Detection Of Mn2 Research Articles

Improving the Sensitivity of a Mn(II)-Specific DNAzyme for Cellular Imaging Sensor through Sequence Mutations.

Detection of Mn2+ in living cells is important in understanding the roles of Mn2+ in cellular processes and investigating its potential implications in various diseases and disorders. Toward this goal, we have previously selected a Mn2+-specific 11-5 DNAzyme through an in vitro selection method and converted it into a fluorescence sensor for intracellular Mn2+ sensing. Despite the progress, the nucleotides responsible for the activity are unclear, and the performance of the DNAzyme needs to be improved in order for more effective applications in biological systems. To address these issues, we herein report site-specific mutations within the catalytic domain of the selected 11-5 DNAzyme. As a result, we successfully identified a variant DNAzyme, designated as Mn5V, which exhibited a twofold increase in activity compared to the original 11-5 DNAzyme. Importantly, Mn5V DNAzyme maintained its high selectivity for Mn2+ over other competing metal ions. Upon the addition of Mn2+, Mn5V DNAzyme exhibited a higher fluorescence signal within the tumor cells compared to that of the 11-5 DNAzyme. This study therefore provides a better understanding of how the DNAzyme functions and a more sensitive probe for investigating Mn2+ in biological systems.

Mn-C micro-electrolysis filler for nutrient removal in constructed wetlands: Performance evaluation and biochemistry processes

Insufficient provision of electron donors for denitrification often hinders nitrogen removal performance. While using a combination of iron and carbon can mitigate this problem, the surface passivation and limited electrical potential difference between Fe and C electrodes restricted the electron transfer efficiency. In this study, a manganese‑carbon carrier (Mn-C) was prepared and used for micro-electrolysis (Mn-C-ME) in conjunction with biological denitrification. Four constructed wetlands (CWs), including three Mn-amended CWs filled with low/middle/high content of Mn-C and one control, were established to investigate nutrient removal performance and underlying mechanisms under low C/N conditions. The results showed that Mn-amended CWs significantly enhanced total nitrogen removal from 31.01% to an optimal 91.06%. Nitrate was directly reduced by Mn(0), while Mn-C-ME generated inorganic electron donors ([H]/H2 and Mn2+) in situ for denitrification. The use of Mn ores oxidized ammonium and immobilized residual Mn2+ produced by Mn-C-ME. High-efficiency total phosphorus removal confirmed the formation of Mn-P precipitation. Moreover, the addition of Mn-C and Mn ores resulted in a noticeable difference in microbial community structures. Autotrophic denitrifying bacteria were abundant and positively correlated with Mn-oxidizing bacteria (MnOB) suggesting Mn(II)-driven autotrophic denitrification occurred. The high proportions of proteins, along with the detection of Mn2+ in extracellular polymeric substances, indicated biofilms might regulate the release of Mn2+ and supply a medium for Mn cycling, thus improving electron utilization. Our findings provide a new strategy to enhance nitrogen removal by coupling with multiple Mn-containing substrates.

Specific discrimination of zinc and manganese ions by label free dual emissive carbon dots by ratio-metric mode

Due to the worldwide ecological and environmental issues induced by heavy metal pollution, including zinc and manganese, the ratio-metric discrimination of Zn2+ and Mn2+ based on CDs is urgently required. In this work, reduced CDs (re-CDs) with the intrinsic dual emissive peaks are obtained, and specific discrimination of Zn2+ and Mn2+ is realized by re-CDs with ratio-metric mode. With the addition of Zn2+, the fluorescent (FL) intensity at 650 nm increases obviously, while that at 680 nm progressively decreases. However, the presence of Mn2+ would induce the quenching of FL intensity at 680 nm while that at 650 nm remains constant. Then the Zn2+ and Mn2+ can be separately determined with the ratio of FL intensity at 650 nm to that at 680 mm (F650/F680). Under optimal conditions, the limit of detection (LOD) of Zn2+ is determined to be 9.09 nmol/L, and that for Mn2+ is estimated to be 0.93 nmol/L, which is much lower than previously reported work and standard level of Zn2+ and Mn2+ permitted in drinking water by WHO. Moreover, the specific recognition of Mn2+ and Zn2+ can be realized via the addition of different masking agents (ethylenediamine for Zn2+ and triethanolamine for Mn2+). Furthermore, our results reveal that the structural changes from –NH–CO to –NC–OH induced by Zn2+ contribute to the shift of FL peak from 680 to 650 nm while both static and dynamic quenching processes are involved in the detection of Mn2+. The ratio-metric probe was successfully applied to Zn2+ and Mn2+ determination in human serum samples and Sandy Lake water.

