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Study of interactions between polymer nanoparticles and cell membranes at atomistic levels.

ABSTRACT: Knowledge of how the structure of nanoparticles and the interactions with biological cell membranes is important not only for understanding nanotoxicological effects on human, animal health and the environment, but also for better understanding of nanoparticle fabrication for biomedical applications. In this work, we use molecular modelling techniques, namely molecular dynamics (MD) simulations, to explore how polymer nanoparticles interact with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid cell membranes. Two different polymers have been considered: 100 monomer units of polyethylene (approx. 2.83 kDa) and polystyrene (approx. 10.4 kDa), both of which have wide industrial applications. We found that, despite the polar lipid head groups acting as an effective barrier to prevent the nanoparticles from interacting with the membrane surface, irreversible adhesion can be initiated by insertion of dangling chain ends from the polymer into the hydrophobic interior of the membrane. In addition, alignment of chain segments from the polymers with that of hydrocarbon chains in the interior of the membrane facilitates the complete immersion of the nanoparticles into the cell membrane. These findings highlight the importance of the surface and the topological structures of the polymer particles that dictate the absorption behaviour into the membrane and, subsequently, induce the possible translocation into the cell.

SUBMITTER: Yong CW

PROVIDER: S-EPMC4275906 | biostudies-other | 2015 Feb

REPOSITORIES: biostudies-other

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Study of interactions between polymer nanoparticles and cell membranes at atomistic levels.

Yong Chin W CW

Philosophical transactions of the Royal Society of London. Series B, Biological sciences 20150201 1661

Knowledge of how the structure of nanoparticles and the interactions with biological cell membranes is important not only for understanding nanotoxicological effects on human, animal health and the environment, but also for better understanding of nanoparticle fabrication for biomedical applications. In this work, we use molecular modelling techniques, namely molecular dynamics (MD) simulations, to explore how polymer nanoparticles interact with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine ( ...[more]

PMID: 25533094

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Project description:The pathology of type 2 diabetes mellitus is associated with the aggregation of human islet amyloid polypeptide (hIAPP) and aggregation-mediated membrane disruption. The interactions of hIAPP aggregates with lipid membrane, as well as the effects of pH and lipid composition at the atomic level, remain elusive. Herein, using molecular dynamics simulations, we investigate the interactions of hIAPP protofibrillar oligomers with lipids, and the membrane perturbation that they induce, when they are partially inserted in an anionic dipalmitoyl-phosphatidylglycerol (DPPG) membrane or a mixed dipalmitoyl-phosphatidylcholine (DPPC)/DPPG (7:3) lipid bilayer under acidic/neutral pH conditions. We observed that the tilt angles and insertion depths of the hIAPP protofibril are strongly correlated with the pH and lipid composition. At neutral pH, the tilt angle and insertion depth of hIAPP protofibrils at a DPPG bilayer reach ~52° and ~1.62 nm with respect to the membrane surface, while they become ~77° and ~1.75 nm at a mixed DPPC/DPPG membrane. The calculated tilt angle of hIAPP at DPPG membrane is consistent with a recent chiral sum frequency generation spectroscopic study. The acidic pH induces a smaller tilt angle of ~40° and a shallower insertion depth (~1.24 nm) of hIAPP at the DPPG membrane surface, mainly due to protonation of His18 near the turn region. These differences mainly result from a combination of distinct electrostatic, van der Waals, hydrogen bonding and salt-bridge interactions between hIAPP and lipid bilayers. The hIAPP-membrane interaction energy analysis reveals that besides charged residues K1, R11 and H18, aromatic residues Phe15 and Phe23 also exhibit strong interactions with lipid bilayers, revealing the crucial role of aromatic residues in stabilizing the membrane-bound hIAPP protofibrils. hIAPP-membrane interactions disturb the lipid ordering and the local bilayer thickness around the peptides. Our results provide atomic-level information of membrane interaction of hIAPP protofibrils, revealing pH-dependent and membrane-modulated hIAPP aggregation at the early stage.

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Study of interactions between polymer nanoparticles and cell membranes at atomistic levels.

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Study of interactions between polymer nanoparticles and cell membranes at atomistic levels.

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