Signal Amplification Factor Research Articles

Differences of interference myogram patterns from forearm muscles at different variants of the hand grip

Background. Most modern bioprostheses use two sensors located on the flexor and extensor muscles of the hand and fingers to register muscle activity, which severely limits the functionality of the device and complicates switching between grips. One of the solutions to this problem is to use an array of more sensors to recognize different grips using a neural network.Aim. To evaluate the possibility in principle of using an array of 8 sensors for recognizing different grips.Materials and methods. Research was conducted on 23 healthy volunteers, whose surface myograms were recorded at 13 different grips. An array of surface-type electroneuromyographic sensors (n = 8) with bipolar electrodes and electroneuromyographic signal amplification factor of 2000 times, myograph and software are of own development were used as a technical base for the research.Results. For most subjects, the differences in the investigated parameters when comparing grips with each other reached thousands of percent, especially when comparing the product of frequency and mean amplitude. In some pairs the differences were less significant and amounted to less than 400 %. The proportion of pairs with reliable differences varies from subject to subject when comparing the product of frequency and mean amplitude and ranges from 71 to 98 %. The average value for the whole group is 87 %. When comparing frequency only, the variation ranges from 67 to 93 %, with an average of 78 %.Conclusion. For most subjects, the majority of grips are confidently differentiated from each other. Due to pronounced individual peculiarities, the decision to use this or that parameter to control the bioprosthesis for a definite person is individual and should be made after a thorough neurophysiological research. Some people will require training in order to develop a new motor stereotype.

Electrochemiluminescence detection of diazinon in vegetables based on the synergistic interaction of WO3-x dots with Au@SiO2 nanocapsules

In this work, a simple synthesis of low-toxicity transition metal material of WO3-x dots was used as a co-reactant with Au@SiO2 as a core-shell material and a signal amplification factor to collaboratively promote Ru(bpy)32+ electrochemiluminescence (ECL) for the construction of a highly sensitive aptasensor for the detection of diazinon (DZN) in vegetables. Electrodes modified with multi-walled carbon nanotubes-chitosan composite membranes (MWCNTs-CS) were used to load and immobilize more Ru(bpy)32+.can load more Ru(bpy)32+. WO3-x dots synthesized by a simple method showed excellent ECL efficiency as a novel co-reactant for Ru(bpy)32+. Under optimized conditions, this aptasensor for DZN has a wide detection range (10 pg mL−1 - 1 μg mL−1.) and a low detection limit (0.0197 ng L−1). The aptasensor has shown good results in the analysis of real samples in the experiment. This work provides a new approach to the construction of a novel electrochemiluminescence sensor for the detection of pesticides.

Enhancing Ion Signals and Improving Matrix Selection in Time-of-Flight Secondary Ion Mass Spectrometry with Microvolume Expansion Using Large Argon Clusters.

The molecular environment has an important impact on the ionization mechanism in time-of-flight secondary ion mass spectrometry (ToF-SIMS). In complex samples, desorption/ionization, and thus the detection of a molecular signal, can be hampered by molecular entanglement, ionization-suppressive neighbors, or even an unfavorable sample substrate. Here, a method called microvolume expansion is developed to overcome these negative effects. Large argon clusters are able to transfer biomolecules from a target to a collector in vacuum. In this study, argon gas cluster ion beams (Arn+-GCIB with n centered around 3000 or 5000) are used to expand a microvolume from the sample to a collector, which is a material ideally enhancing the ionization yield. The collector is then analyzed using a liquid metal ion gun. The signal amplification factor corresponding to the expansion of phosphatidylcholine (PC) lipid on collectors partially covered with acidic matrices was evaluated as an initial proof of concept. In one experiment, the PC expansion on a pattern of four drop-casted matrix-assisted laser desorption/ionization matrices led to the selection of α-cyano-4-hydroxycinnamic (CHCA) as the optimal candidate for cationic PC detection. The ion signal is increased by at least three orders of magnitude when PC was expanded using 10 keV Ar3000+ and Ar5000+ on a sublimated layer of CHCA. Finally, the expansion of the gray matter of a mouse on different materials (Si, Au-coated Si, CHCA, and polyethylene) was achieved with varying degrees of success, demonstrating the potential of the method to further analyze complex and fragile biological assemblies.

Electrochemiluminescence biosensor for determination of lead(II) ions using signal amplification by Au@SiO2 and tripropylamine-endonuclease assisted cycling process.

MXene@Au as the base and Au@SiO2 as signal amplification factor were used for constructing an ultrasensitive "on-off" electrochemiluminescence (ECL) biosensor for the detection of Pb2+ in water. The use of MXene@Au composite provided a good interface environment for the loading of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)32+) on the electrode. Based on resonance energy transfer, the Au (core) SiO2 (shell) (Au@SiO2) nanoparticles stimulate electron transport and promote tripropylamine (TPrA) oxidation. The luminescence effect of Au@SiO2 was five times that of AuNPs and SiO2 nanomaterials alone, and the ECL intensity was greatly improved. In addition, Pb2+ activated the aptamer to exert its endonuclease activity, which realized the signal cycle amplification in the process of Pb2+ detection. When Pb2+ was added, the ECL signal weakened, and the Pb2+ concentration was detected according to the decreased ECL intensity. Under optimized experimental conditions, this aptamer sensor for Pb2+ has a wide detection range (0.1 to 1 × 106ng L-1) and a low detection limit (0.059ng L-1). The relative standard deviation (RSD) of the sensor is 0.39-0.99%, and the recovery of spiked standard is between 90.00 and 125.70%. The sensor shows good selectivity and high sensitivity in actual water sample analysis. This signal amplification strategy possibly provides a new method for the detection of other heavy metal ions and small molecules.

A photoelectrochemical biosensor based on b-TiO2/CdS:Eu/Ti3C2 heterojunction for the ultrasensitive detection of miRNA-21

A novel photoelectrochemical (PEC) biosensor based on b-TiO2/CdS:Eu/Ti3C2 heterojunction was developed for ultrasensitive determination of miRNA-21. In this device, the b-TiO2/CdS:Eu/Ti3C2 heterojunction with excellent energy level arrangement effectively facilitated photoelectric conversion efficiency and accelerated the separation of the photogenerated electron hole pairs, which because that the structure of heterojunction overcomes the drawbacks of single material, such as narrow light absorption range, wide band gap, short carrier lifetime, etc., improves light utilization, extends the lifetime of photogenerated electron hole pairs, and promotes electron transfer. Herein, hairpin DNA1 (H1) decorated on the b-TiO2/CdS:Eu/Ti3C2 electrode surface by Cd–S bonds, after H2/miRNA-21 heterduplex was introduced, the strand-displacement reaction (SDR) was triggered between H1 and H2/miRNA-21, accordingly, miRNA-21 was discharged from the H2/miRNA-21 heterduplex, forming the H1/H2 duplex, and the reuse of miRNA-21 was realized. As a signal amplification factor, the signal amplification factor H3–CdSe was hybridized with H1/H2 duplex, which greatly enhanced the sensitivity of the PEC biosensor. Under optimal conditions, the designed PEC biosensor displayed outstanding sensitivity, selectivity and stability with a wide liner range from 1.0 μM to 10.0 fM and a low detection limit of 3.3 fM. The preparation of the optoelectronic material affords a new direction for the progress of heterojunction photovoltaic materials and the construction of the proposed biosensor also provides a new thought for the PEC detection of human miRNA-21 with superior performance. Simultaneously, the established biosensor exhibiting tremendous possibility for detecting other biomarkers and biomolecules in clinical diagnosis fields.

