Free Mn Research Articles

Enhanced thermochemical heat storage performance of CaO/CaCO3 via pyroligneous acid impregnation and Co/Mn co-doping

Calcium-based thermochemical heat storage (TCHS) is an economical and environmentally friendly technology for efficient heat storage. It can strengthen the flexibility in power systems of renewable energy and promote the recovery and storage of waste heat in energy-intensive industries. However, CaO/CaCO3 is extremely prone to sintering at operational temperatures. Consequently, a cost-effective approach was proposed to synthesize calcium-based TCHS materials modified by pyroligneous acid (PA) impregnation and co-doping with dual transition metals. The heat storage performance, physicochemical property, and anti-sintering mechanism of synthesized CaO were comparatively examined. The sample prepared with a molar ratio of Ca: Co: Mn = 100:3:7 (PACa-Co3Mn7) exhibited an initial energy storage density of 1.76 MJ/kg, which gradually rose to 1.88 MJ/kg. After 20 cycles, the value decreased by only 4.39 % from its peak, indicating outstanding TCHS performance. Characterization results indicated that the specific surface area and pore volume of PACa-Co3Mn7 were 10.48 m2/g and 0.035 cm3/g, which were 2.34 and 2.69 times those of CaO stemmed from the calcination of limestone, respectively. The fruitful pores provided pathways for CO2 diffusion within the CaO particles or CaCO3 product layer. The uniformly distributed Co and Mn elements combined to form Ca3CoMnO6. Ca3CoMnO6 could serve as the inert carrier that mitigated the grain-growth of CaO, thereby stabilizing the pore structure and resisting the sintering of PACa-Co3Mn7. Furthermore, density functional theory (DFT) calculations demonstrated that the free Mn and Co elements efficiently promoted the electrons transfer between CaO and CO2, which improved the reactivity of PACa-Co3Mn7. Therefore, CaO modified by PA impregnation and co-doping with dual transition metal is a promising candidate for the TCHS system.

Quality assessment of various Xiushui Ninghong tea types.

Xiushui Ninghong tea (XSNH) has a long history and is renowned both in China and internationally. Based on different processing techniques, XSNH can be classified into Ninghong Congou, Ninghong Tea Jinhao, Ninghong Tea Longxucha and other types. To investigate the differences in nutrient compounds and mineral element contents among various types of XSNH, 34 samples from seven types were collected, primarily from tea-producing areas. Statistical analysis indicated no significant differences in the contents of crude polysaccharides, K, Mg and Fe, whereas significant differences were observed in the levels of moisture, free amino acids, caffeine, tea polyphenols, thearubigin, theaflavins, Zn, P, Mn, Cu and Se. The data were analyzed using various statistical methods such as hierarchical cluster analysis, principal component analysis and partial least squares discriminant analysis. Characteristic compounds and elements such as theaflavin, Se, free amino acids, P and tea polyphenols were identified as key differential components for distinguishing different sample types. Our research has highlighted the differences in chemical indicators among various types of XSNH, providing a crucial theoretical basis for the future classification and grading of XSNH quality. © 2024 Society of Chemical Industry.

Structure–reactivity relationships in the removal efficiency of catechol and hydroquinone by structurally diverse Mn-oxides

Catechol and hydroquinone are widely present hydroxybenzene isomers in the natural environment that induce environmental toxicities. These hydroxybenzene compounds can be effectively removed by manganese (Mn)-oxides via sorption and oxidative degradation processes. In the present study, we investigated the structure–reactivity relationships in the sorption and oxidation of catechol and hydroquinone on Mn-oxide surfaces. Two widely present Mn-oxides, including hydrous Mn oxide (HMO) and cryptomelane, comprised of layer and tunnel structures, respectively, are specifically studied. Effects of Mn-oxide structures and environmental pH conditions on the removal efficiency of these hydroxybenzene compounds, via sorption and oxidative degradation, are investigated. Cryptomelane, which has a higher specific surface area than HMO, possesses a higher sorption and oxidation capacity. The complexation mechanisms of catechol and hydroquinone vary due to their structure-induced difference in reactivity. Catechol reduced and dissolved more Mn from Mn-oxides than hydroquinone, accompanied by a higher C loss of catechol-C, suggesting a higher reactivity of catechol. Structural changes occurred in the Mn-oxides resulting from reaction with catechol and hydroquinone: reduction of Mn(IV), corresponding formation of Mn(III) and Mn(II) in the mineral, and free Mn2+ ions released into the suspension. These insights could help us better understand and predict the fate of hydroxybenzene compounds in Mn-oxide-rich soils and wastewater treatment systems that generate Mn-oxides via Mn removal and the associated environmental toxicity.

