Probe Response Research Articles

Pristine NiMOF Sandwiched between 1D and 3D Engineered Au Particles and Dendrites for Ultraswift Folic Acid Sensing in Cellular Microenvironment.

Catalytic metal-organic frameworks (MOFs)-based sensor matrices can act synergistically with Au metallic nanostructures to generate amplified signal readouts by causing the electro-oxidation of the target analyte. Folic acid (FA), an essential water-soluble vitamin and a precursor for enzymes, requires timely and precise monitoring in the serum of individuals with varying clinical diagnoses. An attempt has been made in this direction through our work, where the rapid detection of FA through its oxidation at metal centers from hybrid nanomaterials is deployed for signal generation. A nonenzymatic, nonimmunometric approach involving a sandwich model, comprising NiMOF layered between gold nanoparticles (AuNPs) and gold nanodendrites (AuNDs) incorporated within a sensor matrix, has been deployed for this purpose. The probe displayed great analytical performance with a linear dynamic range (LDR) from 1 × 10-11 M to 1 × 10-3 M and a limit of detection (LOD) of 0.43 × 10-11 M. The probe's average response time with respect to changes in FA concentration was recorded as less than 2.1 s, making it a rapid sensing platform for FA detection. The real-life applicability of the developed sensor was tested in serum, followed by analysis in a breast cancer cellular microenvironment, which yielded a current recovery between 95.11 and 98.17%. The in vitro analysis was further validated through live-cell imaging using the standard method of fluorescence. The shorter fabrication time of the developed sensor compared to existing ones makes it a facile and efficient sensing platform for FA detection in clinical settings. This study represents the first report on the conjunction of 1D, 2D, and 3D materials as a sensing matrix for molecular detection applications.

Fluorescent Probes Visualize Phytohormone: Research Status and Opportunities.

Phytohormones, as crucial regulatory factors in plant growth and development, have garnered increased interest in improving crop stress resistance. It is essential to comprehend the distribution of phytohormones in plants to assess their health status and investigate their functions. This knowledge also serves as a guide for developing and using plant growth regulators. The advancement of fluorescent probe technology, along with the wide range of fluorophores and improvements in imaging methods, has made it a successful approach for monitoring phytohormones in plants. This technique has been confirmed to be effective in plants, particularly in detecting the response of fluorescent probes to phytohormones. In this Perspective, we highlight the utility of fluorescent probes in measuring and visualizing the distribution of phytohormones in plants under external stress. However, the visualization of phytohormones with high spatial resolution and the achievement of high biocompatibility in living plants have posed significant challenges for researchers. Nonetheless, there are also many untapped opportunities in this field. This paper seeks to delve into the potential for further discussion on the subject.

A Bicyclic Dioxetane Chemiluminescence Nanoprobe for Peroxynitrite Imaging in Vivo.

Peroxynitrite (ONOO-) is a critical biomarker associated with a wide array of diseases including cancer, inflammatory conditions, and neurodegenerative disorders. This study introduces an innovative chemiluminescence nanoprobe (CLNP) based on a bicyclic dioxetane structure, designed for highly sensitive and specific in vivo imaging of ONOO-. Our CLNP demonstrates exceptional capabilities in generating high-contrast imaging of disease lesions, with applications verified across tumor models, acute inflammation, and acute liver injury scenarios. Key findings highlight the probe's rapid response to oxidative species, superior tissue penetration, and high signal-to-noise ratio, underscoring its potential for real-time diagnostic applications. This work represents an important advance in the field of diagnostic imaging using CL probes, offering promising avenues for the early detection and treatment of ONOO--related pathologies.

Balancing Brightness and Photobasicity: Modulating Excited-State Proton Transfer Pathways in Push-Pull Fluorophores for Biological Two-Photon Imaging.

