Bottom-up synthesis of ultra-small molybdenum disulfide-polyvinylpyrrolidone nanosheets for imaging-guided tumor regression

Abstract

The two-dimensional molybdenum disulfide (MoS₂) nanosheet has been extensively studied as a novel photothermal transducing agent. However, top-down exfoliation to produce MoS₂ nanosheets is inefficient, and MoS₂ nanosheet surface modification procedures are complex. Here, we report the synchronous synthesis and surface modification of 2D MoS₂ nanosheets with a polyvinylpyrrolidone (PVP)-assisted one-pot hydrothermal method. Due to the chelating-coordinating effect between the lone-pair electrons of the PVP carbonyl oxygen and the unoccupied 4d orbitals of molybdenum, the PVP chains could graft onto the surface of MoS₂ and guide the growth of the nanosheets. The resultant MoS₂-PVP nanosheets were ultra-small (21.4 ± 4.4 nm) and exhibited excellent colloidal stability. Moreover, the strong near-infrared absorption of the MoS₂-PVP nanosheets enabled sensitive photothermal conversion performance (with a mass extinction coefficient of 23.33 L g⁻¹ cm⁻¹) and in vitro/in vivo photoacoustic imaging. The MoS₂-PVP nanosheets had excellent in vitro and in vivo compatibility and were used for highly efficient tumor photothermal therapy in xenograft tumor-bearing mice. The findings in this report will facilitate the rational design of stable colloidal 2D transition-metal dichalcogenides for effective photothermal cancer therapy.