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Computational study of the interaction between inhaled carbon nanoparticles and lung membranes

Final Report Summary - PLUM (Computational study of the interaction between inhaled carbon nanoparticles and lung membranes)

The PLUM project studied the interaction between synthetic nanomaterials and biological membranes, by computational means.

The safety of nanomaterials is a primary concern. On the one hand, the past decades have seen hundreds of new applications of nanomaterials developed and patented. Nanomaterials are more and more often synthesized for high-tech applications ranging from data-storage devices to nanomedicine. On the other hand, undesired nanomaterials can be released in the environment. This is the case of amorphous nanocarbon, that is a byproduct of combustion processes. Plastic nanoparticles are another example: they result from the undesired, but inevitable, degradation of everyday-use products. Plastic packaging, for example, releases degraded oligomers into our food. Plastic waste, floating in the ocean or piled up in landfills, is degraded by wear and sunlight, and eventually enters the food chain.

The project is focused on the effects of carbon nanoparticles (CNP) and polystyrene nanoparticles (PNP) on biological membranes.

Independently of the mechanism of exposure, the interaction between synthetic nanoparticles and cells is mediated by cell membranes. But how are biological membranes affected by CNP and PNP? Which molecular processes take place, and what is their effect on the physical properties of the membrane?

Interaction between CNP and model biological membranes.
We focused on the issue of fullerene dispersion in lipid membranes. Indeed, one of the challenges of the extraction, purification and subsequent organic functionalization of fullerenes is their dissolution. C60 is substantially insoluble in polar and H-bonding solvents, such as water. C60 fullerene has indeed a strong tendency towards aggregation even in non-polar solvents, including alkanes, where it has very low solubility. The few good solvents for C60 fullerene are toxic. Finding good solvents for fullerene that are also biocompatible is therefore an important challenge.

Our simulations show that lipid membranes are better than alkanes at dissolving fullerene aggregates. Moreover, we find the characteristics of lipid bilayers that can explain the differences between the fullerene aggregation behavior in lipid bilayers and in bulk alkanes. We isolate three possible physical features that distinguish the lipid membrane interior from bulk alkanes: confinement, chain alignment, and high density. We isolate each of these features and determine its effect on fullerene solubility, concluding that it is especially the high density, characteristic of the lipid membrane core, to favor the dissolution of C60 in the membrane interior.

Spreading of fullerene in lipid bilayers could lead to the use of such membranes as solvents for fullerene. Moreover, changing lipid composition of bilayers can alter several of their properties like density, and chemical affinities. Thus, lipid bilayers could be used as biocompatible and tunable solvents.

Interaction between PNP and model biological membranes.
We studied the interaction between a polymer of everyday use, polystyrene (PS), and biological membranes of various composition. At first we focused on homogeneous 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes, looking at the effects of nanoplastics on the physical properties of the membrane. Our simulations show that the polymer nanoparticles have an influence on the structure of the membrane (area per lipid), on its dynamics and its mechanical properties (membranes are softer after PNP incorporation).
We also studied the interaction of nanoplastics with more realistic multi-component membranes, which present phase separation into liquid-ordered and liquid-disordered phases. Similar lipid mixtures have been used as models for so-called lipid rafts, dynamic assemblies of proteins and lipids observed in eukaryotic cell membranes. Rafts are involved in a number of cellular processes, such as membrane protein sorting and signal transduction. Using massive computer simulations, we found dramatic effects of the nanoparticles on phase-separated membranes: polystyrene chains partition strongly to disordered domains, alter their composition and greatly increase their thermal stability. If similar effects were observed also in vivo, they would have tremendous impact on cellular processes.

Contact details:

Dr. Luca Monticelli, email:
Dr. Giulia Rossi, email: