Thermo-responsive Ionizable Xanthone Bolaamphiphiles for Dynamic Self-Assembly into Nanovesicles Enabling Enhanced Intracellular Drug Release and Tumor Growth Inhibition

Stimuli-responsive supramolecular nanocarriers capable of controlled drug release have emerged as promising alternatives to conventional chemotherapy; however, the development of structurally defined small-molecule systems exhibiting thermo-responsive behavior within biologically relevant temperature ranges remains challenging. Herein, we report a series of ionizable xanthone-based bolaamphiphiles (X1-X3) engineered to undergo temperature-triggered self-assembly in aqueous media. Systematic modulation of oxyethylene-chain density revealed that X3 exhibits a sharp and reversible lower critical solution temperature (LCST) transition within the physiological temperature window (35-40 °C), leading to the formation of stable nanovesicular assemblies. The resulting X3 nanovesicles accommodate doxorubicin (DOX) with an encapsulation efficiency of ∼25% and a drug-loading content of 11% while maintaining good colloidal stability under physiologically relevant conditions. X3-DOX nanovesicles exhibit progressive thermoresponsive drug release near physiological temperature, which is further enhanced under mild hyperthermia, together with an additional acid-responsive release behavior associated with protonation of the piperazine units (apparent pKa ≈ 4.5). Cellular studies performed in 4T1 breast cancer and A549 lung cancer cells demonstrated enhanced intracellular drug accumulation, superior cytotoxicity, and effective suppression of multicellular tumor spheroids compared with free DOX. Furthermore, the nanoformulation exhibited excellent hemocompatibility, favorable biodistribution characteristics, and efficient systemic clearance. In a 4T1 tumor-bearing mouse model, X3-DOX induced remarkable tumor-growth inhibition with minimal systemic toxicity. These findings establish thermo-responsive xanthone-based nanovesicles as a versatile supramolecular platform for controlled anticancer drug delivery and provide a molecularly defined strategy for developing stimuli-responsive nanomedicines.