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Manganese-Enhanced MRI for Preclinical Evaluation of Retinal Degeneration Treatments
摘要： PURPOSE. Apply manganese-enhanced magnetic resonance imaging (MEMRI) to assess ion channel activity and structure of retinas from mice subject to light-induced retinal degeneration treated with prophylactic agents. METHODS. Abca4?/?Rdh8?/? double knockout mice with and without prophylactic retinylamine (Ret-NH2) treatment were illuminated with strong light. Manganese-enhanced MRI was used to image the retina 2 hours after intravitreous injection of MnCl2 into one eye. Contrast-enhanced MRIs of the retina and vitreous humor in each experimental group were assessed and correlated with the treatment. Findings were compared with standard structural and functional assessments of the retina by optical coherence tomography (OCT), histology, and electroretinography (ERG). RESULTS. Manganese-enhanced MRI contrast in the retina was high in nonilluminated and illuminated Ret-NH2–treated mice, whereas no enhancement was evident in the retina of the light-illuminated mice without Ret-NH2 treatment (P < 0.0005). A relatively high signal enhancement was also observed in the vitreous humor of mice treated with Ret-NH2. Strong MEMRI signal enhancement in the retinas of mice treated with retinylamine was correlated with their structural integrity and function evidenced by OCT, histology, and a strong ERG light response. CONCLUSIONS. Manganese-enhanced MRI has the potential to assess the response of the retina to prophylactic treatment based on the measurement of ion channel activity. This approach could be used as a complementary tool in preclinical development of new prophylactic therapies for retinopathies.
关键词： manganese-enhanced MRI,efficacy evaluation,retinal degeneration,retinylamine
更新于2025-09-23 15:22:29
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Artificial Mn4Ca-cluster with Exchangeable Solvent Molecules Mimicking the Oxygen-Evolving Center in Photosynthesis
摘要： The natural Mn4Ca-cluster in photosystem II serves as a blueprint to develop artificial water-splitting catalysts in artificial photosynthesis. Although significant advances have recently been achieved, it remains great challenges to prepare robust artificial Mn4Ca-cluster to precisely mimic the structure and function of the biological catalyst in the laboratory. Here, we report the isolation and structural characterization of two Mn4CaO4-complexes from polar solvents acetonitrile or N, N-dimethylformamide, which closely mimics the two water molecules on calcium ion, as well as, the oxidation states of the four manganese ions and the main geometric structure of the natural Mn4Ca-cluster. These new artificial Mn4Ca-complexes provide important chemical clues to understand the structure and mechanism of its biological paragon.
关键词： bioinorganic chemistry,photosynthesis,manganese,heterometallic complexes,water splitting
更新于2025-09-23 15:22:29
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Spectrophotometric determination of manganese in acidified matrices from (pore)waters and from sequential leaching of sediments
摘要： Manganese (Mn) is a major redox reactive element in marine sediments and it plays an important role in the biogeochemical cycles of carbon, nitrogen, phosphorus, or trace metals. Mn cycle in marine sediments is characterized by an alternation of oxidation and reduction processes depending on physicochemical and biological conditions: assessing the quantification and the speciation of Mn is thus an essential issue to understand redox reaction-transport processes in sedimentary deposits. Solid Mn phases can be determined through chemical extractions techniques that permits selective leaching of operationally defined Mn fractions. Mn oxides and oxyhydroxides are extracted with an ascorbate leaching solution, while the whole Mn (oxyhydr-)oxides and Mn associated to carbonates is extracted with HCl. An existing spectrophotometric method allows to quantify Mn dissolved in (sea) water. We present here a modified version, which permits to measure Mn in acidified matrices, including ascorbate and HCl solutions. A metallic substitution occurs between a Cd-TCPP complex and Mn at pH 7.5–8.0, with imidazole as catalyst. We propose here to use a NaHCO3 solution to dilute the samples in order to be in the necessary pH range to perform the metal substitution. Using this method, Mn(II,III) concentrations were determined in standard solutions with a precision of 3% within a concentration range of 0.5–80 μM. The procedure was successfully applied to determine Mn in acidified pore waters and in ascorbate and HCl sequential extractions from muddy sediments of the Bay of Biscay. Spectrophotometric results agreed closely with results from atomic absorption spectrometry, validating the proposed method.
