Two-dimensional black phosphorus nanosheets for theranostic nanomedicine

The fast progress of theranostic nanomedicine has catalyzed the generation of diverse inorganic nanosystems with intrinsic multifunctionalities for versatile biomedical applications. However, these inorganic biomaterials suffer from the critical issue of low biodegradation rates and subsequently long-term accumulation-induced biosafety risk. Furthermore, the components of some inorganic nanosystems are not the necessary elements/components of the body, unavoidably causing immune response and inducing the toxic potential. The emergence of ultrathin two-dimensional black phosphorus (B.P.) nanosheets as a robust platform promises the clinical translation and biomedical applications of inorganic nanosystems based on their intriguing nature of easy biodegradation and single phosphorus composition, as necessarily required in vivo. This review summarizes and discusses the very recent developments and paradigms of ultrathin B.P. nanosheets in versatile biomedical applications, ranging from design/fabrication strategies, theranostic nanomedicine (PDT/PTT/chemotherapy, synergistic therapy and fluorescence/photoacoustic-based bio-imaging) to biosensing applications. The unique biological behavior and toxicity issue of these B.P. nanosheets are also discussed to guarantee their safe clinical translation. It is highly expected that the elaborately designed/engineered B.P. nanosheets will emerge as one of the most representative biodegradable inorganic nanosystems for versatile and immense biomedical applications to benefit the health of human beings.