Hepatitis E Virus Methyltransferase Inhibits Type I Interferon Induction by Targeting RIG-I.

The type I interferons (IFNs) play a vital role in activation of innate immunity in response to viral infection. Accordingly, viruses have evolved to employ various survival strategies to evade innate immune responses induced by type I IFNs. For example, HEV encoded papainlike cysteine protease (PCP) has been shown to inhibit IFN activation signaling by suppressing K63-linked de-ubiquitination of retinoic acid-inducible gene I (RIG-I) and TANK-binding kinase 1 (TBK1), thus effectively inhibiting down-stream activation of IFN signaling. In present study, we demonstrated that hepatitis E virus (HEV) inhibits poly inosinicpolycytidylic acid (poly(I:C))-induced IFN-ß transcriptional induction. Moreover, by using reporter assay with individual HEV-encoded gene, we showed that HEV methyltransferase (MeT), a non-structural protein, significantly decreases RIG-I-induced IFN-ß induction and NF-κB signaling activities in a dose-dependent manner. Taken together, we report here that MeT, along with PCP, is responsible for the inhibition of RIG-I-induced activation of type I IFNs, expanding the list of HEV-encoded antagonists of the host innate immunity.

Gold nanozyme-based paper chip for colorimetric detection of mercury ions.

In this study, we developed a facile gold nanozyme-based paper chip (AuNZ-PAD) for Hg2+ detection. This device has the advantages of being simple, rapid, cost effective, sensitive, selective, high throughput, and applicable to onsite detection. The colorimetric mercury assay on the AuNZ-PAD is established based on the enzyme-like catalytic activity of gold nanoparticles promoted by the formation of Au-Hg amalgam, which is correlated to the intensity of the colorimetric response resulting from the catalytic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2. Highly sensitive and selective detection of Hg2+ ions is achieved in both distilled and tap water samples, indicating the feasibility and applicability of our device for the determination of mercury pollution in real samples. Moreover, AuNZ-PAD analysis using a smartphone camera eliminates the need for expensive analytical equipment, thereby increasing the practicality of field monitoring of trace Hg2+ compared with other sensing methods.

Three-dimensional paper-based slip device for one-step point-of-care testing.

In this study, we developed a new type of paper-based analytical device (PAD), the three-dimensional (3D) slip-PAD, to detect infectious human norovirus for global healthcare. The 3D configuration of the papers combined with a slip design provides unique features and versatility that overcome the limitations of fluidic manipulation and sensitivity in point-of-care (POC) tests. The assay can be carried out in a single step based on a moveable slip design, making it suitable for unskilled users. The 3D fluidic network developed by layered construction of wax-patterned papers provides different fluidic paths for the sequential delivery of multiple fluids without the need for peripheral equipment. The release and mixing of enhancement reagents on the device improved the sensitivity and detection limit. The assay results could be visualized by naked eye within 10 min, with subsequent amplification of the signal over time (<60 min). The device showed a broad dynamic range of detection and high sensitivity, with a detection limit of 9.5 × 10(4) copies ml(-1) for human norovirus. These results demonstrate that the 3D slip-PAD is a sensitive diagnostic assay for detecting human norovirus infection that is particularly suitable for POC testing in regions where resources are scarce.

Large-scale plasma patterning of transparent graphene electrode on flexible substrates.

Graphene, a two-dimensional carbon material, has attracted significant interest for applications in flexible electronics as an alternative transparent electrode to indium tin oxide. However, it still remains a challenge to develop a simple, reproducible, and controllable fabrication technique for producing homogeneous large-scale graphene films and creating uniform patterns with desired shapes at defined positions. Here, we present a simple route to scalable fabrication of flexible transparent graphene electrodes using an oxygen plasma etching technique in a capacitively coupled plasma (CCP) system. Ascorbic acid-assisted chemical reduction enables the large-scale production of graphene with solution-based processability. Oxygen plasma in the CCP system facilitates the reproducible patterning of graphene electrodes, which allows controllable feature sizes and shapes on flexible plastic substrates. The resulting graphene electrode exhibits a high conductivity of 80 S cm(-1) and a transparency of 76% and retains excellent flexibility upon hard bending at an angle of ±175° and after repeated bending cycles. A simple LED circuit integrated on the patterned graphene film demonstrates the feasibility of graphene electrodes for use in flexible transparent electrodes.

A single-walled carbon nanotube thin film-based pH-sensing microfluidic chip.

