Functionalized metallic nanomaterials, nanozymes and nanomotors for emerging tumor diagnosis and treatment: from design to theranostics strategies.

Cancer is one of the most significant health issues and is the second leading cause of death worldwide. Traditional cancer diagnosis and treatment has serious defects and often fails to provide satisfactory results. Metallic nanomaterials, particularly gold-based nanomaterials, have been rapidly developed in the biomedical field, especially in the tumor theranostics owing to their unique morphological structures, outstanding physical and chemical properties, great biocompatibility and stability. With the development of research, researchers have introduced a second metal on the basis of single metallic nanomaterials to obtain bimetallic nanomaterials with better optical, catalytic and stability properties than single metallic nanomaterials. Based on the advantages of the above-mentioned metallic nanomaterials, many emerging types of metal-based materials have been developed accordingly. A typical example is metal-based nanozyme, which has inherent enzyme-like capabilities and has advantages such as great stability, abundant sources, controllable activity and low-cost preparation process compared with natural enzymes. The limited penetration of nanomaterials into tumor tissues is a major challenge in current cancer diagnosis and treatment. Further, another typical example is the metal-based nanomotor, which features a unique Janus structure and superior mobility, and is expected to enhance the deep penetration of nanomaterials into tumor, thereby improving the therapeutic effect of diseases. This review highlights the synthesis and properties of gold-based nanomaterials and bimetallic nanomaterials, with a focus on recent advances and future expectation in tumor diagnosis and treatment applications. With further research, we believe that the transition from metallic nanoparticles to metal nanozymes and then to metal enzymes-driven nanomotors will become important nanoplatforms for personalized cancer theranostics.