In situ fiber-optical monitoring of cytosolic calcium in tissue explant   cultures
  We present a fluorescence-lifetime based method for monitoring cell and tissue activity in situ, during cell culturing and in the presence of a strong autofluorescence background. The miniature fiber-optic probes are easily incorporated in the tight space of a cell culture chamber or in an endoscope. As a first application we monitored the cytosolic calcium levels in porcine tracheal explant cultures using the Calcium Green-5N (CG5N) indicator. Despite the simplicity of the optical setup we are able to detect changes of calcium concentration as small as 2.5 nM, with a monitoring time resolution of less than 1 s. 
Manuel Ryser, Lisa K\"unzi, Marianne Geiser, Martin Frenz, Jaro   Ri\v{c}ka
physics.bio-ph physics.chem-ph