Liposome targeting agents

Vesicles and liposomes are versatile supermolecular systems and possess numerous potential applications in targeting agents, microreactors, encapsulations, and drug delivery. The Rotello group developed novel recognition-mediated polymersomes... 

The main opportunity for advanced drag delivery systems in this market is in the area of targeted drag delivery. Current research is focused on the development of carriers such as liposomes and on the use of monoclonal antibodies as targeting agents (see Sections 5.2 and 5.3). The eventual market opportunity is considerable—cancer is still one of the commonest fatal diseases, and some of the most deadly forms are resistant to available therapies. The potential market for effective targeting delivery systems may eventually exceed 5 billion. Whether, and how soon, it achieves this figure will depend on the speed with which successful products come to market. 

Vesicles and liposomes are versatile supramolecular systems with unusual stability and great potential as functional materials with applications in biosensors, targeting agents, microreactors, and encapsulation/drug delivery. 

Mix lipids (as showing on Table 2 for preparing 30 mg of appropriate sample) in a 250 mL round bottom flask according to the desired lipid molar ratio. For liposomal conjugation with an antibody or similar targeting agent, MPB-PE or PEG-PE is to be added. 

Kabalka G, Buonocore E, Hubner K, Moss T, Norley N, Huang L (1987) Gadolinium-labeled liposomes targeted MR contrast agents for the liver and spleen. Radiology 163(l) 255-258... 

In recent years, liposomes and supported membranes composed of fluid lipids have seen increased use as biolabeling and targeting agents, coatings for sensor transducers and biocompatible materials, nanoscale bioreactors, and separations media. Due to their enhanced stability, functionalized poly(lipid) materials have also been created and characterized for these applications. 

Finally, the targeting of liposomal antitumour agents on a cellular level requires recognition units. As a simple and readily accessible model system, we chose the interaction of lectins (plant proteins) which have specific recognition sites for certain sugars. The well known lectin Concanavalin A is able to bind four... 

The same authors also investigated intra-liposomal pH measurements and agglutination assays to study more deeply the behavior of the glycosylated liposomes in acidic conditions. The glycosylated vesicles were found to be quite stable and the pH of the internal aqueous compartment remained close to 4 even when more acidic conditions were imposed to the external phase (pH 1.2-2). Such a pH gradient depended essentially on the nature of phospholipids used and was not extensively affected by the incorporation of the targeting agent. 

Fig. 8 Nanosystems that may function as simultaneous drug delivery and imaging agents for targeting T cells (a) liposomal systems, (b) solid biodegradable nanoparticulates, and (c) macro-molecular dendrimer complexes. PEG polyethylene glycol, Gd-DTPA gadolininum-diethylene triamine penta acetic acid. (Adapted from [48])...

Figure 22.17 Antibody-liposome conjugates may be used as targeting reagents for detection or therapeutic applications. The liposome may be constructed to contain fluorescent molecules for detection purposes or bioactive agents for therapy. The antibody component targets the complex for binding to specific antigenic determinants.

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