Browsing by Author "Barker, R"

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    Effect of functionalized gold nanoparticles on floating lipid bilayers
    (American Chemical Society, 2013-06-04) Tatur, S; Maccarini, M; Barker, R; Nelson, A; Fragneto, G
    The development of novel nano-engineered materials poses important questions regarding the impact of these new materials on living systems. Possible adverse effects must be assessed in order to prevent risks for health and the environment. On the other hand, a thorough understanding of their interaction with biological systems might also result in the creation of novel biomedical applications. We present a study on the interaction of model lipid membranes with gold nanoparticles (AuNP) of different surface modifications. Neutron reflectometry experiments on zwitterionic lipid double bilayers were performed in the presence of AuNP functionalized with cationic and anionic head groups. Structural information was obtained that provided insight into the fate of the AuNPs with regard to the integrity of the model cell membranes. The AuNPs functionalized with cationic head groups penetrate into the hydrophobic moiety of the lipid bilayers and cause membrane disruption at an increased concentration. In contrast, the AuNPs functionalized with anionic head groups do not enter but seem to impede the destruction of the lipid bilayer at an alkaline pH. The information obtained might influence the strategy for a better nanoparticle risk assessment based on a surface charge evaluation and contribute to nano-safety considerations during their design. © 2013, American Chemical Society.
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    The relationship between charge density and polyelectrolyte brush profile using simultaneous neutron reflectivity and in situ attenuated total internal reflection FTIR
    (American Chemical Society, 2013-05-21) Topham, PD; Glidle, A; Toolan, DTW; Weir, MP; Skoda, MWA; Barker, R; Howse, JR
    We report on a novel experimental study of a pH-responsive polyelectrolyte brush at the silicon/D2O interface. A poly[2-(diethylamino)ethyl methacrylate] brush was grown on a large silicon crystal which acted as both a substrate for a neutron reflectivity solid/liquid experiment but also as an FTIR-ATR spectroscopy crystal. This arrangement has allowed for both neutron reflectivities and FTIR spectroscopic information to be measured in parallel. The chosen polybase brush shows strong IR bands which can be assigned to the N?D+ stretch, D2O, and a carbonyl group. From such FTIR data, we are able to closely monitor the degree of protonation along the polymer chain as well as revealing information concerning the D2O concentration at the interface. The neutron reflectivity data allows us to determine the physical brush profile normal to the solid/liquid interface along with the corresponding degree of hydration. This combined approach makes it possible to quantify the charge on a polymer brush alongside the morphology adopted by the polymer chains. © 2013, American Chemical Society.