Nanoparticles (NPs) have been actively investigated due to their great benefits in numerous applications; however, less effort has been committed to explore their toxic effects despite high hazardous potential. Until now all in vitro NPs toxicity testing have been performed on the 2D cell culture. However, it has become increasing apparent the discrepancy of toxicity testing results between 2D cell culture and animal models because simplified 2D cell culture is far too limited to recapitulate appropriate level of complexity in vivo tissues. To achieve more realistic toxic effects of NPs, we developed a 3D spheroid culture based NPs toxicity testing system which represents better physiology of natural tissues.

As an initial step, we prepared spheroid formation of human hepatocarcinoma cell (HepG2) utilizing hydrogel inverted colloidal crystal scaffolds. The extensive cell-cell interactions in spheroid culture promoted the recovery of 3D structure and partial function of the liver tissue. In addition, highly regulated and homogeneous spheroid culture allowed systematic and reproducible toxicology assays. Toxic effects of lcysteine-stabilized cadmium telluride (CdTe) nanoparticles were tested in multiple aspects including morphology, membrane integrity, metabolic activity and cell death mechanism. The spheroid culture showed significantly reduced CdTe NPs toxic effects compared to the conventional 2D culture.

Overall this standardized spheroid culture system extends current cellular level NPs cytotoxicity testing on 2D culture to the tissue level toxicity, which is closer to the real human body responses. It can significantly contribute to the realization of emerging opportunities of NPs by providing their toxic information accurately as well as easily.