Dynamic Response Range Research Articles

Selective and Trace Level Detection of Hydrazine Using Functionalized Single-Walled Carbon Nanotube-Based Microelectronic Devices

Microelectronic devices (MEDs) that utilize functionalized single-walled carbon nanotubes (SWCNTs) for hydrazine (HZ) sensing applications were developed and investigated, demonstrating their selective and sensitive detection of trace level HZ (0.01 ppm) in the presence of high-concentration interfering gases in ambient air at room temperature. These MEDs were fabricated with excellent reproducibility by the site-specific deposition of functionalized SWCNTs using a dielectrophoretic technique. Rigorous gas exposure testing conducted on these MEDs demonstrated a fast response with high sensitivity, selectivity, reproducibility, and reliability for detecting HZ. A dynamic response range was established from a linear relationship between the sensor response and the concentration of HZ (0.01 to 0.33 ppm). Additionally, these MEDs exhibited a linear trend relationship between device resistance and sensor response, which provided tunability in selecting and fabricating devices for improving sensing response. Field-emission scanning electron microscopy images showed the morphology of SWCNTs as a bundle on MEDs. Additional analytic gas exposure tests revealed negligible responses from these MEDs for high concentrations of interfering gases, such as 300 ± 17 ppm methanol (MeOH), 85 ± 6 ppm ethanol (EtOH), 145 ± 12 ppm formaldehyde (CH2O), and 500 ppm ammonia (NH3), compared to that of HZ (≤0.33 ppm), with HZ to interfering gas concentration ratios of 1:900, 1:250, 1:440, and 1:1500, respectively, demonstrating high sensor selectivity for HZ.

TCAD Modeling for Si–Ge HBT THz Detectors

Terahertz (THz) response of transistor and integrated circuit yields important information about device parameters and has been used for distinguishing between working and defective transistors and circuits. Using a TCAD model for SiGe HBTs we simulate their current-voltage characteristics and their response to sub-THz (300\,GHz) radiation. Applying different mixed mode schemes in TCAD, we simulated the dynamic range of the THz response for SiGe HBTs and showed that it is comparable with that of the TeraFET detectors. The HBT response to the variations of the detector design parameters are investigated at different frequencies with the harmonic balance simulation in TCAD. These results are useful for the physical design and optimization for the HBT THz detectors and for the identification of faulty SiGe HBT and Si BiCMOS circuits using sub-THz or THz scanning.

Polymerase/Nicking Enzyme Powered Dual-template Multi-cycle G-Triplex Machine for HIV-1 Determination.

We proposed a dual-template, multi-cycle DNA nanomachine driven by polymerase and a nicking enzyme with high efficiency. The reaction system simply consists of two templates (T1, T2) and two enzymes (KF polymerase, Nb.BbvCI). The two templates are similar in structure (X-X'-Y, Y-Y'-C) with a primer recognition region, a primer analogue generation region, an output region (3'-5'), and two nicking sites. The output strand of T1 is the primer of T2, and the G-rich fragment (G3) is designed as the final product. In the presence of HIV-1, numerous G3 were generated through the multi-cycle amplification strategy and formed a G-triplex/ThT complex after the addition of thioflavin T (ThT), which greatly enhanced the fluorescence intensity as a signal reporter in the label-free sensing strategy. A dynamic response range of 50 fM - 2 nM for HIV-1 gene detection can be achieved through this multi-cycle G-triplex machine, and benefiting from the high efficiency amplification strategy, the enzymatic reaction can be completed within 45 min and followed by fluorescence measurements. In addition, the analysis of other targets can be achieved by replacing the template sequence. Thus, there is a certain application potential of this strategy for trace biomarker analysis.

Dynamic performance reliability analysis of rolling linear guide under parameter uncertainty

This paper presents a dynamic reliability analysis method of rolling linear guide considering the uncertainty of geometric parameters. A three degree of freedom (DOF) dynamic motion model of rolling linear guide that considers the complexity of the actual load is established. In order to improve the accuracy of reliability evaluation, interval model is used to express the uncertainty of geometric parameters. The reliability range of dynamic response is determined according to the accuracy grade of rolling linear guide. The interval reliability calculation method is used to analyze and calculate the horizontal and vertical dynamic reliability of rolling linear guide. Then, the comprehensive dynamic reliability of rolling linear guide is obtained. Finally, the dynamic reliability of the SHS-45R rolling linear guide is analyzed by using the reliability evaluation method described in this paper. And the validity and accuracy of the result is demonstrated by comparing with the Monte Carlo simulation.

