Ultrasmall black phosphorus quantum dots: synthesis, characterization, and application in cancer treatment.

Black phosphorus quantum dots (BPQDs) are gaining popularity for applications in various fields because of their unique advantages. For biomedical applications, good biosafety is a prerequisite for the use of BPQDs in vivo. However, currently, little information is available about their basic properties and biocompatibility, which are of great importance for potential biomedical applications. In this work, we prepared BPQDs by an improved solvothermal method and evaluated their fluorescence, biocompatibility, and photothermal therapy (PTT) effectiveness. First, the structures and functions of the BPQDs were investigated at the cellular and molecular levels. It was found that the fluorescence of the BPQDs is wavelength-dependent and that they absorb in the UV-vis range; also, their quantum yield reached 10.2%. In particular, we considered the morphology and lysis of human red blood cells, in vivo blood coagulation, and plasma recalcification profiles. We found that the BPQDs have excellent biocompatibility and hemocompatibility with blood components. Overall, concentrations of the BPQDs ≤0.5 mg mL-1 had few adverse effects on blood components. The resulting BPQDs can efficiently convert near-infrared (NIR) light into heat; thus, they are suitable as a novel nanotheranostic agent for PTT of cancer. Meanwhile, the results of serum biochemistry tests revealed that the indicators were at similar levels for mice exposed to BPQDs and for control mice. Furthermore, from biodistribution analysis of the BPQDs, no apparent pathological damage was observed in any organs, especially in the spleen and kidneys, during the 30 day period. Our research indicates that the BPQDs have bio-imaging capability and biocompatibility and highlights their great potential in the therapy of cancer.