Ratiometric Technique Research Articles

Operando Luminescence Thermometry of a Solid Catalyst in a Reactor during a High‐Temperature Chemical Process

AbstractIn most catalytic processes, thermal energy is released or consumed locally in a reactor due to the exothermicity or endothermicity of the chemical reactions. This causes the actual operating temperature of the catalyst material to deviate from the reactor temperature, which can lead to underperformance, reduced catalyst stability, or even thermal runaway. Conventional methods to measure the catalyst temperature, with a thermocouple in the reactor oven or in the catalyst bed, suffer from complications because of separation between the sensor and catalyst material, chemical activity of the thermocouple/coating material, added complexity of the setup, and disruption of the reactant flow and heat flow through the catalyst bed. Here, we show the possibilities and challenges of luminescence thermometry as an analytical technique for remote temperature monitoring of the local catalyst temperature in a strongly exothermic high‐temperature reaction environment. We observe that the luminescence lifetime depends not only temperature, but also on oxygen concentration, which can introduce a significant systematic error of up to 40 °C in the recorded temperature. In the case of ratiometric luminescence thermometry, this error is strongly reduced to ~5 °C. We use the ratiometric technique to confirm its applicability in the exothermic oxidative coupling of methane (OCM) process at high reaction temperatures, showing an exothermic increase in the local catalyst temperature of up to 100 °C, relative to the constant reactor temperature under inert conditions.

Dual luminescent nano-thermometry based on the selective excitation of optical centers in CaF2:Er3+ nanoparticles

We present a study about the feasibility of using the upconverted luminescence of CaF2:Er3+ nanoparticles (NPs), under near infrared excitation within the 4I15/2 → 4I11/2 absorption band, for thermal detection. In order to perform this study, it has been needed to investigate the upconversion processes as function of the Er3+ concentration and the excitation wavelength by using a tunable Ti:Sapphire laser. The results obtained indicate that, under this excitation scheme, the green (2H11/2:4S3/2) and red (4F9/2) emitting levels are populated through different multiphoton processes: Excited state absorption and energy transfer upconversion. Therefore, the ratio between the green and red emissions is also dependent on the Er3+ concentration and the excitation wavelength. Measurements based on site-selective emission/excitation, performed at room temperature, indicate that in these NPs there are at least two different optical centers whose emission bands can be isolated by an appropriate selection of the excitation wavelength. One these centers is compatible with the presence of isolated Er3+ ions, while the other one is tentatively related to the presense of clusters or aggregates. The upconverted luminescence of each optical center is analyzed as function of temperature by means of the ratiometric Fluorescence Intensity Ratio technique. The results indicate that both optical centers exhibit adequate thermal performances and relative sensitivities to be used in thermal sensing.

Temperature responsive behaviour of SrAl2O4(Eu, Dy):ZnGa2O4(Cr) phosphor-glass composite

The current investigation reports on laser spectroscopy and temperature-sensitive optical response of composite consisting of phosphors (ZnGa2O4:Cr3+ and SrAl2O4:Eu2+, Dy3+) coated on a tellurite glass layer. Based on this composite, a temperature sensor, sensitve in the range of 298 K to 423 K, demonstrates a remarkable temperature sensitivity. Various analytical techniques, such as X-ray Diffraction, Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, laser spectroscopy, etc., were employed to analyze the prepared composite. The investigation reveals the presence of ZGO and SrAl phosphors with crystalline sizes of approximately 36 nm and 25 nm, respectively, while the particle size ranges from 400 nm to 600 nm. A dip coating method was utilized to deposit tellurite-phosphor layers on the glass substrate to create a temperature sensor. SEM analysis indicates a layer thickness of around 93 µm. The existence of Eu2+ and Cr3+ ions was confirmed through photoexcitation and emission spectra on a 405 nm laser excitation. The temperature-dependent luminescence was studied using a ratiometric technique, showing a linear variation with temperature, resulting in an excellent temperature sensitivity of about 1.41 % K−1 at 298 K. Our preliminary study of the phosphor-tellurite composite suggests significant potential for extensive use in the field of dual-mode highly sensitive optical thermometry.

