Drug-carrying liposomes

TABLE 6 Recently Completed and Ongoing Clinical Trials of Low-Molecular-Weight Drug-Carrying Liposomes for Brain Tumors... 

A clever trick to help target the drug-carrying liposome is to include an antibody on the surface of the liposome. These antibodies are proteins designed to bind specifically to the surface of a tumor cell. Upon attaching to the surface of the tumor cell. 

Krause W, Sachse A, Wagner S, KoUenkirchen U, Rossling G (1991) Preclinical characterization of iopromide-carrying liposomes. Invest Radiol 26(Suppl 1 ) 4 discussion 6 Krause W (1999) Delivery of diagnostic agents in computed tomography. Adv Drug Dehv Rev 37 159... 

To control the pharmacokinetics of these complex systems, one must separate out the leakage rate of the drug from the liposome in the blood and the disposition of the intact carrying liposomes in the blood. 

Because of their ability to carry a wide variety of pharmaceuticals, liposomes have been studied for many different therapeutic situations, Therefore, the literature on this topic is abundant. Excellent reviews are available (e.g., Poznansky and Juliano, 1984 Gregoriadis, 1984, 1988b). We will restrict ourselves to the description of certain applications which illustrate the potential benefits of the use of liposomes in the field of drug delivery. 

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. 

Several types of dmg carriers such as microspheres, liposomes, and polymer have been investigated to achieve targetable drug delivery, especially for anticancer drugs. However, nonselective scavenging of such carriers by the reticuloendothelial system (RES) is a serious problem even when monoclonal antibodies are used to carry the dmg [15,16]. 

The general outcome of these studies was that the liposomal drugs were well tolerated and exerted a clinical effect, although larger studies need to be carried out to demonstrate the extent of the effects. Furthermore, in the various studies of liposome-incorporated drugs, it was observed that cardiotoxicity was either absent or only limited, in contrast to studies with non-liposomally formulated drugs. 

The word liposome comprises two terms (from Greek—lipid [fat] and soma [body]). It does not in itself denote any size characteristics. Furthermore, the term liposome does not necessarily mean that it must contain lipophobic contents, such as water, although it usually does. The vesicles may be conceived as microscopic (or nano-sized) containers of carrying molecules (drugs) from one place to another. The structures are suitable for both transporting water-soluble or water-insoluble drugs. Since the lipids used are biocompatible molecules, this may also enhance their adsorption and penetration into the cells. 

During the past decades, liposomes have been used for drug delivery on account of their unique solubilization characteristics for water-insoluble organic substances. A liposome encapsulates a region of aqueous solution inside a hydrophobic membrane dissolved hydrophilic solutes cannot readily pass through the lipids. Hydrophobic chemicals can be dissolved into the membrane, and this way, the liposome can carry... 

---