Sequential Detection Research Articles

Fluorescent “On‐Off‐On” Probe for Cascade Detection of Ag(I) and Ascorbic Acid Using Folic Acid Protected Copper Nanoclusters

AbstractFolic acid (FA) protected copper nanoclusters (FA‐CuNCs, λex=350 nm, λem=445 nm) were synthesized and used as a fluorescent “on‐off‐on” probe for the cascade detection of Ag+ and ascorbic acid (AA). The fluorescence emission of FA‐CuNCs at 445 nm was quenched significantly by Ag+ due to the analyte‐induced aggregation followed by the formation of larger nanoparticles. However, when AA was added to the in‐situ generated Ag@FA‐CuNCs, the fluorescence emission of FA‐CuNCs was recovered at 445 nm because of the AA‐directed reduction of Ag+ to Ag0. The experimental conditions, such as pH, incubation time, and quencher Ag+ concentrations, were optimized to achieve improved sensitivity. The detection limit for Ag+ and AA was estimated as 37.1 nM and 0.27 μM with a linearity range of 2.49–22 μM and 4.71–81.53 μM, respectively. In real sample analysis, the recoveries of Ag+ ions in river water and AA in orange juice samples were found between 99–93 % and 97–94 % using the probes FA‐CuNCs and Ag@FA‐CuNCs, respectively. Overall, this work offers a viable method for the sequential detection of Ag+ and AA using FA‐CuNCs via a fluorescence “on‐off‐on” switch mechanism.

A Multimode fluorescent sensor for sequential detection of Cu2+ and cysteine as well as pH sensor with real sample Applications: Extensive experimental and DFT studies

Highly responsive and optically selective (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN with aggregation induced emission enhancement (AIEE) properties has been developed for the sequential detection of Cu2+ and L- Cysteine through fluorescence On-Off-On strategy. The selectivity of sensor depends on the presence of a diazo functional group and its appropriate cavity location in sensor molecule. Azo dye-based (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN has been synthesized by utilizing a simple diazotization synthetic methodology that showed extraordinary AIEE behavior with bathochromic shift owing to the formation of J-aggregates. The morphology and size of aggregates were analyzed by SEM and DLS analysis, respectively. The calculated LOD of sensor PDN for Cu2+, and L-cysteine is 0.113 nM, and 84 nM, respectively. Fluorescence, UV–visible, 1H and 13C NMR titration were carried out to understand the interaction of sensor with Cu2+. The sensor was practically utilized in the sequential sensing of Cu2+ and Cys in real samples. Interestingly, sensor PDN was successfully employed for the sensing of a strong acid and base as well as the detection of Cu2+ ions in the solid state. Moreover, these experimental results were supported through DFT calculations.

Optimal Sequential Detection by Sparsity Likelihood

Optimal Sequential Detection by Sparsity Likelihood

Lighting up imidazole-based fluorescent chemosensor for selective discrimination of Hg2+ ions and its application in sequential detection of histidine, solid-supported extractant.

A novel turn-on fluorogenic probe based on 4-(bis(2-((2-hydroxyethyl)thio)ethyl) amino)benzaldehyde the detection of Hg2+ ions has been designed and developed. The probe BMA showed high selectivity for Hg2+ ions over the series of other tested cations in an aqueous acetonitrile medium. Only the addition of Hg2+ ions to probe BMA in aqueous acetonitrile solution (CH3CN/H2O (7:3, v/v) could induce a remarkable red shift of about 20 nm in UV-vis absorbance spectra and a dramatic fluorescent enhancement with a blue shift of 10 nm in the emission spectra. With the help of a fluorescence spectrometer, the detection limit was calculated to be 73 nM. The binding stoichiometric ratio between BMA and Hg2+ ions was found to be 1:1 by Jobs plot, which was further confirmed by 1H NMR titration, FT-IR, HR-MS, and density functional theory calculations. The probe BMA can selectively detect Hg2+ ions, with several advantages, including ultra-fast response, low detection limit, conspicuous fluorescent changes, robust anti-interference capability, and exciting reversibility. The probe BMA can also serve as a portable extractant for removing Hg2+ ions in aqueous solution and act as an efficient and practical solid-state fluorescent sensor for mercury in on-field measurements. In addition, the in situ formed BMA-Hg2+ ensemble may be used for fluorescent recognition of histidine over other common amino acids via an indicator displacement assay mechanism. The low detection limits of BMA-Hg2+ for histidine were calculated to be 0.91 µM.

