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).