Dual response signal CdTe QDs@ZIF-8 with butterfly spectrum for dual-mode fluorescence/colorimetric detection of tetracycline in animal feeds.

In this study, a ratiometric fluorescent sensor CdTe QDs@ZIF-8 with butterfly spectra is successfully constructed by in situ encapsulating mercaptopropionic acid-modified CdTe quantum dots in zeolitic imidazolate framework-8 (ZIF-8) with a simple strategy, and used for the detection of tetracycline in fluorescence/smartphone colorimetry dual-mode. ZIF-8 not only reduces the agglomeration of the quantum dots but also surprisingly generates a new green fluorescence signal at 524nm while the red fluorescence of the CdTe quantum dots at 650nm quenches when tetracycline is added. The two opposing fluorescence signals create a butterfly-shaped fluorescence spectrum, allowing the sensor to detect tetracycline over a linear range of 0-70μM with the detection limit (LOD) of 0.0155μM by using a ratiometric fluorescence technique. What is more, based on the obvious color change of the fluorescent sensor gradually from red to green under UV light, a highly stable point-of-care testing sensor has been developed for on-site detection of tetracycline through color recognition by smartphones, which can be used for real-time detection of this antibiotic in the range of 0-1000μM with the LOD of 0.0249μM. This work provides a simple and efficient method for the on-site detection of tetracycline.

Regulating the luminescence properties of Eu2W3O12 red-emitting phosphor via rare-earth ions doping for optical thermometry, white light-emitting diode and plant growth applications

To fulfil various applications, series of rare-earth (RE) ions (i.e., La3+, Gd3+, Sm3+) doped Eu2W3O12 (EWO) phosphors were synthesized. All the designed phosphors can emit glaring visible lights from Eu3+ and their fluorescence intensities were significantly enhanced through RE ions doping. To explore the impact of RE ions doping on the symmetric properties of Eu3+ in studied samples, theoretical calculation based on Judd-Ofelt theory was performed. Moreover, through utilizing temperature-related emission spectra, the thermal quenching behaviors of resultant phosphors were studied and found that their thermal stability had been improved by adding RE ions. Furthermore, the thermometric properties of designed phosphors were examined through adopting the single-band ratiometric technique to analyzing the temperature-dependent fluorescence intensity ratio of the emission band arising from 5D0 → 7F2 transition of Eu3+. It is found that maximum absolute and relative sensitivities of resulting phosphors were 0.197 and 1.202 % K−1, respectively. Additionally, two types of devices, i.e., white light-emitting diode (white-LED) and red-emitting LED, where the prepared phosphors play as red-emitting components, were fabricated. The packaged white-LEDs can emit warm white light with high color rendering index and low correlated color temperature, which are insensitive to operating current. Considering the red-emitting LEDs, their emission bands overlap with the absorption bands of plant pigments, which can promote plant growth and it was verified by peppermint growth experiments. These results verify that the introduction of RE ions is a feasible approach to modify the luminescence performances of phosphors to realize diversified applications.

A hydrogel sensor based on cellulose nanofiber/polyvinyl alcohol with colorimetric-fluorescent bimodality for non-invasive detection of urea in sweat

The concentration of urea in sweat serves as a valuable indicator of an individual's overall health. In this study, we present a novel hydrogel sensor (BAF-CPu), based on cellulose nanofiber and polyvinyl alcohol, designed to achieve non-invasive in situ and highly sensitive detection of urea in sweat by combining the dual-mode response of colorimetric and ratiometric fluorescence techniques. The bright red fluorescent gold‑copper bimetallic nanoclusters and green fluorescent fluorescein isothiocyanate-modified cellulose nanofibers endowed BAF-CPu with proportional fluorescence responsive properties. Under the catalytic action of urease, the hydrolysis of urea raises the pH, resulting in diminished red fluorescence along with enhanced green fluorescence, and the fluorescence color of BAF-CPu changes from red to green. Moreover, BAF-CPu hydrogel encapsulates pH-responsive bromothymol blue (BTB), which changes from yellow to blue in the presence of urea. Importantly, BAF-CPu absorbs sweat by adhering directly to the skin surface, avoiding the complicated sampling process and improving the maneuverability of the detection process. With both ratiometric fluorescence and colorimetric modes, BAF-CPu is not only able to detect sweat in situ, but also can reduce the interference of the complex sweat environment on the urea detection, and realize the high sensitivity detection of urea in sweat.

