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Rotational behaviour of PEGylated gold nanorods in a lipid bilayer system

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posted on 18.06.2018 by Priyanka A. Oroskar, Cynthia J. Jameson, Sohail Murad
PEGylated gold nanorods are widely used as nanocarriers in targeted drug delivery and other nanotechnology applications due to the special optical and photo-thermal characteristics of gold nanorods. In this work, we employ coarse-grain molecular simulations to examine the pathway by which PEGylated gold nanorods enter and exit a dipalmitoylphosphatidylcholine lipid bilayer membrane and follow the behaviour of the system to investigate the consequences. We find that PEGylated gold nanorods rotate during permeation, lying down and straightening up as they make their way through the lipid membrane. We find that this rotational behaviour, irrespective of the initial orientation of the nanorod with respect to the membrane normal, is concomitant with the changing interactions of polyethylene glycol (PEG) beads with lipid head beads in both membrane leaflets. For a nanorod with hydrophilic ligands, such as PEG, lying down appears to be driven by favourable hydrophilic interactions with the phosphate and choline groups of the lipid. Mobility of the ligands offers mechanisms for these favourable interactions and for minimising unfavourable interactions with the hydrophobic lipid tails that constitute the inner section of the membrane; the PEG ligands can stretch out to reach the phosphate and choline groups of both leaflets and they can coil in and interact with each other and avoid the alkane lipid tails. Recently developed experimental techniques for imaging, orientation, and rotation of single gold nanorods may be able to observe this predicted rotational behaviour. We find that lipid flip-flop mechanisms do not differ significantly from a spherical gold nanoparticle to a gold nanorod, and PEGylated gold nanorods like their spherical counterparts do not remove lipid molecules from the bilayer membrane. Our results should be of interest to experimentalists who plan to use functionalised gold nanorods in biomedical applications.

Funding

This research has been funded by a grant from the National Science Foundation (Grant No. CBET-1263107/1545560

History

Publisher Statement

Post print version of article may differ from published version. This is an electronic version of an article published in Oroskar, P. A., Jameson, C. J. and Murad, S. Rotational behaviour of PEGylated gold nanorods in a lipid bilayer system. Molecular Physics. 2017. 115(9-12): 1122-1143.. Molecular Physics is available online at: http://www.informaworld.com/smpp/ DOI:10.1080/00268976.2016.1248515

Citation

Oroskar, P. A., Jameson, C. J. and Murad, S. Rotational behaviour of PEGylated gold nanorods in a lipid bilayer system.Molecular Physics. 2017.115(9-12): 1122-1143. 10.1080/00268976.2016.1248515

Publisher

Taylor & Francis

Language

en_US

issn

0026-8976

Issue date

04/08/2016

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