Liposomes using lectins

Monomers (15) and (16) have been used for the investigation of the recognition of polymeric liposomes by lectins (62). 

Figure 22.15 Glycolipid components included in liposome construction may be used to couple antibody molecules by using conjugates of lectins with the proper specificity for binding the sugar groups.

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. 

Su et al. 2005). Mannosyl lipid containing liposomes have also been used for this purpose (Zhang et al. 2005). The glycolipids are presumed to interact with lectins present on the surface of the bacterial cells. 

Studies of Con A induced agglutination of live cells are susceptible to complications such as irreversibility of the agglutinated cells upon aging (17), endocytosis of bound lectin (18) and effects of experimental conditions such as temperature, pH and ionic strength on membrane properties (J). Alternatively, the use of aldehyde-fixed cells (19), heatkilled cells (20), enucleated cells (21) and glycoprotein-incorporated liposomes (22) may lead to less problems being encountered. 

Active targeting is used to describe the specific liposomal drug localization achieved by grafting various moieties (antibodies, lectins, polymers, etc.) on the carrier surface. 

In vitro, ligand-specific affinity of mannosylated liposomes toward exogenously provided lectin Concanavalin A (Con-A) can be used as a measure of activity for OPM-anchored liposomes toward mannose receptor. 

Szoka F, Magnussen KE Wojcieszn J, et al. Use of lectins and polyethylene glycol for fusion of glycolipid containing liposomes with eukaryotic cells. Proc Natl Acad Sci USA 1981 78 1685-1689. 

An interesting approach to achieve an increased uptake after oral administration of colloidal drug carriers is to use site-specific adherence through surface modification of the colloidal systems with various entities, e.g. lectins, to a selected site in the gastrointestinal tract (124). By using this approach. Lehr et al. were able to achieve an enhanced adherence of polystyrene particles to enterocytes in vitro (125). Similarly, Rubas et al. were able to enhance the uptake of liposomes into Peyer s patches in vitro through incorporation... 

Enzyme replacement is the logical approach for the treatment of lysosomal storage diseases (7) but use of an "address label" for the injected molecule is required (8). Antibodies (5,6), hormones (9), lectins (10), glycoconjugates (11), virus coats (12), bacterial toxins (13) might be used as vectors. Liposomes injected in the blood stream are taken up rapidly by cells in the reticuloendothelial system (3). 

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