Squaraine Rotaxanes: Superior Substitutes for Cy-5 in Molecular Probes for Near-Infrared Fluorescence Cell Imaging

It's hip to be square: Squaraine rotaxanes have very similar photophysical properties to the commonly used Cy‐5 fluorophore, but are substantially more photostable and resist self‐quenching upon aggregation. Molecular probes containing squaraine rotaxanes (see structure) are shown to be versatile, high‐performance NIR fluorescence stains for in vitro fluorescence imaging of cells (middle) and in vivo whole‐body imaging of living mice (right).