Ultrasensitive photoelectrochemical immunosensor based on a g-C3N4/SnS2 nanocomposite for prostate-specific antigen detection

Herein, a novel amplified photoelectrochemical immunosensor based on a g-C3N4/SnS2 nanocomposite was constructed and applied to detect prostate-specific antigen (PSA). The prepared nanocomposite materials were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), ultraviolet–visible absorption spectroscopy (UV–vis), and Fourier transform infrared spectroscopy (FT-IR). The results indicate that g-C3N4/SnS2 nanocomposite materials were successfully synthesized. In a typical assembly process, the immunosensor was constructed by embellishing fluorine-doped tin oxide (FTO) electrode with g-C3N4/SnS2 nanocomposite, chitosan (Chito), monoclonal antibody (Ab1), blocking agent bovine serum albumin (BSA), prostate-specific antigen (PSA), and polyclonal antibody-CdS (Ab2-CdS) bioconjugate in turn. The bioconjugate served as a signal amplification factor, and greatly enhanced the sensitivity of PSA detection. In this sensing strategy, the target PSA detection was based on the change in the amount of the signal amplification factor Ab2-CdS bioconjugate, which caused the change of photocurrent intensity. In the presence of PSA, the Ab2-CdS bioconjugate was specifically binding with PSA, then the signal amplification factor Ab2-CdS bioconjugate was incubated on the sensor electrode surface, increasing the photocurrent intensity significantly. Accordingly, under optimal conditions, a novel enhanced photoelectrochemical immunosensor was constructed, and it exhibited excellent sensitivity, selectivity and repeatability for detecting PSA. The detection limit was 1.3 fg·mL−1, and the range was 10 fg·mL−1 – 10 ng·mL−1. Simultaneously, the sensor also provides a likely sensing device for detecting other protein targets, which is of great significance for early clinical diagnosis.

Experiment to observe an optically induced change of the vacuum index

Quantum electrodynamics predicts that the vacuum must behave as a nonlinear optical medium: the speed of light should be modified when the vacuum is stressed by intense electromagnetic fields. This optical phenomenon has not yet been observed. The DeLLight (Deflection of Light by Light) experiment aims to observe the optically-induced index change of vacuum, a nonlinear effect which has never been explored. The experiment is installed in the LASERIX facility at IJCLab, which delivers ultra-short intense laser pulses (2.5 J per pulse, each of 30 fs duration, with a 10 Hz repetition rate). The proposal is to measure the refraction of a probe laser pulse when crossing a transverse vacuum index gradient, produced by a very intense pump pulse. The refraction induces a transverse shift in the intensity profile of the probe, whose signal is amplified by a Sagnac interferometer. In this article, we describe the experimental method and setup, and present the complete theoretical calculations for the expected signal. With a minimum waist at focus of $5 \,\mu$m (corresponding to a maximum intensity of $\sim 3 \times 10^{20}$ W/cm$^2$), and with the nonlinear vacuum index derived from QED, the expected refraction angle is 0.13 prad. First results of the interferometer prototype are presented. It is shown that an extinction factor $\mathcal{F} = 0.4 \times 10^{-5}$ (corresponding to a signal amplification factor of 250) and a spatial resolution $\sigma_y = 10$ nm are achievable. The expected signal is then about 15 pm, and could be observed at a 5-sigma confidence level with about one month of collected data.

Liposome encapsulated electron donor strategy for signal-on CYFRA 21-1 photoelectrochemical analysis.

Anovel electron donor controlled-release system is proposedbased on liposome encapsulated L-cysteine for the sensitive determination of cytokeratin 19 fragment21-1 (CYFRA 21-1). On the one hand, a defective TiO2 modified with methylene blue was employed as a photoactive platform which exhibited a high photoelectrochemical (PEC) response owing to the introduction of oxygen vacancies and the high photosensitivity of the dye. On the other hand, L-cysteine as the sacrificial electron donor was encapsulated in the vesicles of liposomes, and this composite was used as the signal amplification factor, which is labeled on the secondary antibody of CYFRA 21-1 to further improve the photocurrent sensitivity. The excellent electron transfer path in photoactive materials coupled with the skilful electron donor controlled-release system, contributed to the sensitive PEC analysis of CYFRA 21-1 underoptimumconditions. The PEC immunoassay showed a linear current response in the range 0.0001-100ng/mL with a detection limitof37fg/mL. Enhanced stability and satisfactory reproducibility were also achieved. The proposed concept provides a novel signal-on strategy for the sensitive detection of other cancer markers in the electrochemical sensing field.

