Dual-Mode Imaging Guided Multifunctional Theranosomes with Mitochondria Targeting for Photothermally Controlled and Enhanced Photodynamic Therapy in Vitro and in Vivo

Photodynamic therapy (PDT) is commonly restricted by inefficient tumor selectivity during clinical study. Hence, a mitochondria-targeting multifunctional nanocarrier "theranosome (TNS)" was developed for near-infrared fluorescent (NIRF) imaging and photoacoustic (PA) imaging. What's more, the TNS can also enhance PDT efficacy. In this work, chlorin e6 (Ce6) undertakes reactive oxygen generation and fluorescence emission. Ce6 was quenched when being encapsulated into TNS together with IR780 iodide. When exposed under 808 nm NIR light, IR780 from the TNS can be photobleached; thus, the phototoxicity of Ce6 can be activated. The IR780 induced hyperthermia damaged tumor cells to perform photothermal therapy (PTT) effect. Then lysosomes disruption under PTT facilitated PDT effect induced by Ce6 through enhanced cytoplasmic delivery. Moreover, in vitro subcellular uptake experiments showed that triphenylphosphonium (TPP) group attached to the IR780/Ce6 TNS (ICT) could promote mitochondria targeting capacity. It can lead to PDT induced oxidizing damage to the mitochondria by mitochondrial membrane potential decreasing and cell apoptosis eventually. In in vivo antitumor studies, the TPP/IR780/Ce6 TNS (TICT) substantially repressed tumor growth in nude mice. Besides, we did not find any obvious side effects to normal tissues and organs. The results suggested the TICT conjugate provided a dual NIRF/PA tumor imaging modalities with spatial resolution and superior imaging contrast. This study offered an improved phototherapy for potential theranostic application.