Sensitive Response Research Articles

Design and analysis of a far-infrared metamaterial perfect absorber with sensing applications

In this paper, we present an analysis and design of a metamaterial as the perfect absorber and refractive index sensor in the far-infrared (IR) region, utilizing the finite element method (FEM). The structure consists of a metal resonator on a silicon dielectric with a bottom copper layer beneath the dielectric. Our results demonstrate that the designed structure achieves nearly perfect absorption of transverse electric (TE) polarization at a resonance wavelength of λ r =9.40µm. This occurs because of the perfect impedance matching condition, which achieves a 99.47% absorption efficiency. This condition is also sensitive to the angle of incidence and causes minimal reflection at the resonating wavelength of λ r . This characteristic makes the designed metamaterial structure suitable for use as a sensor. The structure enables maximum electric field confinement in the gap region (g) of the split ring resonator (SRR) at the metal-dielectric interface. The resonance wavelength can be effectively tuned and optimized by varying the gap size (g), dielectric material, dielectric thickness (t d ), copper layer thickness (t c ), and incident angle of the metamaterial absorber (MA). The absorption peak shows a highly sensitive response to changes in the refractive index of the surrounding medium, with a sensitivity of 1600 nm/RIU. This absorber, with its excellent absorption in the far-IR spectrum, holds promising potential for applications in energy harvesting and IR sensing.

2D Flower-like CdS@Co/Mo-MOF as Co-Reaction Accelerator of g-C3N4-Based Electrochemiluminescence Sensor for Chlorpromazine Hydrochloride

In this study, we have proposed an electrochemiluminescence (ECL) signal amplification system which is based on two-dimensional (2D) flower-like CdS@Co/Mo-MOF composites as a co-reaction accelerator of the g-C3N4/S2O82− system for ultrasensitive detection of chlorpromazine hydrochloride (CPH). Specifically, the 2D flower-like Co/Mo-MOF with mesoporous alleviated the aggregation of CdS NPs while simultaneously fostering reactant-active site contact and improving the reactant–product transport rate. This allowed the material to act as a novel co-reaction accelerator, speeding up the transformation of the S2O82− into SO4•− and enhancing the cathodic ECL emission of g-C3N4. Moreover, the signal probe which was synthesized by coupling the 2D CdS@Co/Mo-MOF and graphitic carbon nitride (g-C3N4) achieved the generation of SO4•− in situ and reduced energy loss. The results confirmed that the ECL signal was enhanced 6.2-fold and stabilized by CdS@Co/Mo-MOF. Based on the extremely strong quenching effect of chlorpromazine hydrochloride (CPH) on this system, a “signal-off” type sensor was constructed. The sensor demonstrated excellent sensitivity and linear response to CPH concentrations ranging from 1 pmol L−1 to 100 μmol L−1, with a low detection limit of 0.4 pmol L−1 (S/N = 3).

Thrombin Nanochannel Logic Gate Inspired by BioMemory.

The process of "reading" and "writing" in biomemory involves the transmission of electrical signals between neurons, with ligand-gated ion channels assuming a key role. The solid-state nanochannels exhibit certain similarities with neurons. Information transmission can be achieved by controlling the flow of ions within nanochannels, rendering them potentially suitable for simulating neuron behavior. Herein, thrombin (Thr) was chosen as the target protein, and a functionalized nanochannel sensing system was successfully constructed using DNA aptamers, enabling a highly sensitive Thr response with a detection limit of 0.221 fM. Simultaneously, based on Watson-Crick base pairing and programmable chain displacement reactions, controlled release and cyclic response of the target molecule were further achieved. This mechanism elucidates the rules governing specific input-output relationships, innovatively linking them with memory storage and recognition through the Thr-nanochannel logic gate, thereby realizing the reading of biomemory at the hardware level. In summary, the biological hybrid nanofluidic control device of this invention converts molecular events into electrical signals, providing potential avenues for establishing connections between the mechanisms of biomemory and solid-state nanochannel biosensing and recognition in the future.

