Molecular imaging and disease theranostics with renal-clearable optical agents

Optical imaging in disease diagnosis and treatment benefits from high spatiotemporal resolution and the availability of numerous optical agents. However, many optical imaging probes are cleared by the reticuloendothelial system, which can lead to probe accumulation in the liver and spleen and hence organ toxicity. By contrast, renal-clearable optical agents (RCOAs) are rapidly excreted from the body via the kidneys, undergoing minimal metabolism. In this Review, we discuss the design principles of RCOAs, with a focus on imaging and disease theranostics (the combination of diagnosis and therapy). Renal excretion of RCOAs makes them intrinsically suitable for targeted kidney imaging, including passive monitoring of the glomerular filtration rate and detection of early kidney injury biomarkers. The pharmacokinetics of RCOAs can further be tailored to prolong their circulation in the blood, allowing deep tumour penetration and high-contrast tumour imaging. Finally, we discuss intraoperative image-guided surgery and optical urinalysis, and suggest future applications of RCOAs.