Redox double-switch cancer theranostics through Pt(IV) functionalised manganese dioxide nanostructures.

Manganese dioxide (MnO2)-based nanostructures have emerged as promising tumour microenvironment (TME) responsive platforms. Herein, we used a one-pot reaction to prepare MnO2 nanostructures with Pt(IV) prodrugs as redox- (and thus TME-) responsive theranostics for cancer therapy, in which the Pt(IV) complexes act as prodrugs of cisplatin (Pt(II)), a clinical chemotherapeutic drug. The cytotoxicity of these MnO2-Pt(IV) probes was evaluated in two and three dimensional (2D and 3D) A549 cell models and found to be as effective as active drug cisplatin in 3D models. Moreover, MnO2-Pt(IV) nanoparticles exhibited strong off/ON magnetic resonance (MR) contrast in response to reducing agents, with the longitudinal relaxivity (r1) increasing 136-fold upon treatment with ascorbic acid. This off/ON MR switch was also observed in (2D and 3D) cells in vitro. In vivo MRI experiments revealed that the nanostructures induce a strong and long-lasting T1 signal enhancement upon intratumoral injection in A549 tumour-bearing mice. These results show the potential of MnO2-Pt(IV) NPs as redox responsive MR theranostics for cancer therapy.

Nanomaterials responding to microwaves: an emerging field for imaging and therapy.

In recent years, new microwave-based imaging, sensing and hyperthermia applications have emerged in the field of diagnostics and therapy. For diagnosis, this technology involves the application of low power microwaves, utilising contrast between the relative permittivity of tissues to identify pathologies. This contrast can be further enhanced through the implementation of nanomaterials. For therapy, this technology can be applied in tissues either through hyperthermia, which can help anti-cancer drug tumour penetration or as ablation to destroy malignant tissues. Nanomaterials can absorb electromagnetic radiation and can enhance the microwave hyperthermic effect. In this review we aim to introduce this area of renewed interest and provide insights into current developments in its technologies and companion nanoparticles, as well as presenting an overview of applications for diagnosis and therapy.