Polyoxomolybdate (POM) nanoclusters with radiosensitizing and scintillating properties for low dose X-ray inducible radiation-radiodynamic therapy

In order to overcome the weak penetration of near infrared (NIR) light in photodynamic therapy (PDT), X-ray radiation (X-RT) with high deep tissue penetration could be used as a therapeutic option to completely destroy tumors. Herein, polyoxomolybdate nanoclusters (POMo NCs) with rose Bengal (RB) loading, are functionalized with chitosan (CS) and polyethylene glycol (PEG) for X-ray inducible radiation and radiodynamic therapy (X-RRDT). Our obtained POMo NCs demonstrate a strawberry shape containing 163 Mo (Mo)3 units of three edge sharing MoO6 octahedra and connecting to the central PO4 octahedron. Under low dose X-ray radiation, the communal effect of radiosensitization and scintillation of POMo NCs along with RB, can decrease the side effects of RT and enhance both RT and PDT efficiency. This is because the POMo NCs can not only augment RT efficacy by producing auger electrons which directly provoke DNA damage, but also enhance PDT efficacy by converting high energy X-rays into light to stimulate RB to generate singlet oxygen (O-1(2)). In vivo results show that X-RRDT using POMo NCs significantly inhibits tumor growth under low dose X-ray radiation. More importantly, the as-made PEGylated POMo NCs cause no obvious side-effects to the major normal organs through histological examination. This work describes a simple strategy to design effective X-RRDT agents with multiple properties including X-ray radiosensitization, X-ray scintillation and photosensitization for X-RRDT under low dose X-ray irradiation. Our developed strategy will further promote the cancer therapeutic efficiency under low dose X-ray radiation, and bring hope for clinical cancer treatment.