such as chemotherapy and radiotherapy, have prompted the exploration and development of next-generation high-performance modalities. Recently, phototheranostic strategies, such as photodynamic therapy (PDT) [1,2] and photothermal therapy (PTT), [3][4][5] that provide means for both diagnosis and treatment, have attracted increasing attention owing to their minimal invasiveness, spatiotemporal precision, reproducible activity, negligible acquisition of drug resistance, and phototoxicity confinement to the target region. Despite significant advances in these novel theranostic approaches, most such systems suffer complications and issues involving the requirement of multiple components, nonbiodegradable materials, and time-consuming and complex syntheses. [6][7][8][9] In addition, the low concentration of reagent loading can lead to poor therapeutic outcomes, and the potential toxicity of system complexes may hamper the clinical translation of these "all-inone" systems. [10][11][12][13][14] Accordingly, the development of efficient theranostic systems with enhanced biomarker protein activation Theranostic systems that permit both diagnosis and treatment in vivo are highly appealing means by which to meet the demands of precision medicine. However, most such systems remain subject to issues related to complex molecular design and synthesis, potential toxicity, and possible photoactivity changes. Herein, a novel supramolecular theranostic strategy involving biomarker protein activation (BPA) and a host-guest strategy is proposed. To exemplify BPA, a facile "one-for-all" nanotheranostic agent for both albumin detection and cancer treatment is demonstrated, which utilizes a nanoparticulate heavy-atom-free BODIPY dye derivative (B4 NPs). The fluorescence and photoactivity of BODIPY dyes are completely suppressed by aggregation-induced self-quenching in the nanoparticulate state. However, a Balb/c nude mouse model is used to confirm that following the disassembly of injected B4 NPs, BODIPY specifically binds albumin in vivo, accompanied by significantly enhanced biocompatibility and photothermal conversion efficiency. More importantly, this supramolecular host-guest BPA strategy enables the resultant nanoplatform to act as a facile and efficient strategy for photodynamic and photothermal immunotherapy.