Introduction of enzymes,by means of liposomes,into non-phagocytic human cells in vitro |
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Authors: | Gerald Weissmann Charles Cohen Sylvia Hoffstein |
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Institution: | 1. Division of Rheumatology of the Department of Medicine, New York University of Medicine, New York, NY 10016, USA;2. Physiology Course of the Marine Biological Laboratory, Woods Hole, Mass. 02543 U.S.A. |
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Abstract: | Liposomes containing entrapped horsedish peroxidase were incubated with three human cell lines in vitro. Although these cells did not ingest latex particles, and took up less than 1 minut of free peroxidase/5 · 106 from the medium, significant amounts (41–164 munits/5 · 106) of peroxidase became cell-associated by 30 min if the enzyme was presented in negatively charged liposomes (phosphatidylchloline/dicetyl phosphate/cholesterol, 70 : 20 : 10 molar ratio). Uptake of liposome-entrapped peroxidase by lymphocytes or fibroblasts was enhanced 2–5-fold if one molar percent of lysophosphatidylcholine was incorporated as a “fusogen”, and was not appreciately diminished by cytochalasin B, an inhibitor of phagocytosis. Lysophosphatidylcholine containing liposomes did not release trapped peroxidase into the medium during incubation, and studies employing the metallochromic dye, arsenazo III demonstrated lack of access of external Ca2+ to the internal, enzyme-laden, aqueous compartments; liposome-liposome fusion was also excluded by similar means. Ultrastructural cytochemstry demonstrated peroxidase within liposomes in the free cytosol of cultured cells 15–90 min after apparent liposome-cell fusion. Data provide evidence that multilamellar liposomes can be as vectors for the introjection of missing enzymes into non-phagocytic human cells. |
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Keywords: | L(PC 70: DCP 20: Chol 10) [HRP] liposomes formed with 70 : 20 : 10 molar ratios of egg phosphatidylcholine/dicetyl phosphate/cholesterol with horseradish peroxidase entrapped in the aqueous compartments [6 7 12] LPC lysophosphatidylcholine arsenazo III III [7 7 -bis(arsonophenylazo) 1 8-dehydroxynaphthalene-3 6-disulfonic acid] EGTA HEPES |
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