For real-time, live, cell-based experiments like GFP, it is preferable to read from the microplate bottom. Reading from the bottom allows for a lid to be placed on top to prevent cell contamination and liquid evaporation. Most microplate readers use longer, more flexible fiber optics to reach the microplate bottom. Since fiber optics lose light, more signal (and thus sensitivity) is lost when measuring fluorescent proteins from the microplate bottom.
To improve microplate cell-based assays, BMG LABTECH has eliminated the need for fiber optics for bottom reading. Using a system similar to the microscope, the PHERAstar FS incorporates a series of software-controlled, motor-driven mirrors to focus light through a free air optical path directly onto either the top or bottom of the microplate. Moreover, there is no changing or installation of any additional hardware (i.e., optics, apertures, dichroics, filters, or mirrors) when switching between top and bottom reading modes. Thus direct-optic bottom reading is fully integrated into the PHERAstar FS optical system and it completely eliminates the need for fiber optics.
As shown in the accompanied figure, BAE cells tagged with GFP have a three times higher S:B ratio on the PHERAstar FS when compared to a fiber optic bottom reading instrument. This 300% improvement in the assay window allows cell-based assays to be performed on a microplate reader that were not possible before.
Read more about BMG LABTECH’s Direct-Optic Bottom Reading in a recently published article in GEN: http://www.genengnews.com/gen-articles/bottom-reading-of-cell-based-assays/4091/.