Plasmonic nanobiosensor with chain reaction amplification mechanism.

Herein we demonstrate a plasmonic nanobiosensor that explores chain reaction amplification mechanisms to transduce chemical signals released in biocatalytic reactions, turning optical signals into a visual spectral range. The sensor has a very simple design: gold nanoparticles resting in the surface of a grafted P2VP film. Changes in the gold nanoparticles' position causes changes in the plasmon coupling mode.

Wound-healing with mechanically robust and biodegradable hydrogel fibers loaded with silver nanoparticles.

The objective of this study is to provide a novel synthetic approach for the manufacture of wound-healing materials using covalently cross-linked alginate fibers loaded with silver nanoparticles. Alginate fibers are prepared by wet-spinning in a CaCl(2) precipitation bath. Using this same approach, calcium cross-links in alginate fibers are replaced by chemical cross-links that involve hydroxyl groups for subsequent cross-linking by glutaraldehyde.

Superomniphobic magnetic microtextures with remote wetting control.

Universal remote control of wetting behavior enabling the transition from a superomniphobic to an omniphilic wetting state in an external magnetic field via the alternation of reentrant curvature of a microstructured surface is demonstrated. This reconfigurable microtexture made of Ni micronails repels water, water-surfactant solutions, and practically all organic liquids, whereas it gets wetted by all of these liquids after a magnetic field pulse is applied.

Field-directed self-assembly with locking nanoparticles.

A reversible locking mechanism is established for the generation of anisotropic nanostructures by a magnetic field pulse in liquid matrices by balancing the thermal energy, short-range attractive and long-range repulsive forces, and dipole-dipole interactions using a specially tailored polymer shell of nanoparticles. The locking mechanism is used to precisely regulate the dimensions of self-assembled magnetic nanoparticle chains and to generate and disintegrate three-dimensional (3D) nanostructured materials in solvents and polymers.

Electrochemically controlled drug-mimicking protein release from iron-alginate thin-films associated with an electrode.

Novel biocompatible hybrid-material composed of iron-ion-cross-linked alginate with embedded protein molecules has been designed for the signal-triggered drug release. Electrochemically controlled oxidation of Fe(2+) ions in the presence of soluble natural alginate polymer and drug-mimicking protein (bovine serum albumin, BSA) results in the formation of an alginate-based thin-film cross-linked by Fe(3+) ions at the electrode interface with the entrapped protein. The electrochemically generated composite thin-film was characterized by electrochemistry and atomic force microscopy (AFM).

Mechanism of nanoparticle actuation by responsive polymer brushes: from reconfigurable composite surfaces to plasmonic effects.

The mechanism of nanoparticle actuation by stimuli-responsive polymer brushes triggered by changes in the solution pH was discovered and investigated in detail in this study. The finding explains the high spectral sensitivity of the composite ultrathin film composed of a poly(2-vinylpyridine) (P2VP) brush that tunes the spacing between two kinds of nanoparticles-gold nanoislands immobilized on a transparent support and gold colloidal particles adsorbed on the brush. The optical response of the film relies on the phenomenon of localized surface plasmon resonances in the noble metal nanoparticles, giving rise to an extinction band in visible spectra, and a plasmon coupling between the particles and the islands that has a strong effect on the band position and intensity.

Optical nanosensor platform operating in near-physiological pH range via polymer-brush-mediated plasmon coupling.

The nanosensors' platform made of a stimuli-responsive polymer/noble metal nanoparticle composite thin film exploits the combination of the swelling-shrinking transition in a poly(N,N'-dimethylaminoethyl methacrylate) brush and the localized surface plasmon resonance in metal nanoparticles to enable the transduction of changes in the solution pH in the near-physiological range into a pronounced optical signal.

Stimuli-responsive porous hydrogels at interfaces for molecular filtration, separation, controlled release, and gating in capsules and membranes.

A continuously growing area of controlled and tunable transport and separation of biomolecules and drugs has recently attracted attention to the structures which can be referred to as stimuli-responsive porous hydrogel thin films. Because of spatial constraints, swelling/shrinking of the hydrogel films results in closing/opening (or vice versa) of the film's pores. Such responsive systems can be used in the configuration of plane films or capsules.

Stimuli-responsive hydrogel membranes coupled with biocatalytic processes.

