Human epithelial cell processing of carbon and gold nanoparticles

This paper describes some early cellular and intracellular interactions of human polarised lung and colon epithelial cells (representative of two portals of entry, inhalation and ingestion), following exposure to specific carbon and gold engineered nanoparticles in vitro. Cells were incubated with functionalised and non-functionalised carbon nanotube-derived nanoloops (-28-60 nm diameter), or gold nanoparticles (2 nm and 10 nm Au-core) which were either non-functionalised, or functionalised with biological proteins or ssDNA and analysed using viability staining, transmission electron microscopy (TEM) and field emission scanning (FESEM) electron microscopy. Even with such diverse nanoparticles and functionalisations, we found that the surface properties and size of the nanoparticles determined their cellular binding, incorporation and/or cytotoxicity. However the cells responded to the different types of nanoparticles using various intracellular routes which differed with the cell type, but all of the nanoparticles ultimately were consolidated into aggregates and transported to the basal cell surface. Nanoparticles that were completely covered with biological macromolecules (i.e., recombinant gClq-R protein, non-immune IgGk, monoclonal antibody to gClq-R, or ssDNA) did not cause ultrastructural damage or changes in the cell monolayers. Monoclonal antibody (mAb)-functionalised carbon nanoloops and ssDNA 100% covered Au-nanodots were incorporated and transported within the colon cells using different cellular pathways than those used by the lung cells. Citrate-capped Au-nanoparticles (2 nm and 10 nm) and 20% DNA covered Au-nanoparticles passed into the colon and lung cells through small holes in the apical cell membrane, which could possibly be produced by lipid peroxidation. Serious forms of cell damage were observed with citrate capped 2 nm and 10 nm Au-nanoparticles (i.e., nuclear localisation (2nm-Au); intracellular membrane damage (10 nm-Au)). Vital staining used to identify cellular necrosis following nanoparticle exposure, was sometimes misleading showing cell necrosis statistics similar to normal controls, when TEM analysis revealed intracellular and organellar damage in identically treated cells.