Fluorescent proteins: A journey from the cell to extreme environments in material science.

This review presents the progression from the use of fluorescent proteins (FPs) and chromoproteins as bioimaging labels and sensors to the strategic engineering of their properties for robust functionality in synthetic and non-biological environments. Specifically, engineered variants of the small ultra-red fluorescent protein (smURFP) were developed and optimized for optoacoustic imaging through structure-guided mutagenesis. Reversibly switchable genetically encoded indicators were also created to enhance bioimaging capabilities. To extend the applicability of such proteins to material science and enable their function in everyday applications-such as environmental sensors, encoders, or color components in textiles and electronics-their inherent stability limitations were addressed. For this purpose, supramolecular stabilization strategies, including genetically encoded macro-oligomerization techniques, were explored. These methods effectively enhanced the resilience of FPs under chemically challenging conditions, without compromising their photophysical properties. Finally, the exploration of circularly polarized luminescence (CPL) from FPs is discussed, and their potential as CPL emitters suitable for sustainable photonic applications is identified. Overall, the transformative potential of engineered FPs as essential components for applications beyond bioimaging is emphasized.