<p>Designer
biosurfactants can be used to stabilise and functionalise interfaces. One
particularly promising use is the stabilisation of oil-in-water emulsions,
enabling fine tuning physical, chemical and biological surface properties. The
ability of emulsion systems to carry high payloads makes them attractive for
applications in medicine, food and fragrances, and cosmetics. However, they
have limited long-term stability. Here we sought to use the metal ion-chelating
ability of the biosurfactant peptide, AM1, to precipitate the formation of a
gold metal shell on AM1-stabilised emulsions by electroless plating. We found
that replacing the commonly used zinc(II) with palladium(II) for coordination
by histidine residues of adjacent AM1 peptides produced interfacial films that
maintained elasticity at acidic pH. Proton NMR suggested a coordination
mechanism independent of the imidazole ring of the histidines. Nevertheless. stabilisation
of emulsions at low pH enabled the deposition of a gold shell, albeit by an
unexpected mechanism. We propose that gold nanoparticles forming in bulk are
adsorbed onto the peptide-stabilised interface, accumulating into a particulate
coating. The resulting one-step method for nanoparticle precipitation and shell
formation will be useful for the creation of biocompatible core-shell particles
for applications where large payloads of hydrophobic active compounds require
stability over long time periods.</p>
Templating Core-Shell Particles Using Metal Ion-Chelating Biosurfactants
