Cells were exposed to low, medium and high doses of ZnO NP in DMEM in digests for four hours prior to the cell viability assessment A) Control DMEM, B) control digest, C) low DMEM, D) low digest, E) medium DMEM, F) medium digest, G) high DMEM, H) high digest. Low, medium and high refer to the dose of ZnO, nanoparticles, where low = 9.7 × 10−6 mg/mL, medium = 9.7 × 10−4 mg/mL, and high = 9.7 × 10−2 mg/mL. Digest refers to ZnO nanoparticles that have been subjected to a simulated gastric and intestinal digestion.