Limited Spatial Spread Explains the Dependence of Visual Response Adaptation on Stimulus Size in Rat Superior Colliculus Neurons

Although adaptation to light occurs in the eye and mainly preserves the full dynamic range of neuronal responses during changing background illumination, it affects the entire visual system and helps to optimize visual information processing. We have shown recently that in rat superior colliculus (SC) neurons adaptation to light acts as a local low-pass filter because, in contrast to the primate SC, in rat collicular neurons adaptation to small stimuli is largely limited to the vicinity of the adaptor stimulus. However, it was unclear whether large visual stimuli would induce the same spatially limited adaptation. We addressed this question by evaluating the effects of 1.8°, 6.2° and 20.8° wide adaptor stimuli on test stimuli of variable size. Single unit recordings in the adult rat SC were employed to estimate the response amplitude. Small, 1.8° and 6.2° adaptors habituated visual responses only to stimuli smaller than the adaptive stimuli. However, the 20.8° adaptor dramatically reduced responses even to test stimuli >3 times wider than the adaptor (up to 70° wide). The latter result may be explained by a nearly complete occlusion by a large adaptor of the neuron’s receptive field (RF). All these results are consistent with the idea of a limited spatial spread of adaptation in rat SC neurons that is the consequence of high convergence of retinal inputs, in which small RFs limit the spatial spread of adaptation. It is concluded that, in this limited spatial spread of adaptation, rodent SC resembles higher visual system areas in primates and indicates potential differences in visual information processing between rodents and primates.

Fuel strand-powered self-propelled electrochemical DNA machine for enzyme-free and distinctly amplified detection of nucleic acid with tunable performance

In this work, a self-propelled DNA machine was proposed for enzyme-free and ultrasensitive electrochemical detection of nucleic acid, which was based on a new strategy of the fuel strand-powered target recycling and successive proximity-based inter-strand displacement for distinct signal amplification. A three-strand duplex DNA (TSD) probe was immobilized onto electrode for target DNA recognition via a fuel strand-powered strand displacement circuit, accompanied with the target recycling and the association of fuel strand onto electrode for signal amplification and readout. The associated fuel strand contained a protruding tail sequence that could be used as a target analogy to activate the neighboring TSD probe based on the proximity-based inter-strand displacement effect, inducing the self-propelled association of fuel strand onto electrode for further signal amplification. The detection performance (dynamic response range, linear interval and detection limit) of current electrochemical DNA machine could be interestingly tuned by changing the tail sequence length of fuel strand, showing the potential for different analysis requirements. The lowest detection limit of 0.1 fM could be achieved, which was lower about two orders of magnitude than that by the typical fuel strand-powered target recycling strategy. Therefore, the developed sensing system exhibits a new, simple and powerful means for amplified detection of nucleic acid and may hold great potentials in bioanalysis, disease diagnosis and biomedicine.

Protein Microgel-Stabilized Pickering Liquid Crystal Emulsions Undergo Analyte-Triggered Configurational Transition.

Herein, we report a novel approach that involves Pickering stabilization of micometer-sized liquid crystal (LC) droplets with biocompatible soft materials such as a whey protein microgel (WPM) to facilitate the analysis of analyte-induced configurational transition of the LC droplets. The WPM particles were able to irreversibly adsorb at the LC-water interface, and the resulting WPM-stabilized LC droplets possessed a remarkable stability against coalescence over time. Although the LC droplets were successfully protected by a continuous network of the WPM layer, the LC-water interface was still accessible for small molecules such as sodium dodecyl sulfate (SDS) that could diffuse through the meshes of the adsorbed WPM network or through the interfacial pores and induce an LC response. This approach was exploited to investigate the dynamic range of the WPM-stabilized LC droplet response to SDS. Nevertheless, the presence of the unadsorbed WPM in the aqueous medium reduced the access of SDS molecules to the LC droplets, thus suppressing the configuration transition. An improved LC response to SDS with a lower detection limit was achieved after washing off the unadsorbed WPM. Interestingly, the LC exhibited a detection limit as low as ∼0.85 mM for SDS within the initial WPM concentration ranging from 0.005 to 0.1 wt %. Furthermore, we demonstrate that the dose-response behavior was strongly influenced by the number of droplets exposed to the aqueous analytes and the type of surfactants such as anionic SDS, cationic dodecyltrimethylammonium bromide (DTAB), and nonionic tetra(ethylene glycol)monododecyl ether (C12E4). Thus, our results address key issues associated with the quantification of aqueous analytes and provide a promising colloidal platform toward the development of new classes of biocompatible LC droplet-based optical sensors.

