Molecular endoperoxides for optical imaging and photodynamic therapy

Molecular endoperoxide (MEPO) structuring with heterocycle peroxide (-O-O-) has shown tremendous promise for diseases diagnosis and treatment. Upon excitation by visible light, X-ray, or ultrasound, the afterglow or chemiluminescence emitted by MEPOs contribute to the development of autofluorescence-free optical imaging modes with ultrahigh signal-to-background ratio. Meanwhile, the reversible process of trapping and releasing of singlet oxygen from heterocycle substrates enables MEPOs to accomplish unconventional photodynamic effect featuring with dark and hypoxia tolerance. This review highlights the recent trends in the development of MEPOs as a powerful tool for optical imaging and photodynamic therapy (PDT). A summary was delivered to clarify the formation, decomposition, classification, and working mechanisms of MEPOs. Design strategies were also introduced with MEPOs towards a broad range of biomedical applications in optical imaging and PDT of different diseases. Lastly, perspectives and challenges for clinical translations were discussed for the direction of next-generation MEPOs.