Generalized ratiometric surface-enhanced Raman scattering biosensor for okadaic acid in food based on Au-triggered signal amplification

BackgroundReliability and robustness have been recognized as key challenges for Surface-enhanced Raman scattering (SERS) analytical techniques. Quantifying the concentration of an analyte using a single characteristic peak from SERS has been a controversial topic because the Raman signal is susceptible to highly concentrated electromagnetic hotspots, inhomogeneity of SERS substrate, or non-standardization of measurement conditions. Ratiometric SERS strategies have been demonstrated as a promising solution to effectively balance and compensate for signal fluctuations caused by matrix heterogeneity. However, it is not easy to construct ratiometric SERS sensors with monitoring the ratio of two different signal intensities for target analysis. ResultsAn attempt has been made to develop a novel ratiometric biosensor that can be applied to detect okadaic acid (OA). Aptamer-anchored magnetic particles were first combined with gold-tagged short complementary DNA (Au-cDNA) to create heterogeneous nanostructures. When the target was present, the Au-cDNA was dissociated from nanostructures, and 4-nitrothiophenol (4-NTP) was initiated to reduce to 4-aminothiophenol (4-ATP) in the presence of hydrogen sources. The SERS ratio change of 4-NTP and 4-ATP was finally detected by AuNPs-coated film. OA was successfully quantified, and the detection limit was as low as 2.4524 ng/mL. The constructed biosensor had good stability and reproducibility with a relative standard deviation of less than 4.47%. The proposed method used gold nanoparticles as an intermediate to achieve catalytic signal amplification and subsequently increased the sensitivity of the biosensor. Significance and noveltyCatalytic reaction-based ratiometric SERS biosensors combine the multiple advantages of catalytic signal amplification and signal self-calibration and provide new insights into the development of stable, reproducible, and reliable SERS detection techniques. This ratiometric SERS technique offered a universal method that is anticipated to be applicable for the detection of other targets by substituting the aptamer.

Sensitive Luminescence Thermometry through Excitation Intensity Ratio in Eu-Doped BaTiO3.

Optical ratiometric thermometry techniques have gained much attention in recent years due to their reliable and noncontact temperature sensing capability for industrial and biorelated applications. Herein, we exploited the temperature dependence of the absorption band of BaTiO3 (BTO) for novel excitation intensity ratio (EIR) thermometry. Photoluminescence and excitation properties of Eu3+-doped BTO powders were studied as a function of Eu3+ doping concentration. The excitation peak intensities at 397 and 468 nm, corresponding to the 7F0 → 5L6 and 5D2 transitions of Eu3+, were used as EIR parameters. The temperature dependence of the EIR can be explained by the competitive absorption between Eu3+ and the BTO host. The EIR properties were studied in relation to the doping concentration, registering a maximum relative sensitivity (Sr) of 4.89% K-1 in BTO:Eu3+ (0.5%) at 303 K. An amphoteric Eu3+ occupation mode at both Ba2+ and Ti4+ sites was found to interpret the doping concentration dependence of the Sr. The reduced Ba2+ site occupation ratio proved to be responsible for the low Sr values at high Eu3+ doping concentrations. Accordingly, an Eu3+/Ti3+ codoping method was further proposed to improve the Sr by increasing the Ba2+ site occupation ratio. Our result showed that BTO:Eu3+ (0.5%) demonstrated an enhancement of Sr from 4.89 to 6.42% K-1 at 303 K after 2% Ti3+ codoping.

Design of Multi-Luminescent Silica-Based Nanoparticles for the Detection of Liquid Organic Compounds.

