Attachment, uptake and transport of nanoparticles coated with an internalin A fragment in Caco-2 cell monolayers

Four phases of the interaction with cells in monolayer culture of polystyrene nanoparticles - with and without a putative receptor specific surface protein - have been explored. Attachment of the particles and their adhesion to the surface of the cells, uptake, followed by translocation within the complex milieu of the cell interior and finally the release of the particles from the basolateral aspect of the cell monolayer have been studied. One-micrometre polystyrene particles were observed, uncoated and coated with a fragment of internalin A, the surface protein of Listeria monocytogenes that facilitates the uptake and translocation of the organism from the gut through epithelial tissues through its interaction with E-cadherin receptors. Cell monolayer attachment is facilitated by the decoration of the surface of the nanoparticles, adhesion being reduced by incubation of the monolayer with anti-E-cadherin antibody, or with the internalin A protein. However, uptake into the cells and escape from the cell into the basolateral chamber is not enhanced at all cell loadings: at very low loadings there is some evidence of enhanced uptake, but not at 1:100 ratios. No significant difference was found between basolateral efflux of plain particles and internalin A fragment coated systems, suggesting that the limiting step may be the movement of the nanoparticles in the cytoplasm.