Conventionally, ceramics-based materials, fabricated by high-temperature solid-phase reaction and sintering, are preferred as bone scaffolds in hard-tissue engineering because of their tunable biocompatibility and mechanical properties. However, their possible biomedical applications have rarely been considered, especially the cancer phototherapeutic applications in both the first and second near-infrared light (NIR-I and NIR-II) biowindows. In this work, we explore, for the first time as far as we know, a novel kind of 2D niobium carbide (NbC), MXene, with highly efficient in vivo photothermal ablation of mouse tumor xenografts in both NIR-I and NIR-II windows. The 2D NbC nanosheets (NSs) were fabricated by a facile and scalable two-step liquid exfoliation method combining stepwise delamination and intercalation procedures. The ultrathin, lateral-nanosized NbC NSs exhibited extraordinarily high photothermal conversion efficiency (36.4% at NIR-I and 45.65% at NIR-II), as well as high photothermal stability. The NbC NSs intrinsically feature unique enzyme-responsive biodegradability to human myeloperoxidase, low phototoxicity, and high biocompatibility. Especially, these surface-engineered NbC NSs present highly efficient in vivo photothermal ablation and eradication of tumor in both NIR-I and NIR-II biowindows. This work significantly broadens the application prospects of 2D MXenes by rationally designing their compositions and exploring related physiochemical properties, especially on phototherapy of cancer.

MXenes, an emerging family of graphene-analogues two-dimensional (2D) materials, have attracted continuous and tremendous attention in many application fields because of their intrinsic physiochemical properties and high performance in versatile applications. In this work, we report on the construction of tantalum carbide (TaC) MXene-based composite nanosheets for multiple imaging-guided photothermal tumor ablation, which has been achieved by rational choice of the composition of MXenes and their surface functionalization. A redox reaction was activated on the surface of tantalum carbide (TaC) MXene for in situ growth of manganese oxide nanoparticles (MnO/TaC) based on the reducing surface of the nanosheets. The tantalum components of MnO/TaC acted as the high-performance contrast agents for contrast-enhanced computed tomography, and the integrated MnO component functionalized as the tumor microenvironment-responsive contrast agents for T-weighted magnetic resonance imaging. The photothermal-conversion performance of MnO/TaC composite nanosheets not only has achieved contrast-enhanced photoacoustic imaging, but also realized the significant tumor-growth suppression by photothermal hyperthermia. This work broadens the biomedical applications of MXenes, not only by the fabrication of family members of biocompatible MXenes, but also by the development of functionalization strategies of MXenes for cancer-theranostic applications.

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