Pnictogens in medicinal chemistry: evolution from erstwhile drugs to emerging layered photonic nanomedicine.

Pnictogens (the non-metal phosphorus, metalloids arsenic and antimony, and metal bismuth) possess diverse chemical characteristics that support the formation of extended molecular structures. As witnessed by the centuries-old (and ongoing) clinical utilities, pnictogen-based compounds have secured their places in history as "magic bullet" therapeutic drugs in medicinal contexts. Moreover, with the development of recent metalloproteomics and bio-coordination chemistry, the pnictogen-based drugs functionally binding to proteins/enzymes in biological systems have been underlaid for "drug repurposing" with promising opportunities. Furthermore, advances in the modern materials science and nonotechnology have stimulated a revolution in other newly discovered forms of pnictogens-phosphorene, arsenene, antimonene, and bismuthine (layered pnictogens). Based on their favorable optoelectronic properties, layered pnictogens have shown dramatic superiority as emerging photonic nanomedicines for the treatment of various diseases. This tutorial review outlines the history and mechanism of action of ancient pnictogen-based drugs (e.g., arsenical compounds in traditional Chinese medicine) and their repurposing into modern therapeutics. Then, the revolutionary use of emerging layered pnictogens as photonic nanomedicines, alongside assessments of their in vivo biosafety, is discussed. Finally, the challenges to further development of pnictogens are set forth and insights for further exploration of their appealing properties are offered. This tutorial review may also provide some deep insights into the fields of integrated traditional Chinese and Western medicines from the perspective of materials science and nanotechnology.