sDarken: New developments of a genetically encoded serotonin sensor

For decades, the molecule Serotonin is of interest not only but also because of its various functions within the brain. While the direct measurement of serotonin release in the brain is challenging, new genetically encoded sensors for serotonin opened new possibilities to measure release of serotonin in a high temporal and spatial resolution. Here we report the newest developments of one of these genetically encoded sensors for serotonin, called sDarken.Based on the initial published sDarken (Kubitschke et al. 2023) we now utilized mutagenesis, to develop a new color shifted variant which shows a shifted absorption and emission spectrum. This version increases the use of the sDarken family, by enabling experiments, where light in the range of the emission or excitation wavelength of GFP is needed to observe other fluorescent proteins or to activate optogenetic tools.Additionally, we show that variants of sDarken are able to measure serotonin dynamics using fluorescence lifetime imaging microscopy (FLIM), which is unaffected by expression levels or photo bleaching effects.