NaCl-Responsive Ultrashort Peptide to Trigger Self-Assembly of TPE-Capped Supramolecular Hydrogelator.

With the advantages of less invasiveness and better shape adaptability, in situ-forming hydrogels are desired biomaterials as scaffolds, drug carriers, and so on. Herein, a negatively charged NaCl-responsive ultrashort peptide sequence (EEH) is reported whose electrostatic repulsion can be reduced through the charge-shielding effect. Under physiological conditions, its AIEgen-capped amphiphile TPE-GEEH of low concentration (1 mg/mL) presents NaCl-triggered morphological transformation from micelle to closely packed fiber with enhanced emission, which can be applied to biosense sodium ion (Na+) with high sensitivity and quick response. At a slightly acidic pH, 10 mg/mL TPE-GEEH undergoes sol-gel transition upon addition of NaCl (100 mM) with improved mechanical properties, which should be useful to develop an in situ-forming hydrogel. Overall, our report provides a simple strategy to construct NaCl-responsive assemblies for potential application in biosensors and drug delivery system.

Probing Deep Hydrogen Polysulfides Fluctuations In Vivo by Engineering Activatable Fluorescence Reporters with Second Near-Infrared Window Emission.

Deep and comprehensive understanding of the intricate biochemical processes mediated by H2Sn (n ≥ 1), but not H2S, is of paramount importance. A few fluorescent probes have been developed with the intention of addressing this issue. However, there is currently no evidence of any activatable NIR-II fluorescent probes for H2Sn-specific imaging over H2S. In this study, we developed the inaugural H2Sn-activated NIR-II probe for specific and deep imaging of H2Sn through a series of molecular engineering strategies. Strong electron-absorbing moieties enabled the redshift of the emission of the designed reporter, while leaving groups with different dissociation capacities were responsible for modulating the selective and sensitive responsiveness to H2Sn over H2S. By using this activatable specific probe for deep tissue mapping of endogenous H2Sn fluctuations, accurate identification of acute inflammation in animal models was achieved. It is anticipated that the advancement of this activatable NIR-II probe will facilitate a more profound comprehension of the physiological implications of H2Sn.

High strength, high sensitivity, hydrophobic and conductive vegetable oil-based composites for human motion detection

The vulnerability of infants and young children due to their fragile bodies and inability to effectively express physical discomfort has raised widespread of concern in the society. As it continues to be difficult to develop sensors with superior mechanical qualities and response sensitivity for use in health monitoring and recognition. Here, a polymer known as, Polyurethane Thermoplastic Elastomer, enhanced by crosslinking which is prepared from Isophorone Diisocyanate (IPDI), soybean oil polyol ED, and polycaprolactone triol (PCT-L) also referred to as PTIED, was prepared based on previously prepared soybean oil polyol ED and polycaprolactone triol (PCT-L) as soft segments, with IPDI as hard segments. This was followed by the preparation of the PTIED-CNT sensor by using PTIED as a matrix and hydroxyl carbon nanotubes (CNT) as a conductive filler. The mechanical properties of the obtained PTIED-CNT sensor have been enhanced, with a tensile strength of approximately 5 MPa. The sensitivity GF of the PTIED-CNT7 % can reach up to 805.67 and remains stable after 4500 seconds of continuous operation at 10 % strain. Moreover, the device can support high stability in a simulated sweat environment and exhibit antibacterial and hydrophobic, which could be used to check for small movements, such as those of the face and throat, and could also recognize sound. Therefore, its potential applications in respiratory monitoring of infants as well as other health monitoring applications are expected.

