Abstract
Understanding of interactions between inorganic nanomaterials and biomolecules, and particularly lipid bilayers, is crucial in many biotechnological and biomedical applications, as well as for the evaluation of possible toxic effects caused by nanoparticles. Here, we present a molecular dynamics study of adsorption of two important constituents of the cell membranes, 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), lipids to a number of titanium dioxide planar surfaces, and a spherical nanoparticle under physiological conditions. By constructing the number density profiles of the lipid headgroup atoms, we have identified several possible binding modes and calculated their relative prevalence in the simulated systems. Our estimates of the adsorption strength, based on the total fraction of adsorbed lipids, show that POPE binds to the selected titanium dioxide surfaces stronger than DMPC, due to the ethanolamine group forming hydrogen bonds with the surface. Moreover, while POPE shows a clear preference toward anatase surfaces over rutile, DMPC has a particularly high affinity to rutile(101) and a lower affinity to other surfaces. Finally, we study how lipid concentration, addition of cholesterol, as well as titanium dioxide surface curvature may affect overall adsorption.
Highlights
Other studies have reported that the phosphate group of phosphatidylcholine (PC) lipids can bind to the surface of metal oxides and the formation of supported lipid bilayers on TiO2 NPs is possible.[31,39]
We study interactions of the two most abundant lipids in the plasma membrane, phosphatidylcholine and phosphatidylethanolamine with several low-energy anatase and rutile planar surfaces and a spherical anatase nanoparticle using all-atom molecular dynamics simulations
We found that POPE lipids tend to form partial bilayers on the surface of TiO2
Summary
Titanium dioxide nanoparticles (NPs) are ubiquitous in personal care products,[1,2] food,[3−5] various paint and selfcleaning coatings,[6−10] as well as in advanced applications like photocatalysts and dye-sensitized solar cells.[11−15] TiO2 is bilayers used as a substrate for solid-supported for biosensor applications.[16−19] phospholipid recent studies have raised associated wcoitnhcertnheaibr outotxpicoitteyn.4t,i2a0l−h2e5alTthiOri2sksisofknToiOw2nNPs for producing reactive oxygen species, which can damage neurons,[26] oxidize, and rupture cell membranes.[27,28] Exposure to TiO2 NPs can cause lung inflammation and increased blood coagulation connected with cardiovascular diseases.[23,24] many possible adverse outcomes of TiO2 NPs exposure are known, the molecular mechanisms of the nanotoxicity are uncertain.[29,30] To study the nanotoxicity mechanisms, a large number of experimental studies on model systems were carried out.[19,25,27,31−37] It is well accepted that in an organism, a nanoparticle becomes covered by a layer of proteins, lipids, and other organic molecules,[38] which is called protein corona and which determines, in a large extent, the further fate of NP in the organism and potential toxic effects. Another study has shown that TiO2 NPs can penetrate layers of dipalmitoylphosphatidylcholine (DPPC) lipids.[37] More detailed information about the interactions of lipid molecules with the inorganic surfaces is reported by Yu et al.[25] They have studied the toxicity of anatase and rutile NPs (20−40 nm) and have found that anatase NPs have a higher affinity toward proteins and mainly impair mitochondrial function. Other studies have reported that the phosphate group of phosphatidylcholine (PC) lipids can bind to the surface of metal oxides and the formation of supported lipid bilayers on TiO2 NPs is possible.[31,39] the stability of PC bilayers is relatively low compared to silica NPs because the adsorption is based mainly on weak van der Waals interactions as bulky choline group blocks the phosphate.[35] Wang et al.[35] have demonstrated the importance of phosphate binding by showing that inverse PC lipids with the Received: May 24, 2021 Revised: July 2, 2021 Published: July 16, 2021
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