title: Controlled, simultaneous assembly of polyethylenimine onto nanoparticle silica colloids.
abstract: A novel precision-assembly methodology is described on the basis of the controlled, simultaneous assembly (CSA) of a core nanoparticle substrate and polyelectrolyte solutions. The method is capable of assembly rates at least as fast as 10(16) core particles s(-1) L(-1) and affords concentrated suspensions of stable colloids with an adsorbed polyelectrolyte. The resulting dispersions are highly homogeneous, have a low viscosity and narrow particle-size distribution, and are stable colloids, even at solid concentrations of at least 33 wt %. The adsorption isotherm and the saturation adsorption for polyethylenimine (PEI) assemblies onto a 15 nm silica colloid have been evaluated with 1H NMR spectroscopy. The saturation adsorption is highly dependent upon the pH at assembly and is given by the equation PEIa (micromol m(-2)) = 1.73pH - 1.89, R2 = 0.986, where micromoles refers to the concentration of the EI monomer. The saturation concentration increases from 6.8 micromol m(-2) at pH 5.0 to 13.7 micromol m(-2) at pH 9.0. The adsorbed polyelectrolyte may be cross-linked and thereby permanently fixed to the colloid surface to prepare nanoparticle-polyelectrolyte colloidal assemblies having enhanced colloid stability, high homogeneity, and a high fraction (>80%) of permanently adsorbed polyelectrolyte. These assemblies are stable at physiological pH and ionic strength and may represent ideal substrates for bioconjugation and, ultimately, the design of nanocarriers for in vivo applications.
authors.affiliation: Research and Development, Eastman Kodak Company, Rochester, New York 14650-02002, USA. joseph.bringley@kodak.com
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Bringley
authors.forename: Andrew
authors.initials: A
authors.lastname: Wunder
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Howe
authors.forename: Robin D
authors.initials: RD
authors.lastname: Wesley
authors.forename: Tiecheng A
authors.initials: TA
authors.lastname: Qiao
authors.forename: Nancy B
authors.initials: NB
authors.lastname: Liebert
authors.forename: Brian
authors.initials: B
authors.lastname: Kelley
authors.forename: John
authors.initials: J
authors.lastname: Minter
authors.forename: Brian
authors.initials: B
authors.lastname: Antalek
authors.forename: James M
authors.initials: JM
authors.lastname: Hewitt