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

Single atom non-metal two-dimensional (2D) nanomaterials have shown considerable potential in cancer nanomedicines, owing to their intriguing properties and biocompatibility. Herein, ultrathin boron nanosheets (B NSs) were 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 was developed, which exhibited 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 fluorescent imaging), and (v) complete tumor ablation and excellent biocompatibility. To the best of our knowledge, 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 multi-modal imaging-guided drug delivery platform. We also expect the newly prepared B NSs to provide a robust and useful 2D nanoplatform for various biomedical applications.