Gold–Titanium Dioxide Half-Dome Heterostructures for Plasmonic Hydrogen Evolution

Plasmonic water splitting gains increasing attention due to their broad absorption spectra and excellent chemical stability. However, plasmonic water splitting suffers from low efficiency due to difficulties of utilizing plasmonic energetic charge carriers. Structural factors need to be carefully examined to overcome the short lifetime of plasmonic hot carriers. Here we investigate Au/TiO2 half-dome patterns as a plasmonic photoelectrode to examine the effects of incident light angle and orientation of nanostructures on photochemical hydrogen evolution. Half-dome structures exhibit 4- and 3-fold higher photocurrent density and photovoltage, respectively, than a flat thin film. The enhanced photoreactivity is ascribed to the increased angle between the Au/TiO2 interface and the electric field of irradiated light. The result indicates that the kinetic momentum of the incident photon can significantly contribute to hot electron injection and reaction rate. The monolithic Au/TiO2/Pt half-dome structures are also constructed to show sustainable hydrogen evolution without external bias under visible light illumination

Fabrication of a Micro-omnifluidic Device by Omniphilic/Omniphobic Patterning on Nanostructured Surfaces

We integrate the adhesive properties of marine mussels, the lubricating properties of pitcher plants, and the nonfouling properties of diatoms into nanostructured surfaces to develop a device called a micro-omnifluidic (μ-OF) system to solve the existing challenges in microfluidic systems. Unlike conventional poly(dimethylsiloxane)-based fluidic systems that are incompatible with most organic solvents, the μ-OF system utilizes a variety of solvents such as water, ethanol, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, <i>n</i>-hexane, 1,2-dichloroethane, acetic acid, 2-propanol, acetone, toluene, diesel oil, dioxane, gasoline oil, hexadecane, and xylene. The μ-OF system is based on a phenomenon called microchannel induction that spontaneously occurs when virtually all droplets of solvents are applied on omniphilically micropatterned regions of a slippery liquid-infused porous surface. Any solvents with surface tension greater than that of the lubricant (17.1 mN/m, Fluorinert FC-70) are able to repel the infused lubricant located on top of the omniphilic microlines, triggering controlled movement of the droplet by gravity along the microlines. We also demonstrated that the μ-OF system is reusable by the nonadsorption properties of the silicified layer. Due to the organic solvent compatibility, we were able to perform organic reactions with high portability and energy efficiency in operation

Bioinspired Design of an Immobilization Interface for Highly Stable, Recyclable Nanosized Catalysts

Immobilization of nanometer-sized metal catalysts into porous substrates can stabilize the catalysts and allow their recycled uses, while immobilization often sacrifices the active surface of catalysts and degenerates the local microenvironments, resulting in the reduction of the catalytic activity. To maintain a high activity of immobilized nanocatalysts, it is critically important to design an interface that minimizes the contact area and favors reaction chemistry. Here we report on the application of mussel-inspired adhesion chemistry to the formation of catalytic metal nanocrystal–polydopamine hybrid materials that exhibit a high catalytic efficiency during recycled uses. Electrospun polymer nanofibers are used as a template for in situ formation and immobilization of gold nanoparticles via polydopamine-induced reduction of ionic precursors. The prepared hybrid nanostructures exhibit a recyclable catalytic activity for the reduction of 4-nitrophenol with a turnover frequency of 3.2–5.1 μmol g^–1 min^–1. Repeated uses of the hybrid nanostructures do not significantly alter their morphology, indicating the excellent structural stability of the hybrid nanostructures. We expect that the polydopamine chemistry combined with the on-surface synthesis of catalytic nanocrystals is a promising route to the immobilization of various colloidal nanosized catalysts on supporting substrates for long-term catalysis without the physical instability problem

Bioinspired Templating Synthesis of Metal–Polymer Hybrid Nanostructures within 3D Electrospun Nanofibers

Novel metal nanostructures immobilized within three-dimensional (3D) porous polymeric scaffolds have been utilized for catalysts and biosensors. However, efficient, robust immobilization of the nanostructures both outside and inside of the 3D scaffolds is a challenging task. To address the challenge, we synthesized a redox-active polymer, catechol-grafted poly­(vinyl alcohol), PVA-<i>g</i>-ct. The grafted catechol is inspired by the adhesion mechanism of marine mussels, which facilitates binding and reduction of noble metal ions. Electrospinning the PVA-<i>g</i>-ct polymer results in highly open porous, 3D nanostructures, on which catechol mediates the spontaneous reduction of silver ions to solid silver nanocubes at an ambient temperature. Yet, gold and platinum ions are partially reduced and complexed with the nanofiber template, requiring an additional thermal treatment for complete reduction into solid metal nanostructures. Furthermore, silver–gold and silver–platinum hybrid nanostructures are generated by sequential treatments with metal ion precursor solutions of each. This study suggests that catechol-grafted polymer nanofibers are an attractive reactive template for the facile synthesis and immobilization of noble metal nanostructures within a 3D porous matrix for the potential applications to sensors, catalysis, and tissue engineering

Genetically Programmed Clusters of Gold Nanoparticles for Cancer Cell-Targeted Photothermal Therapy