Tracer testing in reservoir formations is utilised to determine residual oil saturation as part of optimum hydrocarbon production. Here, we present a novel detection method of liquid organic compounds by monodisperse SiO2 nanoparticles (NPs) containing two luminophores, a EuIII:EDTA complex and a newly synthesised fluorophore based on the organic boron-dipyrromethene (BODIPY)-moiety. The particles exhibited stable EuIII PL emission intensity with a long lifetime in aqueous dispersion. The fluorescence of the BODIPY was also preserved in the aqueous environment. The ratiometric PL detection technique was demonstrated by using toluene and 1-octanol as model compounds of crude oil. The optimal synthesis conditions were found to give NPs with a diameter of ~100 nm, which is suitable for transport through porous oil reservoir structures. The cytotoxicity of the NPs was confirmed to be very low for human lung cell and fish cell lines. These findings demonstrate the potential of the NPs to replace the hazardous chemicals used to estimate the residual oil saturation. Moreover, the ratiometric PL detection technique is anticipated to be of benefit in other fields, such as biotechnology, medical diagnostics, and environmental monitoring, where a reliable and safe detection of a liquid organic phase is needed.

θ-Nanopore Ratiometry.

Developing nanoscale ratiometric techniques capable of biochemical response should prove of significance for precise applications with stringent spatial and biological restrictions. Here we present and devise the concept of θ-nanopore ratiometry, which uses ratiometric signals that could well address the serious concerns about device deviation in fabrication and nonspecific adsorption in the detection. As exemplified by a 200 nm θ-nanopore toward miRNA detection, the ±20 nm aperture drift could be mitigated and the issue of nonspecific adsorption could be minimized in the complex cytosolic environment. Practical application of this θ-nanopore ratiometry realizes the measurements of cytosolic miRNA-10b. This work has not only established a nanoscopic ratiometric technique but also enriched the extant armory of nanotools for single-cell studies and beyond.

Precision ratiometric technique for measuring the Peltier coefficient

We present a novel ratiometric approach to independently measure the Peltier coefficient, without using Kelvin’s relation, using the ratio of two temperature signals induced by the Peltier and Joule effects, in addition to readily obtained electrical quantities: electrical resistance and current. One major advantage is that the accuracy of the temperature measurement is not critical to the calculated Peltier coefficient, primarily because of the ratiometric measurement. Crucially, the thermophysical and geometrical properties of the sample are no longer part of the proposed measurement equation under optimal thermal and geometrical conditions. As a demonstration, the Peltier coefficient of a polycrystalline n-type Bi2Te3 sintered sample is measured. The use of an AC current with an amplitude equal to the DC current intensity precisely separates the Joule heating from Peltier heating. The obtained Peltier coefficient agrees well with that calculated from Kelvin’s relation within 3%. Compared with other approaches, the proposed approach requires only one additional AC measurement, which is an accurate and a comparably effortless undertaking. This study aims to significantly advance the development of highly accurate thermoelectric metrology.

Nanobody mediated dual-mode immunoassay for detection of peanut allergen Ara h 3

To improve the performance of peanut allergen Ara h 3 detection, depending on boron and nitrogen carbon dots (B/N-CDs), a nanobody (Nb) mediated dual-mode immunoassay was established, which combines the dominance of colorimetry with ratiometric fluorescence techniques. With the catalysis of Horseradish peroxidase (HRP), the oxidization of o-phenylenediamine (o-PD) in the presence of H2O2, leading to the production of yellow 2,3-diaminophenolazine (DAP) with an absorption peak at 431 nm. Owing to inner filter effect (IFE), DAP quenched the fluorescence of B/N-CDs at 426 nm, and it emerged a new emission peak at 549 nm. The fluorescence intensity ratio and absorption intensity can be utilized for quantitative analysis of Ara h 3 concentration. Under optimal conditions, the detection limits were 6.61 and 9.79 ng·mL−1, respectively. The dual-mode immunoassay was assessed containing specificity, stability, reproducibility, and practicability. This method paved the way for sensitive detection of Ara h 3 without background Interference.

