The work, “Size dependency of gold nanoparticles interacting with model membranes” now published in Nature Communications Chemistry, was initiated as part of the SmarNanoTox project funded by the European Union's Horizon 2020 research and innovation programme. Our contribution to this programme was to focus on investigating the interaction between nanoparticles and model biological systems.
Nanoparticles are used in a wide range of sectors including technologies, cosmetics and food. They can be incredibly useful and provide properties that before were unthinkable. However, their expanding production has led to increasing concerns regarding their impact on human health and the environment in general. Identifying nanoparticle hazards to natural organisms is difficult given the wide variety of nanoparticles, their diverse properties and the complexity of biological entities. One of the key initiating events for a (nano)toxicological response is the interaction of nanoparticles with membranes. By using gold nanoparticles (AuNPs) and a minimal model system, we demonstrated the size dependency of the AuNPs-membrane interaction. In our system, the interaction outcomes are driven by non-specific nanoparticle adhesion (non-receptor mediated) and the fate of a nanoparticle in contact with a membrane is determined by its size.
To study this interaction, we decided to use large unilamellar vesicles as minimal model membrane systems and study how the lipid bilayer behaves in contact with AuNPs of different sizes. We investigated this interaction by coupling qualitative data with quantitative measurement of thermodynamic parameters of interaction. Briefly, the experiments revealed the presence of two critical diameters at around 10 nm and 50 nm. The interaction outcomes change accordingly with the nanoparticle diameter and the area ratio between AuNPs and lipid vesicles. At a diameter equal or below 10 nm, it is possible to observe interesting interaction feature such as cooperative wrapping and tubular membrane structures where the AuNPs appear enclosed within a membrane tube. Partial wrapping with a characteristical penetration depth is instead observable at diameters between 10 and 50 nm while interaction at larger sizes are inhibited by the increase of bending energy contribution.
Our experimental outcomes can be used as direct relevance for theoretical and computational studies on the prediction of nanoparticles interacting with membranes. At the same time, our results provide new insights on the mechanisms of interaction between nanoparticles and membranes offering a two-fold advantage: better understanding of the key initiating events in the development of nanotoxicity as well as the design of efficient nanoparticle vectors for drug delivery.