Development of a fluorescence immunochromatography method for quantitative measurement of matrix metalloproteinase-9

Objective

Abnormal serum matrix metalloproteinase-9 (MMP-9) levels are closely related to the occurrence and development of many diseases. This study aimed to establish a fluorescence immunochromatography (FIC) method using the lanthanide fluorescent element europium(III) (Eu3+) for the quantitative measurement of MMP-9 in serum.

Design & Methods

The FIC method for quantifying MMP-9 was optimized and established, and the FIC test strips (FICTS) were assembled and subsequently evaluated for sensitivity, specificity and precision. Furthermore, the reference interval and clinical sensitivity/specificity were estimated using clinical healthy/positive serum samples, and a commercial ELISA was used for comparison.

Results

We successfully established an FIC method and prepared FICTS. The analytical sensitivity of the FICTS was 0.92 ng/mL, with a linearity range of 0-1000 ng/mL. The cross-reactivity of the 7 common serum interferents was less than 1.56%. All recoveries of the intra-array and inter-array samples ranged from 102.50% to 110.99%, and all CVs were less than 5%. The reference interval of the FICTS was >161.15 ng/mL. The clinical sensitivity was 96.00%, and the specificity was 97.5%. The results of 270 clinical serum samples were highly coincident with the clinical diagnostic results. Pearson correlation analysis and Bland‒Altman plots indicated that the FICTS and commercial ELISA results were consistent with the quantitative MMP-9 concentration.

Conclusions

The designed FIC method and test strips may be suitable for point-of-care quantitative measurement of MMP-9, which provides a new method for screening for atherosclerosis, xerophthalmia, etc.

The Detection of Anthrax Biomarker DPA by Ratiometric Fluorescence Probe of Carbon Quantum Dots and Europium Hybrid Material Based on Poly(ionic)- Liquid

Bacillus anthracis has gained international attention as a deadly bacterium and a potentially deadly biological warfare agent. Dipicolinic acid (DPA) is the main component of the protective layer of anthracis spores, and is also an anthrax biomarker. Therefore, it is of great significance to explore an efficient and sensitive DPA detection method. Herein, a novel ratio hybrid probe (CQDs-PIL-Eu3+) was prepared by a simple one-step hydrothermal method using carbon quantum dots (CQDs) as an internal reference fluorescence and a covalent bond between CQDs and Eu3+ by using a polyionic liquid (PIL) as a bridge molecule. The ratiometric fluorescence probe was found to have the characteristics of sensitive fluorescence visual sensing in detecting DPA. The structure and the sensing properties of CQDs-PIL-Eu3+ were investigated in detail. In particular, the fluorescence intensity ratio of Eu3+ to CQDs (I616/I440) was linear with the concentration of DPA in the range of 0-50 μM, so the detection limit of the probe was as low as 32 nm, which was far lower than the DPA dose released by the number of anthrax spores in human body (60 μM) and, thus, can achieve sensitive detection. Therefore, the ratiometric fluorescence probe in this work has the characteristics of strong anti-interference, visual sensing, and high sensitivity, which provides a very promising scheme for the realization of anthrax biomarker DPA detection.

Photoluminescent and Scintillating Performance of Eu3+-Doped Boroaluminosilicate Glass Scintillators

In comparison with single crystal scintillators, glass scintillators are more promising materials for their benefits of easy preparation, low cost, controllable size, and large-scale manufacture. The emission of Eu³⁺ ion at 612 nm matches well with the photoelectric detector, making it suitable for the activator in glass scintillators. Therefore, the research on Eu³⁺ doped glass scintillators attract our attention. The photoluminescent and scintillating properties of Eu³⁺-activated boroaluminosilicate glass scintillators prepared by the conventional melt-quenching method were investigated in this work. The glass samples present good internal quantum yield. Under X-ray radiation, the optimal sample reveals high X-ray excited luminesce (XEL), and its integrated intensity of XEL is 22.7% of that of commercial crystal scintillator Bi₄Ge₃O₁₂. Furthermore, the optimal specimen possesses a spatial resolution of 14 lp/mm in X-ray imaging. These results suggest that Eu³⁺-doped boroaluminosilicate glass is expected to be applied in X-ray imaging.

