Journal
JOURNAL OF PHYSICAL CHEMISTRY C
Volume 118, Issue 20, Pages 11131-11141Publisher
AMER CHEMICAL SOC
DOI: 10.1021/jp5024026
Keywords
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Funding
- Academy of Finland through its Centre of Excellence Programs [251748, 272130]
- Academy of Finland [128341]
- European Research Council (Advanced Grant CROWDED-PRO-LIPIDS)
- Academy of Finland (AKA) [128341, 128341] Funding Source: Academy of Finland (AKA)
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Despite being chemically inert as a bulk material, nanoscale gold can pose harmful side effects to living organisms. In particular, cationic Au nanoparticles (AuNP+) of 2 nm diameter or less permeate readily through plasma membranes and induce cell death. We report atomistic simulations of cationic Au nanoparticles interacting with realistic membranes and explicit solvent using a model system that comprises two cellular compartments, extracellular and cytosolic, divided by two asymmetric lipid bilayers. The membrane-AuNP+ binding and membrane reorganization processes are discovered to be governed by cooperative effects where AuNP+, counterions, water, and the two membrane leaflets all contribute. On the extracellular side, we find that the nanoparticle has to cross a free energy barrier of about 5 k(B)T prior forming a stable contact with the membrane. This results in a rearrangement of the zwitterionic lipids and nanoparticle side groups in the contact area, giving rise to the initial stage of pore formation on the membrane surface. Such behavior is not seen on the cytosolic side, where AuNP+ is spontaneously captured by the negatively charged phosphatidylserine lipids that diffuse to enrich the membrane leaflet underneath AuNP+, further pointing to AuNP+ accumulation on the inner leaflet of a plasma membrane. The results suggest AuNP+ permeation to take place through the formation of a pore together with partial nanoparticle neutralization/deprotonation, leading to membrane disruption at higher nanoparticle concentrations. The data also suggest a potential mechanism for cytotoxicity as AuNP+ binding to the extracellular leaflet may trigger apoptosis through translocation of phosphatidylserine.
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