Liposome polysaccharide coating

There occurred strong interactions between copolymer B and DL-a-di-palmitoylphosphatidilcholin (DPPC) liposomes. Polysaccharide-coated lipo-... 

Polyelectrolytes have recently found application in the development of pH sensitive liposomal controlled release systems. This application arises from the fact that polyelectrolytes may be used both to stabilize liposomes, and to disrupt liposomes in a pH dependent manner. Although the use of liposomes in oral pharmaceutical compositions has been discussed [424], liposomes generally suffer from poor stability and are therefore prone to leakage of the entrapped active agents. To overcome this problem, several authors have stabilized the liposomes using polyelectrolytes. For example, Tirrell and coworkers have employed ionene [425], and polyethylene imine) [426] to stabilize liposomes. Similarly, Sato and coworkers have studied maleic acid copolymers [427], and Sumamoto and coworkers have studied liposomes [428] coated with polysaccharides. In related work, Kondo and coworkers have emphasized the use of carboxymethyl chitin to produce artificial red blood cells [429-435]. 

Sata T (1990) Polysaccharide coated liposomes, Ph D Thesis, University of Nagasaki... 

Sunamoto, J., and Iwamoto, K. Protein-coated and polysaccharide-coated liposomes as drug carriers. CRC Crit. Rev. Ther. Drug Carrier Sys. 2 117—136, 1987. 

Most of the nucleic acid model compound prepared so far are water insoluble however, when the analogs are water soluble, they may not permeate into the hydrophobic cell membranes. Recently, an improved drug delivery system for water soluble drugs using polysaccharide-coated liposomes [68] was developed. 

Several pharmaceutical activities of nucleic acid analogs such as poly(VAd) have been studied in vitro and in cell-free systems [19]. It was expected that the present polymers would be effectively transferred into phagocytes by encapsulating in polysaccharide-coated liposomes and would show increased pharmaceutical activities similar to poly(maleic acid-a/l-2-cyclohexyl-l, 3-dioxap-5-ene) (MA-CDA) [68]. The activation of human neutrophils by poly(VAd) was evaluated by monitoring the in vitro superoxide anion production from activated human neutrophils. Shown in Table 15 is the superoxide liberated from human neutrophils (1 x 106 cells/ml) activated by poly(VAd) (0.5 mg/ml) as a function of time. Poly(VAd) encapsulated in mannan derivative-coated liposomes showed a... 

Poly(VAd) in the polysaccharide-coated liposomes activated mouse peritoneal macrophages more effectively than free poly(VAd) and the % increase in 02 maximizes at 2 h after administration (Fig. 20). These results show that poly(VAd), which is a typical synthetic analog of nucleic acids [19], modulates immune responses similar to native polynucleotides [70]. Poly(VAd-eo-MAn) in polysaccharide-coated liposome activated mouse peritoneal macrophages more effectively than free poly(VAd-eo-MAn). The percent increase in O2- production at... 

Venkatesan N, Vyas SP (2000) Polysaccharide coated liposomes for oral immimization development and characterization. Int J Pharm 203 169-177... 

Sunamoto, J. et al. Improved drug delivery to target-specific organs using liposomes as coated with polysaccharide, in Proceedings of the International Symposium on Polymers in Medicine, Porto Cervo, Sardinia, p. 3, 1982... 

Il IPROVED DRUG DELIVERY TO TARGET SPECIFIC ORGANS USING LIPOSOMES AS COATED WITH POLYSACCHARIDES... 

Polysaccharide-coated liposomes were prepared by essentially the same procedure as that adopted for the conventional liposomes. ... 

Preparation of polysaccharide-coated liposome encapsulating [ CoQio... 

T. Sato, K. Kojima, T. Ihda, J. Sunamoto, R.M. Ottenbrite, Macrophage activation by poly(maleic acid-alt-2-cyclohexyl-l,3-dioxap-5-ene) encapsulated in polysaccharide-coated liposomes,/. Bioact. Compat. Pol, 1,448-460,1986. 

Partial to complete 3-0-octadecylated polysaccharides exhibited characteristic solution and solid properties based on hydrophilic-hydrophobic structures. These polymers are suggested to form micellar conformations in water and in chloroform polysaccharide-coated liposomes, polymeric membranes, and thermotropic liquid-crystalline mesophase, depending on the octadecyl content. Hydrolysis of 3-deoxygenat-ed, 3-0-methylated, and 3-0-octadecylated dextrans by an endo-acting dextrans is compared. The possibility of a combshaped branched polysaccharide toward cell-specific biomedical materials is discussed. 

Figure 11. A loop-train-tail conformational model of polysaccharide-coated liposome.

In contrast to the previous report, in this study partition of the HP-coated liposomes to the bottom polysaccharide-rich phase occurred significantly. This suggests that a specific interaction takes place between the liposomal polysaccharide and the phase-forming polysaccharide in the bulk bottom... 

TABLE 1 Partition Efficiency (%) of Hydrophobized Polysaccharide-Coated Liposomes into an Aqueous 6.0% (w/w) PEO-20/8.0% (w/w) Pullulan-50 System... 

SUVs have also been stabilized by coating their outer surfaces with chitin [328], polylysine [329-332], polyelectrolytes [333], and polysaccharides [334]. Advantage has also been taken of electrostatic interactions to attract oppositely charged polyelectrolytes to outer SUV surfaces and subsequently polymerize them in situ [335-339]. These systems have been referred to as liposomes in a net [72]. A particularly telling example is the attachment of a two-dimensional polymeric network either to the inner or to the outer surfaces of SUVs by ion exchanging the vesicle counterions with oppositely charged polymerizable short-chain counterions and their subsequent polymerization (Fig. 42) [340-342]. 

Principles to stabilize lipid bilayers by polymerization have been outlined schematically in Fig. 4a-d. Mother Nature — unfamiliar with the radically initiated polymerization of unsaturated compounds — uses other methods to-stabilize biomembranes. Polypeptides and polysaccharide derivatives act as a type of net which supports the biomembrane. Typical examples are spectrin, located at the inner surface of the erythrocyte membrane, clathrin, which is the major constituent of the coat structure in coated vesicles, and murein (peptidoglycan) a macromolecule coating the bacterial membrane as a component of the cell wall. Is it possible to mimic Nature and stabilize synthetic lipid bilayers by coating the liposome with a polymeric network without any covalent linkage between the vesicle and the polymer One can imagine different ways for the coating of liposomes with a polymer. This is illustrated below in Fig. 53. 

J. Sunamoto 110> reported a coating of the outer liposome leaflet with partially palmitoyl-derivatized polysaccharides according to route 2 in Fig. 53. These arti-... 

Fig. 1. Preparation of 0-palmitoyl mannan-anchored vesicles. Liposomes were prepared by hand-shaking method and coating of liposomes with these hydrophobized polysaccharides (OPM) was performed by incubation of aqueous soiutions of polysaccharide derivatives with preformed liposomal dispersion...

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