Push-pull fluorophores with donor-π-acceptor architectures are attractive scaffolds for the design of probes and labels for two-photon microscopy. Such fluorophores undergo a significant charge-delocalization in the excited state, which is essential for achieving a large two-photon absorption cross-section and brightness. The polarized excited state may, however, also facilitate excited-state proton transfer (ESPT) pathways that can interfere with the probe response. Herein, we employed steady-state and time-resolved spectroscopic studies to elucidate whether ESPT is responsible for the pH-dependent emission response of the Zn(II)-selective fluorescent probe chromis-1. Composed of a push-pull architecture with a pyridine ring as the acceptor, the chromis-1 fluorophore core acts as a photobase that promotes ESPT upon acidification. Although the pKa of the pyridine acceptor increases more than six orders of magnitude upon excitation, the photobasicity is not sufficient to deprotonate solvent water molecules under neutral conditions. Rather, the pH-dependent emission response is caused by the pendant bis-isonicotinic acid chelating group which upon protonation facilitates an excited-state intramolecular proton transfer to the pyridine acceptor. A simple permutation of the core pyridine nitrogen from the para- to the ortho-position relative to the thiazole substituent was sufficient to reduce the excited-state basicity by two orders of magnitude without compromising the two-photon excited brightness. These results highlight the importance of choosing the appropriate fluorophore core and chelating moiety for minimizing pH-dependent responses in the design of fluorescent probes for biological imaging.

A porphyrin-based colorimetric and near infrared fluorescent probe for reversible and rapid detection of diethyl chlorophosphate

Given the extremely high toxicity of nerve agents, developing methods for their detection with high sensitivity and specificity is of great significance. In this study, we present single pyridyl-porphyrin (TPPyP) as an effective fluorescent probe for the reversible and rapid detection of the nerve agent simulant diethyl chlorophosphate (DCP). The probe demonstrates excellent spectral properties, with DCP rapidly reacting with the pyridine and pyrrole groups on TPPyP, leading to an enhanced intramolecular charge transfer (ICT) effect. This results in a distinct color change from pink to bright green, accompanied by a gradual disappearance of red fluorescence, all occurring within 35 seconds. Furthermore, the probe can be retrieved from the detection solution by introducing triethylamine, allowing for reversible detection of DCP. Additionally, TPPyP-loaded filter paper serves as a convenient tool for visualizing gaseous DCP. In solution, the probe exhibits sensitive detection capabilities, and when applied to DCP vapor detection, the filter paper shows a color transition and a reduction in red fluorescence that can be quantitatively analyzed using a smartphone application. The green-to-red ratio (G/R) correlates linearly with DCP concentrations in the range of 0–14 ppm, showcasing the probe's potential for field applications. Selectivity and anti-interference tests reveal that only DCP affects the probe's response, confirming its robustness against common interferents. Overall, this TPPyP-based probe offers a rapid, sensitive, and portable solution for detecting nerve agents, with promising implications for environmental monitoring.

Euclid preparation

Context. Deviations from Gaussianity in the distribution of the fields probed by large-scale structure surveys generate additional terms in the data covariance matrix, increasing the uncertainties in the measurement of the cosmological parameters. Super-sample covariance (SSC) is among the largest of these non-Gaussian contributions, with the potential to significantly degrade constraints on some of the parameters of the cosmological model under study – especially for weak-lensing cosmic shear. Aims. We compute and validate the impact of SSC on the forecast uncertainties on the cosmological parameters for the Euclid photo-metric survey, and investigate how its impact depends on the specific details of the forecast. Methods. We followed the recipes outlined by the Euclid Collaboration (EC) to produce 1σ constraints through a Fisher matrix analysis, considering the Gaussian covariance alone and adding the SSC term, which is computed through the public code PySSC. The constraints are produced both by using Euclid’s photometric probes in isolation and by combining them in the ‘3×2pt’ analysis. Results. We meet EC requirements on the forecasts validation, with an agreement at the 10% level between the mean results of the two pipelines considered, and find the SSC impact to be non-negligible - halving the figure of merit (FoM) of the dark energy parameters (w0, wa) in the 3×2pt case and substantially increasing the uncertainties on Ωm,0,w0, w0, and σ8 for the weak-lensing probe. We find photometric galaxy clustering to be less affected as a consequence of the lower probe response. The relative impact of SSC, while highly dependent on the number and type of nuisance parameters varied in the analysis, does not show significant changes under variations of the redshift binning scheme. Finally, we explore how the use of prior information on the shear and galaxy bias changes the impact of SSC. We find that improving shear bias priors has no significant influence, while galaxy bias must be calibrated to a subpercent level in order to increase the FoM by the large amount needed to achieve the value when SSC is not included.

