1. State Key Laboratory of Molecular Vaccinology and Molecular Diagnostics & Center for Molecular Imaging and Translational Medicine, School of Public Health, Xiamen University, Xiamen 361102, China
2. Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, United States
3. Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305, United States
Photodynamic therapy (PDT) has shown great effectiveness in oncotherapy but has not been implemented in broad clinical applications because the limited penetration depth of the light used has been unable to reach deep-seated tumors. However, X-rays have been widely used in the clinical field for imaging and radiation therapy due to their excellent tissue penetration depth. Recently, X-rays have been established as an ideal excitation source for PDT, which holds great promise for breaking the depth limitation of traditional PDT for treatment of deep-seated tumors. This review aims to provide an overview of nanoscintillator-mediated X-ray induced PDT (X-PDT) including the concept, the design considerations of nanosensitizers for X-PDT, the modelling of nanosensitizer energy deposition, the putative mechanism by which X-PDT kills cells, and the prospects of future directions. We attempt to summarize the main developments that have occurred over the past decades. Possibilities and challenges for the clinical translation of X-PDT are also discussed.
Keywords: radiation therapy, X-ray excited optical luminescence, X-ray induced photodynamic therapy, nanosensitizers, deep-seated tumors