Bismuth-based nanosystems for precise tumor theranostics: Recent progress, challenges and perspectives

Precision tumor diagnosis and treatment are constrained by inaccurate early diagnosis, therapeutic resistance, immunosuppressive tumor microenvironments, and toxic side effects of drugs, resulting in unsatisfactory efficacy of monotherapies. Multifunctional nanoplatforms capable of integrating multimodal imaging, synergistic therapy and immune regulation constitute a core research focus in precision oncology. Bi-based nanomaterials exhibit high X-ray attenuation, tunable band structures, excellent photoacoustic/catalytic performance and controllable degradability, rendering them suitable for imaging-guided precision tumor theranostics. This article systematically reviews four categories of Bi-based nanomaterials: elemental/single-phase, heterostructures, core-shell structures, and Bi-based/containing MOFs. We summarize strategies for structural modification and structure-activity relationship optimization, elaborate their advantages in multimodal imaging, as well as synergistic anti-tumor mechanisms combining phototherapy, radiotherapy, sonodynamic therapy and immunotherapy, including activation of regulated cell death, tumor microenvironment remodeling, and tumor growth inhibition and anti-metastasis effects. Furthermore, the bottlenecks hindering their clinical translation are outlined, and prospects for the development of precision nanotheranostics are proposed. This work provides theoretical references for the clinical translation of Bi-based nanomaterials for tumor theranostics.