Short-chained oligo(ethylene oxide)-functionalized gold nanoparticles: realization of significant protein resistance.

Protein corona formed on nanomaterial surfaces play an important role in the bioavailability and cellular uptake of nanomaterials. Modification of surfaces with oligoethylene glycols (OEG) are a common way to improve the resistivity of nanomaterials to protein adsorption. Short-chain ethylene oxide (EO) oligomers have been shown to improve the protein resistance of planar Au surfaces.

Mechanical Response of Thermally Annealed Nafion Thin Films.

Perfluorinated ionomers, in particular, Nafion, are a critical component in hydrogen fuel cells as the ion conducting binder within the catalyst layer in which it can be confined to thicknesses on the order of 10 nm or less. It is well reported that many physical properties, such as the Young's modulus, are thickness dependent when the film thickness is less than 100 nm. Here we utilize a cantilever bending methodology to quantify the swelling-induced stresses and relevant mechanical properties of Nafion films as a function of film thickness exposed to cyclic humidity.

Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine.

Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems.

Particle Fabrication Using Inkjet Printing onto Hydrophobic Surfaces for Optimization and Calibration of Trace Contraband Detection Sensors.

A method has been developed to fabricate patterned arrays of micrometer-sized monodisperse solid particles of ammonium nitrate on hydrophobic silicon surfaces using inkjet printing. The method relies on dispensing one or more microdrops of a concentrated aqueous ammonium nitrate solution from a drop-on-demand (DOD) inkjet printer at specific locations on a silicon substrate rendered hydrophobic by a perfluorodecytrichlorosilane monolayer coating. The deposited liquid droplets form into the shape of a spherical shaped cap; during the evaporation process, a deposited liquid droplet maintains this geometry until it forms a solid micrometer sized particle.

Dithiol-based modification of poly(dopamine): enabling protein resistance via short-chain ethylene oxide oligomers.

We present a facile strategy to modify poly(dopamine) (PDA)-coated substrates. Using thiol-terminated short chain ethylene oxide oligomers (OEG) under aqueous conditions, we explore the creation of a model surface exhibiting resistance to nonspecific protein absorption (RPA) by engineering the surface properties of a PDA adlayer. Surprisingly, dithiol-terminated OEG molecules demonstrated significantly greater coverage on PDA surfaces than analogous monothiol molecules.

Membrane protein resistance of oligo(ethylene oxide) self-assembled monolayers.

As part of an effort to develop biointerfaces for structure-function studies of integral membrane proteins (IMPs) a series of oligo(ethylene oxide) self-assembled monolayers (OEO-SAMs) were evaluated for their resistance to protein adsorption (RPA) of IMPs on Au and Pt. Spectroscopic ellipsometry (SE) was used to determine SAM thicknesses and compare the RPA of HS(CH2)3O(CH2CH2O)6CH3 (1), HS(CH2)3O(CH2CH2O)6H (2), [HS(CH2)3]2CHO(CH2CH2O)6CH3 (3) and [HS(CH2)3]2CHO(CH2CH2O)6H (4), assembled from water. For both substrates, SAM thicknesses for 1 to 4 were found to be comparable indicating SAMs with similar surface coverages and OEO chain order and packing densities.

Dropwise condensation of low surface tension fluids on omniphobic surfaces.

Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces.

A generalized strategy for immobilizing uniformly oriented membrane proteins at solid interfaces.

We have developed a method based on self-assembly of thiols on Au substrates to immobilize membrane proteins at interfaces. Using water soluble nitrilotriacetic acid (NTA)-terminated oligo(ethylene glycol) thiols, a histidine-tagged G protein-coupled membrane receptor (GPCR) was captured in a defined orientation with little nonspecific binding.

Direct imaging of complex nano- to microscale interfaces involving solid, liquid, and gas phases.

Surfaces with special wetting properties not only can efficiently repel or attract liquids such as water and oils but also can prevent formation of biofilms, ice, and clathrate hydrates. Predicting the wetting properties of these special surfaces requires detailed knowledge of the composition and geometry of the interfacial region between the droplet and the underlying substrate. In this work we introduce a 3D quantitative method for direct nanoscale visualization of such interfaces.

Dynamics of nanoparticle self-assembly into superhydrophobic liquid marbles during water condensation.

Nanoparticles adsorbed onto the surface of a drop can fully encapsulate the liquid, creating a robust and durable soft solid with superhydrophobic characteristics referred to as a liquid marble. Artificially created liquid marbles have been studied for about a decade but are already utilized in some hair and skin care products and have numerous other potential applications. These soft solids are usually formed in small quantity by depositing and rolling a drop of liquid on a layer of hydrophobic particles but can also be made in larger quantities in an industrial mixer.

In-situ characterization of self-assembled monolayers of water-soluble oligo(ethylene oxide) compounds.

In-situ spectroscopic ellipsometry (SE) was utilized to examine the formation of the self-assembled monolayers (SAMs) of the water-soluble oligo(ethylene oxide) [OEO] disulfide [S(CH(2)CH(2)O)(6)CH(3)](2) {[S(EO)(6)](2)} and two analogous thiols - HS(CH(2)CH(2)O)(6)CH(3) {(EO)(6)} and HS(CH(2))(3)O(CH(2)CH(2)O)(5)CH(3) {C(3)(EO)(5)} - on Au from aqueous solutions. Kinetic data for all compounds follow simple Langmuirian models with the disulfide reaching a self-limiting final state (d=1.2nm) more rapidly than the full coverage final states of the thiol analogs (d=2.

Oligo(ethylene oxide) self-assembled monolayers with self-limiting packing densities for the inhibition of nonspecific protein adsorption.

We have created a molecule that forms self-assembled monolayers (SAMs) on Au, possessing the characteristics for inhibition of nonspecific protein adsorption, i.e., uniformly distributed, loosely packed, conformationally mobile, hydrated ethylene oxide (EO) chains of near optimal packing densities.

In situ adhesion measurements utilizing layer-by-layer functionalized surfaces.

The adhesion between poly(dimethylsiloxane) (PDMS) hemispheres coated with layer-by-layer (LbL) assemblies of polyelectrolytes and rigid, planar substrates was investigated using Johnson, Kendall, and Roberts (JKR) contact mechanics. Measurements were performed against amine-functionalized glass slides both in air and in aqueous solutions of controlled pH. Despite the increased density of negatively charged carboxylate groups, LbL-functionalized PDMS exhibited lower adhesion because of the combined effects of increased surface roughness and the high Young's modulus of the coating.

Self-assembled monolayers of an oligo(ethylene oxide) disulfide and its corresponding thiol assembled from water: characterization and protein resistance.

Self-assembled monolayers (SAMs) of the disulfide [S(CH2CH2O)6CH3]2 ([S(EO)6]2) on Au from 95% ethanol and from 100% water are described. Spectroscopic ellipsometry and reflection-absorption infrared spectroscopy indicate that the [S(EO)6]2 films are similar to the disordered films of HS(CH2CH2O)6CH3 ((EO)6) and HS(CH2)3O(CH2CH2O)5CH3 (C3EO5) at their protein adsorption minima. The [S(EO)6]2 SAMs exhibit constant film thickness (d) of 1.