Activatable Small Molecule Probes for Photoacoustic Imaging: Dyes and Applications

Abstract

Photoacoustic imaging (PAI) is a non-invasive modality for molecular imaging and on the way to become a routine clinical diagnostic tool. The advantage of PAI over many other currently used modalities is its ability to potentially image in vivo a variety of enzymatic and physiological processes as well as metabolites in real time at high tissue depths. For this purpose, photoacoustic signal generating chromophores, which have the ability to change their signal characteristics upon reaction to their environments or trapping reactive species, are important. This review article provides an overview of the concepts for activateable small molecule probes for photoacoustic imaging, highlights the requirements on structural and optical properties, and describes their responses to the selective triggers.

Optical imaging of in vivo adoptive T‐cell therapy: State of the art and challenges

“…The fluorescence emission wavelengths of these dyes cover the wavelength ranges of visible light (400-600 nm) and NIR-II [43]. Compared with endogenous bioluminescence imaging probes, small-molecule fluorescent probes have the advantages of a low molecular weight, low toxicity, and high fluorescence quantum yields [42]. They have been used in preclinical studies for labeling and in vivo visualization of ACT immune cells, macrophages, and dendritic cells [44].…”

“…Small‐molecule dyes are important reagents in fluorescence imaging of ACT immune cells. Various small‐molecule fluorescent probes have been developed, and some of them have been commercialized, including fluorescein 5‐isothiocyanate and cyanine [42]. The fluorescence emission wavelengths of these dyes cover the wavelength ranges of visible light (400–600 nm) and NIR‐II [43].…”

Environment-Sensitive Fluorescent Probe Enables Assessment of Anaplastic Lymphoma Kinase Activity in Nonsmall Cell Lung Cancer

“…To date, various fluorescent probes have been described, however, the one with "turn-on" switch mechanism is of particular interest due to its high efficiency and low background signals. 29,30 For example, environment-sensitive fluorophores [e.g., 4-sulfonamidebenzoxadiazole (SBD) 31 have unique emission properties that are highly sensitive to the immediate environment, thereby showing "turn-on" properties. 32 Specifically, the environmentsensitive probes usually show weak fluorescence in the polar and protic environment, while they can be activated when in hydrophobic surroundings.…”

“…To address these limitations, small-molecule probes can be alternatives to interrogate ALK activity, mechanism of action, and distribution in (path)­physiological conditions. , Since ALK-TKIs are tailored drugs that specifically target the adenosine 5′-triphosphate (ATP) site of the ALK tyrosine kinase domain and prevent its phosphorylation, we envisage that an ALK-TKI-based probe can mimic the action of ALK-TKI and determine the activity levels of ALK. To date, various fluorescent probes have been described, however, the one with “turn-on” switch mechanism is of particular interest due to its high efficiency and low background signals. , For example, environment-sensitive fluorophores [e.g., 4-sulfonamidebenzoxadiazole (SBD) have unique emission properties that are highly sensitive to the immediate environment, thereby showing “turn-on” properties .…”

“…To address these limitations, small-molecule probes can be alternatives to interrogate ALK activity, mechanism of action, and distribution in (path)­physiological conditions. , Since ALK-TKIs are tailored drugs that specifically target the adenosine 5′-triphosphate (ATP) site of the ALK tyrosine kinase domain and prevent its phosphorylation, we envisage that an ALK-TKI-based probe can mimic the action of ALK-TKI and determine the activity levels of ALK. To date, various fluorescent probes have been described, however, the one with “turn-on” switch mechanism is of particular interest due to its high efficiency and low background signals. , For example, environment-sensitive fluorophores [e.g., 4-sulfonamidebenzoxadiazole (SBD) have unique emission properties that are highly sensitive to the immediate environment, thereby showing “turn-on” properties . Specifically, the environment-sensitive probes usually show weak fluorescence in the polar and protic environment, while they can be activated when in hydrophobic surroundings.…”