Ratiometric fluorescent sensing of melatonin based on inner filter effect and smartphone established detection

Melatonin (MLT) is a crucial neurohormone having inhibitory effects over various types of cancer. In this work, 3,6-Diaminocarbazole (DAC), a fluorescent probe is utilized to detect MLT in a highly sensitive, selective and facile way. The unique feature of present work is that MLT is sensed by ratiometric fluorescent technique based on the inner filter effect (IFE) using DAC at an emission wavelength of 310 nm. As a result, a noticeable change in color from red to cyan is observed and the quantitative analysis of fluorescence signals at these wavelengths are used to detect MLT observing a linear relationship between the ratio of emission intensities and the concentration of MLT over a linear range of 0 to 78 μM. DAC can accurately measure the detailed quantity of MLT with a limit of detection of 30 nM and has proved to be an efficient sensing probe due to its excellent molar absorptivity and high photoluminescence quantum yield (PLQY). Sensing characterization was carried out UV–Vis, steady-state, and time- resolved fluorescence spectroscopic techniques. The smartphone app “RGB colour detector” value has been successfully linked with the considerable detectable color changes of DAC on addition of MLT. HOMO-LUMO have been calculated using DFT with B3LYP/6-31G(d,p) level and band gaps of 3.77 eV and 4.91 eV were found for DAC and MLT, respectively. Electrons are not allowed energetically to transfer from MLT to DAC, as is evident from their band gaps. Therefore, IFE can be considered the foremost method in fluorescence quenching of present investigation. The developed sensor was verified by spiking of MLT in human serum.

Effective ratiometric optical thermometry based on inverse temperature dependent dual near infrared emission of Cr3+ doped BaAl4Sb2O12 phosphor

The device of reliable non-contact ratiometric optical thermometry technique gradually became a cutting-edge research pot over decades due to its intriguing features of rapid response, high accuracy and simple operation. In which, Boltzmann-based optical thermometry has attracted widespread attention for its exceptional reliability. Here in, we put forward an effective ratiometric optical thermometry based on the highly sensitive and effective Boltzmann-based 2E→4A2/4T2→4A2 emission ratio of BaAl3.9Sb2O12:0.1Cr3+. The phosphor shows dual near-infrared luminescence lines at 698 nm and 710 nm (2E→4A2) and the luminescence band near 750 nm (4T2→4A2). With the temperature elevating from 170 to 470 K, the emission intensity of luminescence lines undergoes continuous enhancement and possess excellent anti-thermal quenching property (3.5-fold at 470 K, compared to 170 K). In contrast, the emission intensity of luminescence band shows a monotonic decline trend. The luminescence intensity ratio shows a good linear relationship in the Arrhenius diagram, and the relative sensitivity reaches 2.08 % K−1 at 170 K, which corroborates the BaAl3.9Sb2O12:0.1Cr3+ has the potential as the optical cryogenic thermometer. In the end, the work provides some insights into the development of novel Cr3+-doped thermometry materials based on the 2E and 4T2 energy level transitions in intermediate crystal field environments.

Dual probe difference specimen imaging for prostate cancer margin assessment.

Positive margin status due to incomplete removal of tumor tissue during radical prostatectomy for high-risk localized prostate cancer requires reoperation or adjuvant therapy, which increases morbidity and mortality. Adverse effects of prostate cancer treatments commonly include erectile dysfunction, urinary incontinence, and bowel dysfunction, making successful initial curative prostatectomy imperative. Current intraoperative tumor margin assessment is largely limited to frozen section analysis, which is a lengthy, labor-intensive process that is obtrusive to the clinical workflow within the operating room (OR). Therefore, a rapid method for prostate cancer margin assessment in the OR could improve outcomes for patients. Dual probe difference specimen imaging (DDSI), which uses paired antibody-based probes that are labeled with spectrally distinct fluorophores, was shown herein for prostate cancer margin assessment. The paired antibody-based probes consisted of a targeted probe to prostate-specific membrane antigen (PSMA) and an untargeted probe, which were used as a cocktail to stain resected murine tissue specimens including prostate tumor, adipose, muscle, and normal prostate. Ratiometric images (i.e., DDSI) of the difference between targeted and untargeted probe uptake were calculated and evaluated for accuracy using receiver operator characteristic curve analysis with area under the curve values used to evaluate the utility of the DDSI method to detect PSMA positive prostate cancer. Targeted and untargeted probe uptake was similar between the high and low PSMA expressing tumor due to nonspecific probe uptake after topical administration. The ratiometric DDSI approach showed substantial contrast difference between the PSMA positive tumors and their respective normal tissues (prostate, adipose, muscle). Furthermore, DDSI showed substantial contrast difference between the high PSMA expressing tumors and the minimally PSMA expressing tumors due to the ratiometric correction for the nonspecific uptake patterns in resected tissues. Previous work has shown that ratiometic imaging has strong predictive value for breast cancer margin status using topical administration. Translation of the ratiometric DDSI methodology herein from breast to prostate cancers demonstrates it as a robust, ratiometric technique that provides a molecularly specific imaging modality for intraoperative margin detection. Using the validated DDSI protocol on resected prostate cancers permitted rapid and accurate assessment of PSMA status as a surrogate for prostate cancer margin status. Future studies will further evaluate the utility of this technology to quantitatively characterize prostate margin status using PSMA as a biomarker.