Interpretations of the interactions of nanocarriers with biological cells are often complicated by complex synthesis of materials, broad size distribution, and heterogeneous surface chemistry. Herein, the major capsid proteins of an icosahedral T7 phage (55 nm in diameter) are genetically engineered to display a gold-binding peptide and a prostate cancer cell-binding peptide in a tandem sequence. The genetically modified phage attracts gold nanoparticles (AuNPs) to form a cluster of gold nanoparticles (about 70 nanoparticles per phage). The cluster of AuNPs maintains cell-targeting functionality and exhibits excellent dispersion stability in serum. Under a very low light irradiation (60 mW cm^–2), only targeted AuNP clusters kill the prostate cancer cells in minutes (not in other cell types), whereas neither nontargeted AuNP clusters nor citrate-stabilized AuNPs cause any significant cell death. The result suggests that the prostate cancer cell-targeted clusters of AuNPs are targeted to only prostate cancer cells and, when illuminated, generate local heating to more efficiently and selectively kill the targeted cancer cells. Our strategy can be generalized to target other types of cells and assemble other kinds of nanoparticles for a broad range of applications

Morphological Evolution of Gold Nanoparticles into Nanodendrites Using Catechol-Grafted Polymer Templates

Morphology, dimension, size, and surface chemistry of gold nanoparticles are critically important in determining their optical, catalytic, and photothermal properties. Although many techniques have been developed to synthesize various gold nanostructures, complicated and multistep procedures are required to generate three-dimensional, dendritic gold nanostructures. Here, we present a simple method to synthesize highly branched gold nanodendrites through the well-controlled reduction of gold ions complexed with a catechol-grafted polymer. Dextran grafted with catechols guides the morphological evolution as a polymeric ligand to generate dendritic gold structures through the interconnection of the spherical gold nanoparticles. The reduction kinetics, which is critical for morphological changes, is controllable using dimethylacetamide, which can decrease the metal–ligand dissociation and gold ion diffusivity. This study suggests that mussel-inspired polymer chemistry provides a simple one-pot synthetic route to colloidal gold nanodendrites that are potentially applicable to biosensing and catalysis

Additional file 5: of Human three-dimensional in vitro model of hepatic zonation to predict zonal hepatotoxicity

Figure S5. Effects of H2O2 on zonal toxicity in HepaRG cells. Effects of H2O2 on cell viability, levels of CYP mRNAs, enzymatic activities of CYPs, and cytotoxicity of hepatotoxic drugs were evaluated using the same procedures performed in the CHIR-treated group. (A) Fully differentiated HepaRG cells were exposed to various concentrations of H2O2 for 10 days and the medium with the concentrated chemicals was replaced every 3 days. Cell viability was evaluated using CCK-8 assays after two washes with PBS. No change in the cross-reaction between H2O2 and the CCK-8 reagent was observed in the background values of controls. Levels of CYP mRNAs (CYP2B6, CYP1A2, CYP2E1, and CYP3A4) were analyzed in cells treated with H2O2 for 3 days using qRT-PCR. (B) The activities of CYP1A2 and CYP3A4 were measured using the P450-Glo CYP assay, and CYP2E1 activity was measured using HPLC-tandem mass spectrometry. *P < 0.05. (C) The hepatotoxic drugs tamoxifen, isoniazid, bromobenzene, and APAP were administered to HepaRG cells that had been pretreated with 200 μM H2O2 for 3 days. The viability of HepaRG cells was measured using the CCK-8 assay, and the dose-response curve was analyzed using GraphPad Prism software. (TIF 959 kb

Additional file 1: of Human three-dimensional in vitro model of hepatic zonation to predict zonal hepatotoxicity

Figure S1. Viability of monolayer-cultured HepaRG cells after CHIR treatment (days 1, 3, 6, and 10). (A) Cell viability was evaluated using CCK-8 assays on days 1, 3, 6, and 10 after the CHIR treatment. (B) HepaRG cells was observed before and after 3 days of CHIR treatment under a phase-contrast microscope (scale bar, 100 μm). The microscopic observation showed that fully differentiated HepaRG cells were organized in small clusters and displayed a typical hepatocytes-like morphology. (TIF 2598 kb

Additional file 3: of Human three-dimensional in vitro model of hepatic zonation to predict zonal hepatotoxicity

Figure S3. Histopathologic observation of liver from rats treated with hepatotoxic drugs. The light microscopic image of the tamoxifen-, isoniazid-, bromobenzene-, and APAP-treated liver was obtained from the Open TG-GATEs database. The Sprague-Dawley rats were orally administered each drug for 29 days; tamoxifen, 20 mg/kg; isoniazid, 200 mg/kg; bromobenzene, 100 mg/kg; and APAP, 1000 mg/kg. The yellow, green, and blue arrows indicate the increased centrilobular mitosis, hepatocellular necrosis and inflammatory cell infiltration, respectively. The yellow circle indicates hepatic cellular damage around the central vein. Scale bar, 100 μm. (TIFF 17697 kb

Hydrogel Skin-Covered Neurons Self-Assembled with Gustatory Cells for Selective Taste Stimulation

Many technical challenges exist in the co-culture of multiple types of cells, including medium optimization, cell-to-cell connection, and selective data acquisition of cellular responses. Particularly, mixed cellular responses limit the precise interpretation of intercellular signal transduction. Here, we report the formation of an agarose gel skin on neurons closely assembled with gustatory cells to selectively stimulate gustatory cells by retarding the diffusion of tastants to neurons. The signal transmission, triggered by denatonium benzoate, from gustatory cells to neurons was monitored using intracellular calcium ion concentrations. The agarose gel skin efficiently suppressed the direct transfer of tastants to neurons, decreasing the number of responsive neurons from 56 to 13% and the number of calcium ion signals per neuron from multiple to single. The assembly of neurons with gustatory cells induced the high level of neuronal responses through taste signal transduction from gustatory cells to neurons. However, the calcium ion signal peaks of free neurons coated with agarose gel were much shorter and weaker than those of neurons closely assembled with gustatory cells. This work demonstrated that agarose gel skin is a simple, fast, and effective means to increase the signal selectivity of cellular responses in the co-culture of multiple types of cells