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.

The large-dimensional and rigid ceramic bulks fabricated by high-temperature solid-phase reaction and sintering have never been considered for possibly entering and circulating within the blood vessels for biomedical applications, especially on combating cancer. Here, it is reported for the first time that MAX ceramic biomaterials exhibit unique functionalities for dual-mode photoacoustic/computed tomography imaging and are highly effective for in vivo photothermal ablation of tumors upon being exfoliated into ultrathin nanosheets within atomic thickness (MXene). As a paradigm, 2D ultrathin tantalum carbide nanosheets (Ta C MXenes) with nanosized lateral sizes are successfully synthesized based on a two-step liquid exfoliation strategy of MAX phase Ta AlC by combined hydrofluoric acid (HF) etching and probe sonication. The structural, electronic, and surface characteristics of the as-exfoliated nanosheets are revealed by various characterizations combined with first-principles calculations via density functional theory. Especially, the superior photothermal-conversion performance (efficiency η of 44.7%) and in vitro/in vivo photothermal ablation of tumor by biocompatible soybean phospholipid-modified Ta C nanosheets are systematically revealed and demonstrated. Based on the large family members of MXenes, this work may offer a paradigm that MXenes can achieve the specific biomedical applications (here, theranostic) providing that their compositions and nanostructures are carefully tuned and optimized to meet the strict requirements of biomedicine.

Emerging nanocatalytic tumor therapies based on nontoxic but catalytically active inorganic nanoparticles (NPs) for intratumoral production of high‐toxic reactive oxygen species have inspired great research interest in the scientific community. Nanozymes exhibiting natural enzyme‐mimicking catalytic activities have been extensively explored in biomedicine, mostly in biomolecular detection, yet much fewer researches are available on specific nanocatalytic tumor therapy. This study reports on the construction of an efficient biomimetic dual inorganic nanozyme‐based nanoplatform, which triggers cascade catalytic reactions for tumor microenvironment responsive nanocatalytic tumor therapy based on ultrasmall Au and Fe 3 O 4 NPs coloaded dendritic mesoporous silica NPs. Au NPs as the unique glucose oxidase‐mimic nanozyme specifically catalyze β‐D‐glucose oxidation into gluconic acid and H 2 O 2 , while the as produced H 2 O 2 is subsequently catalyzed by the peroxidase‐mimic Fe 3 O 4 NPs to liberate high‐toxic hydroxyl radicals for inducing tumor‐cell death by the typical Fenton‐based catalytic reaction. Extensive in vitro and in vivo evaluations have demonstrated high nanocatalytic‐therapeutic efficacy with a desirable tumor‐suppression rate (69.08%) based on these biocompatible composite nanocatalysts. Therefore, this work paves a way for nanocatalytic tumor therapy by rationally designing inorganic nanozymes with multienzymatic activities for achieving high therapeutic efficacy and excellent biosafety simultaneously.