Method for Detecting Emission Spectral Change of Bioluminescent Ratiometric Indicators by a Smartphone.

The application of smartphones as detectors is essential to achieve ubiquitous measurement targeting biomolecules. Because bioluminescence (BL), as a tag for a target sample, does not require an excitation light source, it can be combined with a smartphone to constitute a compact and mobile measurement system. A method was recently established to detect the spectral change of ratiometric indicators based on bioluminescence resonance energy transfer with a smartphone camera. For example, it was possible to detect changes in the BL color of the Ca indicator quantitatively and easily calculate the concentration of free Ca by setting appropriate image acquisition conditions in a smartphone application. In this paper, we describe techniques to obtain scientifically relevant and reliable BL data with such a convenient instrument. This protocol expands the potential of the smartphone as a personal imaging device with high mobility that can be used anywhere.