Quantitative Ratiometric Biosensors Based on Fluorescent Ferrocene-Modified Histidine Dipeptide Nanoassemblies.

Fluorescent proteins (FPs) provide a ratiometric readout for quantitative assessment of the destination of internalized biomolecules. FP-inspired peptide nanostructures that can compete with FPs in their capacity are the most preferred building blocks for the synthesis of fluorescent soft matter. However, realizing a ratiometric emission from a single peptide fluorophore remains exclusive since multicolor emission is a rare property in peptide nanostructures. Here, we describe a bioinspired peptidyl platform for ratiometric intracellular quantitation by employing a single ferrocene-modified histidine dipeptide. The intensiometric ratio of green to blue fluorescence correlates linearly with the concentration of the peptide by three orders of magnitude. The ratiometric fluorescence of the peptide is an assembly-induced emission originating from hydrogen bonds and aromatic interactions. Additionally, modular design enables ferrocene-modified histidine dipeptides to use as a general platform for the construction of intricate peptides that retain the ratiometric fluorescent properties. The ratiometric peptide technique promises flexibility in the design of a wide spectrum of stoichiometric biosensors for quantitatively understanding the trafficking and subcellular fate of biomolecules.

Two-photon ratiometric imaging of endogenous reactive inorganic sulfur species in the cellular cushion toward formaldehyde

To address the potential biological relationship between reactive inorganic sulfur species (RISSs) and formaldehyde, the novel two-photon ratiometric RISSs probes (PH-RISSs) were synthesized practically with high selectivity and sensitivity toward RISSs and the related two-photon microscopic imaging assay was established which could be employed in the interpretation of the potential interaction between RISSs and formaldehyde. It was disclosed that the level of RISSs would raise toward formaldehyde and this behavior could be prohibited by CSE (cystathionine gamma lyase) inhibitor and reactive oxygen species (ROS) inhibitor, which indicated that formaldehyde could facilitate the metabolism of biothiols by CSE and this motivation of RISSs should be related with ROS intimately. Thus, RISSs might provide the critical biological compensation toward formaldehyde in a short term for living system and this two-photon ratiometric technique could be a practical tool to understand further the detailed interaction between aldehydes and RISSs in living systems.

Mitochondria-Targetable Ratiometric Time-Gated Luminescence Probe Activated by Selenocysteine for the Visual Monitoring of Liver Injuries.

Liver injury can result from various risk factors including diabetes, virus, alcohol, drugs, and other toxins, which is mainly responsible for global mortality and morbidity. Selenocysteine (Sec), as the main undertaker of selenium function in the life system, features prominently in a series of hepatic injuries and has close association with the pathological progression of liver injuries. Here, we report a mitochondria-targetable lanthanide complex-based probe, Mito-NPTTA-Tb3+/Eu3+, that can be used for accurately determining Sec in live cells and laboratory animals via the ratiometric time-gated luminescence (TGL) technique. This probe is composed of 2,2':6',2″-terpyridine-Tb3+/Eu3+ mixed complexes as the luminophore, 2,4-dinitrophenyl (DNP) as the responsive moiety and a lipophilic triphenylphosphonium cation (PPh3+) as the mitochondria-targeting moiety. Upon reaction with Sec, accompanied by the cleavage of DNP from the probe molecule, the I540/I690 ratio of the probe increased by 55 times, which enabled Sec to be detected with the ratiometric TGL method. After being incubated with living cells, the probe molecules were selectively accumulated in mitochondria to allow the mitochondrial Sec to be successfully imaged under the ratiometric TGL mode. Importantly, using this probe coupled with the ratiometric TGL imaging technique, the fluctuations of liver Sec in various liver injuries of model mice induced by diabetes, drug, toxin, and alcohol were precisely monitored, revealing that Sec plays an important antioxidant role during the oxidative stress process in liver injury, and the Sec levels have a close interrelationship with the degree of liver injury. All the results suggest that the new probe Mito-NPTTA-Tb3+/Eu3+ could be a potential tool for the accurate diagnosis of liver injury.

