BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Endocytosis CYTOSOL (nearly all cells Can be triggered by transp receptor binding cell and retuning to the plant Engulfs volumes -500 ethrane, whether it nm diam or smaller Phagocytosis dendritic cells) ENgulf volumes up to the size of the cel Access to the cytosol is tightly regulated o Typically, internalized material dOES NOT ever reach the cytosol- confined to vesicles For mouse fibroblasts, only 5%of tested protein and 20% of oligonucleotides internalized by a cell could reach the cytosol (Cancer Res 59, 1180(1999); Nucleic Acids Res 25, 3290(1997)) o Special case: dendritic cells and(maybe)macrophages Cross-priming: triggering of certain receptors by pathogens leads to delivery of antigens to the o Drug delivery has been attempted by using high doses to obtain a small 'leak' current into cytosol o Leishmania(Alving 1988 Adv Drug Deliv Rev 2, 107) o Pathway to attack intracellular bacteria Phagocytosis of carrier Fusion of endome with parasite-loaded lysosomes Binding of liposomal carrier to bacterial cell wall and disruption of cell wall o commercial product: Ambisome(Gilead, Boulder CO liposomal formulation of amphotericin b to treat leishmaniasis lipid-like drug inserts in liposomal wall as well as within liposomal internal aqueous compartment Lecture 16-intracellular delivery 2 of 8BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Endocytosis: (nearly all cells) receptor binding ¥Can be triggered by ¥Engulfs volumes ~500 nm diam. or smaller Phagocytosis: (macrophages, neutrophils, dendritic cells) ¥Engulf volumes up to the size of the cell ƒ Access to the cytosol is tightly regulated o Typically, internalized material DOES NOT ever reach the cytosol- confined to vesicles ƒ For mouse fibroblasts, only 5% of tested protein and 20% of oligonucleotides internalized by a cell could reach the cytosol (Cancer Res. 59, 1180 (1999); Nucleic Acids Res. 25, 3290 (1997)) o Special case: dendritic cells and (maybe) macrophages ƒ Cross-priming: triggering of certain receptors by pathogens leads to delivery of antigens to the cytosol o Drug delivery has been attempted by using high doses to obtain a small ‘leak’ current into cytosol ƒ ƒ Delivery of proteins, DNA, small-molecule drugs to the cytosol ƒ Example motivation: treatment of leishmania bacterial infections o Leishmania (Alving 1988 Adv Drug Deliv Rev 2, 107) o Pathway to attack intracellular bacteria: ƒ Phagocytosis of carrier ƒ Fusion of endome with parasite-loaded lysosomes ƒ Binding of liposomal carrier to bacterial cell wall and disruption of cell wall o commercial product: Ambisome (Gilead, Boulder CO) 1 ƒ liposomal formulation of amphotericin B to treat leishmaniasis ƒ lipid-like drug inserts in liposomal wall as well as within liposomal internal aqueous compartment Lecture 16 – intracellular delivery 2 of 8