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- Kronberg, B, et al.
(author)
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Preparation and evaluation of sterically stabilized liposomes: colloidal stability, serum stability, macrophage uptake and toxicology
- 1990
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In: Journal of Pharmaceutical Sciences. - 0022-3549 .- 1520-6017. ; 79, s. 667-671
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Journal article (peer-reviewed)abstract
- Sterically stabilized liposomes were produced by incorporating a nonionic surfactant, polysorbate 80 (Tween 80), into the lipid bilayer. The sterically stabilized liposomes exhibited a superior entrapment stability compared with surfactant-free liposomes (i.e., liposomes prepared with lipids and cholesterol). The sterically stabilized liposomes were stable at high calcium ion concentrations, and liposome-entrapped carboxyflourescein was retained within the stabilized liposomes in the presence of serum for at least 5 h. The macrophage uptake of the sterically stabilized liposomes was comparable to that of liposomes containing lipids and cholesterol. The sterically stabilized liposomes were non-toxic, in concentrations up to 3.0 mM, to macrophages. These results indicate that polysorbate 80 can be used to produce stable liposomes without changing the uniqe macrophage distribution of this drug delivery system.
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| 3. |
- Sjöström, B, et al.
(author)
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A method for the preparation of submicron particles of sparingly water-soluble drugs by precipitation in oil-in-water emulsions. I. Influence of emulsification and surfactant concentration
- 1993
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In: Journal of Pharmaceutical Sciences. - 0022-3549 .- 1520-6017. ; 82, s. 579-583
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Journal article (peer-reviewed)abstract
- In this paper we present a method for the synthesis of small particles of poorly water soluble drug substances using emulsions. In the first place, the drug is dissolved in an organic solvent and a water soluble surfactant is dissolved in water. Secondly, these two solutions are mixed to form an emulsion, where the organic solution is emulsified into small droplets in the aqueous phase. The action of the surfactant is partly to decrease the interfacial tension between the water and the organic solution, thus increasing the ease of emulsification, and partly to stabilize the droplets formed against aggregation, or coalescence. The final step in the process is to remove the organic solvent by evaporation in doing which the drug precipitates and one particle is formed in each droplet. If the surfactant is sufficiently effective in stabilizing the particles formed against coagula--tion, we have a suspension of small spherical drug particles. In this paper we use a model system consisting of cholesteryl acetate and toluene. Particles down to 50 nm were obtained by this method. The sizes of the particles were found to be dependent on the surfactant concentration and the emulsification energy.
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| 4. |
- Sjöström, B, et al.
(author)
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A method for the preparation of submicron particles of sparingly water-soluble drugs by precipitation in oil-in-water emulsions. II. Influence of the emulsifier, the solvent, and the drug substance
- 1993
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In: Journal of Pharmaceutical Sciences. - 0022-3549 .- 1520-6017. ; 82, s. 584-589
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Journal article (peer-reviewed)abstract
- Small particles of two steroids; cholesteryl acetate and b-sitosterol, have been prepared by the following technique: The steroid was dissolved in an organic solvent, which was emulsified in water in the presence of sur--factant, thus giving a water continuous emulsion. As the organic solvent was evaporated the steroid precipitated. One particle was found to form in each emulsion droplet. Particle sizes down to 25 nm were obtained by this method. Particles were prepared from emulsions containing different organic solvents and surfactants and the effect on the size and the colloi--dal stability of the particles were examined. It was found that the final particle suspension is relatively stable provided the initial emulsion is stable. Furthermore, there is a close correlation between the initial emul--sion droplet size and the final particle size. The particle size, therefore, can be varied in the same manner as the size of emulsion droplets, e.g. by changing the emulsification process parameters, the amount and choice of surfactant and the oil/water ratio. Finally, the particle size depends on the choice of solvent and only slightly on the concentration of drug in the oil phase of the emulsion.
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