A Water-Soluble Photothermal Host-Guest Complex with pH-Sensitive Superlarge Redshift Absorption

Near infrared (NIR) absorbers for photothermal therapy are arousing great attention in tumor diagnosis and ablation. However, the inevitably wide distribution of NIR absorbers generally causes equal photothermal injuries to tumor tissues and healthy tissues. An initiative targeting strategy based on pH-sensitive redshift absorption has been proposed for NIR-induced hyperthermia only in tumor tissue. In this work, we develop a NIR absorber with superlarge redshift from the middle visible light region to NIR light region once the pH value drops. We also determined a supramolecular route to improve the water solubility as well as the thermal stability of the NIR absorber in aqueous solutions. Animal experiments reveal that the tumor microenvironment can trigger selective NIR light absorbing, which is thus responsible for the tumor-selective hyperthermia and ablation. Based on easy preparation, low cytotoxicity, and excellent tumor selectivity, this supramolecular complex is a reliable photothermal agent for intelligent tumor-specific diagnosis and treatment.