Bacteria-Mediated Ultrathin Bi₂Se₃ Nanosheets Fabrication and Their Application in Photothermal Cancer Therapy

Bismuth selenide (Bi₂Se₃) attracts a lot of attention nowadays due to its unique electronic and thermoelectric properties. In this study, fabrication of Bi₂Se₃ nanosheets by selenite-reducing bacterium (SeRB) was first reported. Morphology, size, and location of the biogenic Bi₂Se₃ are bacteria-dependent. It is difficult to separate Bi₂Se₃ generated by <i>Bacillus cereus</i> CC-1 (Bi₂Se₃-C) from the biomass because of strong interaction with the cell membrane. However, Bi₂Se₃ produced by <i>Lysinibacillus</i> sp. ZYM-1 (Bi₂Se₃-Z), is highly dispersed in extracellular space with high stability. Further characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) on Bi₂Se₃-Z indicates that the product is a rhombohedral-phase, ultrathin nanosheet-like structure with an average size of ∼100 nm. Subsequently, the photothermal performance of Bi₂Se₃-Z with the irradiation of 808 nm near-infrared (NIR) laser was determined. When the Bi₂Se₃-Z concentration was 26 mg L^–1, and irradiation power was 2 W, the photothermal conversion efficiency was calculated as 30.7%. At the same condition, 100% of the MCF7 and A549 cancer cells were killed within 10 min of irradiation in vitro. Moreover, using 1% (v/v) PVP as surfactant, a novel nanodumbbell structure of Bi₂Se₃ was obtained. Overall, this bacteria-driven Bi₂Se₃ fabrication paves a new way for biocompatible photothermal nanomaterials