Novel fluorescent nanoplatform for all-in-one sensing and removal of acrolein: An ultrasensitive probe to evaluate its removal efficiency

As a highly toxic aldehyde, acrolein is widely found in diet and environment, and can be produced endogenously, posing a serious threat to human health. Herein, we designed a novel fluorescent nanoplatform integrating carbon dots‑manganese dioxide (CDs-MnO2) and glutathione (GSH) for all-in-one sensing and removal of acrolein. By converting Mn4+ to free Mn2+, GSH inhibited the inner filter effect (IFE) of MnO2 nanosheets, and the Michael addition of acrolein with GSH inhibited the GSH-induced Mn4+ conversion, forming an “off-on-off” fluorescence response of CDs. The developed fluorescent nanoplatform exhibited high sensitivity (LOD was 0.067 μM) and selectivity for the simultaneous detection and removal of acrolein. The combination of CDs-MnO2 hydrogels with smartphones realized the point-of-care detection of acrolein, yielding satisfactory results (recovery rates varied between 97.01–104.65%, and RSD ranged from 1.42 to 4.16%). Moreover, the capability of the nanoplatform was investigated for on-site evaluating acrolein scavengers' efficacy, demonstrating excellent potential for practical application.

Manganese-Loaded Liposomes: An In Vitro Study for Possible Diagnostic Application.

The present study investigates the possible use of manganese (Mn)-based liposomal formulations for diagnostic applications in imaging techniques such as magnetic resonance imaging (MRI), with the aim of overcoming the toxicity limitations associated with the use of free Mn2+. Specifically, anionic liposomes carrying two model Mn(II)-based compounds, MnCl2 (MC) and Mn(HMTA) (MH), were prepared and characterised in terms of morphology, size, loading capacity, and in vitro activity. Homogeneous dispersions characterised mainly by unilamellar vesicles were obtained; furthermore, no differences in size and morphology were detected between unloaded and Mn-loaded vesicles. The encapsulation efficiency of MC and MH was evaluated on extruded liposomes by means of ICP-OES analysis. The obtained results showed that both MC and MH are almost completely retained by the lipid portion of liposomes (LPs), with encapsulation efficiencies of 99.7% for MC and 98.8% for MH. The magnetic imaging properties of the produced liposomal formulations were investigated for application in a potential preclinical scenario by collecting magnetic resonance images of a phantom designed to compare the paramagnetic contrast properties of free MC and MH compounds and the corresponding manganese-containing liposome dispersions. It was found that both LP-MC and LP-MH at low concentrations (0.5 mM) show better contrast (contrast-to-noise ratios of 194 and 209, respectively) than solutions containing free Mn at the same concentrations (117 and 134, respectively) and are safe to use on human cells at the selected dose. Taken together, the results of this comparative analysis suggest that these liposome-containing Mn compounds might be suitable for diagnostic purposes.

Biosynthetic MnSe nanobomb with low Mn content activates the cGAS-STING pathway and induces immunogenic cell death to enhance antitumour immunity

