RESUMO
The difference in pH between apical and basolateral side of intestinal epithelial and pH dependence character of the combination of FcRn (neonatal Fc receptor) and ligand might improve the delivery of hydrophobic drugs by facilitating the transcytosis of nanocarriers. Here we designed FcBP (IgG Fc domain-binding peptides) decorated coumarin 6 (C6) loaded poly(ethyl ethylene phosphate)-co-poly(ε-caprolactone) (PEG-PCL) micelles with different ligand densities to study the effect of pH and ligand density on the endocytosis and exocytosis process of micelles on human colon adenanocaricinoma cell lines (Caco-2). Active micelles with different ligand densities and passive micelles were prepared using the thin-film hydration method. The size of the micelles was characterized by dynamic light scattering analysis and the morphology was observed by transmission electron microscope. The endocytosis and exocytosis of the micelles at pH 7.4 and pH 6.0, as well as the effect of FcRn on the endocytosis, were investigated by flow cytometry. The results showed that the size of micelles was about 30 nm, which was not affected by FcBP decoration. We found that pH and ligand density could both influence the endocytosis. The uptake of active micelles was higher at pH 6.0 than at pH 7.4, and an optimal ligand density of endocytosis was appeared in both pH environment. Then we proved that FcBP decorated micelles could be endocytosed at pH 6.0 and exocytosed at pH 7.4, and the exocytosis process was also related to ligand density. Micelles with 10% ligand density had the largest exocytosis, showing the potentiality to deliver drugs through the intestinal epithelial. In addition, the competitive inhibition experiments illustrated that the interaction between FcRn and FcBP were essential to endocytosis. The results will enhance the understanding on the FcBP decorated PEG-PCL micelles for transmemberane drug delivery.
RESUMO
The rapidly increasing implementation of antibodies in therapeutic and diagnostic applications has necessitated the development of antibody production and purification technologies for both academic and industrial usage. Bacterial Protein A and Protein G are known to bind antibodies with high affinity and have facilitated the isolation and purification thereof. Recently, small peptide ligands (i.e. IgG Fc domain-binding peptides, FcBP) that specifically bind to the Fc-domain of antibodies were reported. In the present study we describe the development of a reusable high affinity column for antibody purification utilizing immobilized FcBP, comprising 13 amino acids residues, on a sepharose resin. In addition to FcBP, Cys to Ser substituted FcBP (FcBP-Ser), reduced FcBP (FcBP-Red), commercial Protein A and Protein G resins, packed into columns, were evaluated for antibody purification. All these columns except the FcBP-Ser one showed good binding capacity for a humanized IgG (trastuzumab) and a chimeric IgG (cetuximab). The column packed with FcBP-Red allowed antibody purification at a less acidic pH (pH 4.8) than was required for the other ligand affinity columns used in our experiments (i.e., pH 3.2 for Protein G and FcBP columns, and pH 3.5 for Protein A column, respectively). Utilizing the FcBP column, antibodies from swine human sera were isolated with a purity of 95%. Interestingly, the FcBP column could be easily regenerated and operated without loss of efficiency for up to 60 runs, the maximum number of runs performed in the present study.