Fluorescence polarization gene assay for HIV-DNA based on the use of dendrite-modified gold nanoparticles acting as signal amplifiers.

The authors describe a fluorescence polarization assay for HIV-DNA. It is based on the use of gold nanoparticles (AuNPs) modified with DNA dendritic macromolecules that act as signal amplifiers. In the presence of HIV-DNA, the AuNP-DNA dendritic macromolecules and fluorescently labeled DNA probe combine with HIV-DNA in a sandwich format to form a conjugate. This reaction slows down the rotational speed of the labeled DNA probe because of the increase of molecular weight and volume. This increases fluorescence polarization and the sensitivity of the system. The relative fluorescence polarization values increase linearly in the 150 pM to 6nM HIV-DNA concentration range, with a 73 pM detection limit. The results show this amplification strategy to be most useful for ultrasensitive determination of oligonucleotides by means of fluorescence polarization. Graphical abstract Schematic of a novel fluorescence polarization assay for the HIV-DNA. Ultrasensitive detection is accomplished by using AuNP-DNA dendritic macromolecules as signal amplification factor.

A non-perturbative analytic expression of signal amplification factor in stochastic resonance

We put forward a non-perturbative scheme to calculate the response of an overdamped bistable system driven by a Gaussian white noise and perturbed by a weak monochromatic force (signal) analytically. The formalism takes into account infinite number of perturbation terms of a perturbation series with amplitude of the signal as an expansion parameter. The contributions of infinite number of relaxation modes of the stochastic dynamics to the response are also taken into account in this formalism. A closed form analytic expression of the response is obtained. Only the knowledge of the first non-trivial eigenvalue and the lowest eigenfunction of the un-perturbed Fokker–Planck operator are needed to evaluate the response. The response calculated from the derived analytic expression matches fairly well with the numerical results.

Enhancement of SERS signal using new material based on cerium dioxide facet dielectric films

In this paper, we investigate the potential of facet structures of cerium dioxide for the purpose of increasing the intensity of the surface enhancement Raman scattering (SERS) signal. During the studies, a new metamaterial is developed. The metamaterial is based on facet cerium dioxide films and plasmonic nanoparticles that are immobilized on its surface. The new metamaterial provides an additional SERS signal amplification factor of more than 200. Thus developed material offers the prospect of increasing the sensitivity and selectivity of biochemical and immunological analysis.

Signal amplification factor in stochastic resonance: An analytic non-perturbative approach

The response of an overdamped bistable system driven by a Gaussian white noise and perturbed by a weak monochromatic force (signal) is studied analytically. In order to get amplitude-dependent signal amplification factor a non-perturbative scheme is put forward by taking into account all the terms of a perturbation series with amplitude of the signal as an expansion parameter. An approximate analytic expression of the signal amplification factor is derived and compared with the numerical results. The contributions of infinite number of relaxation modes of the stochastic dynamics to the response are also taken into account in the final expression. The calculation of the response based on the derived expression requires only the knowledge of the first non-trivial eigenvalue and the lowest eigenfunction of the unperturbed Fokker–Planck operator.

New SERS-active junction based on cerium dioxide facet dielectric films for biosensing

Further enhance of the Raman scattering is the priority for the development of the modern molecular diagnostic methods. Expected increasing in detection sensitivity of the biological and chemical agents provides substantial progress in such areas as: proteomics (discovery of new disease markers), pharmacokinetics of drugs, analysis of toxins and infections agents, drug analysis, food safety, and environmental safety.In this paper we investigated the possibility of the facet structures, based on cerium dioxide to further enhance the SERS signal. During the studies a new metamaterial was developed. The metamaterial is based on the facet cerium dioxide films and plasmonic nanoparticles that are immobilized on its surface. The new metamaterial provides additional SERS signal amplification factor of 211. Thus developed material offers the prospect of increasing the sensitivity and selectivity of biochemical and immunological analysis.