A novel microfluidic pH-sensing chip was developed based on pH-sensitive single-walled carbon nanotubes (SWCNTs). In this study, the SWCNT thin film acted both as an electrode and a pH-sensitive membrane. The potentiometric pH response was observed by electronic structure changes in the semiconducting SWCNTs in response to the pH level. In a microfluidic chip consisting of a SWCNT pH-sensing working electrode and an Ag/AgCl reference electrode, the calibration plot exhibited promising pH-sensing performance with an ideal Nernstian response of 59.71 mV pH(-1) between pH 3 and 11 (standard deviation of the sensitivity is 1.5 mV pH(-1), R(2) = 0.985). Moreover, the SWCNT electrode in the microfluidic device showed no significant variation at any pH value in the range of the flow rate between 0.1 and 15 µl min(-1). The selectivity coefficients of the SWCNT electrode revealed good selectivity against common interfering ions.

Microfluidic chips for immunoassays.

The use of microfluidic chips for immunoassays has been extensively explored in recent years. The combination of immunoassays and microfluidics affords a promising platform for multiple, sensitive, and automatic point-of-care (POC) diagnostics. In this review, we focus on the description of recent achievements in microfluidic chips for immunoassays categorized by their detection method. Following a brief introduction to the basic principles of each detection method, we examine current microfluidic immunosensor detection systems in detail. We also highlight interesting strategies for sensitive immunosensing configurations, multiplexed analysis, and POC diagnostics in microfluidic immunosensors.

Electrochemical determination of cadmium and lead on pristine single-walled carbon nanotube electrodes.

A flexible, transparent, single-walled carbon nanotube (SWCNT) film electrode was prepared by vacuum filtering methods, followed by photolithographic patterning of a photoresist polymer on the SWCNT surface. The morphology of the SWCNT film electrode surface was characterized using a field-emission scanning electron microscope coupled to an energy-dispersive X-ray spectrophotometer. The electrodes were successfully used as a mercury-free electrochemical sensor for individual and simultaneous detection of cadmium (Cd(2+)) and lead (Pb(2+)) in 0.02 M HCl by square-wave stripping voltammetry. Some important operational parameters, including deposition time, deposition potential, square-wave amplitude, and square wave-frequency were optimized for the detection of Cd(2+) and Pb(2+). The newly developed sensor showed good linear behavior in the examined concentration. For individual Cd(2+) and Pb(2+) ion detection, the linear range was found from 0.033 to 0.228 ppm with detection limits of 0.7 ppb (R(2) = 0.985) for Cd(2+) and 0.8 ppb (R(2) = 0.999) for Pb(2+). For simultaneous detection, the linear range was found from 0.033 to 0.280 ppm with a limit of detection of 2.2 ppb (R(2) = 0.976) and 0.6 ppb (R(2) = 0.996) for Cd(2+) and Pb(2+), respectively. SWCNT film electrodes offered favorable reproducibility of ± 5.4% and 4.3% for Cd(2+) and Pb(2+), respectively. The experiments demonstrated the applicability of carbon nanotubes, specifically in the preparation of SWCNT films. The results suggest that the proposed flexible SWCNT film electrodes can be applied as simple, efficient, cost-effective, and/or disposable electrodes for simultaneous detection of heavy metal ions.

Simultaneous detection of ultratrace lead and copper with gold nanoparticles patterned on carbon nanotube thin film.

Highly sensitive detection of a Pb(2+)-Cu(2+) mixture using gold nanoparticles patterned on single-walled carbon nanotube (AuNP-SWCNT) film is reported. The gold nanoparticles were deposited electrochemically on carbon nanotube film using a cyclic voltammetry technique. The film showed a homogeneous size and density that could be easily controlled by the potential scanning cycle and gold precursor concentration. Square wave stripping voltammetry (SWSV) was applied to the simultaneous detection of Pb(2+) and Cu(2+) under optimized conditions. The AuNP-SWCNT electrode exhibited a high increase in sensitivity with a limit of detection of 0.546 ppb (R(2) = 0.984) and 0.613 ppb (R(2) = 0.991) for Pb(2+) and Cu(2+) ions, respectively, in a mixture of Pb(2+)-Cu(2+) solution (S/N = 3, n = 5), and a good linear response in the range from 3.31 ppb to 22.29 ppb. The electrode exhibited high reproducibility in repetitive measurements with a relative standard deviation as low as 4.2% and 2.6% for Pb(2+) and Cu(2+) ions, respectively. An interference study showed that Sb(3+), As(3+), Zn(2+), Ca(2+), and Na(+) ions did not have a significant effect. This study demonstrated an alternative approach to the rapid and reliable detection of heavy metals of environmental interest.

Enzyme kinetic measurements using a droplet-based microfluidic system with a concentration gradient.

