Bimodal Detection Research Articles

Dual-probe (colorimetric and fluorometric) detection of ferritin using antibody-modified gold@carbon dot nanoconjugates.

A dual-mode assay is described for immunological determination of the anemia biomarker ferritin. It is based on the use of a gold@carbon dot (Au@CD) nanoconjugate as a colorimetric and fluorescent probe. Au@CD is hydrophilic, easily surface modified and stable in aqueous solution. The Au@CD have a red color with blue-green fluorescence and were modified with antibody against ferritin. This allows bi-modal detection of ferritin. Assays can be performed in phosphate buffer and were also analyzed in (Bovine Serum Albumin) BSA and (Fetal Bovine Serum) FBS. Detection is based on antigen-antibody interaction underlying the classical sandwich model. Response to ferritin can be detected by spectrophotometry (at 570nm) or fluorescence (at excitation/emission maxima of 354/454nm). Under optimal conditions, the assay has a linear response in the 1 to 120ngmL-1 ferritin concentration range and detection limits of 20 ng (colorimetrically) and 64ng (fluorometrically). Graphical abstract Schematic representation of the function of the designed nanoprobe. The Au@CD nanoconjugates are functionalized with ferritin antibody in the initial step which specifically interacts with ferritin molecules leading to aggregation and subsequent changes in the optical and fluorescence signals.

Cover Feature: Bimodal Detection of Proteins by 129Xe NMR and Fluorescence Spectroscopy (ChemBioChem 11/2019)

Cover Feature: Bimodal Detection of Proteins by ¹²⁹Xe NMR and Fluorescence Spectroscopy (ChemBioChem 11/2019)

Colorimetric Assay Conversion to Highly Sensitive Electrochemical Assay for Bimodal Detection of Arsenate Based on Cobalt Oxyhydroxide Nanozyme via Arsenate Absorption.

This study reports a novel and convenient bimodal method for label-free and signal-off detection of arsenate in environmental samples. Cobalt oxyhydroxide (CoOOH) nanoflakes with facile preparation and intrinsic peroxidase-like activity as nanozyme can efficiently catalyze the conversion of chromogenic substrate such as 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) with the presence of H2O2 into green-colored oxidation products. CoOOH nanoflakes can specifically bind with arsenate via electrostatic attraction and As-O bond interaction, which gives rise to inhibition of the peroxidase-like activity of CoOOH. Thus, through arsenate specific inhibition of CoOOH nanozyme toward ABTS catalysis, a simple colorimetric method was developed for arsenate detection with a detection limit of 3.72 ppb. Based on the system of CoOOH nanozyme and ABTS substrate, this colorimetric method can be converted into an electrochemical sensor for arsenate assay by the utilization of CoOOH nanoflake-modified electrode. The electrochemical measurement can be realized by chronoamperometry, which showed more sensitive and a lower limit of detection as low as 56.1 ppt. The applicability of this bimodal method was demonstrated by measuring arsenate and total arsenic in different real samples such as natural waters and soil extracted solutions, and the results are of satisfactory accuracy as confirmed by inductively coupled plasma mass spectrometry analysis. The bimodal strategy offers obvious advantages including a label-free step, convenient operation, on-site assay, low cost, and high sensitivity, which is promising for reliable detection of arsenate and total arsenic in environmental samples.

Bimodal detection of carbon dioxide using fluorescent molecular aggregates.

Cyano-substituted p-phenylenevinylene (R-1) aggregates exhibiting fluorescence and Raman spectroscopic responses towards CO2 are described. The aggregation-induced emission (AIE) as well as the aggregation-enhanced Raman scattering (AERS) of R-1 in aqueous conditions was reduced in the presence of a small amount of CO2, which enabled its easy and fast bimodal detection in different analytical samples.