关键词： Sediment,Acidified matrices,Sequential leaching,Spectrophotometric method,Manganese
更新于2025-09-23 15:22:29
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Smart NIR-Light-Mediated Nanotherapeutic Agents for Enhancing Tumor Accumulation and Overcoming Hypoxia in Synergistic Cancer Therapy
摘要： The efficacy of photodynamic therapy (PDT) still shows limited success in clinical application due to hypoxia in the solid tumor, low tumor accumulation and limited light penetration depth of photosensitizers (PS). The previously reported MnO2-based nanotherapeutic agents always required intratumoral injection or complex targeting modification process to improve the therapeutic efficacy. Herein, new MnO2-based nanotherapeutic agents (honeycomb MnO2/IR780/BSA nanoparticles, HMIB NPs) are designed and prepared to achieve excellent phototherapeutic performance characterized by NIR-light-mediation, deep diffusion via TME response and O2 self-supply. The ex vivo and in vivo NIR fluorescence imaging results demonstrate that the honeycomb nanostructure of HMIB NPs facilitates the high tumor accumulation of hydrophobic IR780 via enhanced permeability and retention (EPR) effect after intravenous injection. The immunofluorescence results demonstrate that the TME response of HMIB NPs not only provides O2 for relieving hypoxia but also reduces size for improving deep intratumoral diffusion. As a result, under the synergy of NIR fluorescence imaging, photothermal effect and PDT of IR780 with TME responsive size-change and O2 self-supply of honeycomb MnO2, the HMIB NPs have achieved all-in-one NIR fluorescence and photothermal dual-model imaging guided synergistic PDT/PTT under a single-wavelength NIR light irradiation.
关键词： nanotherapeutic agents,tumor microenvironment responsive degradation,photodynamic therapy,hypoxia,honeycomb manganese dioxide
更新于2025-09-23 15:22:29
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Optical Properties and Electron Paramagnetic Resonance of MnO2-Doped Fluorozirconate Glasses
摘要： We have studied luminescence and electron paramagnetic resonance (EPR) spectra of manganese-activated fluorozirconate glasses. In ZrF4–BaF2–LaF3–AlF3–NaF (ZBLAN) glasses, manganese gives a green luminescence band peaking at 545 nm. Partial chlorine substitution for fluorine in the glass leads to a shift and broadening of the luminescence band. Complete BaCl2 substitution for BaF2 in ZBLAN?Cl? fluoride chloride glass increases the peak emission wavelength to 610 nm. The observed distinctions between the EPR spectra of the Mn-doped ZBLAN and ZBLAN?Cl? glasses correlate with those between their luminescence spectra. The effect of chlorine substitution for fluorine on the luminescence and EPR spectra of the fluorozirconate glass is tentatively attributed to a change in the oxidation state of the manganese ions.
关键词： doping,fluorozirconate glasses,luminescence,manganese ion,electron paramagnetic resonance
更新于2025-09-23 15:21:21
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Photoluminescence of (Zn, Pb, Mn)S Quantum Dots in Polyacrylate Matrix
摘要： Solutions of (Zn, Pb, Mn)S quantum dots with different molar ratios between cations are produced by colloidal synthesis in a methyl methacrylate (MMA) medium. By the thermal polymerization of MMA in a block, the colloidal solutions are converted into the vitreous state. The optical transparency of the poly(MMA)/(Zn, Pb, Mn)S composites at the wavelengths >500 nm reaches 90% at a thickness of the absorbing layer up to 5 mm. The photoluminescence of the composites in the spectral range 400–480 nm is defined by the recombination of electrons at the levels of defects of the ZnS crystal structure, and photoluminescence in the range 520–620 nm by the 4T1 → 6A1 electronic transition in Mn2+ ions. Photoluminescence excitation is a result of interband transitions in ZnS, with energy transfer from the conduction band of ZnS to the levels of Mn2+ ions. The luminescence spectrum depends on the molar ratio between Mn2+ and Pb2+ ions, the order of introduction of substances into the reaction mixture, and the excitation-radiation wavelength.
关键词： acrylate composites,lead ions,doping,luminescence,manganese ions,zinc sulfide,quantum dots
更新于2025-09-23 15:21:01
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Manganese doping stabilizes perovskite light-emitting diodes by reducing ion migration
摘要： Lead halide perovskite light-emitting diodes have recently emerged as high-performance devices. However, they degrade rapidly. This degradation has been attributed to the mixed ionic-electronic nature of these perovskites. Manganese doping increases the stability of perovskite light-emitting diodes, but the effects of manganese doping on ion migration are not well understood. We use impedance spectroscopy and transient ion-drift measurements to study the effect of manganese doping on ion migration in PEABr0.2Cs0.4MA0.6PbBr3 quasi-bulk 2D/3D perovskite light-emitting diodes. We find that manganese doping enhances the activation energy for ion migration two fold and reduces the diffusion coefficient. These changes in the behavior of mobile ions help to explain the improved stability in perovskite light-emitting diodes upon manganese doping and lead to a better understanding of the influence of passivating agents on ion migration and thus on the stability of the devices.
