The SPECTRAmax GEMINI XS Microplate Spectrofluorometer from Molecular Devices is a microplate reader capable of detecting signal from either fluorescence or luminescence based assays. I have been using the Molecular Devices SPECTRAmax GEMINI XS for the last 6 months, mostly in time-resolved fluorescence, to do enzymatic activity assays. This device has all the features of a standard microplate reader, such as temperature control and shaker, and its sensitivity allowed me to obtain precise and reproducible measurements even if I was dealing with low enzymatic activities.
Perhaps the most important feature of the SPECTRAmax GEMINI XS is that it uses two monochromators, instead of filters, to select the desired wavelengths. This allows the reader to be set in 1-nm increments, as opposed to the 25-nm increments typical of filters, over an excitation/emission range of 250 to 850 nm. The bandwidth for both the excitation and emission monochromators is 9 nm. The combination of setting the best possible wavelength and having a relatively tight bandwidth results in good sensitivity and specificity for any given probe. This also means that you can always choose the best excitation/emission wavelength pair for the fluorochrome of your choice. It is worth noting that the SPECTRAmax GEMINI XS can read both luminescence and fluorescence, the latter as an end-point, in a time-resolved fashion, or by scanning the spectra. The instrument is managed by SOFTmax PRO Software that is available for either the Mac or PC.
The fact that this instrument can be used for both fluorescence and luminescence based assays means that it is very versatile. This feature, as well as the design for multi-well plate tray, makes the SPECTRAmax GEMINI XS a valuable tool for a wide variety of applications: from ELISA to enzymatic assays, from reporter-gene activity measurements to cell survival/death assays. It also has a user-friendly interface – most of the settings can be changed by clicking on the intuitive icons on the machines screen. And this instrument seems to be designed for the benchtop – while it is slightly larger than some other microplate readers, it is not oversized.
The SOFTmax PRO Software that is sold with the spectrofluorometer is neither better nor worse than any other software of this kind. It is worth saying, however, that I could not find any specific defects so far. The files can be easily exported (in Excel format, for example) and the SOFTmax PRO Software directly performs a good number of easily programmable calculations.
The bottom line is that I am enthusiastic about the SPECTRAmax GEMINI XS Microplate Spectrofluorometer. I have not had a single problem with this machine: it is versatile, powerful, reliable and easy to use. Because of this, I recommend it to anyone planning on buying a microplate spectrofluorometer.
Dario Coletti, PhD
Mount Sinai School of Medicine, New York