Synthesis and assembly of poly(ethylene glycol) - Lipids with mono-, di-, and tetraacyl chains and a poly(ethylene glycol) chain of various molecular weights

Shinji Takeoka, Katsura Mori, Haruki Ohkawa, Keitaro Sou, Eishun Tsuchida

    Research output: Contribution to journalArticle

    38 Citations (Scopus)

    Abstract

    We synthesized a series of amphiphiles with poly(ethylene glycol) [MW 2000 (PEG20), 5000 (PEG50), 12 500 (PEG125)] as a headgroup and one, two, or four palmitoyl chains (1C16, 2C16, or 4C16), using a lysine monodendron as a connector. The relationship between the hydrophilic - hydrophobic balance of the multiacyl PEG-lipids and the physicochemical characteristics in self- or co-assembly with phospholipids were studied. The PEG-lipids were easily synthesized by combination of a general liquid-phase peptide synthesis and the acylation of an amino acid. The PEG part of the PEG - lipid films was crystallized to show a typical spherulite pattern. The thermal properties and microscopic observation revealed the phase separation of PEG and acyl chain parts. The critical micelle concentrations (cmcs) mainly depend on the number of acyl chains rather than the molecular weight of the PEG chain, although the area per molecule is dependent on the molecular weight of the PEG chain rather than the number of the acyl chains. The gel-to-liquid crystalline phase transition temperature was increased with the increasing number of acyl chains and the decreasing molecular weight of the PEG chain. The PEG - lipids in the aqueous dispersions assemble to take fibrous structures with bimolecular thickness because of the intermolecular hydrogen bonding. The PEG - lipids were immobilized onto the surface of the phospholipid vesicles by simply adding their aqueous dispersions to the vesicle dispersion; however, they dissociated from the vesicles on dilution of the mixed dispersion because they were incorporated into the vesicles in an equilibrium state. To prevent the dissociation of the PEG - lipids, at least two and four acyl chains were required for PEG with MW 5000 and 12 500, respectively. The aggregation of the vesicles by the addition of water-soluble polymers was significantly inhibited with the increasing molecular weight of the PEG chain. For the tight immobilization of the PEG - lipids with the long PEG chain onto the vesicular surface, an increased number of acyl chains is necessary, and the surface modification with the long PEG chains significantly increases the dispersion stability of the vesicles.

    Original languageEnglish
    Pages (from-to)7927-7935
    Number of pages9
    JournalJournal of the American Chemical Society
    Volume122
    Issue number33
    DOIs
    Publication statusPublished - 2000 Aug 23

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    Ethylene Glycol
    Lipids
    Polyethylene glycols
    Molecular Weight
    Molecular weight
    Phospholipids
    Acylation
    Transition Temperature
    Phase Transition
    Micelles
    Hydrogen Bonding
    Immobilization
    Lysine
    Polymers
    Dispersions
    Hot Temperature
    Gels
    Amino Acids
    Peptides
    Water

    ASJC Scopus subject areas

    • Chemistry(all)

    Cite this

    Synthesis and assembly of poly(ethylene glycol) - Lipids with mono-, di-, and tetraacyl chains and a poly(ethylene glycol) chain of various molecular weights. / Takeoka, Shinji; Mori, Katsura; Ohkawa, Haruki; Sou, Keitaro; Tsuchida, Eishun.

    In: Journal of the American Chemical Society, Vol. 122, No. 33, 23.08.2000, p. 7927-7935.

    Research output: Contribution to journalArticle

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