Oligothiol Graft-Copolymer Coatings Stabilize Gold Nanoparticles against Harsh Experimental Conditions

• Published in: Langmuir Vol. 28; no. 49; pp. 16751 - 16760
• Main Authors: Kang, Jun Sung, Taton, T. Andrew
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 11.12.2012
• Subjects: Adsorption; Binding, Competitive; Biotechnology; Chemistry; Coated Materials, Biocompatible - chemical synthesis; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Gold - chemistry; Hot Temperature; Ligands; Light; Metal Nanoparticles - chemistry; Oxidants; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Polyethylene Glycols - chemical synthesis; Polylysine - analogs & derivatives; Polylysine - chemical synthesis; Scattering, Radiation; Spectrometry, Fluorescence; Spectrophotometry, Atomic; Sulfhydryl Compounds - chemistry; Surface Properties; Thermodynamics; Gold; Thiol; Structure stability; Graft copolymer; Nanoparticle; Stabilization; Light scattering; Fluorescence; Polymer; Transition metal; High temperature; Oxidant; Density; Grafting; Aggregation; Ethylene oxide polymer; Particle; Thermodynamics; Dynamics; Lysine; Light absorption; Spectrophotometry
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la301249a

We report that poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) copolymers that bear multiple thiol groups on the polymer backbone are exceptional ligands for gold nanoparticles (AuNPs). In general, these graft copolymer ligands stabilize AuNPs against environments that would ordinarily lead to particle aggregation. To characterize the effect of copolymer structure on AuNP stability, we synthesized thiolated PLL-g-PEGs (PLL-g-[PEG:SH]) with different backbone lengths, PEG grafting densities, and number of thiols per polymer chain. AuNPs were then combined with these polymer ligands, and the stabilities of the resulting AuNP@PLL-g-[PEG:SH] particles against high temperature, oxidants, and competing thiol ligands were characterized using dynamic light scattering, visible absorption spectroscopy, and fluorescence spectrophotometry. Our observations indicate that thiolated PLL-g-PEG ligands combine thermodynamic stabilization via multiple Au–S bonds and steric stabilization by PEG grafts, and the best graft copolymer ligands balance these two effects. We hope that this new ligand system enables AuNPs to be applied to biotechnological applications that require harsh experimental conditions.