Transferrin receptor specific nanocarriers conjugated with functional 7peptide for oral drug delivery.

In an attempt to increase the interaction of a nanocarrier system with gastrointestinal epithelial cells, a transferrin receptor (TfR) specific 7peptide was conjugated to PEG-b-PCL copolymer and the functional nanocarriers were constructed and characterized. The endocytosis, intracellular trafficking and transcytosis of such nanocarriers loaded with coumarin 6 (7pep-M-C6) in a human colon carcinoma cell line (Caco-2) were investigated, followed by the in vivo intestine distribution study. The real-time imaging of live cell, three dimensional reconstruction of confocal image, quantitative colocalization analysis and other techniques were applied. First, the TfR expression was confirmed in Caco-2. Then, 7pep-M-C6 exhibited higher intracellular uptake compared with unmodified nanocarriers. In a live cell study, 7pep-M-C6 demonstrated faster uptake kinetics especially in the surface of cells. Together with a competition study using TfR antibody, it was proved that the increased cellular uptake was due to a receptor-mediated mechanism. Besides the unspecific endocytosis pathway, 7pep-M-C6 was found to enter the cells through a specific clathrin-mediated mechanism, related to the expression of TfR on Caco-2 cells. Possibly for this reason, 7pep-M-C6 tended to colocalize more with late endosomes and lysosomes than the control micelles. Also for the same mechanism, the increased transport of 7pep-M-C6 across Caco-2 monolayer was found, through a transcellular but not a paracellular pathway, while an increased in vivo intestinal distribution of 7pep-M-C6 was observed. In conclusion, the functional nanocarriers could specifically interact with gastrointestinal endothelial cells, increase their transport and alter their pathway as a result.