Self-aggregate nanoparticles of cholesteryl and galactoside groups-substituted pullulan and their specific binding to galactose specific lectin, RCA120

Abstract

The hydrophobized polysaccharide cholesterol-bearing pullulan (CHP) forms hydrogel nanoparticles upon self-aggregation in water. To endow cell specificity to nanoparticles of CHP, galactosides were additionally substituted to CHP with various spacer lengths and degrees of substitution. The resulting CHP derivatives also form monodisperse nanoparticles by self-aggregation in water. All self-aggregate nanoparticles strongly bind to the β-D-galactose-specific lectin, RCA120 (Ricinus communis agglutinin). The affinity of substituted galactosides to the lectin was quantitatively studied using a fluorescence polarization technique by competitive binding with 4-methylumbelliferyl β-D-galactopyranoside (MUG). This affinity strongly depends on its chemical structure, degree of substitution, and spacer length. The binding constant per galactose moiety drastically increased by substitution to the polymer backbone.