Progress toward Safe Tumor Diagnosis and Therapy via Degradable Inorganic Nanomaterials Constructed with Metabolically Safe Elements

Inorganic nanostructures have become an increasingly important focus in tumor diagnosis and therapy because of their unique functionalities and versatile surface properties, which could be fitted into a lot of distinct roles including tumor imaging, cancer detection, drug delivery, and many other nonconventional treatment modalities. Nevertheless, the clinical translation of inorganic-based nanoformulations has been severely restricted by their potential short- and long-term health risks in vivo because the majority of existing inorganic nanomaterials contain toxic elements and are difficult to degrade in a physiological environment. The emergence of degradable inorganic nanostructures with metabolically safe elements in the human body offers a balanced solution between functionality and safety. From an overall perspective, these novel nanopreparations could retain the favorable functional properties of conventional inorganic nanomaterials, be readily decomposed into nontoxic species in in vivo conditions, and eventually safely eliminated from the body without inducing adverse effects. In this Review, we seek to provide a concise yet comprehensive summary on recently reported metabolically safe degradable inorganic nanostructures for tumor diagnosis/therapy, of which the discussion is outlined according to the specific elemental compositions. Special emphasis was placed on the design concept, functional mechanism, and degradation process of these nanomaterials. It is anticipated that these insights could provide novel opportunities in the biomedical innovation landscape and facilitate the clinical translation of new nanoagents.