A Novel Top‐Down Synthesis of Ultrathin 2D Boron Nanosheets for Multimodal Imaging‐Guided Cancer Therapy

Abstract

Single atom nonmetal 2D nanomaterials have shown considerable potential in cancer nanomedicines, owing to their intriguing properties and biocompatibility. Herein, ultrathin boron nanosheets (B NSs) are prepared through a novel top-down approach by coupling thermal oxidation etching and liquid exfoliation technologies, with controlled nanoscale thickness. Based on the PEGylated B NSs, a new photonic drug delivery platform is developed, which exhibits multiple promising features for cancer therapy and imaging, including: i) efficient NIR-light-to-heat conversion with a high photothermal conversion efficiency of 42.5%, ii) high drug-loading capacity and triggered drug release by NIR light and moderate acidic pH, iii) strong accumulation at tumor sites, iv) multimodal imaging properties (photoacoustic, photothermal, and fluorescence imaging), and v) complete tumor ablation and excellent biocompatibility. As far as it is known, this is the first report on the top-down fabrication of ultrathin 2D B NSs by the combined thermal oxidation etching and liquid exfoliation, as well as their application as a multimodal imaging-guided drug delivery platform. The newly prepared B NSs are also expected to provide a robust and useful 2D nanoplatform for various biomedical applications.

2D Crystal–Based Fibers: Status and Challenges

“…Although the bulk boron is nonmetallic, theoretical calculation shows that single‐layer borophene film is metallic, which has been verified by experiments. Moreover, several research groups have predicted that borophenes are superconducting …”

Solar‐Inspired Water Purification Based on Emerging 2D Materials: Status and Challenges

“…The polymorphism and anisotropic structure of borophene lead to many attractive properties, including the optical transparency, metallicity, phonon‐mediated superconductivity, photoluminescence in visible region (≈626 nm), efficient thermal transport, mechanical flexibility, etc. When considering its photothermal application, there is a drawback of weak absorption with extinction coefficient of ≈2.5 L g −1 cm −1 , making the application of photothermal evaporation full of challenge. Fortunately, the size‐dependent behavior can be observed, which may help to optimize the size and enhance the absorption.…”

“…When considering its photothermal application, there is a drawback of weak absorption with extinction coefficient of ≈2.5 L g −1 cm −1 , making the application of photothermal evaporation full of challenge. Fortunately, the size‐dependent behavior can be observed, which may help to optimize the size and enhance the absorption. Additionally, the metallic nature of borophene may result in the LSPR and efficient photothermal conversion.…”

A Bacteriochlorin‐Based Metal–Organic Framework Nanosheet Superoxide Radical Generator for Photoacoustic Imaging‐Guided Highly Efficient Photodynamic Therapy

“…[36][37][38] It still remains a key challenge to develop novel NIR-trigged O 2 −• generators to circumvent the tumor hypoxia. [41,42] Porphyrins and porphyrin derivatives as photosensitizers are hydrophobic in nature, which not only cause insufficient selectivity to the site of tumor, but also leads to PS polymerization, reducing the efficacy of PDT and making it very attractive for the assembly structure of organic building units of MOF. [39,40] Compared to the traditional inorganic/organic nanoparticles, MOF offers adjustable structural and chemical composition at the molecular level together with tunable porosity and chemical stability, which can as transport vehicles for the delivery of imaging agents and biologically active molecules realize accurate diagnosis and treatment of tumors.…”

“…[39,40] Compared to the traditional inorganic/organic nanoparticles, MOF offers adjustable structural and chemical composition at the molecular level together with tunable porosity and chemical stability, which can as transport vehicles for the delivery of imaging agents and biologically active molecules realize accurate diagnosis and treatment of tumors. [45] 2D nanosheets with large surface area, unique physical, and chemical properties have been widely used as theranostic agents for cancer treatment, such as graphene, transition metal dichalcogenides, black phosphorus, [46][47][48] boron nanosheets, [42] accomplishing multimodal imaging-guided synergistic treatment. [43] Porphyrin-based MOF that have been developed so far for potential PDT outcome, however, almost all of them are compounded with other nanoparticles to form new compounds for synergistic treatment (such as PDT-PTT, PDT-Radiation therapy), [44] the complex structures would reduce the clinical medical value.…”