Biolayer interferometry-SELEX for Shiga toxin antigenic-peptide aptamers & detection via chitosan-WSe2 aptasensor

We report biolayer interferometry based in-vitro selection technique (BLI-SELEX) for fishing out specific aptamers against E. coli Shiga toxin subtypes viz., stx1 & stx2 via epitopic peptides. BLI-SELEX is a one-step technique for rapidly generating aptamers against protein biomarkers in a microtiter plate format, obliterating the need for multiple enrichment rounds to harvest high-affinity aptamers as in conventional SELEX. Two unique aptamers selected against stx1 & stx2 with picomolar Kd (~47 pM & ~29 pM, respectively) were successfully used to fabricate voltammetric diagnostic assay via immobilization onto chitosan exfoliated 2D tungsten diselenide (WSe2) nanosheet platform. These aptamers modified nanosensors showed high sensitivity of ~ 5.0 μA ng-1 mL, a dynamic response range from 50 pg mL-1 to 100 ng mL-1, with a detection limit of 44.5 pg mL-1 & 41.3 pg mL-1 for stx subtypes, respectively and showed low cross-reactivity in spiked urine, serum and milk samples. The synergistic effect of selective aptamers & high sensitivity imparted by 2D transition metal dichalcogenide (TMD) highlights the superior potential of a fabricated nanosensor for bacterial toxin detection.

Exploring the Extra-Virgin Olive Oil Volatilome by Adding Extra Dimensions to Comprehensive Two-Dimensional Gas Chromatography and Time-of-Flight Mass Spectrometry Featuring Tandem Ionization: Validation of Ripening Markers in Headspace Linearity Conditions.

Comprehensive two-dimensional gas chromatography (GC×GC) combined with time-of-flight (TOF) MS is the most informative analytical approach for chemical characterization of the complex food volatilome. Key analytical features include separation power and resolution enhancement, improved sensitivity, and structured separation patterns from chemically correlated analytes. In this study, we explore the complex extra-virgin olive oil volatilome by combining headspace (HS) solid-phase microextraction (SPME), applied under HS linearity conditions to GC×GC-TOF MS and featuring hard and soft ionization in tandem. Multiple analytical dimensions are combined in a single run and evaluated in terms of chemical dimensionality, method absolute and relative sensitivity, identification reliability provided by spectral signatures acquired at 70 and 12 eV, and dynamic and linear range of response provided by soft ionization. Method effectiveness is validated on a sample set of oils from Picual olives at different ripening stages. Ripening markers [3,4-diethyl-1,5-hexadiene (RS/SR), 3,4-diethyl-1,5-hexadiene (meso), (5Z)-3-ethyl-1,5-octadiene, (5E)-3-ethyl-1,5-octadiene, (E, Z)-3,7-decadiene and (E, E)-3,7-decadiene, (Z)-2-hexenal, (Z)-3-hexenal and (Z)-3-hexenal, (E)-2-pentenal, (Z)-2-pentenal, 1-pentanol, 1-penten-3-ol, 3-pentanone, and 1-penten-3-one] and quality indexes [(Z)-3-hexenal/nonanal, (Z)-3-hexenal/octane, (E)-2-pentenal/nonanal, and (E)-2-pentenal/octane] are confirmed for their validity in HS linearity conditions. For the complex olive oil volatilome, the proposed approach offers concrete advantages for the validation of the informative role of existing analytes while suggesting new potential markers to be studied in larger sample sets. The accurate fingerprinting of volatiles by HS-SPME operating in HS linearity conditions followed by GC×GC-TOF MS featuring tandem ionization gives the opportunity to improve the quality of analytical data and reliability of results.