Eu3+ -activated red phosphor Ca3 YAl3 B4 O15 with low thermal quenching behaviour

This paper reports a sequence of a Ca₃ YAl₃ B₄ O₁₅ :xEu³⁺ red phosphor prepared using a high-temperature solid-state reaction. At the excitation of 396 nm, the samples emitted intense red emission centred at ~623 nm, which could be attributed to the ⁵ D₀ →⁷ F₂ transition of the Eu³⁺ ion. The results showed that the optimum Eu³⁺ doping concentration of Ca₃ YAl₃ B₄ O₁₅ :Eu³⁺ phosphor was x = 80 mol%, and the concentration quenching mechanism of Ca₃ YAl₃ B₄ O₁₅ :Eu³⁺ red phosphor belonged to the exchange coupling between Eu³⁺ ions. The Commission Internationale de l'éclairage (CIE) coordinates and colour purity of Ca₃ Y_0.2 Al₃ B₄ O₁₅ :0.8Eu³⁺ were calculated as (0.6375, 0.3476) and 95.5%, respectively. Moreover, the red emission of the obtained phosphor Ca₃ YAl₃ B₄ O₁₅ :0.8Eu³⁺ exhibited a low thermal quenching behaviour with an intensity retention rate of 92.85% at 150°C. The above results manifest that the Eu³⁺ -activated Ca₃ YAl₃ B₄ O₁₅ phosphor is predicted to be a promising red luminescent component for white light-emitting diodes.

Smart Mn7+ Sensing via Quenching on Dual Fluorescence of Eu3+ Complex-Modified TiO2 Nanoparticles

In this work, titania (TiO₂) nanoparticles modified by Eu(TTA)₃Phen complexes (ETP) were prepared by a simple solvothermal method developing a fluorescence Mn⁷⁺ pollutant sensing system. The characterization results indicate that the ETP cause structural deformation and redshifts of the UV-visible light absorptions of host TiO₂ nanoparticles. The ETP also reduce the crystallinity and crystallite size of TiO₂ nanoparticles. Compared with TiO₂ nanoparticles modified with Eu³⁺ (TiO₂-Eu³⁺), TiO₂ nanoparticles modified with ETP (TiO₂-ETP) exhibit significantly stronger photoluminescence under the excitation of 394 nm. Under UV excitation, TiO₂-ETP nanoparticles showed blue and red emission corresponding to TiO₂ and Eu³⁺. In addition, as the concentration of ETP in TiO₂ nanoparticles increases, the PL intensity at 612 nm also increases. When ETP-modified TiO₂ nanoparticles are added to an aqueous solution containing Mn⁷⁺, the fluorescence intensity of both TiO₂ and ETP decreases. The evolution of the fluorescence intensity ratio (I₁/I₂) of TiO₂ and ETP is linearly related to the concentration of Mn⁷⁺. The sensitivity of fluorescence intensity to Mn⁷⁺ concentration enables the design of dual fluorescence ratio solid particle sensors. The method proposed here is simple, accurate, efficient, and not affected by the environmental conditions.

Construction of Core-Shell MOFs@COF Hybrids as a Platform for the Removal of UO22+ and Eu3+ Ions from Solution

