[Ru(bpy)(3)](2+)-doped silica nanoparticles within layer-by-layer biomolecular coatings and their application as a biocompatible electrochemiluminescent tag material

[Ru(bpy)(3)](2+)-doped silica (RuSi) nanoparticles were synthesized by using a water/oil microemulsion method. Stable electrochemiluminescence (ECL) was obtained when the RuSi nanoparticles were immobilized on a glassy carbon electrode by using tripropylamine (TPA) as a coreactant. Furthermore, the ECL of the RuSi nanoparticles with layer-by-layer biomolecular coatings was investigated. Squential self-assembly of the polyelectrolytes and biomolecules on the RuSi nanoparticles gave nanocomposite suspensions, the ECL of which decreased on increasing the number of bilayers.

Layer-by-layer assembly of single-charged ions with a rigid polyampholyte

A novel method to produce multilayer films has been developed by layer-by-layer assembly of single-charged ions and a rigid polyampholyte containing unbalanced charges in each of its repeat units.

Layer-by-layer assembly of viral capsid for cell adhesion

Cowpea mosaic virus (CPMV)-based thin films are biologically active for cell culture. Using layer-by-layer assembly of CPMV and poly(diallyldimethylammonium chloride), quantitatively scalable biomolecular surfaces were constructed, which were well characterized using quartz crystal microbalance, UV-vis and atomic force microscopy. The surface coverage of CPMV nanoparticles depended on the adsorption time and pH of the virus solution, with a greater amount of CPMV adsorption occurring near its isoelectric point. It was found that the adhesion and proliferation of NIH-3T3 fibroblasts can be controlled by the coverage of viral particles using this multilayer technique.

Layer-by-layer assembly of gelatin

Electrostatic assembly of one species can be realized using gelatin as a polyampholyte. Under suitable conditions where the electrostatic attraction and repulsion were both significant and in balance, linear growth of multilayers driven by electrostatic interactions was sustained over many successive assembly steps, and the maximum amount of adsorption of each layer was reached when the solution pH was around the isoelectric point. The rearrangement of the adsorbed chains after drying was confirmed by contact angle analysis. In addition with only one species involved, the assembled thin films should be chemically uniform rather than layered.

Electrostatic layer-by-layer a of platinum-loaded multiwall carbon nanotube multilayer: A tunable catalyst film for anodic methanol oxidation

A simple layer-by-layer (LBL) electrostatic adsorption technique was developed for deposition of films composed of alternating layers of positively charged poly(diallyldimethylammonium chloride) (PDDA) and negatively charged multiwall carbon nanotubes bearing platinum nanoparticles (Pt-CNTs). PDDA/Pt-CNT film structure and morphology up to six layers were characterized by scanning electron microscopy and ultraviolet-visible spectroscopy, showing the Pt-CNT layers to be porous and uniformly deposited within the multilayer films.

Highly conductive, methanol resistant fuel cell membranes fabricated by layer-by-layer self-assembly of inorganic heteropolyacid

Layer-by-layer (LBL) self-assembly is a simple and elegant method of constructing organic-inorganic composite thin films from environmentally benign aqueous solutions. In this paper, we utilize this method to develop proton-exchange membranes for fuel cells. The multilayer film is constructed onto the surface of sulfonated poly(arylene ether ketone) (SPAEK-COOH) membrane by LBL self-assembly of polycation chitosan (CTS) and negatively charged inorganic particle phosphotungstic acid (VIA). The highly conductive inorganic nanoparticles ensure SPAEK-COOH-(CTS/PTA)(n) membranes to maintain high proton conductivity values up to 0.086 S cm(-1) at 25 degrees C and 0.24S cm(-1) at 80 degrees C, which are superior than previous LBL assembled electrolyte systems.

Layer-by-Layer Buildup of Poly(L-glutamic acid)/Chitosan Film for Biologically Active Coating

A new biocompatible film based on chitosan and poly(L-glutamic acid) (CS/PGA), created by alternate deposition of CS and PGA, was investigated. FT-IR spectroscopy, UV-vis spectroscopy and QCM were used to analyze the build-up process. The growth of CS and PGA deposition are both exponential to the deposition steps at first. After about 9 (CS/PGA) depositions, the exponential to linear transition takes place. QCM measurements combined with UV-vis spectra revealed the increase in the multilayer film growth at different pH (4.4, 5.0 and 5.5). The build-up of the multilayer stops after a few depositions at pH = 6.5. A muscle myoblast cell (C2C12) assay showed that (CS/PGA)(n) multilayer films obviously promote C2C12 attachment and growth.

Enhanced amplified spontaneous emission using layer-by-layer assembled cowpea mosaic virus

Layer-by-layer assembly technique was used to construct ultrathin film of cowpea mosaic virus (CPMV) by electrostatic interactions, and the film was employed as a precursor on which an OF8T2 film was deposited by spin coating. Amplified spontaneous emission (ASE) was observed and improved for the OF8T2 film. Compared with OF8T2 film on quartz, the introduction of CPMV nanoparticles reduced the threshold and loss, and remarkably increased the net gain. The threshold, loss, and gain reached 0.05 mJ/ pulse, 6.9 cm(-1), and 82 cm(-1), respectively. CPMV nanoparticles may enormously scatter light, resulting in a positive feedback, thus the ASE is easily obtained and improved.

