Tailoring DNA Surface Interactions on Single-Layer Graphene: Comparative Analysis of Pyrene, Acridine, and Fluorenyl Methyl Linkers.

This study investigates the effect of different linkers and solvents on the immobilization of DNA probes on graphene surfaces, which are crucial for developing high-performance biosensors. Quartz crystal microbalance with dissipation (QCM-D) measurements were used to characterize in situ and real-time the immobilization of ssDNA and hybridization efficiency on model graphene surfaces. The DNA probes immobilization kinetics and thermodynamics were systematically investigated for all the pairings between three bifunctional linkers─1-pyrenebutyric acid succinimidyl ester (PBSE), Fluorenylmethylsuccinimidyl carbonate (FSC), and Acridine Orange (AO) succinimidyl ester─and three organic solvents (DMF, DMSO, and 10% DMF/ethanol).

Nanofluidic resistive pulse sensing for characterization of extracellular vesicles.

This paper describes the development, design and characterization of a resistive pulse sensing (RPS) system for the analysis of size distributions of extracellular vesicles (EVs). The system is based on microfluidic chips fabricated using soft-lithography and operated in pressure-driven mode. This fabrication approach provided reproducible pore dimensions and the best performing chip design enabled, without calibration, sizing of both 252 nm and 460 nm test particles within 8% of theoretically calculated values, based on the size specifications provided by suppliers.

Point-of-care quantification of serum cellular fibronectin levels for stratification of ischemic stroke patients.

The abundance of cellular fibronectin (c-Fn) for ischemic stroke patients and the narrow time-window (<4.5 h) for the decision to administer the thrombolytic treatment with recombinant tissue plasminogen activator (rtPA) are challenging for the development of a point-of-care (PoC) diagnostic platform. We report a case of stratification of ischemic stroke patients based on a magnetoresistive biosensor platform that quantifies the c-Fn levels in a small volume of serum, within the clinically relevant time-window.

Crystallographic facet selective HER catalysis: exemplified in FeP and NiP single crystals.

How the crystal structures of ordered transition-metal phosphide catalysts affect the hydrogen-evolution reaction (HER) is investigated by measuring the anisotropic catalytic activities of selected crystallographic facets on large (mm-sized) single crystals of iron-phosphide (FeP) and monoclinic nickel-diphosphide (-NiP). We find that different crystallographic facets exhibit distinct HER activities, in contrast to a commonly held assumption of severe surface restructuring during catalytic activity. Moreover, density-functional-theory-based computational studies show that the observed facet activity correlates well with the H-binding energy to P atoms on specific surface terminations.

Template-directed self-organization of colloidal PbTe nanocrystals into pillars, conformal coatings, and self-supported membranes.

We demonstrate the formation of three morphologies relevant for integration with miniaturized devices-microscale pillars, conformal coatings, and self-supported membranes- template-directed self-organization of lead telluride (PbTe) colloidal nanocrystals (NCs). Optimizing the self-organization process towards producing one of these morphologies typically involves adjusting the surface chemistry of the particles, as a means of controlling the particle-particle and particle-template interactions. In contrast, we have produced each of the three morphologies of close-packed NCs by adjusting only the solvent and concentration of NCs, to ensure that the high quality of the 10 nm PbTe NCs produced by hot-injection colloidal synthesis, which we used as model "building blocks," remains consistent across all three configurations.

Photocatalytic Microporous Membrane against the Increasing Problem of Water Emerging Pollutants.

Emerging pollutants are an essential class of recalcitrant contaminants that are not eliminated from water after conventional treatment. Here, a photocatalytic microporous membrane based on polyvinylidene difluoride-co-trifluoroethylene (PVDF-TrFE) with immobilised TiO nanoparticles, prepared by solvent casting, was tested against representative emerging pollutants. The structure and composition of these polymeric membranes were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, porosimetry, and contact angle goniometry.

Exposure effects of endotoxin-free titanium-based wear particles to human osteoblasts.

Titanium-based materials are widely employed by the biomedical industry in orthopedic and dental implants. However, when placed into the human body, these materials are highly susceptible to degradation processes, such as corrosion, wear, and tribocorrosion. As a consequence, metallic ions or particles (debris) may be released, and although several studies have been conducted in recent years to better understand the effects of their exposure to living cells, a consensual opinion has not yet been obtained.

Attomolar Label-Free Detection of DNA Hybridization with Electrolyte-Gated Graphene Field-Effect Transistors.

In this work, we develop a field-effect transistor with a two-dimensional channel made of a single graphene layer to achieve label-free detection of DNA hybridization down to attomolar concentration, while being able to discriminate a single nucleotide polymorphism (SNP). The SNP-level target specificity is achieved by immobilization of probe DNA on the graphene surface through a pyrene-derivative heterobifunctional linker. Biorecognition events result in a positive gate voltage shift of the graphene charge neutrality point.

