As part of a broad research effort in the NSF-funded Center for Chemical Innovation on Sustainable Nanotechnology, the goal of this work is to understand the fundamental chemistry of how nanoparticles interact with biologically relevant interfaces in situ at the molecular level. Surface specific nonlinear optical spectroscopies, namely second harmonic (SHG) and sum frequency generation (SFG), are used to investigate the interactions of nanoparticles with lipid bilayers as model cell membranes. Specifically, SHG allows us to probe binding interactions, while SFG allows us to investigate the effect of nanoparticle interactions with the molecular structure of the lipids.We use resonant and nonresonant SHG to quantify interfacial charge densities and potentials in real time for bilayers of various lipid compositions with and without gold nanoparticles present. We have shown how a supported lipid bilayer carrying a negative interfacial potential may interact with positively charged as well as negatively charged gold nanoparticles. For the case where the interaction does not seem favorable based on electrostatics, charge-charge repulsion does not appear to inhibit particle-bilayer interactions. Combining this knowledge with the SFG results detailing the molecular structural changes due to the nanoparticle-membrane interaction, allows us to predict possible pathways for the molecular level nanoparticle-lipid bilayer interactions.The impact of lipid composition, NP core composition, and capping ligand on the nanoparticle-membrane interactions is investigated. Understanding how nanomaterials interact with lipid bilayers at the molecular level is important for predicting and controlling molecular interactions of nanomaterials with living systems as well as designing environmentally and biologically sustainable nanomaterials.

Nanoparticle interactions with supported lipid bilayers studied by nonlinear optics

248th National Meeting (2014)

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