Amplified impedimetric DNA sensor based on graphene oxide–phenylboronic acid for sensitive detection of bleomycins

Due to the significance of bleomycins (BLMs) for the treatment of a variety of cancers, it is highly desirable to develop a sensitive method to quantitatively determine the BLMs content in both pharmaceutical analysis and clinical samples. Here, a simple, rapid, and convenient electrochemical method for BLMs detection was developed. Single-stranded DNA, as the substrate of BLMs, was self-assembled onto a gold electrode to fabricate an electrochemical DNA sensor, with one terminus tethered on the electrode surface and the other terminus labeled with graphene oxide–phenylboronic acid as a signal-amplification factor, giving a remarkable electron-transfer resistance (Ret). In the presence of Fe(II)·BLMs, the electrochemical DNA sensor undergoes an irreversible cleavage event, which can be transduced into a significant decrease in Ret. This sensor reveals a wide linear range from 0.05 nM to 1200 nM (R = 0.9869) and a low detection limit (0.01 nM, S/N = 3) for the determination of BLMs. It exhibits a good performance in a serum sample as well. Based on the high sensitivity and specificity of this electrochemical DNA sensor and the attractive characteristics of the electrochemical technique (cost effective and simple to implement), the developed impedimetric DNA sensor shows distinct advantages over conventional methods and is a promising alternative for the sensitive determination of BLMs in clinical samples.

Detection of Wild-Type Hypoxanthine Guanine Phosphoribosyl Transferase of Lymphocytes in Gamma-Irradiated Mice with Surface Plasmon Resonance

A quick and sensitive detection of the wild-type hypoxanthine guanine phosphoribosyl transferase (HPRT), which is known as a biomarker for radiation exposure, was developed. The conventional HPRT measurement technique is to detect the mutant HPRT, which is time-consuming and has low sensitivity. In this study, the wild-type HPRT was detected as a gamma radiation biomarker using a surface plasmon resonance (SPR) biosensor with 6-thioguanine (6-TG) as a probe and the anti-HPRT antibody as a signal amplification factor. First, we used this system to measure the wild-type HPRT dissolved in PBS. Six-TG immobilized on the surface can specifically detect the wild-type HPRT, and the anti-HPRT antibody enhances about 10 times the primary signal produced by the binding of the wild-type HPRT with 6-TG. A linear relationship (r = 0.991) was obtained between the concentration of the wild-type HPRT and the enhanced signal. The low detection limit (LDL) is 2.1 ng/mL. The regeneration using glycine-HCl was also investigated. Six-TG immobilized on the surface can be used in 9 injection-regeneration cycles. The relative standard deviation (RSD) of baseline changes after regenerations is 2.8%. The applicability of the method to real samples has been demonstrated with comparative analyses of lymphocyte extracts in gamma irradiated and unirradiated mice. The irradiated sample displays a significantly lower level of the wild-type HPRT compared to that in the unirradiated sample. The single sample detection only needs about 20 min. Thus, the SPR biosensor could potentially serve as an attractive technique for rapid and sensitive detection of the wild-type HPRT, a gamma radiation biomarker.

Optimal working point of a Brillouin amplifier for a weak input signal in the transient regime

In order to improve the working performances of a transient Brillouin amplifier, the dependences of the signal-noise-ratio, sensitivity, energy extraction efficiency and signal amplification factor on exponential gain G are numerically studied based on the theoretical model of transient Brillouin amplification including distributed noise, and an optimal working point of a Brillouin amplifier is obtained. Experimental verifications are performed by choosing CS2 and FC-72 as nonlinear media. A frequency-doubled Nd:YAG pulse laser is used. Results show that when the pump pulse lags behind the Stokes signal pulse by an amount of time equal to half the pulse width, Gopt can be set to be above the SBS threshold exponential gain Gth. For a collinear Brillouin amplifier, Gopt is 1.1-1.3 times Gth; while for a non-collinear structure, Gopt can be set to be over 1.3 times Gth. Nearly saturated amplification is achieved.

