Thiazolyl Blue is a membrane-permeable yellow dye that is reduced by mitochondrial reductases in living cells to form the dark blue product. The net positive charge on Thiazolyl Blue appears to be the predominant factor involved in their cellular uptake via the plasma membrane potential. Thiazolyl Blue is used as a direct indicator of cytotoxicity (such as for screening cancer drugs), proliferation and apoptosis. Thiazolyl Blue is also an electron acceptor used for studying NADP-dependent dehydrogenases. Thiazolyl Blue reduction is associated not only with mitochondria, but also with the cytoplasm and with nonmitochondrial membranes including the endosome/lysosome compartment and the plasma membrane. Biological Applications: cell viability assay; microbial growth assays; DNA quantification assays; tissue viability assays; detecting enzymes; measuring membrane potential; treating Alzheimer’s disease, asthma, cancer. Because Thiazolyl Blue forms an insoluble formazan it has usually been applied in endpoint assays.

Evans Blue (EBD) is an azo dye which has a very high affinity for serum albumin. It can be useful in physiology in estimating the proportion of body water contained in blood plasma. Evans Blue Dye is widely used to study blood vessel and cellular membrane permeability as it is non-toxic, it can be administered as an intravital dye and it binds to serum albumin – using this as its transporter molecule. The EBD–albumin conjugate (EBA) can be: (i) identified macroscopically by the striking blue colour within tissue; (ii) observed by red auto-fluorescence in tissue sections examined by fluorescence microscopy; and (iii) assessed and quantified by spectrophotometry for serum samples, or homogenised tissue. has recently been utilised in mdx mice to identify permeable skeletal myofibres that have become damaged as a result of muscular dystrophy. EBD has the potential to be a useful vital stain of myofibre permeability in other models of skeletal muscle injury and membrane-associated fragility. Evans Blue is a potent inhibitor of L-glutamate uptake into synaptic vesicles. It also inhibits AMPA and kainate receptor-mediated currents (IC50 values are 220 and 150 nM respectively). P2X-selective purinoceptor antagonist.