Two-dimensional transition metal dichalcogenide nanomaterials for combination cancer therapy

As demonstrated by preclinical and clinical studies, it is often difficult to eradicate tumors, particularly those that are deep-located, with photothermal therapy (PTT) alone because of the intrinsic drawbacks of optical therapy. To increase the therapeutic effect of PTT and reduce its significant side-effects, a new direction involving the combination of PTT with other therapeutic techniques is highly desirable. Recently, two-dimensional (2D) transition metal dichalcogenides (TMDCs), the typical ultrathin 2D layer nanomaterials, have gained tremendous interest in many different fields including biomedicine, due to their novel physicochemical properties. Benefitting from their intrinsic near-infrared absorbance properties and extremely large specific surface areas, many efforts are being devoted to fabricating 2D TMDC-based multifunctional nanoplatforms for combining PTT with other therapeutics in order to realize 2D TMDC-assisted combination therapy and thus achieve excellent anti-tumor therapeutic efficacy. In addition, various inorganic nanoparticles and fluorescent probes can be attached to the surface of 2D TMDCs to obtain nanocomposites with versatile optical and/or magnetic properties that are useful for multi-modal imaging and imaging-guided cancer therapy. In this review, we mainly summarize the latest advances in the utilization of 2D TMDCs for PTT combination cancer therapy, including PTT/photodynamic therapy, PTT/chemotherapy, PTT/radiotherapy, PTT/gene therapy, and imaging-guided cancer combination therapy, as well as the evaluation of their behaviors and toxicology both in vitro and in vivo. Furthermore, we address the principle for the design of 2D TMDC-assisted photothermal combination theranostics and the future prospects and challenges of using 2D TMDC-based nanomaterials for theranostic applications.