Autophagic blockage by bismuth sulfide nanoparticles inhibits migration and invasion of HepG2 cells.

The biological effects of nanoparticles are of great importance for the in-depth understanding of safety issues in biomedical applications. Induction of autophagy is a cellular response after nanoparticle exposure. Bismuth sulfide nanoparticles (BiS NPs) are often used as a CT contrast agent because of their excellent photoelectric conversion ability. Yet there has been no previous detailed study other than a cell toxicity assessment. In this study, three types of BiS NPs with different shapes (BiS nano rods (BSNR), hollow microsphere BiS NPs (BSHS) and urchin-like hollow microsphere BiS NPs (ULBSHS)) were used to evaluatecytotoxicity, autophagy induction, cell migration and invasion in human hepatocellular carcinoma cells (HepG2). Results showed that all three BiS NPs lead to blockage in autophagic flux, causing p62 protein accumulation. The cell death caused by these BiS NPs is proved to be autophagy related, rather than related to apoptosis. Moreover, BiS NPs can reduce the migration and invasion in HepG2 cells in an autophagy-dependent manner. ULBSHS is the most cytotoxic among three BiS NPs and has the best tumor metastasis suppression. These results demonstrated that, even with relatively low toxicity of BiS NPs, autophagy blockage may still substantially influence cell fate and thus significantly impact their biomedical applications, and that surface topography is a key factor regulating their biological response.