Triple-negative breast cancer (TNBC) is a relatively “cold” tumour with low immunogenicity compared to other tumour types. Especially, the immune checkpoint inhibitors to treat metastatic TNBC only shows the modest immune response rates. Here, we used Chlorella vulgaris as a bioreactor to synthesize an efficient nanobomb (Bio-MnSe) aimed at eliciting systemic anti-tumour immune response. Despite possessing extremely low Mn content, Bio-MnSe effectively produced more ROS and activated stronger cGAS-STING signal pathway compared to pure Se nanoparticles and free Mn2+ ions, promoting the infiltration of natural killer (NK) cells, cytotoxic T lymphocytes (CTLs) in tumour, effectively turning “cold” tumour into “hot” tumour, and achieving strong antitumour immunotherapy. Additionally, the use of αPD-L1 as an immune checkpoint antagonist further increased the anti-tumour immune response of Bio-MnSe, resulting in enhanced anti-tumour effects. Doxorubicin (Dox), an immunogenic cell death (ICD) inducer, was combined with Bio-MnSe to form Bio-MnSe@Dox. This Bio-MnSe@Dox not only directly damaged tumour cells and induced tumour ICD but also promoted dendritic cell maturation, cytotoxic T lymphocyte infiltration, and NK cell recruitment, synergistically intensifying anti-tumour immune responses and suppressing tumour relapse and lung metastasis. Collectively, our findings propose an effective strategy for transforming ‘cold’ tumours to ‘hot’ ones, thereby advancing the development of anti-tumour immune drugs. Statement of significanceA biogenic MnSe (Bio-MnSe) nanocomposite was synthesized using Chlorella vulgaris as a bioreactor for enhanced immunotherapy of TNBC. Bio-MnSe demonstrated a stronger ability to activate the cGAS-STING signalling pathway and generate more ROS compared to pure Se nanoparticles and free Mn2+ ions. Apoptotic cells induced by Bio-MnSe released a significant amount of interferon, leading to the activation of T and natural killer (NK) cells, ultimately transforming immunologically ‘cold’ breast tumours to ‘hot’ tumours and enhancing the tumour's response to immune checkpoint inhibitors. The combination of Bio-MnSe with Dox or αPD-L1 further enhanced the anti-tumour immune response, fostering dendritic cell maturation, infiltration of cytotoxic T lymphocytes, and recruitment of NK cells, thereby enhancing the anti-tumour immunotherapy of TNBC.

Artificial neural network modeling for the oxidation kinetics of divalent manganese ions during chlorination and the role of arsenite ions in the binary/ternary systems

This study investigated the coexistence and contamination of manganese (Mn(II)) and arsenite (As(III)) in groundwater and examined their oxidation behavior under different equilibrating parameters, including varying pH, bicarbonate (HCO3−) concentrations, and sodium hypochlorite (NaClO) oxidant concentrations. Results showed that if the molar ratio of NaClO: As(III) was >1, the oxidation of As(III) could be achieved within a minute with an extremely high oxidation rate of 99.7 %. In the binary system, the removal of As(III) prevailed over Mn(II). The As(III) oxidation efficiency increased from 59.8 ± 0.6 % to 70.8 ± 1.9 % when pH rose from 5.7 to 8.0. The oxidation reaction between As(III) and NaClO releases H+ ions, decreasing the pH from 6.77 to 6.19 and reducing the removal efficiency of Mn(II). The presence of HCO3− reduced the oxidation rate of Mn(II) from 63.2 % to 13.9 % within four hours. Instead, the final oxidation rate of Mn(II) increased from 68.1 % to 87.7 %. This increase can be attributed to HCO3− ions competing with the free Mn(II) for the adsorption sites on the sediments, inhibiting the formation of H+. Moreover, kinetic studies revealed that the oxidation reaction between Mn(II) and NaClO followed first-order kinetics based on their R2 values. The significant factors affecting the Mn(II) oxidation efficiency were the initial concentration of NaClO and pH. Applying an artificial neural network (ANN) model for data analysis proved to be an effective tool for predicting Mn(II) oxidation rates under different experimental conditions. The actual Mn(II) oxidation data and the predicted values obtained from the ANN model showed significant consistency. The training and validation data sets yielded R2 values of 0.995 and 0.992, respectively. Moreover, the ANN model highlights the importance of pH and NaClO concentrations in influencing the oxidation rate of Mn(II).

Noninvasive ROS imaging and drug delivery monitoring in the tumor microenvironment

