Kinetic assembly tuning NIR-II cyanine aggregated states: Remarkable photothermal-mediated sustained retention in orthotopic hepatoma.

Conventional photothermal nanotheranostics suffer from fluorescence quenching caused by energy transfer between imaging and photothermal agents. Although unimolecular nanotheranostic systems circumvents the issue, it remains inadequate for generating substantial fluorescence and photothermal effects simultaneously under single-wavelength excitation. Herein, we develop a molecular aggregation engineering strategy by spectrally decoupling the monomeric state for fluorescence from the aggregated state for photothermal conversion within a unimolecular dye nanoplatform, enabling simultaneous theragnostic. We introduce a kinetic assembly method to encapsulate both NIR-II dyes (DQP) and protein in polymers, precisely regulating the aggregated state. Moreover, strong π-π stacking of the aggregated state of DQP drives photothermal effect, which functions as a thermal stimuli trigger for temperature-responsive DQPNPs to achieve charge reduction and size enlargement, promoting intracellular tumor retention, which ultimately improves fluorescence intensity and enhances photothermal efficacy. Such a molecular aggregation engineering strategy ensures precise tuning of the aggregated state of dyes, which realizes a breakthrough for balance NIR-II fluorescence with photothermal effect, supporting personalized and long-term cancer therapy.