Combining CXCR4-targeted and nontargeted nanoparticles for effective unassisted in vitro magnetic hyperthermia.

The use of targeted nanoparticles for magnetic hyperthermia (MHT) increases MHT selectivity, but often at the expense of its effectiveness. Consequently, targeted MHT is typically used in combination with other treatment modalities. This work describes an implementation of a highly effective monotherapeutic in vitro MHT treatment based on two populations of magnetic particles.

Adapting Bobbert-Vlieger model to spectroscopic ellipsometry of gold nanoparticles with bio-organic shells.

We investigate spectroscopic imaging ellipsometry for monitoring biomolecules at surfaces of nanoparticles. For the modeling of polarimetric light scattering off surface-adsorbed core-shell nanoparticles, we employ an extension of the exact solution for the scattering by particles near a substrate presented by Bobbert and Vlieger, which offers insight beyond that of the Maxwell-Garnett effective medium approximation. Varying thickness and refractive index of a model bio-organic shell results in systematic and characteristic changes in spectroscopic parameters [Formula: see text] and [Formula: see text].

Up-scaling the synthesis of Cu₂O submicron particles with controlled morphologies for solar H₂ evolution from water.

The synthesis of Cu2O was studied to examine the effects of up-scaling on the size and morphology of the resultant particles. As a result, a successful protocol employing an automated laboratory reactor was developed for large-scale synthesis of phase-pure Cu2O colloids with specific sizes in the submicron to micrometer range (0.2-2.

Analytical protocols for separation and electron microscopy of nanoparticles interacting with bacterial cells.

An important step toward understanding interactions between nanoparticles (NPs) and bacteria is the ability to directly observe NPs interacting with bacterial cells. NP-bacteria mixtures typical in nanomedicine, however, are not yet amendable for direct imaging in solution. Instead, evidence of NP-cell interactions must be preserved in derivative (usually dried) samples to be subsequently revealed in high-resolution images, for example, via scanning electron microscopy (SEM).

High-Temperature Magnetism as a Probe for Structural and Compositional Uniformity in Ligand-Capped Magnetite Nanoparticles.

To investigate magnetostructural relationships in colloidal magnetite (FeO) nanoparticles (NPs) at high temperature (300-900 K), we measured the temperature dependence of magnetization () of oleate-capped magnetite NPs ca. 20 nm in size. Magnetometry revealed an unusual irreversible high-temperature dependence of for these NPs, with dip and loop features observed during heating-cooling cycles.

Evaluating protocols and analytical methods for peptide adsorption experiments.

This paper evaluates analytical techniques that are relevant for performing reliable quantitative analysis of peptide adsorption on surfaces. Two salient problems are addressed: determining the solution concentrations of model GG-X-GG, X5, and X10 oligopeptides (G = glycine, X = a natural amino acid), and quantitative analysis of these peptides following adsorption on surfaces. To establish a uniform methodology for measuring peptide concentrations in water across the entire GG-X-GG and X n series, three methods were assessed: UV spectroscopy of peptides having a C-terminal tyrosine, the bicinchoninic acid (BCA) protein assay, and amino acid (AA) analysis.

Residue-dependent adsorption of model oligopeptides on gold.

The adsorption to gold surfaces in aqueous solutions has been systematically evaluated for a series of model oligopeptides. The series includes GG-X-GG "host-guest" sequences, where the central X residue is one of 19 proteinogenic amino acids, and water-soluble X5 and X10 homo-oligopeptides. Irreversible adsorption on gold of GG-X-GG peptides, which lack significant secondary structure, was quantitatively analyzed by X-ray photoelectron spectroscopy (XPS).

Nickel foam supported mesoporous MnO2 nanosheet arrays with superior lithium storage performance.

Mesoporous MnO2 nanosheet arrays have been directly grown on nickel foam current collectors and exhibited a reversible capacity as high as 1690 mA h g(-1) even after one hundred cycles at 100 mA g(-1). They also reveal good rate capability and excellent cycling stability.

Circular dichroism analysis of cyclic β-helical peptides adsorbed on planar fused quartz.

Conformational changes of three cyclic β-helical peptides upon adsorption onto planar fused-quartz substrates were detected and analyzed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy. In trifluoroethanol (TFE), hydrophobic peptides, Leu β and Val β, form left- and right-handed helices, respectively, and water-soluble peptide WS β forms a left-handed helix. Upon adsorption, CD spectra showed a mixture of folded and unfolded conformations for Leu β and Val β and predominantly unfolded conformations for WS β.

Divalent-anion salt effects in polyelectrolyte multilayer depositions.