Dual-responsive ratiometric fluorescence detection of Ce4+ and ascorbic acid by regulating oxidase-mimicking activity of Ce4+-based nanocomplex

Herein, a dual-responsive ratiometric fluorescence sensor was developed for highly sensitive and accurate detection of Ce4+ and ascorbic acid (AA) by regulating oxidase-mimicking activity of Ce4+-based nanocomplex. Complexing with fluorescent polydopamine nanoparticles (FPDA NPs) and N-2-hydroxyethylpiperazine-N′-ethanesulfonic acid (HEPES) buffer was demonstrated to enhance the oxidase-mimicking activity of Ce4+, which greatly boosted the catalytic oxidization of 1,2-diaminobenzene (OPD) into fluorescent 2,3-diaminophenazine (DAP) with yellow emission. Meanwhile, the fluorescence of FPDA NPs with blue emission was effectively quenched owing to electron transfer effect and the inner filter effect. Contrastingly, with addition of AA, Ce4+ was chemically reduced to Ce3+ that without oxidase-mimicking activity and quenching property to FPDA NPs. Thus, the emission ratio of DAP to FPDA NPs should act as signal output for Ce4+ and AA detection. Benefiting from the dual-responsive ratiometric fluorescence technique with reverse change profile and the controllably catalytic oxidation activity of the nanocomplex, good performances for Ce4+ and AA detection in solution and in practical samples were achieved. This work not only expands the fluorescence sensing application of FPDA NPs but also offered a new sight for artificial enzymes research.

Activation of Piezo1 Increases Na,K-ATPase-Mediated Ion Transport in Mouse Lens.

Lens ion homeostasis depends on Na,K-ATPase and NKCC1. TRPV4 and TRPV1 channels, which are mechanosensitive, play important roles in mechanisms that regulate the activity of these transporters. Here, we examined another mechanosensitive channel, piezo1, which is also expressed in the lens. The purpose of the study was to examine piezo1 function. Recognizing that activation of TRPV4 and TRPV1 causes changes in lens ion transport mechanisms, we carried out studies to determine whether piezo1 activation changes either Na,K-ATPase-mediated or NKCC1-mediated ion transport. We also examined channel function of piezo1 by measuring calcium entry. Rb uptake was measured as an index of inwardly directed potassium transport by intact mouse lenses. Intracellular calcium concentration was measured in Fura-2 loaded cells by a ratiometric imaging technique. Piezo1 immunolocalization was most evident in the lens epithelium. Potassium (Rb) uptake was increased in intact lenses as well as in cultured lens epithelium exposed to Yoda1, a piezo1 agonist. The majority of Rb uptake is Na,K-ATPase-dependent, although there also is a significant NKCC-dependent component. In the presence of ouabain, an Na,K-ATPase inhibitor, Yoda1 did not increase Rb uptake. In contrast, Yoda1 increased Rb uptake to a similar degree in the presence or absence of 1 µM bumetanide, an NKCC inhibitor. The Rb uptake response to Yoda1 was inhibited by the selective piezo1 antagonist GsMTx4, and also by the nonselective antagonists ruthenium red and gadolinium. In parallel studies, Yoda1 was observed to increase cytoplasmic calcium concentration in cells loaded with Fura-2. The calcium response to Yoda1 was abolished by gadolinium or ruthenium red. The calcium and Rb uptake responses to Yoda1 were absent in calcium-free bathing solution, consistent with calcium entry when piezo1 is activated. Taken together, these findings point to stimulation of Na,K-ATPase, but not NKCC, when piezo1 is activated. Na,K-ATPase is the principal mechanism responsible for ion and water homeostasis in the lens. The functional role of lens piezo1 is a topic for further study.