A novel nonenzymatic hydrogen peroxide amperometric sensor based on AgNp@GNR nanocomposites modified screen-printed carbon electrode

Abstract A nonenzymatic hydrogen-peroxide sensor was developed by utilization of silver nanoparticles and graphene nanoribbons. The mentioned composite was inflicted on a screen-printed carbon electrode which provides disposable, ready-to-use sensor. The structure and morphology of the nanocomposite were analyzed by scanning electron microscopy and X-ray diffraction. The sensor has excellent performance toward H2O2 amperometric detection. Figures of merit include dynamic response range from 0.05 to 5 mM and detection limit of 20 μM (at S/N = 3). The fabricated sensor was used for the determination of H2O2 in milk samples. The obtained results showed that the proposed AgNp@GNR/SPCE sensor can be used for the determination of hydrogen peroxide in real samples.

Development of Novel Riboswitches for Synthetic Biology in the Green Alga Chlamydomonas.

Riboswitches are RNA regulatory elements that bind specific ligands to control gene expression. Because of their modular composition, where a ligand-sensing aptamer domain is combined with an expression platform, riboswitches offer unique tools for synthetic biology applications. Here we took a mutational approach to determine functionally important nucleotide residues in the thiamine pyrophosphate (TPP) riboswitch in the THI4 gene of the model alga Chlamydomonas reinhardtii, allowing us to carry out aptamer swap using THIC aptamers from Chlamydomonas and Arabidopsis thaliana. These chimeric riboswitches displayed a distinct specificity and dynamic range of responses to different ligands. Our studies demonstrate ease of assembly as 5′UTR DNA parts, predictability of output, and utility for controlled production of a high-value compound in Chlamydomonas. The simplicity of riboswitch incorporation in current design platforms will facilitate the generation of genetic circuits to advance synthetic biology and metabolic engineering of microalgae.

Single-Beam Atomic Magnetometer Based on the Transverse Magnetic-Modulation or DC-Offset

We constructed a compact single-beam atomic magnetometer operated in a transverse magnetic-modulation mode or a DC-offset mode. By coupling the laser beam into a polarization maintaining fiber, with a vapor cell of the dimensions 4 mm $\times4$ mm $\times4$ mm, a sensitivity of 30 fT/Hz1/2 has been achieved in the single-beam configuration. In addition to the experimental study of the sensitivity, we perform a theoretical analysis of the single-beam atomic magnetometer in the transverse magnetic-modulation mode and the DC-offset mode. The results indicate both of two modes have almost the same scale factor. We also studied the dynamic working range of the sensor and found, experimentally, that our sensor reaches a dynamic response range of ± 3 nT, with a nonlinear error of 1%. The frequency responses of the transverse magnetic-modulation mode and the DC-offset mode are 125 Hz and 65 Hz, respectively. This sensor will be particularly suitable for applications that require high sensitivity, low cost and compact size, e.g., magnetoencephalography (MEG) and magnetocardiography (MCG).

Smartphone assisted colorimetric and fluorescent triple-channel signal sensor for ascorbic acid assay based on oxidase-like CoOOH nanoflakes.

Ascorbic acid (AA) is an important diet-derived antioxidant to human body. Thus, efficient and accurate detection of AA is of considerable significance in food analysis. Herein, smartphone assisted colorimetric and fluorescent triple-channel signal sensor has been developed for AA monitoring based on oxidase-like CoOOH nanoflakes. CoOOH nanoflakes can efficiently catalyze the oxidation of p-phenylenediamine (p-PD) into reddish brown p-PDox. The carbon dots (C-dots) are further introduced, of which the fluorescence can be quenched by p-PDox. However, in the presence of AA, the CoOOH nanoflakes is reduced and thus collapsed. As a result, the oxidation of p-PD is restrained, and thus the fluorescence of C-dots keeps strong. Based on AA induced light color, low absorbance, and strong fluorescence, triple-channel signal sensor has been proposed for AA determination. The AA assay shows a dynamic response range from 0.5 to 10μM with a detection limit of 0.09μM. The method assay allows detection of AA in real samples such as fruit juices. Combination with portable smartphone, the developed sensor is potential for AA determination in resource-poor settings.