The binary nanocomposites of metal/covalent-organic frameworks (NH₂-MIL-125(Ti)@TpPa-1) were constructed by solvothermal method, which was developed as a multifunctional platform with adsorption and photocatalysis for radionuclides removal. The batch experiments and physicochemical property (FT-IR, XRD, SEM, TEM, XPS, etc.) corroborated: (i) core-shell NH₂-MIL-125(Ti)@TpPa-1 had a more stable, multilayer pore structure and abundant active functional groups; (ii) NH₂-MIL-125(Ti)@TpPa-1 had fast a removal rate, as well as a high adsorption capacity of 536.73 mg (UO₂²⁺)/g and 593.97 mg (Eu³⁺)/g; (iii) the pseudo-second-order and Langmuir model provided a more reasonable description, indicating the immobilization process was endothermic, spontaneous chemisorption; (iv) the adsorption mechanism was chelation and electrostatic attraction, ascribed to the nitrogen/oxygen-containing functional groups. These results illustrated that NH₂-MIL-125(Ti)@TpPa-1 was a prospective adsorbent for the remediation polluted by radionuclides. In addition, the research provided the theoretical basis for further investigation on the UO₂²⁺(VI) photoreduction.

Novel Multicomponent Titanate-Germanate Glasses: Synthesis, Structure, Properties, Transition Metal, and Rare Earth Doping

Novel multicomponent titanate-germanate glasses singly doped with transition metal (Cr³⁺) and rare earth ions (Eu³⁺) were synthesized and the glass transition temperatures and thermal stability parameters were determined using DSC measurements. X-ray diffraction analysis confirmed fully amorphous nature of the received samples. Their structural and optical properties were compared with germanate glasses without TiO₂. Correlation between local structure and optical properties in titanate-germanate glasses is well evidenced by FT-IR, Raman, EPR, and luminescence spectroscopy. In particular, luminescence spectra and their decays are examined for glass samples, where GeO₂ was partially substituted by TiO₂.

Synthesis, Structure, Morphology, and Luminescent Properties of Ba2MgWO6: Eu3+ Double Perovskite Obtained by a Novel Co-Precipitation Method

Eu³⁺ doped Ba₂MgWO₆ (BMW) double-perovskite was successfully synthesized for the first time by the co-precipitation method. The synthesis procedure, crystal structure, as well as morphology of obtained samples are presented. Domination of the ⁵D₀-⁷F₁ magnetic-dipole over forced electric-dipole transitions in the emission spectra indicates that Eu³⁺ ions are located in the high symmetry site with inversion center. Only one emission line assigned to the ⁵D₀-⁷F₀ transition was observed, confirming that europium substituted for only one host cation site. The photoluminescence excitation (PLE) spectrum is dominated by a strong and broad band related to the O^2- → Eu³⁺ and O^2- → W⁶⁺ charge transfer. The decay of the emission from the ⁵D₀ and ⁵D₁ levels was investigated. The temperature-dependent emission spectra showed that the T_0.5 is equal to 350 K. Extinguishing mechanisms of the Eu³⁺ luminescence in the studied host are discussed.

TemperatureDependent Luminescence of RedEmitting Ba2Y5B5O17: Eu3+ Phosphors with Efficiencies Close to Unity for NearUV LEDs

Solid state white light sources based on a near-UV LED chip are gaining more and more attention. This is due to the increasing efficiency of near-UV-emitting LED chips and wider phosphors selection if compared to devices based on blue LED chips. Here, a brief overview is given of the concepts of generating white light employing near-UV LED and some optical properties of the available phosphors are discussed. Finally, the synthesis and optical properties of very efficient red-emitting Ba₂Y₅B₅O₁₇:Eu³⁺ phosphor powder and ceramics is reported and discussed in terms of possible application as a red component in near-UV LED-based white light sources.

Synthesis, Luminescence, and Energy Transfer Properties of YPO4:Gd3+, Eu3+ and YP3O9:Sm3+, Eu3+ Phosphors

This work is concerned with the search for new luminescent materials emitting in the orange-red color. We have synthesized YPO₄ doped with Gd³⁺0.25% and/or Eu³⁺0.50% by hydrothermal method and YP₃O₉ doped with Sm³⁺0.25% and/or Eu³⁺0.50% by ultraphosphate decomposition reaction. Phase purity was checked by FTIR and XRD. Excitation and emission spectra and fluorescence decay measurements were recorded at room temperature (RT). Emission spectra allow to determine the site symmetry of rare earth (RE³⁺) in the crystallographic structure of matrices. Weak Eu³⁺ emission is detected from YPO₄:Gd³⁺, Eu³⁺ under excitation at 273 nm. Sm³⁺ levels were detected in excitation spectrum of YP₃O₉:Sm³⁺, Eu³⁺ monitoring Eu³⁺ principal emission at 618 nm. Excited states lifetimes of Gd³⁺ and Sm³⁺ sensitizers (S) decrease from mono-doped to co-doped matrices indicating an Energy transfers (ET) from S to Eu³⁺ with a rate higher than 19%.

