LiGa₅O₈:Cr-based theranostic nanoparticles for imaging-guided X-ray induced photodynamic therapy of deep-seated tumors

Using X-rays as the irradiation source, a photodynamic therapy process can be initiated in deep tissues. This technology, referred to as X-ray induced PDT, or X-PDT, holds great potential to treat tumors in internal organs. To this end, one question is how to navigate the treatment of tumors with accuracy using external irradiation. Herein we address this issue using a novel LiGa₅O₈:Cr (LGO:Cr)-based nanoscintillator, which emits persistent, near-infrared X-ray luminescence. This permits deep-tissue optical imaging that can be employed to guide irradiation. Specifically, we encapsulated LGO:Cr nanoparticles and a photosensitizer, 2,3-naphthalocyanine, into mesoporous silica nanoparticles. The nanoparticles were conjugated with cetuximab and systemically injected into H1299 orthotopic non-small cell lung cancer tumor models. The nanoconjugates can efficiently accumulate in tumors in the lungs, confirmed by monitoring the X-ray luminescence from LGO:Cr. Guided by the imaging, external irradiation was applied, leading to efficient tumor suppression while minimally affecting normal tissues. To the best of our knowledge, the present study is the first to demonstrate, with systematically injected nanoparticles, that X-PDT can suppress the growth of deep-seated tumors. The imaging guidance is also new to X-PDT, and is significant to the further transformation of the technology.