Supervised by Dr. Rebecca Notman

Publication: Thake, T. H. F., Webb, J. R., Nash, A., Rappoport, J. Z. and Notman, R. (2013) "Permeation of Polystyrene Nanoparticles across Model Lipid Bilayer Membranes". Soft Matter. 2013. 9(43). 10265-10274.

Background

Nanoparticles (NPs) have a variety of applications including in medicine for drug and gene delivery, biology for cell sensing and labeling, and commercially in sunscreens and toothpastes.¹ They are also released in vehicle and industrial emissions. Despite increased use, the environmental and health issues associated with NPs has been overlooked; it is unclear where NPs go once in the body, how they enter cells, and the damage they cause.²

In this project, I used molecular dynamics (MD) simulations to investigate the interactions of polystyrene NPs with lipid bilayers, specifically focusing on the effects of NP size and membrane composition on the passive diffusion of NPs. This involved building a coarse-grained model of polystyrene NPs³ and phospholipid bilayer with and without cholesterol (Fig. 1). Spontaneous NP-membrane interaction was first examined, followed by free energy calculations of nanoparticle insertion using umbrella sampling.

Fig 1: Coarse-Grained Model of a Polystryene Nanoparticle (NP) and Phospholipid Bilayer used as the starting point for NP-Membrane interaction analysis using molecular dynamics (MD) simulations. Both structures were built from scratch during the project.

References

^{[1] Monticelli L; Salonen E; Ke PC; Vattulainen I (2009) Effects of carbon nanoparticles on lipid membranes: a molecular simulation perspective. Soft Matter 5: 4433-4445}

^{[2] Hoet PHM; Bruske-Hohlfeld I; Salata OV (2004) Nanoparticles - known and unknown health risks. Journal of Nanobiotechnology 2: 12}

^{[3] Rossi G; Monticelli L; Puisto SR; Vattulainen I (2011) Coarse-graining polymers with the MARTINI force-field: polystyrene as a benchmark case. Soft Matter 7: 698-708}