Engineering biocompatible TeSe_x nano-alloys as a versatile theranostic nanoplatform

Photothermal nanotheranostics, especially in the near infrared II (NIR-II) region, exhibits a great potential in precision and personalized medicine, owing to high tissue penetration of NIR-II light. The NIR-II-photothermal nanoplatforms with high biocompatibility as well as high photothermal effect are urgently needed but rarely reported so far. Te nanomaterials possess high absorbance to NIR-II light but also exhibit high cytotoxicity, impeding their biomedical applications. In this work, the controllable incorporation of biocompatible Se into the lattice of Te nanostructures is proposed to intrinsically tune their inherent cytotoxicity and enhance their biocompatibility, developing TeSe_x nano-alloys as a new kind of theranostic nanoplatforms. We have uncovered that the cytotoxicity of Te nanomaterials primarily derives from irreversible oxidation stress and intracellular imbalance of organization and energy, and can be eliminated by incorporating a moderate proportion of Se (x=0.43). We have also discovered that the as-prepared TeSex nano-alloys have extraordinarily high NIR-II-photothermal conversion efficiency (77.2%), ⁶⁴Cu coordination and computed tomography (CT) contrast capabilities, enabling high-efficacy multimodal photothermal/photoacoustic/positron emission tomography (PET)/CT imaging-guided NIR-II-photothermal therapy of cancer. The proposed nano-alloying strategy provides a new route to improve the biocompatibility of biomedical nanoplatforms and endow them with versatile theranostic functions.