Oligonucleotide loading determines cellular uptake of DNA-modified gold nanoparticles

The cellular internalization of oligonucleotide-modified nanoparticles is investigated. Uptake is dependent on the density of the oligonucleotide loading on the surface of the particles, where higher densities lead to greater uptake. Densely functionalized nanoparticles adsorb a large number of proteins on the nanoparticle surface. Nanoparticle uptake is greatest where a large number of proteins are associated with the particle.     

Applications of dip-pen nanolithography

The ability to tailor the chemical composition and structure of a surface at the sub-100-nm length scale is important for studying topics ranging from molecular electronics to materials assembly, and for investigating biological recognition at the single biomolecule level. Dip-pen nanolithography (DPN) is a scanning probe microscopy-based nanofabrication technique that uniquely combines direct-write soft-matter compatibility with the high resolution and registry of atomic force microscopy (AFM), which makes it a powerful tool for depositing soft and hard materials, in the form of stable and functional architectures, on a variety of surfaces. The technology is accessible to any researcher who can operate an AFM instrument and is now used by more than 200 laboratories throughout the world. This article introduces DPN and reviews the rapid growth of the field of DPN-enabled research and applications over the past several years.     

Effect of Processing Parameters on the Morphology of Hydrothermally Derived PbTiO3 Powders

The influence of processing parameters on the growth and morphology of hydrothermally derived lead titanate (PbTiO₃) powders was investigated. PbTiO₃ powder was synthesized by suspending nanocrystalline powders of TiO₂ in aqueous solutions of KOH and Pb(CH₃COO)₂·3H₂O at temperatures ranging from 120° to 200°C. PbTiO₃ growth initiated in the <100> exposing the (001) surfaces and resulting in a faceted platelet morphology. Particle growth proceeded by further nucleation and growth on existing (001) surfaces. Through repeated dissolution and precipitation, the platelet clusters coarsened into larger cuboidal particles. PbTiO₃ particle size was controlled by either inhibiting or promoting dissolution-precipitation. Dissolution-precipitation was inhibited by lowering the KOH concentration or the reaction temperature, or maintaining an excess of lead ions in solution, while it was promoted by increasing the KOH concentration and temperature. Coarsening of PbTiO₃ particles coincided with decreases in the X-ray diffraction (XRD) peak breadth, the asymmetry of l component XRD reflections, and the c -axis length.     

A radial infusion model for transverse permeability measurements of fiber reinforcement in composite materials

The goal of this article was to develop a method for simultaneously determining the principal values of an unsaturated permeability tensor for fibrous reinforcements which accounts for finite dimension of the inlet gate, when its diameter is comparable or larger than thickness of a fabric preform. An analytic solution for the direct problem of liquid spreading in a transversely orthotropic fabric preform is derived and analyzed. This solution is compared with a point source approximate solution used by other authors. Algorithms for evaluating the principal components of transverse and equivalent in-plane permeability are proposed. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Maximizing DNA loading on a range of gold nanoparticle sizes

We have investigated the variables that influence DNA coverage on gold nanoparticles. The effects of salt concentration, spacer composition, nanoparticle size, and degree of sonication have been evaluated. Maximum loading was obtained by salt aging the nanoparticles to approximately 0.7 M NaCl in the presence of DNA containing a poly(ethylene glycol) spacer. In addition, DNA loading was substantially increased by sonicating the nanoparticles during the surface loading process. Last, nanoparticles up to 250 nm in diameter were found have approximately 2 orders of magnitude higher DNA loading than smaller (13-30 nm) nanoparticles, a consequence of their larger surface area. Stable large particles are attractive for a variety of biodiagnostic assays.     

Improving nanoprobes using surface-enhanced Raman scattering from 30-nm hollow gold particles

We report the development of nanoprobes that exploit the surface-enhanced Raman scattering (SERS) from nonaggregated, hollow, gold nanospheres (HGNSs). The homogeneity of the HGNSs leads to a nearly 10-fold improvement in signal consistency over standard silver SERS substrates, which translates into a significant increase in sensitivity and dynamic range for the model application of pH sensing. Moreover, the small size (30-nm diameter) of these SERS-active nanoparticles represents a major step in advancing sensing technology based on SERS, making this technology more amenable to intracellular sensing.     

Phase field crystal model of solute drag

The atomic scale interaction of solute with a migrating grain boundary has been studied using a binary phase field crystal (PFC) model. This model bridges between atomistic and continuum simulation techniques as it operates on diffusive timescales but at atomistic length scales. For this study, a two-dimensional channel containing two grains separated by a flat grain boundary has been constructed that allows for a channel length on the order of one micrometer. A new formalism has been developed to allow for the application of an external driving pressure for the growth of one grain. These simulations account for solute/grain boundary interactions, resulting in a solute drag effect on the grain boundary motion. The PFC simulations show good agreement with classical solute drag theory, though deviations due to the atomic scale nature of the interface exist.