title: Resonance elastic light scattering (RELS) spectroscopy of fast non-Langmuirian ligand-exchange in glutathione-induced gold nanoparticle assembly.
abstract: The interactions of a biomolecule glutathione (GSH) with citrate-capped gold nanoparticles (AuNP) have been investigated to evaluate the viability of a rapid GSH-capture by gold nanoparticle carriers, as a model system for applications ranging from designing nanoparticle-enhanced functional biosensor interfaces to nanomedicine. The measurements, performed using resonance elastic light scattering (RELS) spectroscopy, have shown a strong dependence of GSH-induced scattering cross-section on gold nanoparticle size. A large increase in RELS intensity after injection of GSH, in a short reaction time (tau=60 s), has been observed for small AuNP (5nm dia.) and ascribed to the fast ligand-exchange followed by AuNP assembly. The unexpected non-Langmuirian concentration dependence of scattering intensity for AuNP (5 nm) indicates on a 2D nucleation and growth mechanism of the ligand-exchange process. The ligand-exchange and small nanoparticle ensemble formation followed by relaxation have been observed in long term (10 h) monitoring of GSH-AuNP interactions by RELS. The results of molecular dynamics and quantum mechanical calculations corroborate the mechanism of the formation of hydrogen-bonded GSH-linkages and interparticle interactions and show that the assembly is driven by multiple H-bonding between GSH-capped AuNP and electrostatic zwitterionic interactions. The RELS spectroscopy has been found as a very sensitive tool for studying interparticle interactions. The application of RELS can be expanded to monitor reactivities and assembly of other monolayer-protected metal clusters, especially in very fast processes which cannot be followed by other techniques.
authors.affiliation: Department of Chemistry, State University of New York at Potsdam, Potsdam, NY 13676, USA.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Stobiecka
authors.forename: Kaitlin
authors.initials: K
authors.lastname: Coopersmith
authors.forename: Maria
authors.initials: M
authors.lastname: Hepel
mesh_terms: D005978:Glutathione / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D006860:Hydrogen Bonding; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D008954:Models, Biological; D013057:Spectrum Analysis
chemical_list: D008024:Ligands; D006046:Gold; D005978:Glutathione