Drug carriers, liposomes

Phospholipids e.g. form spontaneously multilamellar concentric bilayer vesicles73 > if they are suspended e.g. by a mixer in an excess of aqueous solution. In the multilamellar vesicles lipid bilayers are separated by layers of the aqueous medium 74-78) which are involved in stabilizing the liposomes. By sonification they are dispersed to unilamellar liposomes with an outer diameter of 250-300 A and an internal one of 150-200 A. Therefore the aqueous phase within the liposome is separated by a bimolecular lipid layer with a thickness of 50 A. Liposomes are used as models for biological membranes and as drug carriers. 

Eppstein, D. A., and Feigner, P. L. (1988). Applications of liposome formulations for antimicrobial/antiviral therapy, in Liposomes as Drug Carriers Recent Trends and Progress (G. Gregoriadis, ed.), John Wiley and Sons, Chichester, pp. 311-323. 

Gabizon, A. (1989). Liposomes as a drug delivery system in cancer chemotherapy, in Drug Carrier Systems Horizons in Biochemistry and Biophysics, Vol. 9 (F. H. Roerdink and A. M. Kroon, eds.), John Wiley and Sons, Chichester, pp. 185-211. 

Gregoriadis, G. (ed.) (1988b). Liposomes as Drug Carriers Recent Trends and Progress. John Wiley and Sons, Chichester. 

Senior, J. (1987). Fate and behavior of liposomes in vivo A review of controlling factors, CRC Grit. Rev. Therapeut. Drug Carrier Syst, 3, 123-193. 

Weinstein, J. N., and Leserman, L. D. (1984). Liposomes as drug carriers in cancer chemotherapy, Pharmacol. Ther., 24. 207-233. 

Numerous experimental therapeutics have shown potency in vitro however, when they are tested in vivo, they often lack significant efficacy. This is often attributed to unfavorable pharmacokinetic properties and systemic toxicity, which limit the maximum tolerated dose. These limitations can be overcome by use of drug carriers. Two general types of carrier systems have been designed drug conjugation to macromolecular carriers, such as polymers and proteins and drug encapsulation in nanocarriers, such as liposomes, polymersomes and micelles. 

Size and homogeneity of liposomes are important in their use as drug carriers, since these characters affect the pharmacokinetics and distribution of liposomes in vivo. Light scattering, electron microscopy, NMR, and gel filtration are used for evaluating liposomal size and homogeneity (32,33)... 

Liposomes as Drug Carriers Gregoriadis, G., Ed., John Wiley Sons Ltd. New York, NY, 1987. 

An excellent carrier is needed to deliver a sufficient amount of prostaglandins to the diseased site. Liposomes have been studied for a long time as possible drug carriers. However, the clinical use of liposomes has delayed because of some difficulties in mass production, sterilization, stability and safety. Since 1980 we have attempted to use lipid microspheres (lipid emulsions) instead of liposomes as a better carrier for lipophilic drugs (7). 

The most important application recently developed for synthetic liposomes is as potential drug carriers for controlled release, especially for cancer chemotherapy (7). In general, the success of liposomes as vehicles for the transport of specific drugs will largely depend on their stability under physiological conditions. Unlike the naturally occurring membranes, the synthetic vesicles have very limited stability, and this is a... 

The important attributes of liposomes as a drug carrier are (a) they are biologically inert and completely biodegradable (b) they pose no concerns of toxicity, antigenicity, or pyrogenicity, because phospholipids are natural components of all cell membranes (c) they can be prepared in various sizes, compositions, surface charges, and so forth, depending on the requirements of... 

Besides the possible use of such stabilized liposomes as drug carriers (10) another application could be their use as models for the ceTT-cell interaction and as polymeric antitumor agents on a cellular level (11) i.e. trying to mimic the body defense against tumor cells (17J. We hope that this article which in many terms is more a pre- than a review will help to stimulate the discussions on polymeric antitumor agents not only on the al-... 

In the previous chapters it has been shown that stable cell membrane models can be realized via polymerization of appropriate lipids in planar monolayers at the gas-water interface as well as in spherical vesicles. Moreover, initial experiments demonstrate that polymeric liposomes carrying sugar moieties on their surface can be recognized by lectins, which is a first approach for a successful targeting of stabilized vesicles being one of the preconditions of their use as specific drug carriers in vivo. 

Lo, Y.L. and Y.E. Rahman. 1995. Protein location in liposomes, a drug carrier a prediction by differential scanning calorimetry. J Pharm Sci 84 805-814. 

Barenholz Y. Design of liposome-based drug carriers from basic research to application as approved drugs. In Lasic DD, Papahadjopoulos D, eds. Medical Applications of Liposomes. Amsterdam Elsevier Science, 1998 541-565. 

Barenholz Y, Cohen R. Rational design of amphiphile-based drug carriers and sterically stabilized carriers. J Liposome Res 1995 5 905-932. 

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