The presence of uncoated gold nanoparticle aggregates may alter the phase of phosphatidylcholine lipid as evidenced by vibrational spectroscopies

AbstractSpherical structures built from uni- and multilamellar lipid bilayers (LUV and MLV) are nowadays considered not just as nanocarriers of various kinds of therapeutics, but also as the vehicles that, when coupled with gold (Au) nanoparticles (NPs), can also serve as a tool for imaging and discriminating healthy and diseased tissues. Since the presence of Au NPs or their aggregates may affect the properties of the drug delivery vehicle, we investigated how the shape and position of Au NP aggregates adsorbed on the surface of MLV affect the arrangement and conformation of lipid molecules. By preparing MLVs constituted from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) in the presence of uncoated Au NP aggregates found i) both within liposome core and on the surface of the outer lipid bilayer, or ii) adsorbed on the outer lipid bilayer surface only, we demonstrated the maintenance of lipid bilayer integrity by microscopic techniques (cryo-TEM, and AFM). The employment of SERS and FTIR-ATR techniques enabled us not only to elucidate the lipid interaction pattern and their orientation in regards to Au NP aggregates but also unequivocally confirmed the impact of Au NP aggregates on the persistence/breaking of van der Waals interactions between hydrocarbon chains of DPPC.Keywords: 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC)Gold nanoparticle (Au NP) aggregatesinteraction pattern and lipid phase changemicroscopy (cryo-EMTEMAFM)spectroscopy (SERS and FTIR-ATR) and calorimetry AcknowledgementWe sincerely thank Dr. Lucija Horvat (Laboratory for Molecular Plant Biology and Biotechnology, Division of Molecular Biology, Ruđer Bošković Institute) for the measurements performed on the confocal microscope and to the members of Laboratory for biocolloids and surface chemistry (Division for Physical Chemistry, Ruđer Bošković Institute) for who enabled the access to the Zetasizer Nano ZS (Malvern).Disclosure statementThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests.Additional informationFundingThis paper was supported by Croatian Science Foundation, Project No. UIP-2020–02-7669. L. P. thanks to Dr. David M. Smith for giving the grant for visiting the University of Le Mans and Prof. Dr. Marc Lamy de la Chapelle's lab. Q. L. acknowledges the région Pays de la Loire, France, for the financial support (contract n°: TE_2021_POSTDOC_IMMM_LMU_154225).