Nanoparticle-lipid membrane interactions

Nanoparticles are increasingly prevalent in the environment due to release from the myriad of products that already rely on them, and that list is constantly growing. Nano-structured carbon and polymer nanoparticles are important examples. C60 fullerenes, nanocarbons, are hydrocarbon fuel additives released into the atmosphere as a by-product of combustion. Polystyrene nanoparticles are ubiquitous in plastic packaging.

Computational models of particle-cell interactions can provide enhanced understanding of biological risks and lead to fast screening tools. Scientists launched the EU-funded project 'Computational study of the interaction between inhaled carbon nanoparticles and lung membranes' (PLUM) to investigate the effects of C60 and polystyrene nanoparticles on biological membranes.

Researchers employed molecular dynamics modelling of interacting particles using Newton's equation of motion. Because there are no a priori assumptions made about the processes of interaction, simulation results can often point to new physics or mechanisms.

The study of fullerene dispersion in lipid membranes provided unexpected insight into dissolution mechanisms. Lack of solubility has hampered fullerene extraction, purification, and use in components and devices. The team showed that lipid membranes are candidate solvents and pointed to the likely reason: the high density characteristic of the lipid membrane core. This opens the door to the use of lipid bilayers as biocompatible solvents of fullerenes.

Realistic models of membranes with liquid-ordered and liquid-disordered phases showed that polystyrene nanoparticles interact strongly with such phase-separated membranes. They become highly localised in the disordered domains, changing their mechanical and thermal properties. Such membranes are models for so-called lipid rafts that play important roles in membrane protein sorting and signal transduction. The data highlight the importance of further studies to determine if similar effects occur in vivo.

Molecular dynamics simulations provided important insight related to PLUM project objectives and beyond. The dramatic effects on membranes of ubiquitous polystyrene nanoparticles emphasise the critical need for further investigation. Results also pointed to a novel way to dissolve fullerenes, until now a stumbling block in processing for use in devices. Exploitation of results should improve the safety of nanoparticles and enable new devices using them.