Viability of Saccharomyces cerevisiae incorporated within silica and polysaccharide hosts monitored via time-resolved fluorescence

The viability of Saccharomyces cerevisiae in biocompatible polymers under different growth conditions and studied using time-resolved fluorescence techniques is presented. Two fluorophores, the viscosity sensitive probe 4-(4-(dimethylamino) styryl)-N-methyl-pyridiniumiodine (DASPMI) and the yeast viability stain 2-chloro-4-(2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene)-1-phenylquinolinium iodide (FUN-1) are used to elucidate information on the incorporated yeast cell viability. Variations in cell viscosity, which are indicative of the cell state, were obtained using DASPMI. Prior to observing FUN-1 in yeast cells using fluorescence lifetime imaging, its photophysics in solution and heterogeneous media were investigated. Time-resolved emission spectra were measured and analysed to associate lifetimes to the spectral emission. Preliminary results show that monitoring the fluorescence lifetime of FUN-1 may give a useful insight into cellular metabolism. The results indicate that both fluorophores may be used to monitor the entrapped yeast cell viability, which is important for in vitro studies and applications, such as that in the biofuel industry, where Saccharomyces cerevisiae are required to remain active in high ethanol environments.