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Abstract
The continuous release of engineered nanomaterial (ENM) into the environment may bring along health concerns following human exposure. One important source of ENMs are silver nanoparticles (NPs) that are extensively used as anti-bacterial additives. The introduction of ENMs into the human body can occur via ingestion, skin uptake, or the respiratory system. Therefore, evaluating how NPs translocate over bio-membranes is essential in assessing their primary toxicity. Unfortunately, data regarding membrane-NP interaction is still scarce, as is a theoretical and in-silico insight that governs adhesion and translocation for the most relevant NPs and membranes. Coarse-grained (CG) molecular descriptions alleviate this situation but are hampered by the absence of a direct link to specific NP materials and membrane adhesion mechanisms. Here, we interrogate the relationship between the standard CG NP representation and the adhesion characteristics of a model lung membrane. We find that the standard model is inapt of describing silver (Ag) NPs of different sizes, meaning that a matching CG representation for one size is not transferable to other sizes. In addition, we identify two basic types of primary adhesion - (partial) NPs
wrapping by the membrane and NP insertion into the membrane - that depend on the NP’s overall hydrophobicity and significantly differ in terms of lipid coatings. The
non-transferability of the standard CG model forms an inspiration for introducing a core-shell model even for bare NPs that are uniform in composition. We show that this
extension allows us to reproduce the size-dependent adhesion properties of bare Ag NPs at the atomistic scales. Next, we evaluate adhesion signatures for bare Ag NPs up
to 10 nm diameter, illustrating that the previously atomically resolved lipid response to binding is correctly reproduced at the CG level. The simulation for the largest NP provides insight into the role of water in trapping NPs into defected mixed monolayer- bilayer states. This metastable situation is well beyond the previously considered elastic models and implicit-solvent molecular descriptions. We expect this development to be instrumental for simulating NP membrane adhesion towards experimental length and time scales for particular NP materials.
Supplementary materials
Title
A systematic core-shell approach for coarsening nanoparticle-membrane interactions: application to silver nanoparticles
Description
Understanding the hazards of engineered nanomaterial poses to biological interfaces is of utmost importance in carefully assessing their associated toxicity.
Here, we employed constrained and unconstrained CG-MD simulations of Ag NP with three NP diameters (3, 5 & 10 nm), we extract the NP binding propensity at membrane-comparable NP dimensions, as well as the NP-induced structural and dynamical membrane perturbation based on our previous work (Nanoscale Adv., 2021,3, 6635-6648). We employed a different modelling scheme to model NP by separating it into a core and shell instead of a uniform representation. The combination of a systematic coarse-graining of Ag NP & size transferability and a realistic bio-interface, provide new fundamental insight into the role of NP properties in membrane binding. We found that the Ag NP prefers to insert itself into the membrane rather than budding out of it, a new metastable state first time observed with a modelling approach.
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