Highly sensitivity and wide-range flexible humidity sensor based on LiCl/cellulose nanofiber membrane by one-step electrospinning

Cellulose is considered an ideal material for flexible electronic humidity sensors due to its green renewable nature, rich surface groups and strong hydrophilicity. However, the traditional cellulose-based humidity sensor cannot simultaneously have wide detection range, high sensitivity and fast response time, which seriously hinder their development and application. Here, an ultrathin Lithium chloride (LiCl)/cellulose nanofiber membrane as moisture sensitive materials was prepared by one-step electrospinning and used to assemble a high-performance humidity sensor. N, N-Dimethylacetamide/Lithium chloride (DMAc/LiCl) solvent system was used to dissolve the cellulose, and DMAc volatilized into the air while LiCl remained in the cellulose nanofibers during the electrospinning process. LiCl as a highly moisture-sensitive inorganic salt has strong hydrophilicity and enhances the moisture sensing detection limit of cellulose fiber (especially under low humidity conditions), thus giving the cellulose moisture sensor excellent sensitivity (up to 4191 %) and a wide detection range (5–98 % RH). The nanometer size of cellulose fibers, the extremely low thickness and large pores of cellulose membranes accelerate the mass exchange of moisture between the air and the membrane, thus giving cellulose humidity sensor a fast response/recovery time (99/110 s) and low hysteresis (2.9 %). Moreover, the performances of humidity sensors didn’t degrade even after being subjected to long-term application (>30 days), high/low temperatures (73.6/0.1 ℃) and thousands of bending cycles. The proposed LiCl/cellulose nanofiber humidity sensor brings innovative solutions for the design of cellulose based sensor with great potential for use in non-contact humidity detection, respiratory monitoring and sleep apnea detection applications.

Design of fluorescent sensors for the detection of human serum albumin structure employing nitrogen-by modulation of molecular containing heterocycles

Serum albumin is the most abundant protein in mammalian plasma. It occupies an extremely important position in organisms as an early indicator of the development of many diseases. The development of fluorescence sensing technology has revolutionized the drawbacks of traditional methods. In this strategy, we designed and synthesized three dual fluorophore organic sensors TPA-IPA-T1, TPA-QL-T2, and TPA-Py-T3 for the detection of serum albumin. The rotation of the C–C bond of sensors is restricted and the molecular structure forms a rigid plane that contributes to the fluorescent emission intensity of the sensor. The fluorescent skeletons were successfully constructed by triphenylamine composed the electron-withdrawing nitrogen-containing compounds benzopyrrole (indole), benzopyridine (quinoline), and pyridine, respectively, with piperazine as a rigid connecting bridge. The addition of human serum albumin (HSA) turned on the fluorescent emission of the sensor near 580–600 nm. The color of the sensor solution changed from colorless to pink and bright orange, respectively. The fluorescent intensity increased by 24, 67, and 31 fold, respectively. The sensors have the advantages of sensitivity and fast response, strong anti-interference ability, low detection limit and good water solubility. Drug experiments in artificial urine demonstrate the characteristics of sensors, which has a very high potential for biological feasibility and medical applications. The sensors facilitaty the binding of the HSA through electrostatic interactions. The sensors were explored to be able to efficiently bind the IB structural domain of HSA, which had a good meaningful of avoiding the interference of commonly drugs in clinical medicine and in artificial urine on the detection of HSA.

Preparation of carboxylated-silk nanofibers by the one-pot method of maleic acid hydrolysis.

In this study, a maleic acid (MA) hydrolysis one-pot method is proposed to prepare carboxylated silk nanofibers (MA-SNFs). The MA concentration, hydrolysis temperature, and processing time were optimized. Combined with high-pressure homogenization, MA-SNFs with a carboxyl content of 0.617±0.019mmol/g and length of 333±116nm were obtained with a yield of 54.90±1.98% at the optimal conditions: 50wt% of MA concentration, 110°C of hydrolysis temperature and 120min of processing time. The morphology, chemical structure, and crystal structure of raw silk fibroin (SF), acid-hydrolyzed silk fibroin and nanofibers were studied. Furthermore, MA was reused several times with a recovery rate of >94% and maintained almost the same treatment effect. Finally, due to the presence of carboxyl groups, MA-SNF hydrogels were successfully prepared by an acetic coagulation vapor bath which exhibited excellent self-supporting ability and mechanical properties as well as a more sensitive pH response compared with regenerated silk fibroin solution and other non-carboxylated silk nanofibers. The MA-SNF aerogels had the characteristics of light weight, high strength and porous with cross-linked nanostructures.

Antibody-Modified 2D MXene Nanosheet Probes for Selective, picolevel Detection of Cancer Biomarkers

Cancer biomarkers are crucial indicators found in clinical samples, playing a key role in early detection, diagnosis, and treatment of cancer. Detecting these biomarkers with high sensitivity is essential for early diagnosis, especially in aggressive cancers like lung cancer, which is the leading cause of cancer-related deaths. Carcinoembryonic antigen (CEA) is a critical biomarker for lung cancer, and its detection aids in identifying the disease at an early stage. Electrochemical sensing, known for its high sensitivity and rapid response, has shown great promise in cancer biomarker detection. MXenes, two-dimensional materials composed of carbides and nitrides, offer excellent electrochemical performance due to their high surface area and conductivity. In this study, MXenes were modified via hydrothermal treatment to produce MXene nanosheets (MNS) with increased interlayer spacing, enhancing their electron transfer capabilities. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) revealed the superior electrochemical properties of MNS compared to pristine MXene. These MNS were functionalized with CEA-specific antibodies using EDC-NHS chemistry, creating a highly specific electrochemical biosensor for CEA detection. The sensor exhibited a remarkable limit of detection at the picogram level and was validated through real-time blood analysis, achieving a 95% recovery rate. This MNS-based biosensor demonstrates significant potential for clinical diagnostics, particularly for the early detection of cancer biomarkers, paving the way for improved cancer treatment outcomes.

Self-assembly Pt hollow nanospheres for highly selective and ultrasensitive detection of dopamine

Abnormal concentration of dopamine, one critical neurotransmitter in central nervous system, causes several neurological diseases associated with behavioral responses and brain functions in human beings. Highly sensitive detection of dopamine is of great significance yet challengeable. In this work, Pt hollow nanospheres (Pt HNSs) with a uniform diameter of 30 nm were successfully synthesized in water by self-assembly method under room temperature. The fabricated Pt hollow/Nafion nanospheres modified glassy carbon electrode (Pt HNSS/Nafion/GCE) exhibited superior electrocatalytic performance, with peak currents 2.24 and 4.54 times higher than those of Nafion-modified glassy carbon electrode (Nafion/GCE) and bare glassy carbon electrode (GCE), respectively. Theoretical calculations indicate that dopamine has an adsorption energy of −3.18 eV on the Pt(111) surface, with an electron transfer of + 1.84 |e|, aligning with the 2-electron transfer mechanism. Furthermore, the low energy barrier observed during dopamine oxidation process suggests that the Pt(111) surface is highly favorable for dopamine oxidation. Meanwhile, Pt HNSS/Nafion/GCE electrochemical sensor exhibits highly sensitive and selective response in determination of dopamine ranging from 0.01 to 250 μM with low detection limits of 0.804 nM (S/N = 3). Moreover, the electrochemical sensor shows reliable signals in real test with great anti-interference and stability during the experiments, making it a promising candidate for applications in dopamine sensing.

