Differential Genomic Effects of Six Different Nanomaterials on Human Liver HepG2 Cells

Human Hepatocellular Carcinoma cells (HepG2) were exposed to six nanomaterials containing either Cerium oxide (CeO2) or Titanium oxide (TiO2) nanoparticles. Three different concentrations were tested: 0.3, 3, or 30 μg/mL) for 3 days. Microarray analysis was performed to identify genes differentially expressed following exposure to these chemicals. HepG2 cell cultures were maintained in a humidified incubator at 37°C and 95% air/5% CO2 during the study. Cells were plated at 40,000 cells/cm2 in vented T-25 flasks (Corning) for 48 h prior to nanomaterial exposure. Individual flasks were treated with 200 uL per cm2 of the appropriate nanomaterial dilution and incubated for 72 h. Six nano-TiO2 or nano-CeO2 formulations from different vendors were used in this study. The chemical purity was high (>98.8% for all cases and as high as 99.9% for five cases), the primary dry particle sizes ranged from 22 to 214 nm. The final concentrations for treatments were 0.3 (low dose), 3 (medium dose), and 30 (high dose) μg/mL. Each treatment was performed in multiple biological replicates. At the end of 72 h of cell exposure to the treatment, the media was vacuum aspirated and the flasks rinsed with warm Dulbecco’s phosphate-buffered saline. Total RNA was extracted from cells using a mirVanaTM RNA extraction kit (Life Technologies, Grand Island, NY) following the manufacturer’s protocol. The global gene expression change was analyzed by using Illumina Human HT-12 v4 Expression Beadchips following the manufacturer’s protocol. The data processing was performed using Bioconductor’s beadarray package (version 2.4.1) for the R language (version 2.14.0).