Shape and Phase Transitions in a PEGylated Phospholipid System

Lauri Viitala, Saija Pajari, Luigi Gentile, Jukka Määttä, Marta Gubitosi, Jan Deska, Maria Sammalkorpi, Ulf Olsson, Lasse Murtomäki*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

24 Citations (Scopus)
262 Downloads (Pure)


Poly(ethylene glycol) (PEG) polymers and PEG-conjugated lipids are widely used in bioengineering and drug transport applications. A PEG layer in a drug carrier increases hydrophilic repulsion, inhibits membrane fusion and serum opsonin interactions, and prolongs the storage and circulation time. It can also change the carrier shape and have an influence on many properties related to the content release of the carrier. In this paper, we focus on the physicochemical effects of PEGylation in the lipid bilayer. We introduce laurdanC as a fluorophore for shape recognition and phase transition detection. Together with laurdanC, cryogenic transmission electron microscopy, differential scanning calorimetry, molecular dynamics simulations, and small-angle X-ray scattering/wide-angle X-ray scattering, we acquire information of the particle/bilayer morphology and phase behavior in systems containing 1,2-dipalmitoyl-sn-glycero-3-phosphocholine:1,2-distearoyl-sn-glycero-3-phosphoethanolamine-PEG(2000) with different fractions. We find that PEGylation leads to two important and potentially usable features of the system. (1) Spherical vesicles present a window of elevated chain-melting temperatures and (2) lipid packing shape-controlled liposome-to-bicelle transition. The first finding is significant for targets requiring multiple release sequences and the second enables tuning the release by composition and the PEG polymer length. Besides drug delivery systems, the findings can be used in other smart soft materials with trigger-polymers as well.

Original languageEnglish
Pages (from-to)3999-4010
Number of pages12
Issue number11
Publication statusPublished - 19 Mar 2019
MoE publication typeA1 Journal article-refereed


  • liposome
  • PEGylation
  • Drug delivery
  • light triggering
  • SAXS
  • Calorimetry
  • molecular dynamics simulation
  • Fluorescence spectroscopy
  • TEM


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