Programmed sequential nanostructural conversion at nano-bio interface for synergistic cancer phototheranostics.

Prodrugs usually convert into active compounds within cells via endogenous or external stimuli to improve the diagnostic accuracy and therapeutic efficacy, but this singular release profile often fails to meet the multifunctional needs of cancer therapeutics. In this study we proposed a strategy of "nanostructural conversion at nano-bio interface" and constructed a small-molecule nanoprodrug (APO-S-Cy7-TCF) for multifunctional anti-tumor phototheranostics. Upon exposure to redox biomolecules (ROS/GSH) in tumor microenvironment, the pristine nanostructure of APO-S-Cy7-TCF disassembled, releasing Cy7-TCF-OH and APO that interacted with heat shock proteins to initiate apoptosis. Cy7-TCF-OH could then re-assemble into smaller nanosaucers with enhanced photothermal properties and self-augmented ROS-generating capacity, enabling synergistic phototherapy for tumor ablation. In particular, Cy7-TCF-OH nanosaucers were long retained in residual tumors and could further interact with albumin to form smaller Cy7-TCF-OH@albumin nanocomposites that time-dependently activated near-infrared fluorescence for prognostic assessment. Using these biomolecule-derived elements to program supramolecular sequential structural conversions at nano-bio interface, our study establishes a new way for small-molecule-based multifunctional phototheranostic platform.