title: Ethylene glycol monolayer protected nanoparticles: synthesis, characterization, and interactions with biological molecules.
abstract: The usefulness of the hybrid materials of nanoparticles and biological molecules on many occasions depends on how well one can achieve a rational design based on specific binding and programmable assembly. Nonspecific binding between nanoparticles and biomolecules is one of the major barriers for achieving their utilities in a biological system. In this paper, we demonstrate a new approach to eliminate nonspecific interactions between nanoparticles and biological molecules by shielding the nanoparticle with a monolayer of ethylene glycol. A direct synthesis of di-, tri-, and tetra(ethylene glycol)-protected gold nanoparticles (Au-S-EGn, n = 2, 3, and 4) was achieved under the condition that the water content was optimized in the range of 9-18% in the reaction mixture. With controlled ratio of [HAuCl4]/[EGn-SH] at 2, the synthesized particles have an average diameter of 3.5 nm and a surface plasma resonance band around 510 nm. Their surface structures were confirmed by 1H NMR spectra. These gold nanoparticles are bonded with a uniform monolayer with defined lengths of 0.8, 1.2, and 1.6 nm for Au-S-EG2, Au-S-EG3, and Au-S-EG4, respectively. They have great stabilities in aqueous solutions with a high concentration of electrolytes as well as in organic solvents. Thermogravimetric analysis revealed that the ethylene glycol monolayer coating is ca. 14% of the total nanoparticle weight. Biological binding tests by using ion-exchange chromatography and gel electrophoresis demonstrated that these Au-S-EGn (n = 2, 3, or 4) nanoparticles are free of any nonspecific bindings with various proteins, DNA, and RNA. These types of nanoparticles provide a fundamental starting material for designing hybrid materials composed of metallic nanoparticles and biomolecules.
authors.affiliation: Central Research and Development, Du Pont, Experimental Station, Wilmington, Delaware 19880, USA.
authors.forename: Ming
authors.initials: M
authors.lastname: Zheng
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Li
authors.forename: Xueying
authors.initials: X
authors.lastname: Huang
mesh_terms: D001672:Biocompatible Materials / Q000138:chemical synthesis*; D001704:Biopolymers / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D019855:Ethylene Glycol; D006046:Gold; D008422:Materials Testing; D049329:Nanostructures / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry; D012313:RNA / Q000737:chemistry; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D001704:Biopolymers; D011506:Proteins; D012313:RNA; D006046:Gold; D004247:DNA; D019855:Ethylene Glycol