A novel carbazolyl thiophene-based fluorescent “off-on” probe PCTMF for sequential detection of Cu2+ and cysteine in aqueous

Copper ions and cysteine play a crucial role in pathophysiologic processes in the human body and the environment, so the development of probes with high sensitivity and specificity for continuous detection has become the focus of current research. In the paper, a novel fluorescent compound (named PCTMF) is synthesized with a carbazolyl thiophene group as a fluorescent moiety and formyl hydrazine as a recognition group of Cu2+. In the given DMSO-H2O solvent system, the PCTMF exhibits a highly selective and sensitive turn-off fluorescence response towards Cu2+ with its detection limit (LOD) of 0.14 μM, in the presence of other competing metal ions. The turn-off response mechanism of the probe can be attributed to the formation of complex 2PCTMF-Cu. The 2PCTMF-Cu complex presents good sensing capacity on cysteine (Cys) with a LOD of 52 nM. The molecule designing method provides an “off-on” strategy for sequentially fluorescence detecting metal ions and ligands related.

A dual emission ratiometric fluorescent probe constructed based on MOF-embedded dye for sequential detection of Al3+ and PPA

The ratiometric fluorescence probe has a self-calibration system that greatly reduces interference from the external environment, it has high sensitivity and accuracy in qualitative and quantitative experiments. In this work, a novel ratio fluorescence probe (RhB@1) was constructed by enclosing Rhodamine B (RhB) in the channel of [Cd2(H2L)2(1,4-bib)2]•DMA (H2L=2-hydroxyterephthalic acid, 1,4-bib=1, 4-bis (imidazol-1-ylmethyl) benzene). The probe can display dual emission characteristics under a single excitation. Al3+ ion was detected by RhB@1. The results showed that the fluorescence of 1 in RhB@1 was increased, the fluorescence of RhB is unchanged, and limit of detection (LOD) of Al3+ is as low as 20.9nM. Interestingly, when PPA (phenylpyruvic acid) is added to the mixture of RhB@1 and Al3+, PPA competes with RhB@1 for Al3+ result in achieving continuous ratio sensing of Al3+ and PPA, and LOD of PPA is 3.21nM. More importantly, the response of RhB@1 to Al3+ in tap water and PPA in artificial urine was quantitatively determined by label recovery method. The results showed that the recovery rate were 97.706%-99.060% (Al3+) and 94.732%-98.100% (PPA). In addition, we prepared a portable test paper modified with carboxymethyl cellulose. This test paper has obvious color change when detecting Al3+ under ultraviolet light, which is easy to detect Al3+ by naked eye.

Sequential Detection of Hg2+ and TNT Using a Nitrogen‐Doped Polymeric Carbon Dots On–Off–On Fluorescence Sensor

ABSTRACTThis work presents a fluorescence sensor based on nitrogen‐doped carbon dots (N‐CDs) utilized for sequential detection of Hg2+ and TNT. The N‐CDs were produced by a simple and efficient hydrothermal process involving the combination of black bean extract with citric acid (CA) and ethylenediamine (EDA). The resulting N‐CDs exhibit a steady blue fluorescence with a significant quantum yield of 12%. We conducted a thorough investigation into the mechanism by which the fluorescence of NCDs is reduced in the presence of Hg2+. Our analyses, which included Stern–Volmer quenching tests, confirmed the development of a stable complex between N‐CDs and Hg2+. When the NCDs‐Hg2+ complex was exposed to TNT, the fluorescence was selectively restored. This sequential “on–off–on” sensing capacity allows for efficient monitoring of both Hg2+ and TNT, demonstrating good sensitivity and selectivity. The sensor has a low detection limit (LOD) of 3.1 and 46 nM for Hg2+ ions and TNT in a linear range of 0–40 and 0–30 μM, respectively. This study emphasizes the potential application of N‐CDs for detecting heavy metals and explosives at the same time. It highlights their usefulness in sophisticated environmental sensing technologies that are suitable for important applications.

Multifunctional Sensors for Successive Detection of Endogenous ONOO- and Mitochondrial Viscosity: Discriminating Normal to Cancer Models.

