Gadolinium polytungstate nanoclusters: a new theranostic with ultrasmall size and versatile properties for dual-modal MR/CT imaging and photothermal therapy/radiotherapy of cancer

The development of a new generation of nanoscaled theranostics with simple compositions and versatile properties to realize enhanced diagnoses and treatment outcomes and to avoid side effects is highly desirable but remains a great challenge. Here we report a new ultrasmall theranostic based on bovine serum albumin-coated GdW10O36 nanoclusters (GdW10 NCs) as multifunctional theranostics for multifunctional bio-imaging, highly effective in vitro photothermal ablation of cancer cells and in vivo radiotherapy of tumors. The as-synthesized GdW10 NCs afford significantly enhanced computed tomography/magnetic resonance imaging signals and remarkable photothermal therapy (PTT)/radiotherapy therapy (RT) therapeutic effects for tumor treatment. Moreover, toxicity studies confirmed their low toxicity and efficient renal clearance, suggesting their potential for practical applications. These results indicated that the as-prepared GdW10 nanoclusters are promising as multifunctional nanotheranostics for multimodal imaging-guided PTT/RT of tumors. These results also encourage the further exploration of other polyoxometalate-based multifunctional nanotheranostics for cancer diagnoses and therapy. Nanostructures that can diagnose tumours and treat them with laser light and radiotherapy have been developed by researchers in China. ‘Theranostic’ nanoparticles that combine bioimaging with targeted action against cancer cells are often too large to pass safely through the kidney, leading to cytotoxicity issues. To overcome such problems, Zhanjun Gu from the Chinese Academy of Sciences and co-workers synthesized polytungstates nanoclusters containing rare-earth gadolinium ions and coated them with a biocompatible protein film. These water-soluble, sub-5-nanometre particles enhanced magnetic resonance and computed tomography imaging thanks to the gadolinium components. In vivo tests in mice revealed that the nanoclusters localized in tumour microstructures where they could be excited by laser or X-ray beams to damage and repress tumour formation. Afterwards, the nanoparticles were cleared through the kidney harmlessly. In this work, a new theranostics based on GdW10@BSA NCs with ultrasmall size, but versatile properties, were fabricated, which possesses not only significant CT/ MR imaging signal enhancement but also remarkable photothermal therapy (PTT)/radiotherapy (RT) therapeutic effects for tumor. Therefore, our work may open an avenue in developing other POM-based multifunctional nanomedicines with better therapeutic outcome and fewer side effects.