Reactive oxygen species (ROS) that are overproduced in certain tumors can be considered an indicator of oxidative stress levels in the tissue. Here, we report a magnetic resonance imaging (MRI)-based probe capable of detecting ROS levels in the tumor microenvironment (TME) using ROS-responsive manganese ion (Mn2+)-chelated, biotinylated bilirubin nanoparticles (Mn@bt-BRNPs). These nanoparticles are disrupted in the presence of ROS, resulting in the release of free Mn2+, which induces T1-weighted MRI signal enhancement. Mn@BRNPs show more rapid and greater MRI signal enhancement in high ROS-producing A549 lung carcinoma cells compared with low ROS-producing DU145 prostate cancer cells. A pseudo three-compartment model devised for the ROS-reactive MRI probe enables mapping of the distribution and concentration of ROS within the tumor. Furthermore, doxorubicin-loaded, cancer-targeting ligand biotin-conjugated Dox/Mn@bt-BRNPs show considerable accumulation in A549 tumors and also effectively inhibit tumor growth without causing body weight loss, suggesting their usefulness as a new theranostic agent. Collectively, these findings suggest that Mn@bt-BRNPs could be used as an imaging probe capable of detecting ROS levels and monitoring drug delivery in the TME with potential applicability to other inflammatory diseases.

Immobilized Dipeptidase in Manganese Ion-Loaded Polyethylenimine-Induced Calcium Phosphate Nanocrystals for Carnosine Synthesis.

Carnosine is a natural bioactive dipeptide with important physiological functions widely used in food and medicine. Dipeptidase (PepD) from Serratia marcescens can catalyze the reverse hydrolytic reaction of β-alanine with l-histidine to synthesize carnosine in the presence of Mn2+. However, it remains challenging to practice carnosine biosynthesis due to the low activity and high cost of the enzyme. Therefore, the development of biocatalysts with high activity and stability is of significance for carnosine synthesis. Here, we proposed to chelate Mn2+ to polyethylenimine (PEI) that induced rapid formation of calcium phosphate nanocrystals (CaP), and Mn-PEI@CaP was used for PepD immobilization via electrostatic interaction. Mn-PEI@CaP as the carrier enhanced the stability of the immobilized enzyme. Moreover, Mn2+ loaded in the carrier acted as an in situ activator of the immobilized PepD for facilitating the biocatalytic process of carnosine synthesis. The as-prepared immobilized enzyme (PepD-Mn-PEI@CaP) kept similar activity with free PepD plus Mn2+ (activity recovery, 102.5%), while exhibiting elevated thermal stability and pH tolerance. Moreover, it exhibited about two times faster carnosine synthesis than the free PepD system. PepD-Mn-PEI@CaP retained 86.8% of the original activity after eight cycles of batch catalysis without the addition of free Mn2+ ions during multiple cycles. This work provides a new strategy for the co-immobilization of PepD and Mn2+, which greatly improves the operability of the biocatalysis and demonstrates the potential of the immobilized PepD system for efficient carnosine synthesis.

Transition metal doped into defective boron nitride nanotubes for CO2RR: Regulation of catalytic activity and mechanism by curvature effect

Utilizing electrochemical CO2 reduction reaction (CO2RR) to synthesize chemical fuels is an effective strategy to alleviate environmental pollution and energy crisis. In this work, a series of single transition metal atoms (TM = Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd) are doped into boron nitride nanotubes (BNNTs) of BN divacancy defect with different curvature parameters, which are named as TM-DVBNNT(n, n), and their CO2RR catalytic performance is systematically studied by density functional theory (DFT) methods. To begin with, the calculation results of formation energy and dissolution potential show that all TM-DVBNNT(n, n) have good thermodynamic and electrochemical stability. Secondly, after calculation of Gibbs free energy, Mn-, Fe-, Ru-, and Rh-DVBNNT(5, 5) have good catalytic performance with the corresponding limiting potential (UL) values of −0.43, −0.40, −0.27, and −0.50 V, respectively. Based on this, we further investigate the influence of curvature on the stability, activity, and mechanism of Ru-DVBNNT(n, n) with the highest activity. It is worth noting that as the diameter of Ru-DVBNNT(n, n) continues to increase, their stability and activity also continue to enhance, and Ru-DVBNNT(8, 8) with the largest diameter is expected to become the best performing CO2RR electrocatalyst with the UL value of −0.16 V. Besides, for Ru-DVBNNT(3, 3) and Ru-DVBNNT(4, 4), their final product is HCOOH. In contrast, the CH4 product is more inclined to form on Ru-DVBNNTs with chiral indexes of (5, 5), (6, 6), (7, 7), and (8, 8). In summary, this work has laid a solid theoretical foundation for future experimental design of nanotube structures.