Ultrasensitive Thin-Film Pressure Sensors with a Broad Dynamic Response Range and Excellent Versatility Toward Pressure, Vibration, Bending, and Temperature

Flexible pressure sensors with high sensitivity and wide pressure response range are attracting considerable research interest for their potential applications as e-skins. Nowadays, it seems a dilemma to realize high-performance, multifunctional pressure sensors with cost-effective, scalable strategy, which can simplify wearable sensing systems without additional signal processing, enabling device miniaturization and low power consumption. Herein, pressure sensors with ultrahigh sensitivity and broad response pressure range are developed with a low-cost, facile method by combining strain-induced percolation behavior and contact area contributions. Due to their special surface structure and strain induced conductive network formation behavior, these unique pressure sensors exhibit wide sensing range of 1 Pa-500 kPa, ultra-high sensitivity (1×106 kPa-1and 3.1×104 kPa-1 in the pressure ranges of 1 Pa-20 kPa and 20-500 kPa, respectively), fast signal response (< 50 ms), low detect limit (1 Pa) and high stability over 500 loading/unloading cycles. These characteristics allow the devices work as e-skins to monitor human pulse signals and finger touch. Moreover, these sensors illustrate precise electrical response to mechanical vibration, bending and temperature stimuli, which afford the ability of detecting cell phone call-in vibration signals, joint bending and spatial pressure & temperature distributions, indicating promising applications in next-generation wearable, multifunctional e-skins.

Indirect Competitive Immunoassay on a Blu-ray Disc for Digitized Quantitation of Food Toxins.

We report herein a Blu-ray disc technology enabled immunoassay (namely, assay-on-a-Blu-ray) protocol for the quantitation of food toxins. In particular, commercial Blu-ray discs (BDs) are activated as substrates to create indirect competitive immunoassays with the aid of microfluidic channel plates for the quantitation of aflatoxins; an unmodified Blu-ray drive is employed to read the digitized signal (error counts generated from gold/silver-particle-enhanced binding sites); and a free disc-quality control software is adapted to process the raw data. The performance of this BD-based digital detection platform has been tested for the quantitation of aflatoxin B1 (AFB1) in spiked corn samples and validated with standard high-performance liquid chromatography measurements. The detection limit attained is as low as 0.27 ppb with a dynamic response range up to 200 ppb, which meets the standards established by government agencies worldwide for food products. We truly believe that the application potential of such a BD-technology-based, portable device for multiplex on-site quantitative analysis of food products as well as environmental and biomedical samples in real time is unlimited.

Combining genetically-encoded biosensors with high throughput strain screening to maximize erythritol production in Yarrowia lipolytica

Erythritol is an important sweetener ingredient and chemical precursor for synthesizing materials with phase transition behavior. Commercial erythritol is primarily produced by industrial fermentation. Further strain engineering necessitates the development of high throughput screening method for rapid detection and screening of mutant strain libraries. In this work, we took advantage of the erythritol-responsive transcription factor EryD, and constructed a sensor-regulator system for rapid screening and characterization of erythritol overproducers. We configured the optimal architecture of the EryD sensor-regulator construct with improved sensitivity, specificity and dynamic response range. Coupled with mutagenesis and strain screening based on biosensors, we rapidly screened and characterized a strain library containing 1152 mutants derived from combined UV and ARTP mutagenesis, in a relatively short period of time (1 week). The optimal strain produced more than 148 g/L erythritol in bench-top reactors. This work provides a reference for other metabolic engineering researchers to develop industrially-relevant strains. The reported framework enables us to rapidly improve strain performance and engineer efficient microbial cell factories for industrial applications.

A Highly Sensitive Impedimetric DNA Biosensor Based on Hollow Silica Microspheres for Label-Free Determination of E. coli.