An Acid-Activatable Fluorescent Probe for Sulfur Dioxide in Traditional Chinese Medicines and Living Cells.

Excessive sulfur dioxide (SO₂) disturbs physiology of lysosomes causing diseases and threatening human health. A fluorescent probe has been regarded as one of the most attractive approaches, which is compatible with living cells and possesses high sensitivity. However, most of fluorescent probes' reaction sites are activated before they reach the destination. In this work, an acid-activatable fluorescent probe PT1 was synthesized, characterized, and used for SO2 detection. The introduction of oxazolines in PT1 enables the intelligent response of probe to release the activation stie for SO2 derivatives through Michael addition upon exposure to acid. In vitro studies showed a remarkable selectivity of PT1 to SO₂ derivatives than other biothiols with a limit of detection as low as 62 nM. By using this acidic pH-controlled fluorescence responsiveness to SO₂, precise spatiotemporal identification of lysosomal SO2 fluctuations has been successfully performed. Furthermore, probe PT1 can be applied for monitoring SO₂ derivatives in traditional Chinese medicines.

Research on on-orbit relative radiometric calibration method based on solar diffuse reflector hyperspectral camera

Abstract In the original image data obtained by optical remote sensing satellite sensors, there is stripe noise caused by inconsistent probe response, which will seriously affect the application effect and accuracy of the image. The importance of relative radiometric calibration is that it can eliminate the stripe noise in the image, thus improving the quality and clarity of the image. In this paper, a relative radiometric calibration method based on the data of a solar diffuse reflector downloaded from the satellite is proposed. The relative radiation calibration coefficient is calculated by using the least square method by obtaining the calibration image of the on-board diffuse reflector covering all the detectors. To verify the method proposed in this paper, the on-board relative radiometric calibration experiment is carried out by using the on-orbit hyperspectral camera of a terrestrial ecological carbon monitoring satellite, and the calibration effect of the calibration coefficient on the original image is tested, and the relative radiometric calibration accuracy is quantitatively analyzed. The experimental results show that the calibration coefficient can effectively eliminate the band noise of the original hyperspectral image. From the quantitative evaluation, the signal-to-noise ratio index of the corrected hyperspectral image is greater than 200, and the generalized noise index is better than 3%, which achieves a good calibration effect and meets the requirements of high-quality remote sensing image application. It provides a reliable guarantee for quantitative remote sensing applications during the satellite’s on-orbit operation.

Molecular dynamics simulation and experiment study on a displacement-based electrochemical dual-signal response of interfacial kanamycin aptamer probe

A displacement-based electrochemical dual-signal kanamycin (KAN) aptamer sensing method was developed using a theory-driven approach, with methylene violet (MV) and toluidine blue (TB) as dual-signal labels. The binding poses were elucidated using molecular dynamics simulation (MDS) while simulating the kinetic evolution process of the displacement reaction. The binding system’s binding free energy (ΔG) was calculated using the g_mmpbsa algorithm. The MDS results guided the sensor fabrication process, and the sensing analytical performance was subsequently investigated. The study demonstrated the thermodynamic feasibility of the displacement reaction, with ΔG values of −3079 ± 122, −955 ± 78, and −879 ± 46 KJ·mol−1 for the three binding systems, respectively. The simulated kinetic evolution process aligned with the displacement reaction’s behavior characteristics, primarily driven by electrostatic attraction, thereby deciphering the sensor’s signaling mechanism. Under optimized conditions, the sensor exhibited a dual-signal response, a detection limit of 0.17 μM, a linear range of 1.0 μM to 2.0 mM, a response equilibrium time of ∼ 45 min., and a discriminated selectivity clarified by the MDS. The mutual support between MDS and experimental results establishes a communication bridge between simulation and experimentation, guiding the sensor fabrication direction and providing a methodological basis and new research example for aptamer-based sensor designs.