Diagnosing cancer in its early stages can play an important role in prolonging the lifespan of patients, which demands the use of powerful tools to detect biomarkers accurately. However, since most fluorescent probes described for cancer diagnosis are limited to recognizing a single molecule, achieving the high accuracy criteria remains difficult. Here, sensor 1 is constructed for the sequential detection of D, ONOO-, and viscosity. Initially, sensor 1 detected D and underwent an intramolecular charge transfer mechanism, resulting in the formation of 2 and fluorescence quenching at 587 nm. Subsequently, the intermediate (2) monitored ONOO- and reproduced sensor 1 reversibly with fluorescence enhancement at 496 nm, showing concentration-related quantitative analysis. Similar sensing processes were observed in monitoring ONOO- and viscosity by synthetically developed sensor 2. The proposed mechanisms of sensors 1 and 2 are verified through various characterizations (1H NMR, HR-MS, and HPLC) and DFT calculations. Investigations on endogenous ONOO- and mitochondrial viscosity in cancer (HeLa) and normal (NCM460) cells were conducted to distinguish cancerous cells from normal cells. We anticipated that sensor 2 could effectively serve as a reliable bioanalytical reagent for cancer diagnosis at an earlier stage through sequential detection of two cancer markers, ONOO- and mitochondrial viscosity, in living cells. Importantly, sensor 2 has been employed for imaging ONOO- in normal and liver injury mouse models and tissues, achieving outstanding results.

A Fast Sequential Similarity Detection Algorithm for Multi-Source Image Matching

A Fast Sequential Similarity Detection Algorithm for Multi-Source Image Matching

Hidden Markov Mixtures for Change Detection in Unevenly Spaced Time Series

This work tackles sequential data change-point detection, a research area with various applications in different fields. It focuses on analyzing sequential data such that the distance between locations of consecutive observations is not fixed. The models developed here for change detection extend a Hidden Markov Mixture approach originally designed to handle irregular spacing to improve the identification of atypical values. These models consider the probability of Markov dependence explained by the distance between locations. Bayesian inference is carried out via Gibbs Sampling. Informative priors for the dependency structure are crucial to identify clusters. The models adapt these priors to enable change identification in a general setting. Two mixture models are formulated: one for mean changes and another for mean or variance changes. Post-processing strategies are suggested to categorize observations among the components to facilitate change identification by the mixtures. These strategies are based on maximum posterior probability and consider the uncertainty associated with classifications. Models and clustering performances are evaluated in simulation studies including a Monte Carlo scheme. The analysis also explores three real illustrations. Finally, the proposed approaches are compared to existing clustering and change detection methods available in the literature.

Sequential label shift detection in classification data: An application to dengue fever.

Classifiers have been developed to help diagnose dengue fever in patients presenting with febrile symptoms. However, classifier predictions often rely on the assumption that new observations come from the same distribution as training data. If the population prevalence of dengue changes, as would happen with a dengue outbreak, it is important to raise an alarm as soon as possible, so that appropriate public health measures can be taken and also so that the classifier can be re-calibrated. In this paper, we consider the problem of detecting such a change in distribution in sequentially-observed, unlabeled classification data. We focus on label shift changes to the distribution, where the class priors shift but the class conditional distributions remain unchanged. We reduce this problem to the problem of detecting a change in the one-dimensional classifier scores, leading to simple nonparametric sequential changepoint detection procedures. Our procedures leverage classifier training data to estimate the detection statistic, and converge to their parametric counterparts in the size of the training data. In simulated outbreaks with real dengue data, we show that our method outperforms other detection procedures in this label shift setting.

The Shigella flexneri effector IpaH1.4 facilitates RNF213 degradation and protects cytosolic bacteria against interferon-induced ubiquitylation.

A central signal that marshals host defense against many infections is the lymphocyte-derived cytokine interferon-gamma (IFNγ). The IFNγ receptor is expressed on most human cells and its activation leads to the expression of antimicrobial proteins that execute diverse cell-autonomous immune programs. One such immune program consists of the sequential detection, ubiquitylation, and destruction of intracellular pathogens. Recently, the IFNγ-inducible ubiquitin E3 ligase RNF213 was identified as a pivotal mediator of such a defense axis. RNF213 provides host protection against viral, bacterial, and protozoan pathogens. To establish infections, potentially susceptible intracellular pathogens must have evolved mechanisms that subdue RNF213-controlled cell-autonomous immunity. In support of this hypothesis, we demonstrate here that a causative agent of bacillary dysentery, Shigella flexneri, uses the type III secretion system (T3SS) effector IpaH1.4 to induce the degradation of RNF213. S. flexneri mutants lacking IpaH1.4 expression are bound and ubiquitylated by RNF213 in the cytosol of IFNγ-primed host cells. Linear (M1-) and lysine-linked ubiquitin is conjugated to bacteria by RNF213 independent of the linear ubiquitin chain assembly complex (LUBAC). We find that ubiquitylation of S. flexneri is insufficient to kill intracellular bacteria, suggesting that S. flexneri employs additional virulence factors to escape from host defenses that operate downstream from RNF213-driven ubiquitylation. In brief, this study identified the bacterial IpaH1.4 protein as a direct inhibitor of mammalian RNF213 and highlights evasion of RNF213-driven immunity as a characteristic of the human-tropic pathogen Shigella.

