Influence of Cholesterol Composition on the Association of Serum Mannan-Binding Proteins with Mannosylated Liposomes

Multivalent glycoliposomes and micelles to study carbohydrate-protein and carbohydrate-carbohydrate interactions

This tutorial review describes multivalent carbohydrate-protein and carbohydrate-carbohydrate interaction studies that utilize self-assembled aggregates of thermodynamically stable liposomes and micelles. Strategies to prepare multivalent glycoliposomes and micelles include: (i) insertion of synthetic glycolipids into matrix lipids; (ii) preparation of glycolipids that aggregate to liposomes and micelles and (iii) modification of the hydrophilic surfaces with desired sugars. Several design strategies have been developed in order to obtain constituent glycolipids, having multivalent sugar moieties and their subsequent interactions with proteins were assessed in relation to the type of linkers that connect the hydrophilic and lipophilic segments. Lipophilic segments other than alkyl chains have also been developed. Polymer based glycoliposomes and micelles form an emphasis. Further, glycoliposomes facilitate studies of carbohydrate-carbohydrate interactions. An overview of the various types of glycoliposomes and micelles used to study carbohydrate-protein and carbohydrate-carbohydrate recognition phenomena is presented.

Pharmacokinetic considerations for targeted drug delivery

Drug delivery systems involve technology designed to maximize therapeutic efficacy of drugs by controlling their biodistribution profile. In order to optimize a function of the delivery systems, their biodistribution characteristics should be systematically understood. Pharmacokinetic analysis based on the clearance concepts provides quantitative information of the biodistribution, which can be related to physicochemical properties of the delivery system. Various delivery systems including macromolecular drug conjugates, chemically or genetically modified proteins, and particulate drug carriers have been designed and developed so far. In this article, we review physiological and pharmacokinetic implications of the delivery systems.

New insights on the structural/functional properties of recombinant human mannan-binding lectin and its variants

Inefficient activation of complement lectin pathway in individuals with variant mannan-binding lectin (MBL) genotypes has been attributed to poor formation of higher order oligomers by MBL. But recent studies have shown the presence of large oligomers of MBL (approximately 450 kDa) in serum of individuals with variant MBL alleles. The recombinant forms of MBL (rMBL) variants except MBL/B that assemble into higher order oligomers have not yet been reported. In the present study, structural/functional properties of recombinant forms of wild type MBL (rMBL/A) and its three structural variants, rMBL/B, C, and D generated in insect cells were examined. Western blot analysis indicated covalently linked monomers to hexamers while gel filtration chromatography exhibited non-covalently linked higher order oligomers in addition to prevalent low oligomeric forms. Mannan binding determined by ELISA showed rMBL/A but not the structural variants bind to mannan. Apparent avidity of monoclonal antibody used was found to be about 18- to 52-fold weaker for rMBL structural variants than rMBL/A. Complement activation varied with maximum impairment apparent in rMBL/C followed by rMBL/B, but rMBL/D was functional to the same extent as rMBL/A. Comparison of rMBL/A to MBL purified from plasma (pMBL/A) indicated 8- and 24-fold weaker binding to mannan by BIAcore analysis and ELISA and about 5-fold lesser efficiency in activating complement. The findings provide new insights on the structural/functional properties of rMBL variants and imply that lectin pathway activation may be impaired in individuals, homozygous for the mutant alleles, MBL/C and to a lesser extent MBL/B but not MBL/D.

Optimization of tumor-selective targeting by basic fibroblast growth factor-binding peptide grafted PEGylated liposomes

We have previously shown that the peptide, KRTGQYKLC (bFGF), is recognized by fibroblast growth factor (FGF) receptor (FGFR) via binding to basic FGF (bFGF), and is capable of being used for drug delivery to tumors highly expressing FGFR and bFGF. However, although the binding and uptake of the liposomes (bFGFp-liposomes) modified by the peptide increased in the presence of bFGF, the modification induced non-specific uptake. To overcome this problem, here, we prepared bFGFp-liposomes including mPEG-DSPE. The 5 and 10% mPEG(5000)/ and 10% mPEG(3000)/bFGFp-liposomes reduced most of the interaction with erythrocytes and the uptake by macrophages, suggesting the sustained blood circulation of bFGFp grafted PEGylated liposomes. Furthermore, 10% mPEG(3000)/bFGFp-liposomes produced a significant increase in uptake in NIH3T3, A549, and B16BL6 cells with the expression of FGFR following pre-incubation with bFGF, but no increase in CHO-K1 cells lacking FGFR expression. Taken together, these results lead us to believe that bFGFp grafted PEGylated liposomes possess the functions of both PEGylated stealth liposomes and the tumor-targeting liposomes. This strategy could be applied to the development of novel tumor-selective drug delivery systems.