Mercapto–palygorskite decreases the Cd uptake of wheat by changing Fe and Mn fraction in Cd contaminated alkaline soil

Wheat is one of the major sources of dietary nutrition for human body, and excessive Cadmium (Cd) in wheat poses a serious risk to human health. Mercapto–palygorskite (MP) has been proven to efficiently reduce Cd stress in wheat, but the contribution of major soil oxides to the stability of soil Cd under MP treatment is unclear. Here, a wheat pot experiment was conducted to evaluate the effects of soil Fe and Mn oxides on the Cd fraction under MP treatment. The results showed that the application of MP decreased the diethylenetriaminepentaacetic acid (DTPA)–extractable Cd by 24.0–34.7 %, increased the Fe and Mn oxide-bound Cd (OX–Cd) by 5.0–12.0 % and significantly reduced the Cd content in wheat grains (17.9–69.5 %). It also decreased the soil’s free Fe and Mn oxides by 6.1–11.7 %and 6.9–12.4 %, respectively, and increased the amorphous Fe and Mn oxides by 19.3–32.5 % and 21.9–24.1 %, respectively. In addition, the application of MP increased the concentration of Fe and Cd in soil colloid by 19.3–33.3 % and 11.3–45.3 %, respectively. Correlation analysis indicated that the amorphous Fe, Mn oxides in soil had a significant positive correlation with the content of Fe and Mn bound Cd in soil (P < 0.01). Primary component analysis (PCA) analysis shows colloidal Fe and Mn on the soil available Cd had relatively high positively loadings. Meanwhile, soil colloidal Fe exhibited a significant positive correlation with colloidal Cd (P < 0.01) and amorphous Fe oxides (P < 0.01). These results indicated that MP remediated Cd-contaminated soil by promoting an increase in amorphous Fe, Mn oxides and their adsorption and precipitation of Cd on these oxides.

Mechanistic Study of Reaction between 5-Sulfosalicylic Acid and Colloidal MnO2

The reaction between 5-sulfosalicylic acid (5-SSA) and colloidal MnO2 has been studied kinetically in acidic medium. During the reaction the concentration of 5-SSA was kept highly excess than the concentration of colloidal MnO2 to maintain the pseudo-first-order condition. The reaction was studied by following decrease in absorbance of colloidal MnO2 at 390 nm and the first order rate constants were determined from linear log (Abs.) against time plots. The linearity of the first-order plots did not involve any autocatalytic part. The oxidation of 5-sulfosalicylic acid (5-SSA) by colloidal MnO2 involves intervention of free radicals and Mn(III). The product of reaction in colloidal MnO2 was p-hydroxy benzene sulfonate ion as confirmed by LCMS-MS analysis. The oxidation by colloidal MnO2 consists of acid dependent and independent mechanisms. The results of added Mn(II), Na4P2O7 and acrylonitrile indicate involvement of Mn(III) and free radical during oxidation by colloidal MnO2. The probable mechanisms for acid dependent and independent paths were predicted and the rate expressions were also obtained. The activation parameters also support the proposed mechanisms.

Competitive Mn(II) removal occurs in Lysinibacillus sp. MHQ-1 through microbially-induced carbonate precipitation (MICP) and indirect Mn(II) oxidation

Biological Mn(II) removal usually involves adsorption and precipitation of Mn(II) in the form of various minerals. Manganese oxides (MnOx) formation through the activity of Mn(II) oxidation bacteria (MnOB) contributes to the majority of Mn(II) removal. However, whether other bacterial-mediated pathway could couple or competitive with Mn(II) oxidation during Mn(II) removal is scarcely reported. In this study, we reported a competitive Mn(II) removal occurred in nutrient-rich condition during the indirect Mn(II) oxidation of Lysinibacillus sp. MHQ-1, i.e., microbially-induced carbonate precipitation (MICP). In the presence of 1 mM Mn(II), 39.4% of free Mn(II) converted to MnCO3(s) quickly within 100 h, and then 11.6% of initial Mn(II) slowly oxidized to MnOx within 442 h. The urease activity assay and the genome sequencing confirmed the existence of urease and the absence of Mn(II)-oxidizing enzymes in the genome of strain MHQ-1. The urease catalyzed the formation of carbonate ion that reacts with Mn(II) and the formed ammonia raises the pH to initiate indirect Mn(II) oxidation. Genome survey suggests the urease widely exists in various Mn(II)-oxidizing bacteria (MnOB), emphasizing the importance to reconsider the composition, stability and environmental effects of biological Mn(II) removal products in nutrient-rich environment.

