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Hybrid lipid/block copolymer vesicles display broad phase coexistence region.

Authors
  • Hamada, Naomi1
  • Gakhar, Sukriti1
  • Longo, Marjorie L2
  • 1 Department of Chemical Engineering, University of California Davis, Davis, CA 95616, United States. , (United States)
  • 2 Department of Chemical Engineering, University of California Davis, Davis, CA 95616, United States. Electronic address: [email protected] , (United States)
Type
Published Article
Journal
Biochimica et biophysica acta. Biomembranes
Publication Date
Jan 11, 2021
Volume
1863
Issue
4
Pages
183552–183552
Identifiers
DOI: 10.1016/j.bbamem.2021.183552
PMID: 33444620
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

The fluidity and polar environment of ~100 nm hybrid vesicles combining dipalmitoylphosphatidylcholine (DPPC) and poly(1,2-butadiene)-block-polyethylene oxide (PBd-PEO, average molecular weight 950 g/mol) were studied upon vesicle heating using the fluorescence spectroscopy techniques of DPH anisotropy and laurdan generalized polarization (GP). These techniques indicated PBd-PEO membranes are less ordered than solid DPPC, but slightly more ordered than fluid DPPC or dioleoylphosphatidylcholine (DOPC) membranes. We find the DPH anisotropy values are less than expected from additivity of the components' anisotropies in the fluid phase mixture of DPPC and PBd-PEO, inferring that DPPC strongly fluidizes the PBd-PEO. We use transitions in DPH anisotropy and laurdan GP to create a temperature/composition phase diagram for DPPC/PBd-PEO which we find displays a significantly broader solid/fluid phase coexistence region than DPPC/DOPC, showing that DPPC partitions less readily into fluid PBd-PEO than into fluid DOPC. The existence of a broad solid/fluid phase coexistence region in DPPC/PBd-PEO vesicles is verified by Förster resonance energy transfer results and the visualization of phase separation in giant unilamellar vesicles containing up to 95% PBd-PEO and a single phase in 100% PBd-PEO vesicles at room temperature. These results add to the limited knowledge of phase behavior and phase diagrams of hybrid vesicles, and should be useful in understanding and tailoring membrane surface architecture toward biomedical applications such as drug delivery or membrane protein reconstitution. Copyright © 2021 Elsevier B.V. All rights reserved.

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