Construction of high quality ultrathin lanthanide oxyiodide nanosheets for enhanced CT imaging and anticancer drug delivery to efficient cancer theranostics.

Two-dimensional (2D) ultrathin nanomaterials have shown extensive attention and potential biomedical applications in cancer theranostics. Herein, for the first time, we report the synthesis of monodisperse ultrathin lanthanum oxyiodide (LaOI) nanosheets with a thickness of merely 3 nm based on a facile wet chemistry strategy. By tuning the solvent composition and molar ratios of the precursors, we can modulate the shape and thickness of the nanosheets. Furthermore, a series of ultrathin lanthanide oxyiodides are synthesized by this method with tunable morphology. LaOI nanosheets as drug delivery platform showed ultrahigh anticancer doxorubicin (DOX) loading capacity (300 wt%) and pH-responsive release behaviour, as well as excellent cellular biocompatibility and efficiently intracellular nucleus delivery of DOX. LaOI with low dose DOX demonstrate enhanced cancer cell killing ability in vitro compared with DOX. The intravenous melanoma model shows that LaOI with low dose (1 mg mL^-1) could significantly inhibit the tumor growth without side toxicity, relative to pure DOX. In addition, LaOI nanosheets also act as high resolution contrast agent for enhanced X-ray computed tomography imaging relative to the commercial iohexol. In summary, the LaOI nanosheets could serve as a competitive safe and low dose drug delivery platform for highly efficiently cancer imaging and therapy.