A General Method for Calibration of Active Scanning Thermal Probes

Scanning thermal microscopy (SThM) is a scanning probe technique aimed at quantitative characterization of local thermal properties at the length scale down to tens of nanometers. With many probe designs and approaches to interpretation of probe responses, there is a need for a universal framework, which would allow probe calibration and comparison of probe performance. Herein, a calibration framework based on an abstracted, formal, probe model for active SThM probes is developed. The calibration can be accomplished through measurements with two or three calibration samples. Requirements for calibration samples are described with examples of structures of suitable samples identified in published literature. A link to a published experimental work indirectly verifying the proposed procedure is provided. The calibration does not require knowledge of internal probe properties and yields a small and universal set of parameters that can be used to quantify thermal resistance presented to the probe by samples as well as to characterize active‐mode SThM probes of any type and at any measurement frequency. How the probe calibration parameters can be used to guide probe design is illustrated. When the calibration approach can be used directly to measure the thermal conductivity of unknown samples is also analyzed.

Unambiguous Detection of LTR-III G-Quadruplex in the HIV Genome Using a Tailored Fluorogenic Probe-based Assay.

The noncanonical conformations within the genomes of viral pathogens is of significant diagnostic value, due to their unique secondary structures and interactions with specific fluorogenic molecules. In particular, adaptation of the G-quadruplex (GQ) conformation by the specific gene sequence leads to distinct topological features, resulting in unique binding sites that are crucial for the selective recognition of human immunodeficiency virus (HIV) by small molecules. Leveraging the selective fluorescence response of a benzobisthiazole-based fluorogenic probe to the LTR-III GQ target, we developed a GQ-based diagnostic platform for HIV detection. The successful fluorescence recognition of an amplified 176-nucleotide genomic segment harboring the LTR-III GQ, facilitated by pH-controlled GQ-targeted reliable conformational polymorphism (GQ-RCP), validates this method as an effective GQ-topology-targeted diagnostic tool for HIV.

Uncertainties in measurements of bubbly flows using phase-detection probes

The analysis of bubbly two-phase flows is challenging due to their turbulent nature and the need for intrusive phase-detection probes. However, accurately characterizing these flows is crucial for safely designing critical infrastructure such as dams and their appurtenant structures. The combination of dual-tip intrusive phase-detection probes with advanced signal processing algorithms enables the assessment of pseudo-instantaneous 1-D velocity time series; for which the limitations are not fully fathomed. In this investigation, we theoretically define four major sources of error, which we quantify using synthetically generated turbulent time series, coupled with the simulated response of a phase-detection probe. Based on the analysis of 1010 simulated bubble trajectories, our findings show that typical high-velocity flows in hydraulic structures hold up to 15% error in the mean velocity estimations and up to 35% error in the turbulence intensity estimations for the most critical conditions, typically occurring in the proximity of the wall. Based on thousands of simulations, our study provides a novel data-driven tool for the estimation of these baseline errors (bias and uncertainties) in real-word phase-detection probe measurements of bubbly flows (air concentrations c<40%).

Measuring mind wandering with experience sampling during task performance: An item response theory investigation

The tendency for individuals to mind wander is often measured using experience sampling methods in which probe questions embedded within computerized cognitive tasks attempt to catch episodes of off-task thought at random intervals during task performance. However, mind-wandering probe questions and response options are often chosen ad hoc and vary between studies with extant little guidance as to the psychometric consequences of these methodological decisions. In the present study, we examined the psychometric properties of several common approaches for assessing mind wandering using methods from item response theory (IRT). IRT latent modeling demonstrated that measurement information was generally distributed across the range of trait estimates according to when probes were presented in time. Probes presented earlier in time provided more information about individuals with greater tendency to mind wandering than probes presented later. Furthermore, mind-wandering ratings made on a continuous scale or using multiple categorical rating options provided more information about individuals’ latent mind-wandering tendency – across a broader range of the trait continuum – than ratings dichotomized into on-task and off-task categories. In addition, IRT provided evidence that reports of “task-related thoughts” contribute to the task-focused dimension of the construct continuum, providing justification for studies conceptualizing these responses as a kind of task-related focus. Together, we hope these findings will help guide researchers hoping to maximize the measurement precision of their mind wandering assessment procedures.

Aggregation in Deep Eutectic Solvents (DESs): Formation of Polar DES-in-Nonpolar DES Microemulsions.