In this paper, we propose a microfluidic device that is capable of generating a concentration gradient followed by parallel droplet formation within channels with a simple T-junction geometry. Linear concentration gradient profiles can be obtained based on fluid diffusion under laminar flow. Optimized conditions for generating a linear concentration gradient and parallel droplet formation were investigated using fluorescent dye. The concentration gradient profile under diffusive mixing was dominated by the flow rate at sample inlets, while parallel droplet formation was affected by the channel geometry at both the inlet and outlet. The microfluidic device was experimentally characterized using optimal layout and operating conditions selected through a design process. Furthermore, in situ enzyme kinetic measurements of the ß-galactosidase-catalyzed hydrolysis of resorufin-ß-d-galactopyranoside were performed to demonstrate the application potential of our simple, time-effective, and low sample volume microfluidic device. We expect that, in addition to enzyme kinetics, drug screening and clinical diagnostic tests can be rapidly and accurately performed using this droplet-based microfluidic system.

Control of ZnO morphologies on carbon nanotube electrodes and electrocatalytic characteristics toward hydrazine.

We controlled the morphologies of zinc oxide (ZnO) nanostructures on single-walled carbon nanotube electrodes by an electrochemical deposition method and investigated the dependence of the electrocatalytic characteristics toward hydrazine on the different morphologies. ZnO nanorods provided high electrocatalytic activity with unique electrochemical behaviours, associated with the H(+) ion generated by the electro-oxidation of hydrazine.

Electrochemical characterization of a single-walled carbon nanotube electrode for detection of glucose.

We developed glucose biosensing electrodes using single-walled carbon nanotube (SWCNT) films on flexible, transparent poly(ethylene terephthalate). The homogeneous SWCNT films were fabricated by a vacuum filtration method, and the averaged resistivity and transparency of the fabricated flexible SWCNT films were 400 Omega sq(-1) and 80%, respectively. The glucose sensing electrodes were constructed by encapsulating glucose oxidase (GOx) by Nafion binder into the SWCNT film, and the variation in current response as a function of enzyme loading amount, Nafion thickness were investigated. 30 mg mL(-1) GOx and 2% Nafion was optimal for the detection of glucose. When ferrocene monocarboxylic acid (FMCA) was introduced as diffusional electron mediator, the current responses toward glucose of the Nafion/GOx/SWCNT electrodes in glucose solution containing FMCA were dramatically improved, and the developed sensor was independent of oxygen. In the application of GOx immobilized SWCNT films for glucose detection, a linear electrical response was observed for concentrations ranging from 0.25 to 3.0 mM, and the detection limit and the sensitivity were assessed to be 97 microM and 9.32 microA mM(-1) cm(-2), respectively. Moreover, according to the Lineweaver-Burk plot, the apparent Michaelis-Menten constant was calculated to be 23.8 mM, and the current responses did not interfere with coexisting electroactive species, indicating that Nafion is an effective permselective polymer barrier.

Edge-directed [(M2)2L4] tetragonal metal-organic polyhedra decorated using a square paddle-wheel secondary building unit.

A general strategy was developed for edge-directed self-assembly of tetragonal metal-organic polyhedra (MOPs) having a C(4) symmetry Cu(II)(2)(COO)(4) paddle-wheel as a secondary building unit, using C(2) symmetric dicarboxylic ligands as pincer-type primary building units.

Electrochemical patterning of transparent single-walled carbon nanotube films on plastic substrates.

We report a new patterning method for single-walled carbon nanotubes (SWCNTs) films on flexible, transparent poly(ethylene terephthalate) using electrochemical etching in an aqueous electrolyte solution. Electrochemical etching of the SWCNT films patterned with photoresist polymer was accomplished in a three-electrode system, and the electrochemically patterned SWCNT films were then characterized by scanning electron microscopy (SEM) and Raman spectroscopy. The voltammetry curve showed that SWCNTs underwent drastic oxidation above an applied potential of 1.315 V with the generation of gas bubbles, and the oxidation current became constant above 2.6 V due to the mass transfer limit. SEM images showed that the networks of SWCNTs in the area protected with the photoresist polymer had no damage and vivid connections were obvious, while the connections and shapes of SWCNTs in the area exposed to electrochemical etching were indistinct and slightly damaged. In the Raman spectra of the area protected with the photoresist polymer and the exposed SWCNT area, the intensity ratio of the D-line to the G-line increased from 0.077 to 1.136, which indicated that the ordered carbons of the SWCNT film gradually became amorphous carbons due to electrochemical etching. For optimal patterning, the electrochemical etchings of SWCNT films were performed under various conditions (the applied potential, pH of the electrolyte solution, and electrolyte concentration). An applied potential of 3.0 V in 0.1 M NaCl electrolyte solution (pH 7.0) was optimal for homogeneous electrochemical patterning of SWCNT films. In an electrochemiluminescence reaction, the SWCNT films patterned by this technique could be used successfully as flexible and transparent electrodes.

