Optoacoustic tomography (photoacoustic tomography) is an emerging imaging technology displaying great potential for medical diagnosis and preclinical research. Rationally designing activatable optoacoustic probes capable of diagnosing diseases and locating their foci can bring into full play the role of optoacoustic tomography (OAT) as a promising noninvasive imaging modality. Here we report two xanthene-based optoacoustic probes (C1X-OR1 and C2X-OR2) for temporospatial imaging of hepatic alkaline phosphatase (or β-galactosidase) for evaluating and locating drug-induced liver injury (or metastatic tumor). The probes rapidly respond to the disease-specific biomarkers by displaying red-shifted NIR absorption bands and generate prominent optoacoustic signals. Using multispectral optoacoustic tomography (MSOT), we can precisely localize the focus of drug-induced liver injury in mice using C1X-OR1, and the metastatic tumors using C2X-OR2. This work suggests that the activatable optoacoustic chromophores may potentially be applied for diagnosing and localizing disease foci, especially smaller and deeper ones.

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A FRET ratiometric fluorescent sensor was developed for detecting H(2)S in aqueous media and serum, as well as inside live cells. For this sensor, carbon dots serve as the energy donor and also the anchoring site for the probe. This sensor is highly selective and sensitive with a detection limit of 10 nM which is the lowest among fluorescent H(2)S sensors.

An activatable nanoprobe for imaging breast cancer metastases through near infrared‐I (NIR‐I)/NIR‐II fluorescence imaging and multispectral optoacoustic tomography (MSOT) imaging was designed. With a dihydroxanthene moiety serving as the electron donor, quinolinium as the electron acceptor and nitrobenzyloxydiphenylamino as the recognition element, the probe can specifically respond to nitroreductase and transform into an activated D‐π‐A structure with a NIR emission band extending beyond 900 nm. The activated nanoprobe exhibits NIR emission enhanced by aggregation‐induced emission (AIE) and produces strong optoacoustic signal. The nanoprobe was used to detect and image metastases from the orthotopic breast tumors to lymph nodes and then to lung in two breast cancer mouse models. Moreover, the nanoprobe can monitor the treatment efficacy during chemotherapeutic course through fluorescence and MSOT imaging.