AuNS@Ag core-shell nanocubes grafted with rhodamine for concurrent metal-enhanced fluorescence and surfaced enhanced Raman determination of mercury ions

Mercury ion (Hg2+) is a highly hazardous and widespread pollutant with bio-accumulative properties. Although the existing Hg2+ detection methods have high sensitivity and reliability, whereas there have few reports concerning bimodal detection for Hg2+ with one sensor. Toward this goal, a novel sensor based on rhodamine derivatives (RhD) grafted AuNS@Ag core-shell nanocubes (CSN) has been synthesized and shown the bimodal detection capabilities with metal enhanced fluorescence (MEF) and surface enhanced Raman scattering (SERS) for Hg2+. Herein, resultant CSN acts as the signal enhancing material; RhD was modified on the outside of the shell to ensure the signal sensitive of the CSN-RhD hybrids. In this work, we investigate the size- and shape-dependent SERS activity of plasmonic CSN comprised of AuNS as cores and Ag cuboids as shells. The SERS activity of CSN with spherical core was found to increase with the increasing thickness of the Ag cubic shell. Sequel, under an optimized condition, a display of strong MEF and SERS signals of the resulting mixtures with increasing of Hg2+ concentrations was observed. The proposed bimodal sensor showed excellent performances for Hg2+ along with wide linear range of 0.001–1000 ppm and 0.01–1000 ppm as well as the relatively low detection limit of 0.94 and 5.16 ppb for MEF and SERS assays, respectively. Furthermore, the ability of the sensor to detect Hg2+was also confirmed in adulterated milk samples.

Disassembly-driven signal turn-on probes for bimodal detection of DNA with 19F NMR and fluorescence

To image DNAs in vivo, molecular probes that can detect DNA with a highly transparent signal are required. In this study, we designed and synthesized amphiphilic molecular probes that can detect DNA with a highly transparent 19F NMR signal in a signal turn-on manner based on the self-assembly and target-dependent-disassembly of the probe molecules in aqueous solution. Fluorescence and dynamic light scattering studies revealed that these amphiphilic probes consisting of bisbenzimide H 33258 and 3,5-bis(trifluoromethyl)benzene are assembled and form aggregates in aqueous solution, and that the aggregates are collapsed when the probes bind to double-stranded DNA via selective interaction between the bisbenzimide H 33258 moiety and AATT double-stranded region of DNA. Since the target-dependent-disassembly of the probes caused turn-on of 19F NMR and fluorescence signals, bimodal detection of double-stranded DNA was successfully achieved.

Detection radius of EMG for fasciculations: Empiric study combining ultrasonography and electromyography

ObjectiveThe aims of this study were to investigate the detection radius and sensitivity of EMG for fasciculations. MethodsMuscle ultrasonography was performed simultaneously to EMG recordings in patients with fasciculations in the context of amyotrophic lateral sclerosis. Ultrasonography and EMG parameters were analyzed for selected fasciculations. ResultsA total of 381 fasciculations were detected by ultrasonography in 18 muscles of 10 patients. Out of these, 125 (33%) were EMG-negative. In contrast, none of the fasciculations detected by EMG were ultrasonography-negative. EMG detection probability decreased significantly with increasing distance from the center of the fasciculation. EMG detection rate was 98% when the EMG needle was located within the fasciculation and 50% at 7.75 mm distance from the fasciculation center. In addition, EMG detection depended significantly on cross-sectional area of the fasciculation and presence of neurogenic changes. ConclusionsFor detecting the same fasciculations, EMG is less sensitive than ultrasonography. EMG detection probability decreases sharply at a distance comparable to motor unit size. SignificanceThese results extend previous knowledge about superior sensitivity of ultrasonography for fasciculations. Moreover, our novel bimodal detection method provides first in vivo data about the EMG detection radius for fasciculations in a clinical setting.

Detection and vocalisations of three owl species (Strigiformes) in temperate rainforests of southern Chile

ABSTRACTConspecific broadcasts are effective to increase detection of owls. To determine the most appropriate time of the year to survey owls, we played conspecific owl vocalisations monthly in a temperate rainforest of southern Chile. From 12 broadcast points surveyed we recorded detections of Glaucidium nana, Strix rufipes and Tyto alba. Glaucidium nana presented a bimodal detection curve throughout the year and we recorded two regular vocalisations in response to broadcasting: contact pair call and territorial call. Strix rufipes and T. alba both showed a peak of detection between February and May. Strix rufipes presented three vocalisations: territorial call, contact pair call and female contact pair call while T. alba uttered two vocalisations: territorial call and twittering call. We recommend surveys during the end of the breeding season (austral summer–autumn) when detection is higher in most owls. Surveys should also take into consideration the variability of the vocalisations and include covariates in monitoring to evaluate occupancy/detection models.