Simulating a Temperature, Stress And Strain FBG Sensor for Troposphere Layer

In this study, a simulation and design for a temperature (T) sensor are investigated by using the fiber Bragg gratings (FBG). The study investigated and characterized the FBG regarding maximum reflectivity, bandwidth, and the influence of applied strain on the shift in Bragg wavelength (λB). This is via measuring sensitivity of wavelength shift under strain in an optical sensing system. The response of FBG sensors was also investigated and optimized. Uniform FBG spectra and theoretical comparisons were conducted considering the influence of several selected external strain/stress (S) values: 101.325, 89.874, 79.495, 70.108, 61.640, 54.019, 47.181, 41.060, 35.599, 30.742, 26.436. The Optisystem 16 software is analyzing these two types of effects. The measured parameters, such as sensitivity, were determined by using a white light source. The light source operating wavelength was 1550 nm. This is to design the sensor especially for troposphere that have high sensitivity (1279.7472 pm/oC. The sensitivity obtained exhibited varying values between 1279.7472 and 1239.7551 for strain. The peak sensitivity observed is associated with 550 nm of wavelength. Result for measured sensitivity against S by the FBG sensor was 15.5087 pm/oC with sensor length 20 mm. While it was found equals 15.5131 pm/oC with sensor length 10 mm. T sensing is simulated for selected values (15, 8.5, 2, -4.5, -11, -17.5, -24, -30.5, -37, -43.5, -50 oC). Resulted sensitivity was found to fluctuate fitting sine, Long Normal, and Boltzmann functions, indicating large sensitivity for the simulated sensor responses.

Multilevel Cu-LIG Tactile Sensing Arrays for 3D Touch Human-Machine Interaction.

High-performance flexible tactile sensors have attracted significant attention in the domains of human-machine interactions. However, the efficient fabrication of sensors with highly sensitive responses over a broad load range still remains a challenge. Here, we propose a one-step laser writing route to construct a distinctive multilevel piezoresistive structure, consisting of Cu nanoparticle-doped graphene protrusions and surrounding porous Cu sheets. This multilevel structure enables the assembled tactile sensors to exhibit superior sensitivity at both low-pressure (1468 kPa-1 at 0-200 kPa) and high-pressure (1345 kPa-1 at 600-800 kPa) stimulations. Its enhancement mechanism for piezoresistive sensing has been investigated. The programmable laser writing process facilitates the development of human-machine interaction devices that recognize multidimensional gestures such as sliding, clicking, and pressing. This advancement serves to promote the development of high-performance interactive sensing technologies.

Estimating response of structures to earthquake-induced tsunami: A simple approach per unidirectional analysis

The orientation of a structure with respect to the direction of propagation of tsunami wave may often be arbitrary. As such, it may be convenient to consider the tsunami wave as a combination of two orthogonal pair. The response of structures may then be computed to the simultaneous action of two components (bidirectional) covering multiple incidence angles. However, analysis of structures in three-dimension under two orthogonal components is a daunting exercise for routine design. Against this backdrop, beginning with the validation of the simulation of tsunami against real records, a detailed scrutiny of the response of simple building frames to tsunami is made over a range of orientations per both unidirectional and bidirectional analyses. This indicates the sensitivity of response over orientations and suggests that the maximum response to a bidirectional tsunami attack can be closely estimated by unidirectional analysis at appropriate orientations. This reveals the existence of the most intense orientations in which the response to unidirectional loading may approximately represent the maximum response to bidirectional loading over all orientations. Observing statistically significant positive correlation of tsunami potential (Pd) and peak destructive potential (Id) to the response to unidirectional tsunami attacks, these pure tsunami parameters are selected as suitable intensity measures (IM). Analytical (as well as graphical through standard Mohr’s circle) expressions are then derived for the orientations in which such IM can assume the maximum. It is shown that the unidirectional analysis conducted in these orientations can closely estimate the maximum response to bidirectional attacks out of all possible orientations for single story and multistorey building frames. Hence, the straightforward unidirectional analysis in the most intense orientations may be adopted for design of coastal structures.

An intelligent chitosan/polyvinyl alcohol film with two types of anthocyanins for improved color recognition accuracy and monitoring fresh-cut pineapple freshness

In this study, chitosan (CS), polyvinyl alcohol (PVA), and sodium tripolyphosphate (STPP) were used as bases to introduce a blend of black wolfberry (BW) and red cabbage (RC) anthocyanins. The chelation reaction of CS, PVA, and STPP resulted in the composite anthocyanins being fixed within the matrix with an appropriate ratio of composite anthocyanins stably distributed in the film. The FTIR and X-ray analyses revealed that the addition of both types of anthocyanins strengthened hydrogen bond interactions. Moreover, the CP/BR-4 film exhibited excellent antioxidant, mechanical, and antibacterial properties, as well as a sensitive and rapid response to acidic substances. The freshness of pineapples stored under refrigeration for 6 d was also evaluated, showing more significant color changes with the CP/BR-4 film than the other treatment groups. Therefore, the composite anthocyanin film can potentially serve as an intelligent film for the detection of postharvest freshness in practical applications.

