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Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy
Published on: August 13, 2019
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Interfacial Structure and Hydration of 3D Lipid Monolayers in Aqueous Solution
Halil I Okur1, Yixing Chen1, Nikolay Smolentsev1
1Laboratory for Fundamental BioPhotonics (LBP), Institute of Bioengineering (IBI), and Institute of Materials Science (IMX), School of Engineering (STI), and Lausanne Centre for Ultrafast Science (LACUS), École Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
The Journal of Physical Chemistry. B
|March 7, 2017
Summary
Phosphatidylcholine (PC) lipids form 3D monolayers on nanodroplets. Lipid structure, including acyl chain length and saturation, affects monolayer packing and disorder, with implications for drug delivery systems.
Area of Science:
- Biophysics
- Materials Science
- Surface Chemistry
Background:
- Three-dimensional (3D) phospholipid monolayers on hydrophobic surfaces are crucial in biological systems (e.g., adiposomes) and synthetic applications like drug delivery.
- A detailed molecular-level understanding of these 3D monolayers is currently lacking.
Purpose of the Study:
- To investigate the molecular structure and packing of phosphatidylcholine (PC) lipid monolayers on hexadecane nanodroplets.
- To elucidate how variations in lipid acyl chain length, saturation, and number of tails influence monolayer organization.
Main Methods:
- Utilized vibrational sum frequency (VSF) and second harmonic scattering (SHS) techniques.
- Examined various phosphatidylcholine lipids, including DPPC, DMPC, DLPC, DOPC, and lyso-PC, on hexadecane nanodroplets.
Main Results:
- Lipid acyl chain length significantly impacts monolayer packing; shorter chains (DMPC, DLPC) introduce more gauche defects compared to longer chains (DPPC).
- Unsaturated lipids (DOPC) and single-acyl chain lipids (lyso-PC) exhibit increased disorder within the monolayers.
- Despite packing variations, headgroup orientation remained consistently parallel to the nanodroplet interface.
- Lyso-PC uniquely formed diluted and "patchy" 3D monolayers.
Conclusions:
- Lipid molecular structure dictates the organization and packing density of 3D phospholipid monolayers on hydrophobic surfaces.
- Understanding these structure-property relationships is vital for designing advanced materials, particularly in drug delivery systems.
- The observed headgroup orientation suggests a general interfacial behavior for PC lipids in this 3D context.
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