Investigating the Cytotoxicity of Montmorillonite Nanoparticles as a Carrier for Oral Drug Delivery Systems

Montmorillonite (MMT), a nanolayered silicate, is recently used as an oral drug delivery vehicle and also as a functional component in many oral bio-organic drug delivery nanosystems, resulting in increasing the drug bioavailability. This raises concerns about the possible toxic effects of MMT on the intestine and liver as the first and second organs exposed to MMT after oral administration. Here, we investigated the effects of MMT on human intestinal HT-29 (as an enterocyte model) and hepatic HepG2 cells in cellular and molecular levels using MTT assay, flow cytometry and qRT-PCR. The results showed that the tolerable MMT concentrations for HT-29 and HepG2 cells were up to 500 and 300 μg/mL in the presence of serum proteins and reduced to 50 and 25 μg/mL in the absence of serum proteins, respectively, indicating that MMT is much more toxic before absorption into the body. At the higher concentrations, MMT arrested HT-29 and HepG2 cells in G0/G1 and S phases, respectively. Also, MMT induced apoptosis in both HepG2 and HT-29 cells, and necrosis in HT-29 cells. These results suggest that, although MMT over a wide range of concentrations is safe for the intestinal and hepatic cells in the presence of serum proteins, in the intestinal lumen, where serum proteins are absent, high concentrations of MMT may cause cell damage if other free proteins are not present. Also, MMT may cause hepatotoxicity if it is accumulated in the liver following long-term/high-dose administrations.