A nanostructured signal-responsive thin hydrogel membrane was coupled with enzyme-based systems to yield "smart" multisignal-responsive hybrid systems with built-in "logic". The enzyme systems transduce biochemical input signals into structural changes of the membrane, thus resulting in the amplification of the biochemical signals and their transformation into the gated transport of molecules through the membrane. Coupling of the biocatalytic systems with a stimuli-responsive membrane is a promising approach for the development of materials that can regulate transport and release of chemicals/drugs by receiving and processing the biochemical information via biochemical reactions.

Reversible "closing" of an electrode interface functionalized with a polymer brush by an electrochemical signal.

The poly(4-vinyl pyridine) (P4VP)-brush-modified indium tin oxide (ITO) electrode was used to switch reversibly the interfacial activity by the electrochemical signal. The application of an external potential (-0.85 V vs Ag|AgCl|KCl, 3M) that electrochemically reduced O(2) resulted in the concomitant consumption of hydrogen ions at the electrode interface, thus yielding a higher pH value and triggering the restructuring of the P4VP brush on the electrode surface.

Switchable selectivity for gating ion transport with mixed polyelectrolyte brushes: approaching 'smart' drug delivery systems.

A pH-responsive mixed polyelectrolyte brush from tethered polyacrylic acid (PAA) and poly(2-vinylpyridine) (P2VP) (PAA:P2VP = 69:31 by weight) was prepared and used for selective gating transport of anions and cations across the thin film. An ITO glass electrode was modified with the polymer brush and used to study the switchable permeability of the mixed brush triggered by changes in pH of the aqueous environment in the presence of two soluble redox probes: [Fe(CN)(6)](4-) and [Ru(NH(3))(6)](3+). The responsive behavior of the brush was also investigated using the in situ ellipsometric measurements of the brush swelling, examination of the brush morphology with atomic force microscopy (AFM), and contact angle measurements of the brush samples extracted from aqueous solutions at different pH values.

"Chemical transformers" from nanoparticle ensembles operated with logic.

The pH-responsive nanoparticles were coupled with information-processing enzyme-based systems to yield "smart" signal-responsive hybrid systems with built-in Boolean logic. The enzyme systems performed AND/OR logic operations, transducing biochemical input signals into reversible structural changes (signal-directed self-assembly) of the nanoparticle assemblies, thus resulting in the processing and amplification of the biochemical signals. The hybrid system mimics biological systems in effective processing of complex biochemical information, resulting in reversible changes of the self-assembled structures of the nanoparticles.

Gold-nanoparticle-enhanced plasmonic effects in a responsive polymer gel.

Localized surface plasmon resonance excited in gold nanoparticles coupled with a responsive polymer gel is explored. A specially designed structure (vertically aligned cylindrical pores decorated with gold nanoparticles) of responsive polymer gel thin films allows for the transduction of external signal/ stimuli into a strong optical effect enhanced by interactions of gold nanoparticles.

An electrochemical gate based on a stimuli-responsive membrane associated with an electrode surface.

The electrochemical gate based on a chemical signal-responsive membrane was assembled on a Au electrode surface. The polyelectrolyte gel membrane was capable to bind cholesterol because of the hydrogen bonding between cholesterol and the polymer backbone resulting in the gel swelling. The membrane channels were reversibly closed and opened upon addition and washing out cholesterol, respectively.

Nonwettable thin films from hybrid polymer brushes can be hydrophilic.

Hybrid brushes composed of two liquid polymers, poly(dimethylsiloxane) (PDMS) and a highly branched ethoxylated polyethylenimine (EPEI), were synthesized on Si wafers by the "grafting to" method and by applying a combinatorial approach (fabrication of gradient brushes). The combinatorial approach revealed a strong effect of "layer assisted tethering", which allowed us to synthesize hybrid brushes twice as thick as the reference homopolymer brushes. The hybrid brushes are stable thin films that can rapidly and reversibly switch between hydrophilic and hydrophobic states in water and air, respectively.

Ultrathin molecularly imprinted polymer sensors employing enhanced transmission surface plasmon resonance spectroscopy.

An ultrathin novel nanosensor (31.5 +/- 4.1 nm thick in the absence of analytes), employing a molecularly imprinted polymer as a recognition element for cholesterol and gold nanoparticle enhanced transmission surface plasmon resonance spectroscopy for detection, was constructed.