Chemical Design and Synthesis of Functionalized Probes for Imaging and Treating Tumor Hypoxia

Hypoxia development in tumor is closely associated with its increased aggressiveness and strong resistance to therapy, leading to the poor prognosis in several cancer types. Clinically, invasive oxygen microelectrode and high dosage radiotherapy are often utilized to accurately detect and effectively fight hypoxia. Recently, however, there has been a surge of interdisciplinary research aiming at developing functional molecules and nanomaterials that can be used to noninvasively image and efficiently treat hypoxic tumors. In this review, we will provide an overview of the reports published to date on the imaging and therapy of hypoxic tumors. First, we will present the design concepts and engineering of various hypoxia-responsive probes that can be applied to image hypoxia noninvasively, in an order of fluorescent imaging, positron emission tomography, magnetic resonance imaging, and photoacoustic imaging. Then, we will summarize the up-to-date functional nanomaterials which can be used for the effective treatments of tumor hypoxia. The well-established chemical functions of these elaborately designed nanostructures will enable clinicians to adopt specific treatment concepts by overcoming or even utilizing hypoxia. Finally, challenges and future perspectives facing the researchers in the field will be discussed.