Strain release in organic photonic nanoparticles for protease sensing.

Proteases are overexpressed in most cancers and proteolytic activity has been shown to be a viable marker for cancer imaging in vivo. Herein, we describe the synthesis of luminescence-quenched shell cross-linked nanoparticles as photonic nanoprobes for protease sensing. Protease sensing scheme is based on a "turn-on" mechanism where the protease cleaves peptide cross-linkers of the fluorescence-quenched shell cross-linked NP (OFF state) leading to a highly emissive non-cross linked NP (ON state). The cross-linked particles can be strained by exposure to a good solvent and proteolysis allows for particle expansion (swelling) and a recovery of the luminescence.