Inner salt-shaped small molecular photosensitizer with extremely enhanced two-photon absorption for mitochondrial-targeted photodynamic therapy

Herein, we experimentally and theoretically demonstrate an unprecedentedly enhanced two-photon absorption in a small organic molecule by a simple introduction of an inner salt-shaped structure. Moreover, such an inner salt-shaped small molecule also exhibits superior singlet oxygen quantum yield and fascinating structure-inherent mitochondrial-targeting ability for highly efficient two-photon photodynamic therapy via a mitochondrial apoptosis pathway.