Surface plasmon resonance and electrochemistry characterization of layer-by-layer self-assembled DNA and Zr4+ thin films, and their interaction with cytochrome c

Through electrostatic layer-by-layer (LbL) assembly, negatively charged calf thymus double stranded DNA (CTds-DNA), and positively charged Zr4+ ions were alternately deposited on gold substrate modified with chemisorbed cysteamine. Thus-prepared three-dimensional DNA networks were characterized by surface plasmon resonance (SPR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IR-RAS). SPR spectroscopy indicates that the effective thickness of DNA monolayer in the (DNA/Zr4+), bilayer was 1.5 +/- 0.1 nm, which corresponds to the surface coverage of 79% of its full packed monolayer. At the same time, a linear increase of film thickness with increasing number of layers was also confirmed by SPR characterizations. The data of XPS and IR-RAS show that Zr4+ ions interact with both the phosphate groups and nitrogenous bases of DNA and load into the framework of DNA. Furthermore, the interactions between this composite film and heme protein cytochrome c (Cyt c) were investigated by SPR spectroscopy and electrochemistry.

Surface plasmon resonance and electrochemistry characterization of layer-by-layer self-assembled DNA and Zr4+ thin films, and their interaction with cytochrome c

Through electrostatic layer-by-layer (LbL) assembly, negatively charged calf thymus double stranded DNA (CTds-DNA), and positively charged Zr4+ ions were alternately deposited on gold substrate modified with chemisorbed cysteamine. Thus-prepared three-dimensional DNA networks were characterized by surface plasmon resonance (SPR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and infrared reflection-absorption spectroscopy (IR-RAS). SPR spectroscopy indicates that the effective thickness of DNA monolayer in the (DNA/Zr4+), bilayer was 1.5 +/- 0.1 nm, which corresponds to the surface coverage of 79% of its full packed monolayer. At the same time, a linear increase of film thickness with increasing number of layers was also confirmed by SPR characterizations. The data of XPS and IR-RAS show that Zr4+ ions interact with both the phosphate groups and nitrogenous bases of DNA and load into the framework of DNA. Furthermore, the interactions between this composite film and heme protein cytochrome c (Cyt c) were investigated by SPR spectroscopy and electrochemistry. Compared with the adsorption of Cyt c on DNA monolayer, this composite multilayer film can obviously enhance the amount of immobilized Cyt c confirmed by SPR reflectivity-incident angle (R-theta) curves.

Layer-by-layer electrodeposition of redox polymers and enzymes on screen-printed carbon electrodes for the preparation of reagentless biosensors

Layer-by-layer electrodeposition of redox polymer/enzyme composition films on screen-printed carbon electrodes for fabrication of reagentless enzyme biosensors has been proposed and the resulting films were found to be very stable and rigid.

Immunosensors based on layer-by-layer self-assembled Au colloidal electrode for the electrochemical detection of antigen

Colloidal Au particles have been deposited on the gold electrode through layer-by-layer self-assembly using cysteamine as cross-linkers. Self-assembly of colloidal Au on the gold electrode resulted in ail easier attachment of antibody, larger electrode surface and ideal electrode behavior. The redox reactions of [Fe(CN)(6)]-/[Fe(CN)(6)](3-) on the gold surface were blocked due to antibody immobilization, which were investigated by cyclic voltammetry and impedance spectroscopy. The interaction of antigen with grafted antibody recognition layers was carried out by soaking the modified electrode into a phosphate buffer at pH 7.0 with various concentrations of antigen at 37degreesC for 30 min. Further, an amplification strategy to use biotin conjugated antibody was introduced for improving the sensitivity of impedance measurements. Thus, the sensor based oil this immobilization method exhibits a large linear dynamic range, from 5 - 400 mug/L for detection of Human IgG. The detection limit is about 0.5 mug/L.

Polyhedral oligomeric silsesquioxane nanocomposite thin films via layer-by-layer electrostatic self-assembly

Fabrication of ultrathin polymer composite films with low dielectric constants has been demonstrated. Octa( aminophenyl) silsesquioxane (OAPS) was synthesized and assembled with poly( acrylic acid) (PAA) and poly( styrene sulfonate) (PSS) via a layer-by-layer electrostatic self-assembly technique to yield nanoporous ultrathin films. The OAPS was soluble in water at pH 3 or lower, and suitable pH conditions for the OAPS/PAA and OAPS/PSS assemblies were determined. The multilayer formation process was studied by contact angle analysis, X-ray photoelectron spectroscopy, atomic force microscopy, quartz crystal microgravimetry, UV-vis spectroscopy, and ellipsometry. The multilayer growth was found to be steady and uniform, and the analysis of the film surface revealed a rough topography due to OAPS aggregates. The incorporation of porous OAPS molecules into the thin films significantly lowered their dielectric constants. The OAPS/PAA multilayer thin film thus prepared exhibited a dielectric constant of 2.06 compared to 2.58 for pure PAA film. The OAPS/PAA multilayer film was heated to effect cross-linking between the OAPS and the PAA layers, and the transformation was verified by reflection-absorption Fourier transform infrared spectroscopy.