Activatable Small Molecule Probes for Photoacoustic Imaging: Dyes and Applications

Photoacoustic imaging (PAI) is a non-invasive modality for molecular imaging and is on the way to becoming 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 envi-ronments or trapping reactive species, are important. This review article provides an overview of the concepts for activatable small molecule probes for photoacoustic imag-ing, highlights the requirements for structural and optical properties, and describes their responses to the selective triggers.