Tb3+, Eu3+ Co-doped CsPbBr3 QDs Glass with Highly Stable and Luminous Adjustable for White LEDs

Herein, we have introduced rare-earth cations Tb³⁺ and Eu³⁺ into CsPbBr₃ QDs glass by conventional melt-quenching. Rare-earth cations like Tb³⁺ emit green light, causing the main peak of bromide lead cesium to exhibit some redshift, owing to the energy transfer between CsPbBr₃ and Tb³⁺. To achieve adjustable light, Eu³⁺ emits red light, which was doped in this glass with different proportions to solve the problem of red deficiency. More importantly, Tb³⁺ and Eu³⁺ co-doped CsPbBr₃ QDs glass shows a series of desirable characteristics due to the energy transfer between Tb³⁺ and Eu³⁺. Interestingly, the blue light radiated by blue chip can excite Tb³⁺, Eu³⁺, and CsPbBr₃ perovskite effectively. We acquired high-performance white light-emitting diodes with color-rendering index, color coordinate transformation, and luminous efficiency of 85.7, 4945 K, and 63.21 lm/W under the current of 20 mA. This acquired Tb³⁺, Eu³⁺ co-doped CsPbBr₃ QDs glass proved the significant feasibility of luminescent materials in solid warm light source.

Colorimetric chiral fluorescent sensors for Eu3+ and sequential enantioselective sensing of malate anion

Novel phenanthroline Schiff base fluorescent sensors L1, L2, and D1 were designed and synthesized. The sensing abilities of the compounds in the presence of metal cations (Li⁺ , Na⁺ , K⁺ , Ag⁺ , Mg²⁺ , Ba²⁺ , Ca²⁺ , Mn²⁺ , Pb²⁺ , Hg²⁺ , Ni²⁺ , Zn²⁺ , Cd²⁺ , Co²⁺ , Cu²⁺ , Cr³⁺ , Fe³⁺ , Fe²⁺ , Al³⁺ , and Eu³⁺ ) were studied by UV-vis and fluorescent spectroscopy. The compounds L1, L2, and D1 could act as Eu³⁺ ion turn-off fluorescent sensors based on ligand-to-metal binding mechanism in DMSO-H₂ O solution (v/v = 1:1, 10 mM Tris, pH = 7.4). Additionally, the L1-Eu³⁺ and D1-Eu³⁺ complexes could be applied as turn-on enantioselective sensors sensing of malate anion isomers with color changes. Furthermore, biological experiments using living PC-12 cells demonstrated that L1 and D1 had excellent membrane permeability and could be used as effective fluorescent sensors for detecting Eu³⁺ and malate anion in living cells.

Synthesis and Properties of the La1 - x - y Eu y Ca x VO4 (0 ≤ x, y ≤ 0.2) Compounds