A Highly Sensitive Bimodal Detection of Amine Vapours Based on Aggregation Induced Emission of 1,2-Dihydroquinoxaline Derivatives.

The detection of food spoilage is a major concern in food safety as large amounts of food are transported globally. Direct analysis of food samples is often time-consuming and requires expensive analytical instrumentation. A much simpler and more cost-effective method for monitoring food fermentation is to detect biogenic amines generated as a by-product during food decomposition. In this work, a series of 1,2-dihydroquinoxaline derivatives (DQs) with aggregation-induced emission (AIE) characteristics were synthesised and their protonated forms, that is, H+ DQs, can be utilised for the sensitive detection of biogenic amines. For example, upon exposure to amine vapours, deprotonation occurs that converts the red-coloured, non-emissive H+ DQ2 back to its yellow-coloured, fluorescent parent form. The bimodal absorption and emission changes endow the system with high sensitivity, capable of detecting ammonia vapour at a concentration of as low as 690 ppb. Taking advantage of this, H+ DQ2 was successfully applied for the detection of food spoilage and was established as a robust and cost effective technique to monitor food safety.

Nitric Oxide Sensing through Azo-Dye Formation on Carbon Dots.

Carbon dots (C-dots) prepared through heating of aminoguanidine and citric acid enable bimodal (colorimetric and fluorescence) detection of nitric oxide (NO) in aqueous solutions. The C-dots retained the functional units of aminoguanidine, which upon reaction with NO produced surface residues responsible for the color and fluorescence transformations. Notably, the aminoguanidine/citric acid C-dots were noncytotoxic, making possible real-time and high sensitivity detection of NO in cellular environments. Using multiprong spectroscopic and chromatography analyses we deciphered the molecular mechanism accounting for the NO-induced structural and photophysical transformations of the C-dots, demonstrating for the first time N2 release and azo dye formation upon the C-dots' surface.

A nanoclay-based magnetic/fluorometric bimodal strategy for ascorbic acid detection

Ascorbic acid (AA) plays an essential role in biochemical processes, as a scavenger for preventing oxidative damage. Although various optical measurement strategies for AA detection have been developed, there is an increasing demand for a multi-modal sensor to obtain detailed information. Herein, we propose a facile ion-exchange/coordination strategy for the preparation of a magnetic resonance (MR)/fluorescence nanohybrid by using laponite (Lap) as a matrix and Eu(DPA)3/Gd(DPA)3 (DPA=Pyridine-2, 6-dicarboxylic acid) as a bimodal signal source. This nanohybrid was observed to have a higher MR response than Gd−DPA, because Gd−DPA was coordinated with Lap to affect proton relaxation parameters, while excellent Eu−DPA fluorescence remained. Moreover, potential applications of the nanohybrid had been extended to transparent films and MR/fluorescent inks. Interestingly, the MR/fluorescence of this nanohybrid was simultaneously suppressed by AA. We found that this decrease was attributed to a synergistic effect of acidity and redox. The MR/fluorescence bimodal detection of Eu(DPA)3/Gd(DPA)3@Lap makes it as a potential biological probe for clinical applications and commercialization because of its simple preparation procedure, excellent MR/fluorescence properties, high sensitivity, and high selectivity.

A magnetic/fluorometric bimodal sensor based on a carbon dots-MnO2 platform for glutathione detection.