Tissue-level distribution and speciation of foliar manganese in Eucalyptus tereticornis by µ-SXRF and µ-XANES shed light on its detoxification mechanisms

This study is the first to investigate the speciation and spatial distribution patterns of manganese (Mn) accumulated at elevated concentrations in Eucalyptus leaves by X-ray fluorescence (µ-XRF) and absorption near-edge spectroscopy (µ-XANES). Eucalyptus tereticornis is a tree species with great economic value and potential to accumulate and tolerate high Mn despite not being considered a hyperaccumulator. Seedlings grown under glasshouse conditions were irrigated with two Mn treatments: control Mn (9 µM) and high Mn solution (1000 µM). Biomass and total nutrient concentrations were assessed in roots, stems and leaves. Manganese, calcium (Ca) and potassium (K) spatial patterns were imaged by µ-SXRF in different foliar structures, and Mn speciation was conducted in these compartments by µ-XANES. Under high supply, Mn was distributed across the leaf mesophyll suggesting vacuolar sequestration in these cells. High Mn decreased cytosolic Ca by almost 50% in mesophyll cells, but K remained unaltered. Speciation suggests that a majority of the Mn fraction was complexed by organic ligands modeled as Mn-bound malate and citrate, instead of as free aqueous Mn2+ or oxidised forms. These two detoxification mechanisms: effective vacuolar sequestration and organic acid complexation, may be responsible for the impressively high Mn tolerance found in eucalypts.

A pH-dependent CT sensitive method for detection of trace Mn in milk by UV-spectrophotometry

In this study, a new method was developed for the extractive pre-concentration/detection of trace Mn in milk prior to analysis by UV-spectrophotometry. The method is based on the pH-controlled intra-ligand charge transfer (ICT) complexation of modifier, 2-HBT in presence of trace Mn (II), and then the extraction of the complexes, where the hydrazine and hydrazone tautomers are predominant at pHs of 2.0/ 3.0, and pH 6.0 because of CT at pH 4.0. The free Mn (II) and total Mn levels of the samples were detected at 269 nm by UV-spectrophotometry. For total Mn, the method was validated by analysis of two certified milk samples. The results were statistically in good agreement with the certified values, and the precision was lower than 6.4%. After a pre-concentration of 62.5-fold, the limits of detection were 1.45/1.92 and 1.54/2.12 μg L−1 in range of 5–165 and 5–150 µg L−1 from the solvent-based and matrix-matched calibration curves, respectively. There is not a matrix effect from comparison of the calibration curves’s slopes. The method was successfully applied to analysis of milk samples. In terms of speciation, the free Mn (II) and total Mn levels in milk were in the range of 7.65–30.4 μg L−1, and 10.2–34.7 and 10.7–35.5 μg L−1 after the microwave and ultrasound assisted extraction.

Coaxial 3D printing of hierarchical structured hydrogel scaffolds for on-demand repair of spinal cord injury.

After spinal cord injury (SCI), endogenous neural stem cells (NSCs) near the damaged site are activated, but few NSCs migrate to the injury epicenter and differentiate into neurons because of the harsh microenvironment. It has demonstrated that implantation of hydrogel scaffold loaded with multiple cues can enhance the function of endogenous NSCs. However, programming different cues on request remains a great challenge. Herein, a time-programmed linear hierarchical structure scaffold is developed for spinal cord injury recovery. The scaffold is obtained through coaxial 3D printing by encapsulating a dual-network hydrogel (composed of hyaluronic acid derivatives and N-cadherin modified sodium alginate, inner layer) into a temperature responsive gelatin/cellulose nanofiber hydrogel (Gel/CNF, outer layer). The reactive species scavenger, metalloporphyrin, loaded in the outer layer is released rapidly by the degradation of Gel/CNF, inhibiting the initial oxidative stress at lesion site to protect endogenous NSCs; while the inner hydrogel with appropriate mechanical support, linear topology structure and bioactive cues facilitates the migration and neuronal differentiation of NSCs at the later stage of SCI treatment, thereby promoting motor functional restorations in SCI rats. This study offers an innovative strategy for fabrication of multifunctional nerve regeneration scaffold, which has potential for clinical treatment of SCI. STATEMENT OF SIGNIFICANCE: Two major challenges facing the recovery from spinal cord injury (SCI) are the low viability of endogenous neural stem cells (NSCs) within the damaged microenvironment, as well as the difficulty of neuronal regeneration at the injured site. To address these issues, a spinal cord-like coaxial scaffold was fabricated with free radical scavenging agent metalloporphyrin Mn (III) tetrakis (4-benzoic acid) porphyrin and chemokine N-cadherin. The scaffold was constructed by 3D bioprinting for time-programmed protection and modulation of NSCs to effectively repair SCI. This 3D coaxially bioprinted biomimetic construct enables multi-factor on-demand repair and may be a promising therapeutic strategy for SCI.

