Dual Ratiometric Single-Molecule Theranostic Probes for Photothermal Therapy and Real-Time Quantitative Evaluation of Therapeutic Efficacy <i>In Vivo</i>

Tracking the quantitative evaluation of therapeutic efficiency in tumors is essential for the precision management of cancer patients. Theranostic probes, which integrate diagnostic molecular imaging and therapeutic capabilities into a single entity, can be used to monitor the treatment process and reflect the therapeutic effect. However, current theranostic probes lack precise quantitative evaluations <i>in vivo</i> due to the use of single-wavelength imaging during tumor therapy. Here we present a portal library of dual ratiometric single-molecule theranostic probes for precise tumor therapy through photothermal therapy (PTT) and quantitative evaluation of tumor cell death <i>in vivo</i> via ratiometric near-infrared fluorescence (NIRF) and ratiometric photoacoustic (PA) imaging. One optimal single-molecule dye is further modified into an activatable probe (AF-1F-NO₂), whose dual ratiometric NIRF/PA signal and photothermal activity are only activated in the presence of a tumor biomarker (nitroreductase). By eliciting a dual ratiometric response (NIRF/PA: NIRF₈₅₀/NIRF₇₅₀; PA₇₇₀/PA₆₇₀) to tumor hypoxia, the new probe acts as a hypoxia-activated PTT theranostic agent, enabling real-time quantitative evaluation <i>in vivo</i> during PTT. Thus, this study not only presents the first dual ratiometric single-molecule theranostic probe for PTT and real-time quantitative evaluation of therapeutic efficacy <i>in vivo</i>, but also opens up a promising paradigm for engineering other single-molecule dual ratiometric theranostic probes in combination with more therapeutic modalities for precision medicine.