Rapid Detection of Staphylococcus Epidermidis Using Electric-Double-Layer (EDL) Field-Effect Transistor (FET) Biosensors with Loop-Mediated Isothermal Amplification

Staphylococcus epidermidis is a Gram-positive bacterium which commonly grows in human skin, nasal passages, respiratory tract, intestinal tract, air, and water. Although it is harmless to healthy individuals, immunocompromised patients are at risk of infection, which can lead to severe symptoms. With the increased reliance on antibiotics in hospitals, the antimicrobial resistance of Staphylococcus epidermidis has also risen, pointing out a challenge in clinical treatment.Therefore, the diagnosis of this bacterium has gained significant attention. The aim of this experiment is to detect bloodstream infections (BSIs) in the shortest possible time. The study is intended to be implemented in hospitals to provide a more convenient method for medical professionals to conduct screenings. The approach involves screening for the most common disease sequence, ssDNA, followed by sequential detection of corresponding cDNA, plasmids, and bacteria. To detect bacteria with the least amount of bacteerial load, a novel isothermal amplification method called Loop-mediated isothermal amplification (LAMP) is employed to increase the concentration of DNA of BSIs bacteria before measurement. The overall time required for this process doesn’t exceed one day, significantly increasing speed for the detection of blood-borne bacteria in hospitals. The core mechanism of this platform involves the use of electric-double-layer-gated field-effect-transistors (EDL-gated FETs) to amplify the gate voltage changes generated when the ssDNA binds with complementary DNA. These voltage changes are then converted into numerical values for analysis and interpretation.Currently, the research results show that this biomedical sensor can detect concentrations ranging from 1fM to 1pM. With the assistance of LAMP, it has successfully achieved a concentration of approximately 1yM (10-24 M) and detected with EDL-gated FETs. The experiment was also carried out step by step on simulated clinical specimens. The experiments have found successful serum nucleic acid amplification methods that provide excellent detection limits. Compared with other biomedical sensors in the past, it not only has lower detection limits but also brings features such as faster, more convenient, and more portable.Keywords: EDL, FET, Staphylococcus epidermidis, Biosensor, LAMP Figure 1

Ordered spatial configuration protects representations of dissimilar items and reduces the similarity effect in visual working memory.

Although similarity could improve visual working memory (VWM) performance, it remains unclear how the spatial configuration of visual information influences the similarity effect in VWM. We explored this question by manipulating the orderliness of spatial configuration (ordered vs. scrambled) in the simultaneous (Experiment 1) and sequential (Experiment 2) change detection tasks. The results showed that similarity improved VWM performance when memory items were presented simultaneously and sequentially. For the simultaneous memory array containing similar and dissimilar items, the performance of the ordered spatial configuration was better than that of the scrambled spatial configuration when probing dissimilar items, while no such difference was found when probing similar items. Further, the similarity effect value in the scrambled spatial configuration was higher than that in the ordered spatial configuration. For the sequential memory array containing similar and dissimilar items, spatial configuration did not affect the similarity effect in VWM. Taken together, these findings suggest that spatial configuration could modulate the similarity effect when memory items are presented simultaneously, in which the ordered spatial configuration protects representations of dissimilar items and reduces the similarity effect in VWM. Our study provides additional evidence for the role of spatial configuration in the similarity effect in VWM, and supports the hierarchical model.

Covariance Intersection-Based Kalman Consensus Filtering With Sequential Replay Attack Detection Over Sensor Networks

Covariance Intersection-Based Kalman Consensus Filtering With Sequential Replay Attack Detection Over Sensor Networks

Sequential detection with feedback information for two‐way cooperative spectrum sensing in cognitive internet of things

Sequential detection with feedback information for two‐way cooperative spectrum sensing in cognitive internet of things

Analysis of Runs of Homozygosity in Aberdeen Angus Cattle.

A large number of cattle breeds have marked phenotypic differences. They are valuable models for studying genome evolution. ROH analysis can facilitate the discovery of genomic regions that may explain phenotypic differences between breeds affecting traits of economic importance. This paper investigates genome-wide ROH of 189 Aberdeen Angus bulls using the Illumina Bovine GGP HD Beadchip150K to structurally and functionally annotate genes located within or in close ROH of the Aberdeen Angus cattle genome. The method of sequential SNP detection was used to determine the ROH. Based on this parameter, two ROH classes were allocated. The total length of all ROH islands was 11,493 Mb. As a result of studying the genomic architecture of the experimental population of Aberdeen Angus bulls, nine ROH islands and 255 SNPs were identified. Thirteen of these overlapped with regions bearing 'selection imprints' previously identified in other breeds of cattle, and five of these regions were identified in other Aberdeen Angus populations. The total length of the ROH islands was 11,493 Mb. The size of individual islands ranged from 0.038 to 1.812 Mb. Structural annotation showed the presence of 87 genes within the identified ROH islets.

