Controllable synthesis and biomedical applications of bismuth-based nanospheres: enhanced photothermal therapy and CT imaging efficiency

The advancement and utilization of nano-scale biomaterials in the diagnosis and treatment of tumors have been notable over the last few decades, primarily owing to their appealing characteristics such as small particle size, adjustable properties, and remarkable biocompatibility. The creation of nanomaterials possessing versatility and a customizable nature, consequently, holds great promise for advancing healthcare and improving patient outcomes. Here, we report the controllable synthesis of monodisperse bismuth-based (Bi₂S₃, Bi, and Bi₂O₃) nanoparticles with uniform spherical morphology and size distribution, and evaluate their potential for CT imaging and photothermal therapy applications. Monodisperse Bi₂S₃ nanospheres were initially synthesized in aqueous solution using a low-temperature precipitation method. Subsequently, Bi and Bi₂O₃ nanospheres were prepared through the NaBH₄ reduction and the H₂O₂ oxidation of the as-synthesized Bi₂S₃ templates, respectively. Photothermal conversion and CT imaging characterizations confirm the superiority of Bi nanospheres over Bi₂S₃ and Bi₂O₃ nanospheres in terms of their excellent photothermal conversion efficiency (∼40.10%) and CT contrast efficiency (∼34.32 HU mL mg^-1). Furthermore, it is demonstrated that Bi nanospheres exhibit significant advantages in CT imaging and photothermal effects by using the glioma mouse model, notably achieving a tumor area temperature increase to 53.6 °C after near-infrared laser irradiation. This work furnishes theoretical and experimental evidence for bismuth-based nanomaterials as valuable tools in various biomedical applications.