关键词： capacitance,perovskites,manganese,mobile ions,transient ion drift,impedance,light-emitting diodes
更新于2025-09-23 15:21:01
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A sensitive immunoassay for simultaneous detection of foodborne pathogens using MnO2 nanoflowers-assisted loading and release of quantum dots
摘要： In this study, a sensitive immunoassay using immunomagnetic nanobeads (MNBs), manganese dioxide nanoflowers (MnO2 NFs) and quantum dots (QDs) was developed for simultaneous detection of E. coli O157: H7 and Salmonella typhimurium. MnO2 NFs were synthesized, functionalized and incubated with QDs to obtain QDs@MnO2 nanocomposites, followed by modification with antibodies (pAbs) to obtain pAb-QDs@MnO2 nanocomposites (QM NCs). Target bacteria were first conjugated with MNBs and QM NCs to form MNB-bacteria-QM complexes. Then, QDs were quickly released from the complexes using glutathione to reduce MnO2 to Mn2+. Finally, fluorescent intensity at characteristic wavelength was measured by optical detector to determine target bacteria. This immunoassay could simultaneously and quantitatively detect E. coli from 1.5 × 101 to 1.5 × 106 CFU/mL with detection limit of 15 CFU/mL and Salmonella from 4.0 × 101 to 4.0 × 106 CFU/mL with detection limit of 40 CFU/mL in 2 h. The mean recovery for both bacteria in spiked chicken samples was ～96%.
关键词： Pathogenic bacteria,Quantum dots,Simultaneous detection,Manganese dioxide nanoflowers,Fluorescent immunoassay
更新于2025-09-23 15:21:01
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Improvement of Power Conversion Efficiency of Quantum Dot-Sensitized Solar Cells by Doping of Manganese into a ZnS Passivation Layer and Cosensitization of Zinc-Porphyrin on a Modified Graphene Oxide/Nitrogen-Doped TiO <sub/>2</sub> Photoanode
摘要： It is vital to acquire power conversion efficiencies comparable to other emerging solar cell technologies by making quantum dot-sensitized solar cells (QDSSCs) competitive. In this study, the effect of graphene oxide (GO), nitrogen, manganese, and a porphyrin compound on the performance of QDSSCs based on a TiO2/CdS/ZnS photoanode was investigated. First, adding GO and nitrogen into TiO2 has a conspicuous impact on the cell efficacy. Both these materials reduce the recombination rate and expand the specific surface area of TiO2 as well as dye loading, reinforcing cell efficiency value. The maximum power conversion efficiency of QDSSC with a GO N-doped photoelectrode was 2.52%. Second, by employing Mn2+ (5 and 10 wt %) doping of ZnS, we have succeeded in considerably improving cell performance (from 2.52 to 3.47%). The reason for this could be for the improvement of the passivation layer of ZnS by Mn2+ ions, bringing about to a smaller recombination of photoinjected electrons with either oxidized dye molecules or electrolyte at the surface of titanium dioxide. However, doping of 15 wt % Mn2+ had an opposite effect and somewhat declined the cell performance. Finally, a Zn-porphyrin dye was added to the CdS/ZnS by a cosensitization method, widening the light absorption range to the NIR (near-infrared region) (>700 nm), leading to the higher short-circuit current density (JSC) and cell efficacy. Utilizing an environmentally safe porphyrin compound into the structure of QDSSC has dramatically enhanced the cell efficacy to 4.62%, which is 40% higher than that of the result obtained from the TiO2/CdS/ZnS photoelectrode without porphyrin coating.
关键词： graphene oxide,nitrogen doping,manganese doping,quantum dot-sensitized solar cells,cosensitization,Zn-porphyrin,power conversion efficiency
更新于2025-09-23 15:21:01
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Dual responsive enzyme mimicking of ternary polyaniline-MnO2-Pd nanowires and its application in colorimetric biosensing
摘要： In recent years, a significant challenge in material science is to fabricate novel functional nanomaterials to mimic the function of natural enzymatic systems. Herein, ternary polyaniline (PANi)-MnO2-Pd nanowires (NWs) are synthesized through a two-step redox reaction process. The prepared PANi-MnO2-Pd NWs were explored to exhibit dual responsive enzyme-like efficiencies, e.g. peroxidase and oxidase-like activities. With the assistance of H2O2, the obtained ternary PANi-MnO2-Pd NWs were able to oxidize the typical peroxidase substrate of 3,3’,5,5’-tetramethylbenzidine (TMB) to yield the oxidized TMB with a blue color, exhibiting a much better peroxidase-like activity than the synthesized PANi-MnO2 NWs alone and Pd nanoparticles owing to the interfacial electron transfer effect among the components. In addition, in the absence of H2O2, the prepared PANi-MnO2-Pd NWs could also oxidize TMB to display an excellent oxidase-like activity. Based on the dual responsive enzyme-like characteristic of the obtained ternary PANi-MnO2-Pd NWs, a rapid and applicative colorimetric way to sensitively determine L-cysteine and ascorbic acid (AA) has been developed. The limits of detection based on the two systems were estimated to be as low as 118 and 34 nM, respectively. We believe that the prepared ternary PANi-MnO2-Pd NWs with both peroxidase and oxidase-like activities will show broad potential applications in bioscience and bioengineering.
关键词： palladium,colorimetric biosensing,enzyme-mimicking,manganese dioxide,polyaniline
更新于2025-09-23 15:21:01