Synthesis of Ultrathin Biotite Nanosheets as an Intelligent Theranostic Platform for Combination Cancer Therapy

Biotite, also called black mica (BM), is a group of sheet silicate minerals with great potential in various fields. However, synthesis of high-quality BM nanosheets (NSs) remains a huge challenge. Here, an exfoliation approach is provided that combines calcination, n-butyllithium exchange and intercalation, and liquid exfoliating processes for the high-yield synthesis of ultrathin BM NSs. Due to the presence of MgO, Fe₂O₃, and FeO in these NSs, PEGylated BM can be engineered as an intelligent theranostic platform with the following unique features: i) Fe³⁺ can damage the tumor microenvironment (TME) through glutathione consumption and O₂ production; ii) Generated O₂ can be further catalyzed by MgO with oxygen vacancy to generate ·O₂ ^-; iii) The Fe²⁺-catalyzed Fenton reaction can produce ·OH by disproportionation reactions of H₂O₂ in the TME; iv) Reactions in (i) and (iii) circularly regenerate Fe²⁺ and Fe³⁺ for continuous consumption of glutathione and H₂O₂ and constant production of ·OH and O₂; v) The NSs can be triggered by a 650 nm laser to generate ·O₂ ^- from O₂ as well as by an 808 nm laser to generate local hyperthermia; and vi) The fluorescent, photoacoustic, and photothermal imaging capabilities of the engineered NSs allow for multimodal imaging-guided breast cancer treatment.