The versatility of environmentally benign and inexpensive deep eutectic solvents (DESs) lies in their widely varying physicochemical properties. Depending on its constituents, a DES may be highly polar or nonpolar in nature. This offers an enticing possibility of formation of novel nonaqueous microemulsions (MEs). Evidence of the presence of polar DES-in-nonpolar DES MEs is presented with reline (formed by mixing choline chloride and urea in 1 : 2 mol ratio) as the polar DES forming the ME pools, Thy : DA [formed by mixing thymol (Thy) and n-decanoic acid (DA) in 1 : 1 mol ratio] nonpolar DES as the bulk oil phase and nonionic surfactant Brij-35 as the emulsifying agent. While only sparingly miscible in Thy : DA, as high as 2.5 M reline can be solubilized in this DES in the presence of 100 mM Brij-35; reline loading (w Rel = [reline]/[Brij-35]) as high as 25 can be achieved. The ternary phase diagram of the Thy : DA/Brij-35/reline system reveals a clear and transparent single-phase region where MEs may be forming. Dynamic light scattering confirms the presence of MEs of 2-10 nm size. Even as up to 2.5 M (ca. 0.35 mole fraction) reline, whose dynamic viscosity (η) and electrical conductivity (κ) are very high, is added to 100 mM Brij-35 solution of Thy : DA, the η and κ values of the solution increase insignificantly, thus conforming to the formation of MEs in the solution. Fourier transform infrared (FTIR) absorbance spectra and fluorescence probe responses further indicate that reline is not dispersed in the medium but rather forms polar pools of the MEs. These novel nonaqueous polar DES-in-nonpolar DES MEs will not only expand the application potential of DESs but also offer a new class of organized media with widespread potential.

Unveiling the effect of paper matrix on the electrochemical response of diffusive redox probes

This study evaluates the influence of paper substrate selection on the electrochemical response of an electrochemical paper-based analytical device (ePAD). Various paper substrates commonly employed in this type of devices such as cellulose, nitrocellulose and glass-fibre based medical grade materials are evaluated using chronoamperometric measurements. Both theoretical modelling and experimental analyses are conducted to understand the diffusion behaviour of widely employed two redox probes, [Fe(CN)6]3− and FcMeOH. Findings show that glass fibre substrates show similar performance to liquid drop conditions while nitrocellulose cause a decrease in current after a short measurement period, mainly due to a thin-layer effect. Cellulose-based substrates decrease the diffusivity of redox species, especially for charged species, indicating potential limitations in their use for chronoamperometric measurements. The study offers valuable insights into the electrochemical behaviour of paper substrates in ePADs, laying the groundwork for future research in this area.

Selenium Supplementation Sensor Based on Direct Electrochemistry of Urinary Selenosugar and Total Selenium.

Emerging point-of-care testing methods are extremely beneficial for personalized assessments of trace element metabolism including selenium (Se). Given the lack of timely evaluation methods for well-received Se fortification, an electrochemical solution was developed based on the recently identified urinary selenosugar (Sel) as a marker. The Se content of crude urine was rapidly determined (∼5 min), and the square-wave voltammetric responses of a Se-selective probe (SeSE) composed of liquid metal amalgam demonstrated comparable performance (e.g., detection limit: 19 nM) to central lab benchtop equipment within the physiological range. Meanwhile, SeSE enabled total urinary Se detection via a mere one-step oxidation. Additionally, SeSE was utilized to jointly assess the apparent internalization and utilization rate of two typical nutrients, selenite and selenomethionine, in a rat nutrition model, demonstrating consistent results with those obtained by HPLC-MS and ICP-MS. Upon systematic standardization directed by Ramaley's theory, SeSE was integrated into a battery-operated portable kit (dubbed "SeEye") with a micro electrochemical drive and tablet PC console for one-stop service trials in a local commercial scenario. This study establishes (1) a nutritive value classifier in a low-cost consumer electronic format and (2) noninvasive diagnostic technology for Se supplementation.

