Comparative analysis of biological effects of molybdenum(IV) sulfide in the form of nano- and microparticles on human hepatoma HepG2 cells grown in 2D and 3D models

Significance of MoS2 nanoparticles as a lubricant or drug carriers indicates the need to assess their safety. In the study we analyzed the effects of MoS2 nano- and microparticles and their internalization in vitro, using 2D and 3D culture models of human hepatoma HepG2 cell line. MoS2 micro- and nanoparticles were characterized with high resolution electron microscopy (HR-SEM), X-ray diffraction (XRD) and Energy Dispersive X-Ray Spectroscopy (EDS). The cells were exposed to a range of concentrations of the nano-and microparticles suspensions (maximum of 250 mu g/mL) for 72 h. Cell viability was assessed using WST-1 reduction test and LDH release assay. Particle internalization was analyzed using scanning transmission electron microscopy (STEM). The nanoparticles were internalized into the 2D and 3D cultured cells, in spheroids more efficiently into the outer layer. For microparticles mainly particles of less than 1 mu m in diameter underwent internalization. This process, however, did not affect cell viability as measured with the WST-1 and LDH assays. STEM observation showed well preserved integrity of the cell membrane and no apparent cytotoxic effect. Although the particles seemed to be safely sequestered in vacuoles or the cytoplasm, their fate and eventual biological effects are not certain and deserve further studies.