Aggregation of PEGylated liposomes driven by hydrophobic forces.

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  • Additional Information
    • Source:
      Publisher: Elsevier Country of Publication: Netherlands NLM ID: 9315133 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1873-4367 (Electronic) Linking ISSN: 09277765 NLM ISO Abbreviation: Colloids Surf B Biointerfaces Subsets: MEDLINE
    • Publication Information:
      Original Publication: Amsterdam ; New York : Elsevier, c1993-
    • Subject Terms:
      Ammonium Sulfate/*chemistry ; Liposomes/*chemistry ; Polyethylene Glycols/*chemistry ; Polymers/*chemistry; Biophysical Phenomena ; Hydrophobic and Hydrophilic Interactions ; Salts/chemistry ; Thermodynamics
    • Abstract:
      Polyethylene glycol (PEG) is widely used to sterically stabilize liposomes and improve the pharmacokinetic profile of drugs, peptides and nanoparticles. Here we report that ammonium sulfate (AS) can evoke the aggregation of PEGylated vesicles in a concentration-dependent manner. Liposomes with 5mol% PEG were colloidally stable at AS concentrations up to 0.7mM, above which they precipitated and formed micron-size aggregates with irregular shape. While aggregation was reversible up to 0.9M of AS, above 1M fusion occurred, which irreversibly distorted the size distribution. Zeta potential of liposomes markedly increased from -71±2.5mV to 2±0.5mV upon raising the AS concentration from 0 to 0.1M, but no considerable increase was seen during further AS addition, showing that the aggregation is independent of surface charge. There was no aggregation in the absence of the PEG chains, and increasing PEG molar% shifted the aggregation threshold to lower AS concentrations. Changes in the FTIR spectral features of PEGylated vesicles suggest that AS dehydrates PEG chains. Other kosmotropic salts also led to aggregation, while chaotropic salts did not, which indicates a general kosmotropic phenomenon. The driving force behind aggregation is likely to be the hydrophobic effect due to salting out the polymer similarly to what happens during protein purification or Hydrophobic Interaction Chromatography. Since liposome aggregation and fusion may result in difficulties during formulation and adverse reaction upon application, the phenomena detailed in this paper may have both technological and therapeutical consequences.
      (Copyright © 2016 Elsevier B.V. All rights reserved.)
    • Contributed Indexing:
      Keywords: Aggregation; Ammonium sulfate; Fusion; Hydrophobic effect; Kosmotropic salt; Liposome; PEG
    • Accession Number:
      0 (Liposomes)
      0 (Polymers)
      0 (Salts)
      3WJQ0SDW1A (Polyethylene Glycols)
      SU46BAM238 (Ammonium Sulfate)
    • Publication Date:
      Date Created: 20160903 Date Completed: 20170216 Latest Revision: 20181202
    • Publication Date:
      20240829
    • Accession Number:
      10.1016/j.colsurfb.2016.06.056
    • Accession Number:
      27588427