A novel magnetic/fluorometric bimodal sensor was built from carbon dots (CDs) and MnO2. The resulting sensor was sensitive to glutathione (GSH), leading to apparent enhancement of magnetic resonance (MR) and fluorescence signals along with visual changes. The bimodal detection strategy is based on the decomposition of the CDs-MnO2 through a redox reaction between GSH and MnO2. This process causes the transformation from non-MR-active MnO2 to MR-active Mn(2+), and is accompanied by fluorescence restoration of CDs. Compared with a range of other CDs, the polyethylenimine (PEI) passivated CDs (denoted as pCDs) were suitable for detection due to their positive surface potential. Cross-validation between MR and fluorescence provided detailed information regarding the MnO2 reduction process, and revealed the three distinct stages of the redox process. Thus, the design of a CD-based sensor for the magnetic/fluorometric bimodal detection of GSH was emphasized for the first time. This platform showed a detection limit of 0.6 μM with a linear range of 1-200 μM in the fluorescence mode, while the MR mode exhibited a linear range of 5-200 μM and a GSH detection limit of 2.8 μM with a visible change being observed rapidly at 1 μM in the MR images. Furthermore, the introduction of the MR mode allowed the biothiols to be easily identified. The integration of CD fluorescence with an MR response was demonstrated to be promising for providing detailed information and discriminating power, and therefore extend the application of CDs in sensing and imaging.

Functionalized Au-Fe3O4 nanocomposites as a magnetic and colorimetric bimodal sensor for melamine

Au-Fe3O4 nanocomposites were synthesized and modified with l-(2-mercaptoethyl)-1,2,3,4,5,6-hexanhydro-s-triazine-2,4,6-trione (MTT) for the bimodal detection of melamine. The bimodal detection is based on the aggregation of Au-Fe3O4@MTT nanoparticles (NPs) from the dispersed state upon the formation of special triple hydrogen bonds between melamine and MTT. This phenomenon causes the red shift of the absorption peak and the increase of the spin–spin relaxation time (T2) of the water protons upon addition of melamine at different concentrations to an aqueous solution of Au-Fe3O4@MTT NPs. Furthermore, the dual-modal method exhibits a clear selectivity toward melamine.

Patent Blue Derivatized Dendronized Iron Oxide Nanoparticles for Multimodal Imaging

AbstractDendronized nanoparticles were designed for the bimodal (optical and magnetic) detection of lymph nodes with a hand‐held probe during surgery. Patent Blue VF dye and iron oxide nanoparticles with 20 nm diameter, displaying high magnetization and located at the superparamagnetic/blocked monodomain boundary, were associated through a dendritic PEGylated coating to obtain stable water suspensions. Conjugation procedures (the sulfonamide link formed between the PEGylated dendron and the dye, together with the phosphonate anchoring on the iron oxide surface) were shown to be strong enough to survive in vivo conditions when the prepared nanohybrids were tested in an inflammatory node model. Moreover, magnetization of 20 nm nanoparticles increased when dendrons were grafted onto the surface, showing that they are good candidates for magnetic particle imaging, which requires high magnetization values. Preliminary lymphatic node uptake experiments performed in an inflammatory animal model showed higher uptake of the 10 nm nanoparticles relative to that of 20 nm nanoparticles. The highest probe concentration was reached 2 d after injection.

Crossmodal integration improves sensory detection thresholds in the ferret.

During the last two decades ferrets (Mustela putorius) have been established as a highly efficient animal model in different fields in neuroscience. Here we asked whether ferrets integrate sensory information according to the same principles established for other species. Since only few methods and protocols are available for behaving ferrets we developed a head-free, body-restrained approach allowing a standardized stimulation position and the utilization of the ferret’s natural response behavior. We established a behavioral paradigm to test audiovisual integration in the ferret. Animals had to detect a brief auditory and/or visual stimulus presented either left or right from their midline. We first determined detection thresholds for auditory amplitude and visual contrast. In a second step, we combined both modalities and compared psychometric fits and the reaction times between all conditions. We employed Maximum Likelihood Estimation (MLE) to model bimodal psychometric curves and to investigate whether ferrets integrate modalities in an optimal manner. Furthermore, to test for a redundant signal effect we pooled the reaction times of all animals to calculate a race model. We observed that bimodal detection thresholds were reduced and reaction times were faster in the bimodal compared to unimodal conditions. The race model and MLE modeling showed that ferrets integrate modalities in a statistically optimal fashion. Taken together, the data indicate that principles of multisensory integration previously demonstrated in other species also apply to crossmodal processing in the ferret.