A novel label-free electrochemical DNA biosensor was constructed for the determination of Escherichia coli bacteria in environmental water samples. The aminated DNA probe was immobilized onto hollow silica microspheres (HSMs) functionalized with 3-aminopropyltriethoxysilane and deposited onto a screen-printed electrode (SPE) carbon paste with supported gold nanoparticles (AuNPs). The biosensor was optimized for higher specificity and sensitivity. The label-free E. coli DNA biosensor exhibited a dynamic linear response range of 1 × 10−10 µM to 1 × 10−5 µM (R2 = 0.982), with a limit of detection at 1.95 × 10−15 µM, without a redox mediator. The sensitivity of the developed DNA biosensor was comparable to the non-complementary and single-base mismatched DNA. The DNA biosensor demonstrated a stable response up to 21 days of storage at 4 ℃ and pH 7. The DNA biosensor response was regenerable over three successive regeneration and rehybridization cycles.

Enhanced sensitivity and detection range of FRET-based vitamin B12 nanosensor.

Vitamin B12 (cobalamin) is a cobalt-containing compound that acts as an essential co-factor for various enzymes involved in the metabolic processes of the living cells. The constructed FRET Sensor for Vitamin Anemia Linked (SenVitAL) displayed marginal FRET efficiency. Here, we report the development of a molecular SenVitAL containing enhanced cyan fluorescent protein (ECFP) and venus as FRET pair to improve the FRET efficiency for optical imaging and screening of already developed sensor by our group. The sensor is the improved version of previously reported SenVitAL and consists of ECFP/venus as FRET pair instead of the originally used pair CFP/YFP. To increase the physiological range of vitamin B12 measurement, affinity mutants were created. Compared to the wild type, SenVitAL-5 with W44Q mutation has higher affinity and displayed large dynamic detection range (0.10-480µM) in response to vitamin B12 binding. For cell-based monitoring and dynamic measurement of vitamin B12 flux rates, SenVitAL-5 was successfully expressed in cytosol of yeast and mammalian cells. Changes in the emission intensities of the two fluorophores were detected using confocal microscopy in both cell types in response to vitamin B12. With the addition of 50µM extracellular vitamin B12 to the cells, the emission intensity of venus increased and that of ECFP decreased over the time. Furthermore, the results show that the variant SenVitAL-5 measures the vitamin B12 in a concentration-dependent manner, showing the resulting increase in the FRET ratio and thus confirming its utility as an ideal fluorescent indicator for the detection of vitamin B12 in eukaryotic systems in real time.

Immobilized dye-decolorizing peroxidase (DyP) and directed evolution variants for hydrogen peroxide biosensing

Immobilized dye-decolorizing peroxidase from Pseudomonas putida MET94 (PpDyP) and three variants generated by directed evolution (DE) are studied aiming at the design of a biosensor for H2O2 detection. Structural properties of the enzymes in solution and immobilized state are addressed by resonance Raman (RR) and surface enhanced RR (SERR) spectroscopy, and the electrocatalytic properties are analyzed by electrochemistry. The wild-type (wt) and 29E4 variant (with E188K and H125Y mutations) represent excellent candidates for development of H2O2 biosensors, since they exhibit a good dynamic response range (1–200 μM H2O2), short response times (2 s) and a superior sensitivity (1.3–1.4 A⋅M−1⋅cm−2) for H2O2, as well as selectivity and long term stability. In contrast to the solution state, 6E10 (with E188K, A142V and H125Y mutations) and 25F6 (with E188K, A142V, H125Y and G129D mutations) variants display much lower activity and are inhibited by high concentrations of H2O2 upon adsorption on an electrode. In terms of sensitivity, the bioelectrodes employing wt PpDyP and 29E4 variant outperform HRP based counterparts reported in the literature by 1–4 orders of magnitude. We propose the development of wt or 29E4 PpDyP based biosensor as a valuable alternative to devices that rely on peroxidases.

Novel electrochemiluminescence solid-state pH sensor based on an i-motif forming sequence and rolling circle amplification.

Based on a pH-dependent i-motif forming sequence and rolling circle amplification (RCA) strategy, a novel electrochemiluminescence (ECL) solid-state pH sensor was proposed herein. The sensor showed a wide dynamic response range from pH 4 to 7.4. Furthermore, our sensor could be used to determine glucose, demonstrating its practical applicability.