Patterning of single-walled carbon nanotube films on flexible, transparent plastic substrates.

We report a simple patterning method for single-walled carbon nanotubes (SWCNTs) films on flexible, transparent poly(ethylene terephthalate) using an O(2)-plasma technique in a capacitively coupled plasma (CCP) system. The homogeneous SWCNT films in a large area were fabricated by the vacuum filtration method. The plasma patterning process of SWCNT films includes conventional photolithography and subsequent O(2)-plasma treatment. During the plasma treatment, SWCNTs underneath the patterned photoresist polymer are protected from etching and damage by O(2)-plasma while the exposed SWCNTs are destroyed. The morphological changes and the effect of plasma treatment on the chemical properties of SWCNT films were investigated by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The physical properties of SWCNT films such as transparency and conductivity were systematically characterized under various plasma conditions. In an electrochemiluminescence reaction, the SWCNT films patterned by the CCP system-based O(2)-plasma treatment could be used as flexible and transparent electrodes.

Electrochemical patterning of gold nanoparticles on transparent single-walled carbon nanotube films.

We report a simple, low cost, electrochemical deposition method to pattern gold nanoparticles on flexible, transparent, single-walled carbon nanotube (SWCNT) films, and demonstrate the application of the gold-patterned SWCNT films as surface-enhanced Raman spectroscopy substrates and biosensing electrodes for non-enzymatic glucose detection.

Preparation of monodisperse and size-controlled poly(ethylene glycol) hydrogel nanoparticles using liposome templates.

Liposomes were used as templates to prepare size-controlled and monodisperse poly(ethylene glycol) (PEG) hydrogel nanoparticles. The procedure for the preparation of PEG nanoparticles using liposomes consists of encapsulation of photopolymerizable PEG hydrogel solution into the cavity of the liposomes, extrusion through a membrane with a specific pore size, and photopolymerization of the contents inside the liposomes by UV irradiation. The size distributions of the prepared particles were 1.32+/-0.16 microm (12%), 450+/-62 nm (14%), and 94+/-12 nm (13%) after extrusion through membrane filters with pore sizes of 1 microm, 400 nm, and 100 nm, respectively. With this approach, it is also possible to modify the surface of the hydrogel nanoparticles with various functional groups in a one-step procedure. To functionalize the surface of a PEG nanoparticle, methoxy poly(ethylene glycol)-aldehyde was added as copolymer to the hydrogel-forming components and aldehyde-functionalized PEG nanoparticles could be obtained easily by UV-induced photopolymerization, following conjugation with poly-L-lysine-FITC through amine-aldehyde coupling. The prepared PEG particles showed strong fluorescence from FITC on the edge of the particles using confocal microscopy. The immobilization of biomaterials such as enzymes in hydrogel particles could be performed with loading beta-galactosidases during the hydration step for liposome preparation without additional procedures. The resorufin produced by applying resorufin beta-D-galactopyranoside as the substrate showed the fluorescence under the confocal microscopy.

Development of a photodiode array biochip using a bipolar semiconductor and its application to detection of human papilloma virus.

We describe a DNA microarray system using a bipolar integrated circuit photodiode array (PDA) chip as a new platform for DNA analysis. The PDA chip comprises an 8 x 6 array of photodiodes each with a diameter of 600 microm. Each photodiode element acts both as a support for an immobilizing probe DNA and as a two-dimensional photodetector. The usefulness of the PDA microarray platform is demonstrated by the detection of high-risk subtypes of human papilloma virus (HPV). The polymerase chain reaction (PCR)-amplified biotinylated HPV target DNA was hybridized with the immobilized probe DNA on the photodiode surface, and the chip was incubated in an anti-biotin antibody-conjugated gold nanoparticle solution. The silver enhancement by the gold nanoparticles bound to the biotin of the HPV target DNA precipitates silver metal particles at the chip surfaces, which block light irradiated from above. The resulting drop in output voltage depends on the amount of target DNA present in the sample solution, which allows the specific detection and the quantitative analysis of the complementary target DNA. The PDA chip showed high relative signal ratios of HPV probe DNA hybridized with complementary target DNA, indicating an excellent capability in discriminating HPV subtypes. The detection limit for the HPV target DNA analysis improved from 1.2 nM to 30 pM by changing the silver development time from 5 to 10 min. Moreover, the enhanced silver development promoted by the gold nanoparticles could be applied to a broader range of target DNA concentration by controlling the silver development time.