Modeling violations of the race model inequality in bimodal paradigms: co-activation from decision and non-decision components.

The redundant-signals paradigm (RSP) is designed to investigate response behavior in perceptual tasks in which response-relevant targets are defined by either one or two features, or modalities. The common finding is that responses are speeded for redundantly compared to singly defined targets. This redundant-signals effect (RSE) can be accounted for by race models if the response times do not violate the race model inequality (RMI). When there are violations of the RMI, race models are effectively excluded as a viable account of the RSE. The common alternative is provided by co-activation accounts, which assume that redundant target signals are integrated at some processing stage. However, “co-activation” has mostly been only indirectly inferred and the accounts have only rarely been explicitly modeled; if they were modeled, the RSE has typically been assumed to have a decisional locus. Yet, there are also indications in the literature that the RSE might originate, at least in part, at a non-decisional or motor stage. In the present study, using a distribution analysis of sequential-sampling models (ex-Wald and Ratcliff Diffusion model), the locus of the RSE was investigated for two bimodal (audio-visual) detection tasks that strongly violated the RMI, indicative of substantial co-activation. Three model variants assuming different loci of the RSE were fitted to the quantile reaction time proportions: a decision, a non-decision, and a combined variant both to vincentized group as well as individual data. The results suggest that for the two bimodal detection tasks, co-activation has a shared decisional and non-decisional locus. These findings point to the possibility that the mechanisms underlying the RSE depend on the specifics (task, stimulus, conditions, etc.) of the experimental paradigm.

A doubly responsive probe for the detection of Cys4-tagged proteins.

Recombinant proteins bearing a tag are crucial tools for assessing protein location or function. Small tags such as Cys4 tag (tetracysteine; Cys-Cys-X-X-Cys-Cys) are less likely disrupt protein function in the living cell than green fluorescent protein. Herein we report the first example of the design and synthesis of a dual fluorescence and hyperpolarized (129)Xe NMR-based sensor of Cys4-tagged proteins. This sensor becomes fluorescent when bound to such Cys4-tagged peptides, and the (129)Xe NMR spectrum exhibits a specific signal, characteristic of the biosensor-peptide association.

Fluorine-modified bisbenzimide derivative as a molecular probe for bimodal and simultaneous detection of DNAs by (19)F NMR and fluorescence.

3,5-Bis(trifluoromethyl)benzene modified bisbenzimide H 33258 was synthesized as a (19)F magnetic resonance-based DNA detection probe. The chemical shift and fluorescence of the probe were significantly changed by the addition of hairpin DNAs having an AATT sequence. The probe enables (19)F NMR/fluorescence bimodal detection of the model DNA double strands simultaneously.

Measuring Electric Field Induced Subpicometer Displacement of Step Edge Ions

We provide unambiguous evidence that the applied electrostatic field displaces step atoms of ionic crystal surfaces by subpicometers in different directions via the measurement of the lateral force interactions by bimodal dynamic force microscopy combined with multiscale theoretical simulations. Such a small imbalance in the electrostatic interaction of the shifted anion-cation ions leads to an extraordinary long-range feature potential variation and is now detectable with the extreme sensitivity of the bimodal detection.

Emotion Detection System Based on Speech and Facial Signals

This paper introduces the present status of speech emotion detection. In order to improve the emotion recognition rate of single mode, the bimodal fusion method based on speech and facial expression is proposed. First, we establishes emotional database include speech and facial expression. For different emotions, calm, happy, surprise, anger, sad, we extract ten speech parameters and use the PCA method to detect the speech emotion. Then we analyze the bimodal emotion detection of fusing facial expression information. The experiment results show that the emotion recognition rate with bimodal fusion is about 6 percent points higher than the recognition rate with only speech prosodic features