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Reactive species (RS) play important roles in vital physiological processes. However, excessive RS damages cells and may contribute to the onset of several diseases. Therefore, there is a clear demand for sensitive probes that precisely monitor cellular RS with a high spatio-temporal resolution to understand the multifaceted role of RS in redox biology. Genetically encoded redox probes derived from green fluorescent protein (GFP), such as roGFP2 and Grx1-roGFP2, are promising tools for quantitative and dynamic observation of RS with spatio-temporal resolution. However, the excitation light used to read-out the fluorescence of these proteins can lead to irreversible modification of cell constituents, which may result in either immediate or long-lasting alterations of molecular functions.

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