The La_1 - x Ca _x VO₄ and La_{1 - x - y} Eu _y Ca _x VO₄ (0 ≤ x, y ≤ 0.2) micro/nanosized powders were prepared by aqueous nitrate-citrate sol-gel synthesis. Phase composition of the sample depends on the x and y values. The La_0.9Ca_0.1VO₄ is crystallized in monoclinic structure up to the x = 0.1. The La_0.9Eu_0.05Ca_0.05VO₄ sample was also attributed to the monoclinic structure. Increasing concentration of europium and calcium ions in La_{1 - x - y}Eu _y Ca _x VO₄ solid solutions leads to the change of the crystal structure, and subsequently, stabilization of the tetragonal phase takes place.The obtained samples were characterized by XRD analysis, SEM microscopy, and IR spectroscopy. Luminescence properties of the synthesized powders were studied. Emission of the La_1 - x Ca _x VO₄ samples is weak and consists of wide bands in the 450-800 nm spectral range. The observed bands at 570 and 630 were ascribed to electron transitions in the distorted VO₄^3- vanadate groups. Emission of the La_{1 - x - y} Eu _y Ca _x VO₄ samples consists of narrow spectral lines in the 550-730 nm spectral range. The lines are caused by the ⁵D₀ → ⁷F_J electron transitions in the Eu³⁺ ions. The Ca²⁺ ions incorporation increases the intensity of the Eu³⁺ ions luminescence. Structure of the spectra depends on Ca²⁺ concentration and excitation wave length. The carried out analysis has revealed that Eu³⁺ ions form at least two different types of emission centers in the La_{1 - x - y} Eu _y Ca _x VO₄ samples. The assumption is made that type I centers are formed by the Eu³⁺ ions in their regular positions in the crystal lattice, while the type II centers have complex structure and consist of Eu³⁺ ions, Ca²⁺ cations, and oxygen vacancies.

Synthesis and Optical Properties of Novel Red-Emitting PbNb2O6: Eu(3+) Phosphors

Undoped and PbNb2O6:Eu(3+) (1.0 ≤ x ≤ 6.0 mol%) phosphors were synthesized at 1100 °C for 3.5 h by the conventional solid state reaction method. Synthesized PbNb2O6:Eu(3+) phosphors were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and Photoluminescence (PL) analyses. The PL spectra showed series of excitation peaks between 350 and 430 nm due to the 4f-4f transitions of Eu(3+). For 395.0 nm excitation, emission spectra of Eu(3+) doped samples were observed at 591 nm (orange) and 614 nm (red) due to the (5)D0 → (7)F1 transitions and (5)D0 → (7)F2 transitions, respectively. PL analysis results also showed that the emission intensity increased by increasing Eu(3+) ion content. No concentration quenching effect was observed. The CIE chromaticity color coordinates (x,y) of the PbNb2O6:Eu(3+) phosphors were found to be in the red region of the chromaticity diagram.

Temperature-controlled down-conversion luminescence behavior of Eu3+ -doped transparent MF2 (M = Ba, Ca, Sr) glass ceramics

Eu³⁺ -doped transparent glass ceramics containing MF₂ (M = Ba, Ca, Sr) nanocrystals were fabricated using a melt-quenching method, and the resulting structures were studied using X-ray diffraction. Levels ⁵ D₁ and ⁵ D₀ of Eu³⁺ ions were verified as thermally coupled levels using the fluorescence intensity ratio method. The fluorescence intensity ratios, optical temperature sensitivity and thermal quenching ratios of the transparent glass ceramics were studied as a function of temperature. With an increase in temperature, the relative sensitivity (S_R ) decreased sharply at first, then slowly increased, before finally decreasing. The minimum S_R values of GCBaF₂ (GCB), GCCaF₂ (GCC) and GCSrF₂ (GCS) were 2.8 × 10^-4 , 0.8 × 10^-4 and 1.9 × 10^-4  K^-1 at 360, 269 and 319 K, respectively. Glass ceramics with an intense emission intensity can be used to convert the measured spectrum into temperature and may have an important role in temperature detectors.

Enhanced Luminescence of Eu-Doped TiO2Nanodots

Monodisperse and spherical Eu-doped TiO2nanodots were prepared on substrate by phase-separation-induced self-assembly. The average diameters of the nanodots can be 50 and 70 nm by changing the preparation condition. The calcined nanodots consist of an amorphous TiO2matrix with Eu3+ions highly dispersed in it. The Eu-doped TiO2nanodots exhibit intense luminescence due to effective energy transfer from amorphous TiO2matrix to Eu3+ions. The luminescence intensity is about 12.5 times of that of Eu-doped TiO2film and the luminescence lifetime can be as long as 960 μs.