Vitamin B12-mediated transport of nanoparticles across Caco-2 cells

Several studies have shown that Caco-2 cells have the capability to transport peptides and proteins from their apical to basal surfaces when these molecules are linked to vitamin B12 (VB12). In this study we have extended these studies and have shown that Caco-2 cells are also able to internalize and transport VB12-modifed nanoparticles from their apical to basal surfaces. Uptake and transport of nanoparticles was found to occur in both a VB12-dependent intrinsic factor (IF)-independent manner as well as in a VB12-dependent IF-dependent manner. Both IF-independent and IF-dependent VB12-mediated uptake and transport were dependent upon the surface density of VB12 as a reduction in surface modification of the nanoparticles with VB12 resulted in a reduced level of both VB12-mediated and IF-mediated uptake. At lower levels of VB12 modification there was no apparent non-IF-mediated uptake; however, VB12-IF-mediated uptake was still measurable. These studies show that Caco-2 cell cultures are a suitable model for the study of VB12-mediated uptake and transport of nanoparticles, and suggest that for effective oral uptake of VB12-coated nanoparticles high surface densities of VB12 are required.