Electrochemical DNA Detection via Exonuclease and Target-Catalyzed Transformation of Surface-Bound Probes

We report a single-step, single-reagent, label-free, isothermal electrochemical DNA sensor based on the phenomenon of target recycling. The sensor exploits strand-specific exonuclease activity to achieve the selective enzymatic digestion of target/probe duplexes. This results in a permanent change in the probe structure that yields an increased faradaic current and liberates the intact target molecule to interact with additional detection probes to achieve further signal amplification. Using this architecture, we achieve an improved detection limit in comparison to hybridization-based sensors without amplification. We also demonstrate a 16-fold signal amplification factor at low target concentrations. Combined with the advantages of electrochemical detection and its ready integration with microelectronics, our approach may represent a promising path toward direct DNA detection at the point of care.

Solvation, transduction and independent component analysis for pattern recognition in SAW electronic nose

This paper revisits the fundamental basis for signal generation in polymer coated SAW vapor sensors and applies the independent component analysis (ICA) for feature extraction from the SAW sensor array data to explore whether the independent components could represent analyte-specific solvation parameters and whether they could form the feature vector for reliable pattern classification. Thermodynamic partitioning of analytes between vapor and polymer phases is treated as independent contributions from different solvation mechanisms, each associated with characteristic ‘environment swap’ energy. The overall equilibrium partition coefficient of an analyte is modeled as product of partial partition coefficients associated with different solvation mechanisms. The polymer films on SAW devices are treated to be acoustically thin. The theory of signal generation accounts for effects from both the mass as well as the viscoelastic loadings. It explains the signal amplification factor due to viscoelastic effects, and models the sensor signal to be proportional to the equilibrium partition coefficient. Thus, the logarithmic signal becomes a linear combination of the partial free energies associated with various solvation mechanisms. A linear-solvation-energy relationship (LSER) like factorization is assumed for the partial free energies where the latter are expressed as product of analyte and complimentary polymer associated solvation parameters. The problem of sensor array signal analysis is then treated as a blind source separation problem with the analyte solvation parameters being the independent sources, the polymer solvation parameters being the mixing weights and the log(signals) being the measured variables. The FastICA algorithm with Gram-Schmidt orthogonalization is applied to determine independent components. The principal component analysis (PCA) is done as pre-processing step for ICA. An experimental SAW sensor array data available in the literature [Rose-Pehrsson et al., Anal. Chem. 60 (1988) 2801–2811] is used to seek validation for our approach, and to examine the role of ICA in SAW sensor array signal processing. In brief, the paper establishes a direct relationship between the independent components and the analyte solvation parameters, and presents ICA as an effective method for feature extraction for pattern recognition in SAW electronic noses.

P-Type 6H-SiC Films in the Creation of Triode Structures for Low Ionization Radiation

The signal value of the transistor-like detector on applied voltage was investigated. It was measure induced-current recording from fluxes of X-ray and optical quanta. A superlinear rise in the resulting signal was observed with increasing voltage. The signal was amplified by a factor of several tens with respect to the value chosen for normalization. A description in terms of the phototriode model gives acceptable values for the main parameters: base width, diffusion length of electrons, and space charge region of the collector. It is important that SiC films with the thickness d similar to 10 mum can be used to detect penetrating radiation, for example, X-ray. The effective thickness of the films exceeds d by the signal amplification factor (and proves to be in range of hundred mum).

Detection of Escherichia coli in water by culture-based amperometric and luminometric methods

The application of amperometric biosensor- and chemiluminiscence based methods for rapid detection of viable E. coli in water has been investigated. An amplification of the amperometric signal by a factor of 4 was obtained when the cellobiose dehydrogenase (CDH) biosensor was used instead of a plain graphite electrode for detection of b-galactosidase (b-GAL) activity at 22.5 degrees C. A linear correlation was demonstrated for detection time (DT) vs. initial concentrations (logarithmic units) of E. coli IT1 and E. coli in environmental samples, respectively, by use of the CDH biosensor or a chemiluminometric technique. The study has shown that an E. coli concentration > or = 10(4) cfu/100 mL in environmental samples was determined by the CDH biosensor within one working day. However, further reduction of the DT can be obtained, e.g. by increasing the signal amplification factor using other biosensors.