Ultrasensitive Electrochemiluminescence Biosensing Platform Based on Polymer Dots with Aggregation-Induced Emission for Dual-Biotoxin Assay.

Multitarget assay has always been a hot topic in electrochemiluminescence (ECL) methods. Herein, a "on-off-on" ECL aptasensor was developed for the ultrasensitive and sequential detection of possible biological warfare agents, deoxynivalenol (DON) and abrin (ABR). As a luminophore, polymer dots (Pdots) with aggregation-induced emission exhibit high ECL efficiency in the aptasensor, i.e., the signal "on" state. The DON assays mainly depend on ECL quenching due to the efficient quenching effect between ferrocene-H2-ferrocene (Fc-H2-Fc) and Pdots, i.e., the signal "off" state. When the aptasensor is incubated with the oligonucleotide sequence S2 to replace Fc-H2-Fc, obvious ECL recovery occurs, i.e., the signal "on" state, which can be used to sequentially detect ABR. The limit of detection (LOD) for DON is 0.73 fg·mL-1 in the range of 5.0 to 50 ng·mL-1; and the LOD for ABR is ∼0.38 pg·mL-1 in the range of 1.25 pg·mL-1 to 1.25 μg·mL-1. The as-designed ECL aptasensor exhibits good stability and reproducibility, high specificity, and favorable practicality. Therefore, this work provides a new approach for assays of DON and ABR in food safety and can be used as a model to design an ultrasensitive ECL biosensor for multitarget detection.

High-efficient nickel-doped lignin carbon dots as a fluorescent and smartphone-assisted sensing platform for sequential detection of Cr(VI) and ascorbic acid

Using lignin as a raw material to prepare fluorescent nanomaterials represents a significant pathway toward the high-value utilization of waste biomass. In this study, Ni-doped lignin carbon dots (Ni-LCDs) were rapidly synthesized with a yield of 63.22 % and a quantum yield of 8.25 % using a green and simple hydrothermal method. Exploiting the inner filter effect (IFE), Cr(VI) effectively quenched the fluorescence of the Ni-LCDs, while the potent reducing agent ascorbic acid (AA) restored the quenched fluorescence, thus establishing a highly sensitive fluorescence switch sensor platform for the sequential detection of Cr(VI) and AA. Importantly, the integration of a smartphone facilitated the portability of Cr(VI) and AA detection, enabling on-site, in-situ, and real-time monitoring. Ultimately, the developed fluorescence and smartphone-assisted sensing platform was successfully applied to detect Cr(VI) in actual water samples and AA in various fruits. This study not only presents an efficient method for the conversion and utilization of waste lignin but also broadens the application scope of the CDs in the field of smart sensors.

Facile colorimetric sensor development for sequential detection of coralyne and calf-thymus DNA via tannic acid-assisted silver nanoparticles

Owning to unique size dependent optical properties, plasmonic nanoparticles have been explored as chemical read-outs for assaying various biological and chemical analytes. We propose colorimetric sensing strategy based on tannic acid mediated silver nanoparticles (TA-AgNPs) for the detection of Coralyne (COR) and calf thymus DNA (CT-DNA). Aggregation of TA-AgNPs is observed on addition of COR molecule because of electrostatic interaction between them, which is established by change in color from yellow to brown. TA-AgNPs/COR based colorimetric probe was then employed for CT-DNA detection, utilizing anti-aggregation of nanoparticles. Formation of intercalated complex between CT-DNA and COR prevents the aggregation of nanoparticles and color of TA-AgNPs solution remains yellow. Under optimum sensing conditions, extent of aggregation and anti-aggregation of TA-AgNPs was studied. A linear correlation between absorbance value at 437 nm and COR concentration is obtained in the range of 0 to 1.2 μM with detection limit of 0.44 μM. TA-AgNPs/COR based detection probe exhibited linear response to CT-DNA in concentration range of 0 to 7.62 μM with a limit of detection down to 1.63 μM. The applicability of sensing strategy verified by analysis of COR and CT-DNA in human urine samples, which demonstrated the practical utility of method in biomedical applications.