Near-infrared fluorescent probe for visualization of nitroxyl in the plant response to stress

BackgroundNitroxyl (HNO) is an emerging signaling molecule that plays a significant regulatory role in various aspects of plant biology, including stress responses and developmental processes. However, understanding the precise actions of HNO in plants has been challenging due to the absence of highly sensitive and real-time in situ monitoring tools. Consequently, it is crucial to develop effective and accurate detection methods for HNO. Establishing such methodologies will enable researchers to elucidate the functional roles of HNO in plant physiological processes, thereby advancing our knowledge of plant resilience and adaptation under environmental stressors. ResultHerein, we successfully constructed a near-infrared fluorescent probe, DCIF-HNO, based on the dicyanoisophorone platform as fluorophore and 2-(diphenylphosphino)benzoate as HNO recognition site for identifying HNO in plants. Probe DCIF-HNO exhibited rapid response, excellent selectivity, and high sensitivity to HNO in vitro spectroscopic tests, while also demonstrating low toxicity and biocompatibility. A rapid and portable smartphone sensing platform for HNO in actual samples was successfully constructed based on probe DCIF-HNO and color recognition application. Moreover, probe DCIF-HNO was successfully applied to plant cells and tissues, enabling real-time visualization and detection of HNO and revealing the complex network of HNO interactions during H2S/NO crosstalk in plants. Furthermore, the increase in HNO levels in plants response to high salt and Cr stress was observed using probe DCIF-HNO. Transcriptome sequencing and differential metabolites analysis were employed to gain insight into the mechanism of HNO production under Cr stress. SignificanceDue to the optical properties and high-resolution imaging capabilities of DCIF-HNO, this study offers a novel framework for elucidating the signaling role of HNO in plant stress responses. The precise visualization of HNO dynamics enhances our understanding of the complex molecular pathways involved in plant adaptation to abiotic stressors. This research not only advances plant physiology but also has significant implications for developing strategies to enhance agricultural resilience in challenging environmental conditions.

Detection of dithiocarbamate pesticide residues in tea by colorimetric and fluorescent double-mode probe regulated by tyrosinase

In this study, a colorimetric/fluorescent double-mode probe for sensitive detection of dithiocarbamates (DTCs) pesticides residues was constructed based on the fluorescence controllable property of Mn3+-sealed metal-organic framework (MnMOF), the chromogenic reaction of enzyme reaction products, and inhibition of tyrosinase activity by DTCs. DTCs inhibited the activity of tyrosinase and impeded the consumption of catechol (CC), thereby weakening the colorimetric signal. The redox reaction between residual CC and MnMOF led to backbone collapse and release of free porphyrin (TCPP), which caused fluorescence enhancement of the probe solution. As the concentration of DTCs increased, the color of probe solution gradually transitioned from reddish brown to light pink in daylight, and the red fluorescence was gradually enhanced under 365 nm UV light. Under the optimal conditions and using zineb as a representative of DTCs, the probe achieved the sensitive response to zineb over the concentration range of 0.03 ∼ 1.1 μg mL−1. The detection limits were 9.23 ng mL−1 and 5.95 ng mL−1 in colorimetric and fluorescent modes, respectively. The practical applicability of the probe was demonstrated by the detection of zineb residues in tea. In this study, a simple, sensitive, and reliable double-mode analysis platform was established for the identification of DTCs residues in tea, which is of great significance for ensuring the quality and safety of tea and human health.