Investigation on the principle and performance of fiber optical reflectometer based on wave optics simulation

Fiber optical reflectometer (FOR) is a novel technique for dense droplet detection that combines conventional phase detection with non-invasive velocity measurement capabilities. In this study, the mechanism of FOR technique and its sensitivity to droplet trajectory are investigated by wave optics simulation and experiment. This paper first describes the simulation method and analyzes the dynamic response of probe during the droplet piercing process. Next, an exploration is conducted on the effective field of view for the probe and the detectable interface inclination. Afterwards, by precisely controlling the droplet size, eccentricity, and trajectory, the simulation reveals the sensitivity of FOR technique to droplet parameters and quantifies the accuracy of measurement on droplet velocity, which provides specific guidance for the design and application of FOR technique. Finally, in the static experiment, the measurement error of the droplet axial velocity is controlled within 13 %, which verifies the reliability of the simulation results.

Concurrent maintenance of both veridical and transformed working memory representations within unique coding schemes

Abstract In the dynamic environment we live in, the already limited information that human working memory can maintain needs to be constantly updated to optimally guide behaviour. Indeed, previous studies showed that leading up to a response, representations maintained in working memory representations are transformed continuously. This goes hand-in-hand with the removal of task-irrelevant items. However, does such removal also include the representations of stimuli as they were originally, prior to transformation? Here, we assessed the neural representation of task-relevant transformed representations, and the no-longer-relevant veridical representations they originated from. We applied multivariate pattern analysis to electroencephalographic data during maintenance of orientation gratings with and without mental rotation. During maintenance, we perturbed the representational network by means of a visual impulse stimulus, and were thus able to successfully decode veridical as well as imaginary, transformed orientation gratings from impulse-driven activity. The impulse response reflected only task-relevant (cued), but not task-irrelevant (uncued) items, suggesting that the latter were quickly discarded from working memory. By contrast, even though the original cued orientation gratings were also no longer task-relevant after mental rotation, these items continued to be represented next to the rotated ones, in different representational formats. This seemingly inefficient use of scarce working memory capacity was associated with reduced probe response times and may thus serve to increase precision and flexibility in guiding behaviour in dynamic environments.

Factors Influencing Fans to Attend Matches Amid Pandemic: Exploring the Role of Trio of Team Affiliation, Sportscape, and Team Quality

Football is a sport that has attracted global attention. Individuals who attend competitive football associate with teams and athletes to a point where they become ardent attendees. Post-pandemic, fans have returned in droves to watch live matches at stadiums following the relaxation of strict observance of safety protocols. The purpose of this phenomenological study was to determine the factors that prompt fans to attend matches during games by focusing on three main factors including team affiliation, sportscape and star players. We used a qualitative phenomenological approach to obtain deeper comprehension regarding factors that influence fans to crowd at stadiums to watch football. We deployed semi-structured interviews which gave us the opportunity to probe and gather relevant responses. Interviews were audio taped and transcribed to pave the way for content analysis. Results show that fan affinity and star players are prime determinants of fans’ match day attendance at stadiums. Sportscape yielded mix results with some fans putting premium on sportscape but others lamented the deplorable conditions of stadium amenities such as washrooms, insecurity, and malfunctioning scoreboard on whose evidence sportscape does little to motivate them to attend matches. We recommend the need for teams to pool resources into recruitment of star players and build a groundswell of loyal fans through outstanding in-field performances to attract crowds to the stadium.

Defect identification method for capacitive-inductive dual-mode sensors with lift-off interference

The capacitive-inductive dual-mode probe provides a defect detection solution that allows simultaneous or sequential eddy current detection and capacitive imaging detection, known as capacitive-inductive dual-mode detection. The dual-mode detection combines the advantages of the two detection techniques and can be used to detect multiple types of defects in “insulator-conductor” multilayer hybrid structures. However, its high sensitivity poses a challenge as the probe's responses a susceptible to interference from lift-off variations, leading to non-relevant indications in the results that is not indicative of defects or anomalies. In this study, the Lift-off Characteristics (LoC) of the hybrid structures are studied, and an effective method for identifying relevant indications such as defect and anomaly for dual-mode sensor response signals with lift-off interference by combining the testing data of both detection modes and the LoC curve is proposed. A series of validation experiments were conducted to demonstrate the effectiveness of the proposed method in defect identification and classification. The results confirmed that the method effectively identified defect from lift-off interference and significantly reduced the occurrence of false judgments, thereby enhancing the reliability of the dual mode detection. Furthermore, the feasibility of utilizing the method to identify relevant indication when the sensor is tilted was also demonstrated.