Photoluminescence of Mn2+ in the Borosulfate Zn[B2(SO4)4]:Mn2+ - A Tool to Detect Weak Coordination Behavior of Ligands.

The impact of the surrounding ligand field is successfully exploited in the case of Eu2+ to tune the emission characteristics of inorganic photoactive materials with potential application in e.g., phosphor-converted white light-emitting diodes (pc-wLEDs). However, the photoluminescence of Mn2+ related to intraconfigurational 3d5-3d5 transitions is also strongly dependent on local ligand field effects and has been underestimated in this regard so far. In this work, we want to revive the idea how to electronically tune the emission color of a transition metal ion in inorganic hosts by unusual electronic effects in the metal-ligand bond. The concept is explicitly demonstrated for the weakly coordinating layer-like borosulfate ligand in the Mn(II)-containing solid solutions Zn1-xMnx[B2(SO4)4] (x = 0, 0.03, 0.04, 0.05, 0.10). Zn[B2(SO4)4]:Mn2+ shows orange narrow-band luminescence at 590 nm, which is an unusually short wavelength for octahedrally coordinated Mn2+ and indicates an uncommonly weak ligand field. On the other hand, the analysis of the interelectronic Racah repulsion parameters reveals ionic Mn-O bonds with values close to the Racah parameters of the free Mn2+ ion. Overall, this strategy demonstrates that electronic control of the metal-ligand bond can be a tool to make Mn2+ a potent alternative emitter to Eu2+ for inorganic phosphors.

Photolumineszenz von Mn2+ in dem Borosulfat Zn[B2(SO4)4] : Mn2+ – Eine Möglichkeit zum Nachweis schwach koordinierender Liganden

AbstractDer Einfluss des umgebenden Ligandenfelds wird im Fall von Eu2+ erfolgreich genutzt, um die Emission anorganischer photoaktiver Materialien durchzustimmen, die z. B. in phosphor‐konvertierten Weißlicht‐emittierenden Dioden (pc‐wLEDs) Anwendung finden. Allerdings ist auch die Photolumineszenz von Mn2+, die auf intrakonfiguralen 3d5–3d5‐Übergängen basiert, stark von lokalen Ligandenfeldeffekten abhängig. Dieser Aspekt wurde bislang eher vernachlässigt. In der vorliegenden Arbeit wollen wir daher die Idee wieder aufleben lassen, die Emissionsfarbe eines Übergangsmetall‐Ions in anorganischen Wirtsverbindungen durch ungewöhnliche elektronische Effekte in der Metall‐Ligand‐Bindung einzustellen. Das Konzept wird explizit für das schwach koordinierende, schichtartigen Borosulfat‐Anion in den Mn2+‐haltigen festen Lösungen Zn1‐xMnx[B2(SO4)4] (x=0; 0.03; 0.04; 0.05; 0.10) demonstriert. Zn[B2(SO4)4] : Mn2+ zeigt orange Schmalbandlumineszenz bei 590 nm, was eine ungewöhnlich kurze Wellenlänge für oktaedrisch koordiniertes Mn2+ darstellt und auf ein besonders schwaches Ligandenfeld hinweist. Eine Analyse der interelektronischen Racah‐Abstoßungsparameter deutet stark ionische Mn−O‐Bindungen mit Werten nahe der Racah‐Parameter des freien Mn2+‐Ions an. Insgesamt demonstriert diese Strategie, dass elektronische Anpassungen der Metall−Ligand‐Bindung als Instrument genutzt werden können, um Mn2+ zu einem potenten alternativen Emitter anstelle von Eu2+ für anorganische Leuchtstoffe zu machen.

