Supramolecular Assembly with Near‐Infrared Emission for Two‐Photon Mitochondrial Targeted Imaging

Two‐photon supramolecular assembly with near‐infrared (NIR) fluorescence emission is constructed from tetraphenylethene derivative possessing methoxyl and vinyl pyridine salt (TPE‐2SP), cucurbit[8]uril (CB[8]), and β‐cyclodextrin modified hyaluronic acid (HA‐CD). The obtained experimental results indicate that the TPE‐2SP exhibits a very weak fluorescence emission at 650 nm, and then complexes with cucurbit[7]uril (CB[7]) to form 1:2 supramolecular pseudorotaxane with an enhanced NIR fluorescence emission at 660 nm. Compared with CB[7], CB[8] can assemble with TPE‐2SP to be two‐axial netlike pseudopolyrotaxane, resulting in close packing to increase TPE‐2SP fluorescence emission with a redshift of 30 nm. Interestingly, TPE‐2SP/CB[8] continues to assemble with cancer cell targeting agent HA‐CD into nanoparticles, leading to assembling‐induced further enhancement of NIR emission. Surprisingly, supramolecular nanoparticles have the two‐photon character, and are successfully applied to mitochondrial targeting imaging. This supramolecular assembly system, with two‐photon absorption and assembly‐induced enhanced NIR luminescence properties, opens new way for biological targeted imaging. Due to host–guest induced emission by cucurbit[8]uril, supramolecular nanosquares display near‐infrared emission in aqueous solution. Further assembling with cancer cell targeting agent, β‐cyclodextrin modified hyaluronic acid (HA‐CD) into supramolecular nanoparticles leads to assembling‐induced enhancement of NIR emission dramatically. Furthermore, supramolecular nanoparticles can be applied for two‐photon mitochondrial targeted NIR imaging.