Improving fluorescent probes

Cell imaging is one important tool to verify protein expression, localization and interaction in living cells. Several probes are now available to specifically colour cells, but intracellular retention is a problem for an high number of them. It’s great challenge to improve intracellular retention and also a great deal because improving intracellular retention means also improve the sensitivity of fluorescent detection.

Calcein, a fluorescein derivative, contains two imino- diacetic acid groups which are responsible for the optimal intracellular retention. Researchers of the University of Tokyo synthesized membrane- permeant derivatives of fluorescein containing either one or two imino- diacetic acid group and decided that two groups, as are present in calcein, are optimal for improving intracellular retention.

They designed novel fluorescent probes for imaging highly reactive oxygen species and nitric oxide. With these new probes they visualized low levels of target proteins in living cells over a relatively long period of time, which it’s not possible to monitor with traditional probes. This chemical approach to prevent cellular leakage should be broadly applied for all probes fluorescein- based as well as on other kind of scaffolds and could be considered a general strategy to increase the sensitivity in living cells.