We systematically investigate the effects of divalent anions on the assembly of polyelectrolyte multilayers by fabricating polystyrene sulfonate (PSS)/polyallylamine hydrochloride (PAH) multilayer films from aqueous solutions containing SO(4)(2-), HPO(4)(2-), or organic dicarboxylate dianions. The chosen concentrations of these anions (i.e.

Impact of DNA-surface interactions on the stability of DNA hybrids.

The structure and stability of single- and double-stranded DNA hybrids immobilized on gold are strongly affected by nucleotide-surface interactions. To systematically analyze the effects of these interactions, a set of model DNA hybrids was prepared in conformations that ranged from end-tethered double-stranded to directly adsorbed single-stranded (hairpins) and characterized by surface plasmon resonance (SPR) imaging, X-ray photoelectron spectroscopy (XPS), fluorescence microscopy, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The stabilities of these hybrids were evaluated by exposure to a series of stringency rinses in solutions of successively lower ionic strength and by competitive hybridization experiments.

Vibrational circular-dichroism spectroscopy of homologous cyclic peptides designed to fold into β helices of opposite chirality.

Cyclic β-helical peptides have been developed as model structured biomolecules for examining peptide adsorption and conformation on surfaces. As a key prerequisite to circular-dichroism (CD) analysis of these model peptides on surfaces, their conformations and the corresponding vibrational spectra in the 1400-1800 cm⁻¹ range were analyzed by vibrational circular-dichroism (VCD) spectroscopy in solution. The two model peptides ("β Leu and β Val") were examined in chloroform, where they each fold into a homogeneous well-defined antiparallel double-stranded β-helical species, as determined previously by NMR and electronic CD spectroscopy.

Surface composition, chemistry, and structure of polystyrene modified by electron-beam-generated plasma.

Polystyrene (PS) surfaces were treated by electron-beam-generated plasmas in argon/oxygen, argon/nitrogen, and argon/sulfur hexafluoride environments. The resulting modifications of the polymer surface energy, morphology, and chemical composition were analyzed by a suite of complementary analytical techniques: contact angle goniometry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and reflection electron energy loss spectroscopy (REELS). The plasma treatments produced only minimal increases in the surface roughness while introducing the expected chemical modifications: oxygen-based after Ar/O(2) plasma, oxygen- and nitrogen-based after Ar/N(2) plasma, and fluorine-based after Ar/SF(6) plasma.

Controlled and efficient hybridization achieved with DNA probes immobilized solely through preferential DNA-substrate interactions.

Quantitative and reproducible data can be obtained from surface-based DNA sensors if variations in the conformation and surface density of immobilized single-stranded DNA capture probes are minimized. Both the conformation and surface density can be independently and deterministically controlled by taking advantage of the preferential adsorption of adenine nucleotides (dA) on gold, as previously demonstrated using a model system in Opdahl, A.; Petrovykh, D.

Self-assembled monolayers of alkanethiols on InAs.

We describe the deposition and properties of self-assembled monolayers (SAMs) of methyl-terminated alkanethiols on InAs(001) surface. For these model hydrophobic films, we used water contact angle measurements to survey the preparation of alkanethiol monolayers from base-activated ethanolic solutions as a function of the solution and deposition parameters, including chain length of alkanethiols, deposition time, and solution temperature and pH. We then used X-ray photoelectron spectroscopy (XPS), ellipsometry, and electrochemistry to characterize the composition and structure of octadecanethiol (ODT) monolayers deposited on InAs under optimized conditions.

Independent control of grafting density and conformation of single-stranded DNA brushes.

We describe self-assembly of ssDNA brushes that exploits the intrinsic affinity of adenine nucleotides (dA) for gold surfaces. The grafting density and conformation of these brushes is deterministically controlled by the length of the anchoring dA sequences, even in the presence of thymine nucleotides (dT). We produce and characterize brushes of model block-oligonucleotides, d(T(m)-A(n)), with systematically varied lengths m and n of the thymine and adenine blocks [denoted d(T(m)) and d(A(n)), respectively].

Alkanethiols on platinum: multicomponent self-assembled monolayers.

We have studied the formation of self-assembled monolayers (SAMs) of n-alkanethiols on platinum thin films using X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIRS), spectroscopic ellipsometry (SE), and contact angle (CA) measurements. Specifically, SAMs of 1-hexanethiol, 1-dodecanethiol, and 1-octadecanethiol were grown on polycrystalline Pt films, and the effects of Pt surface preparation, deposition conditions, and solvent treatments on the initial quality and stability of the monolayer in air were investigated. The SAMs prepared under ambient conditions on piranha-cleaned and UV/ozone-cleaned substrates were compared to monolayers formed on template-stripped Pt in an inert atmosphere.