, assessment of thiamine status was by animal bioassay (the correction of bradycardia in thiamine-deficient rats) and later by microbiological assays using the fungus Phycomyces hlakesleeanus, yeast fermentation, or bacteria of the Staphylococcus, Streptococcus, or Lactobacillus species. Some bacterial microbiological assays are still in use in the food industry. Early chemical methods were often based upon the production of a fluorophore, thiochrome, when thiamine is oxidized with ferricyanide in alkaline solution, a property that is used in some modern chromatographic methods. 

Formerly, myo-inositol analysis was by microbiological method only, based on growth or certain yeasts. Later, a time-consuming chemical method became available. Today, microbiologic and chemical assays are giving way to chromatographic methods and enzyme assays. 

Li and Harrison carried out the first cell assay in microchannels [2]. This seminal work made use of electrokinetically driven flow (electroosmosis and electrophoresis) to transport bacteria, yeast, and mammalian cells in channels and to implement low-volume chemical lysis (cell death). This theme of microfluidics-based cell transport, sorting, and lysis has continued to be a popular application, as well as related work in using microfluidics to culture cells and to pattern them into structures. The utility of these methods is acknowledged (and that they are featured in several good reviews [1] and other entries in the encyclopedia) but focuses here on describing microfluidics-based cell assays that fit the definition described above - application of a stimulus and measurement of a response. 

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