Fast Near-Infrared Organic Photodetectors with Enhanced Detectivity by Molecular Engineering of Acceptor Materials.

Organic photodetectors (OPDs) with a near-infrared (NIR) response beyond 900nm are intriguing electronics for various applications. It is challenging to develop NIR OPDs with high sensitivity and fast response. Herein, the acceptor materials of OPDs are tuned to extend detection to ≈1100nm with improved sensitivity. A new fused ring electron acceptor, ICS (2,2'-((2Z,2'Z)-(((4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl)bis(4-((2-ethylhexyl)thio)thiophene-5,2-diyl))bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile), is developed with alkylthio thiophene as the bridge, achieving a small bandgap of 1.35eV while decreasing dark current densities under reverse bias. By further introducing a secondary acceptor of PC61BM, the doping compensation, and unfavored hole injection blocking enable further improvement of detectivity. The PTB7-Th (Poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl]): ICS: PC61BM OPDs deliver a low dark current density of 1.23 × 10-9 A cm-2, a high peak specific detectivity of 1.09 × 1013 Jones at 950nm under -0.2V, and a fast response speed with a -3dB bandwidth of 720kHz biased under -2V. The photoplethysmography system with the PTB7-Th: ICS: PC61BM OPD can reliably monitor heartbeats under 980nm NIR light. This study promises the development of organic NIR OPDs with high detectivity and fast response by tuning active materials.

Robust Fluorescent Nanoprobe for Rapid Evaluation of the Selenium Supplementation Effect and Imaging.

At present, an increasing number of people pay more attention to selenium-enriched food, but the quality of the selenium-enriched food varies. Therefore, there is an urgent need to develop a new tool to assess the effects of selenium supplementation in foods by rapidly detecting the levels of the metabolite selenium selenocysteine (Sec). In this work, a fluorescent nanoprobe CS-Sec was designed, synthesized, and characterized for Sec detection and imaging in living biosystems, which exhibited the advantages of good biocompatibility, excellent water solubility, high sensitivity, high selectivity, and rapid response (2.5 min) for Sec detection and imaging in vitro and in vivo and evaluation of selenium supplementation in selenium-rich foods. Specifically, CS-Sec was constructed by grafting alkyne groups on organic small-molecule fluorescent probes with azide groups on azido chitosan by click chemistry. A 2,4-dinitrophenyl ether (DNB) with a strong intramolecular charge transfer (ICT) effect was selected as a response group and fluorescence-quenching group, which had excellent chemical specificity toward Sec. In addition, CS-Sec has high selectivity and sensitivity toward Sec over other analytes, and an excellent limit of detection (LOD) is as low as 15 nM. Impressively, CS-Sec has been successfully used to detect and image the concentration of Sec in living HepG2 cells and mouse models with exciting results, indicating that the newly constructed CS-Sec can provide a robust molecule tool for the rapid evaluation of the selenium supplementation effect and imaging in the future.

Introducing the Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations—I: Mathematical Framework

This work introduces the mathematical framework of the novel “First-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations” (1st-FASAM-NODE). The 1st-FASAM-NODE methodology produces and computes most efficiently the exact expressions of all of the first-order sensitivities of NODE-decoder responses with respect to the parameters underlying the NODE’s decoder, hidden layers, and encoder, after having optimized the NODE-net to represent the physical system under consideration. Building on the 1st-FASAM-NODE, this work subsequently introduces the mathematical framework of the novel “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)”. The 2nd-FASAM-NODE methodology efficiently computes the exact expressions of the second-order sensitivities of NODE decoder responses with respect to the NODE parameters. Since the physical system modeled by the NODE-net necessarily comprises imprecisely known parameters that stem from measurements and/or computations subject to uncertainties, the availability of the first- and second-order sensitivities of decoder responses to the parameters underlying the NODE-net is essential for performing sensitivity analysis and quantifying the uncertainties induced in the NODE-decoder responses by uncertainties in the underlying uncertain NODE-parameters.