Separator-free Zn-ion Battery with Mn:V3O7·H2O Nanobelts and a Zn2+-Polyacrylamide Semisolid Electrolyte with Ultralong Cycle Life.

Vanadium based oxides are immensely suitable for zinc-ion-batteries (ZIBs) due to their layered and stable crystal structures. In this study, Mn doped V3O7·H2O nanobelts were synthesized and used as cathodes in ZIBs for the very first time and the doped oxide exhibited an enhanced capacity of 258 mAh g-1 compared to its undoped counterpart (208 mAh g-1) at the same current density of 40 mA g-1. Mn:V3O7·H2O outperforms the V3O7·H2O due to the superior bulk electrical conductivity as well as higher nanoscale current carrying capability imparted by a high proportion of mixed valent states of Mn3+, Mn2+, V5+, and V4+ and the smaller crystallite size that affords short diffusion lengths for Zn2+ ions. The Mn:V3O7·H2O cathode is coupled with a Zn2+ ion conducting polyacrylamide gel electrolyte and a Zn flakes/activated carbon (Zn Fs/C) composite anode to yield a unique separator free Mn:V3O7·H2O/Zn2+-PAM gel/Zn-Fs/C battery. The cell exhibits a capacity of ∼205 mAh g-1 (at 40 mA g-1) and retains 99% of its original capacity after 3500 cycles. The Zn2+-PAM gel shows a high ionic conductivity in the range of 5.9 to 28.2 S cm-1, over a wide temperature span of 0 to 70 °C, and a wide electrochemical potential stability window of -0.5 to +2.3 V, thus rendering it suitable for low temperature applications as well. The gel also inhibits dendritic growth of Zn over the Zn-Fs/C anode through regulated flow of Zn2+ ions during charging, prevents cathode dissolution, and improves cycle life via preservation of structural integrity of the Mn:V3O7·H2O cathode after 200 charge-discharge cycles. This is a highly scalable cell configuration and opens up opportunities to produce long lasting batteries completely free of costly separators with a semisolid free-standing electrolyte and a robust doped oxide.

Carbonic Anhydrase IX Targeting Mn(II)-Based Magnetic Resonance Molecular Imaging Probe for Hypoxia Tumors.

Physiological hypoxic conditions in the tumor microenvironment and consequential overexpression of carbonic anhydrase IX (CA IX) are two characteristics shared by numerous types of solid malignant tumors. Early detection with hypoxia assessment is crucial to improve the prognosis and therapy outcomes of hypoxia tumors. Herein, using acetazolamide (AZA) as a CA IX-targeting moiety, we design and synthesize an Mn(II)-based MR imaging probe (named AZA-TA-Mn) incorporating AZA and two Mn(II) chelates of Mn-TyEDTA on a rigid triazine (TA) scaffold. The per Mn relaxivity of AZA-TA-Mn is 2-fold higher than its monomeric Mn-TyEDTA, which allows it for low-dose imaging of hypoxic tumors. In a xenograft mice model of esophageal squamous cell carcinoma (ESCC), a low dosage of AZA-TA-Mn (0.05 mmol/kg) can selectively produce prolonged and stronger contrast enhancement in the tumor compared to the non-specific Gd-DTPA (0.1 mmol/kg). A competition study of co-injection of free AZA and Mn(II) probes confirms the in vivo tumor selectivity of AZA-TA-Mn, resulting in a more than 2.5-fold decreased tumor-to-muscle contrast-to-noise ratio (ΔCNR) at 60 min post-injection. MR imaging results were further supported by the quantitative analysis of Mn tissue levels, as the co-injection of free AZA resulted in significantly reduced Mn accumulation in tumor tissues. Finally, immunofluorescence staining of tissue sections confirms the positive correlation between the tumor accumulation of AZA-TA-Mn and CA IX overexpression. Hence, using CA IX as the hypoxia biomarker, our results illustrate a practical strategy for the development of novel imaging probes for hypoxic tumors.