Analysis of Mn2+ and Zn2+ Ions in Macroalgae with Heteroelement-Doped Carbon-Based Fluorescent Probe.

Kelp and laver are large economic macroalgae in China, which are rich in nutrients, especially Mn and Zn. Excessive intake of Mn and Zn can be harmful to the human body. Therefore, it is necessary to develop a convenient and efficient method to detect the contents of Mn and Zn in macroalgae. In this experiment, red carbon dots (R-CDs) doped with N and S elements were prepared by the thermal solvent method. The obtained R-CDs displayed excitation wavelength-independent fluorescent emission in the red spectral region. The R-CDs were used to construct a fluorescent probe for specific recognition of Mn2+ and Zn2+, achieving high-sensitivity detection of Mn2+ and Zn2+. The detection results showed a good linear relationship between fluorescence intensity and Mn2+ concentration, and the calculated detection limit was 0.23 nmol/L. For the detection of Zn2+, the detection limit was estimated as 19.1 nmol/L. At the same time, the content distribution of Mn and Zn elements in macroalgae produced in Fujian was investigated by the constructed fluorescence probe. It was found that kelp, laver, and their products are rich in Mn and Zn elements, and the content of Mn and Zn elements in laver is higher than that in kelp, which can be used as the optimal food supplement for Mn and Zn elements.

Utilization of waste biomass of Poa pratensis for green synthesis of n-doped carbon dots and its application in detection of Mn2+ and Fe3+

In this study, a novel and sustainable approach was used to synthesize nitrogen-doped carbon dots (NCDs) from the waste biomass of Poa Pratensis (Kentucky bluegrass (KB)) by a facile hydrothermal method. The prepared KBNCDs were subjected to various characterization techniques, including X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Fourier-transform infrared spectroscopy to verify the formation of carbon dots and their surface functional groups. The KBNCDs exhibited good hydrophilic fluorescence (FLU) properties with an acceptable quantum yield (7%). The synthesized KBNCDs showed excitation wavelength-dependent FLU emission behavior with strong cyan-blue FLU upon irradiation with 365 nm UV-light. The hydrophilic optical properties of the as-synthesized KBNCDs were used to detect Fe3+ and Mn2+ ions in an aqueous medium with good selectivity and sensitivity. It was found that the FLU of the KBNCDs is quenched in the presence of Fe3+ and Mn2+ ions, and the quenching rate was linear with the concentration of Fe3+ and Mn2+ ions. The limit of detection (LOD) of KBNCDs with metal ions was calculated using the Stern–Volmer relationship. The LOD values for Fe3+ or Mn2+ ions were calculated as 1.4 and 1.2 μM, respectively with the detection range from 5.0 to 25 μM. Based on these results, this study provides an underpinning for the development of KBNCD as FLU sensors that can be used in aqueous media.

The Performance of Various SWCNT Loading into CuO–PMMA Nanocomposites Towards the Detection of Mn2+ Ions

The well-dispersed CuO doped poly(methyl methacrylate) (CuO–PMMA) nanocomposites (NCs) with a successful loading of SWCNT as carbon nanofillers with different percentages (2%, 5%, and 10%) were fabricated effectively via the ex-situ polymerization technique. XRD, SEM–EDX, SEM-Map, TEM, AFM, Raman, and FTIR were carried out to confirm the formation of CuO–PMMA NCs, as well as the formation of CuO–PMMA–SWCNT NCs on the surface of CuO–PMMA sheet nanocomposite. The morphology of both CuO nanoparticles and SWCNT on the PMMA sheet, as well as agglomeration, concentration, roughness profiles, and size distribution, were considered during the experiments. BET surface area was carried out to determine the effect of various percentages of SWCNT loading on CuO–PMMA NC on the BET surface area. Furthermore, thermogravimetric analysis was conducted to evaluate the thermal behavior. Interestingly, the thermal stability of the NCs was inferred to significantly enhance with a proper amount of SWCNTs. EDX and elemental mapping of Cu, C, and O confirmed the presence of SWCNTs and CuO on the PMMA polymer matrix. In this approach, various loadings of SWCNT were performed into the CuO–PMMA–SWCNT NCs for the selective detection of metal ions using the electrochemical method. It exhibited the best performance in the detection of particular Mn2+ cation to 2% of SWCNT loading into NCs. The Mn2+ cationic sensor analytical response was investigated by CuO–PMMA–SWCNT (2%) NCs with glassy carbon electrode (GCE) coated uniform thin film using conductive nafion (5% nafion) binder. The sensor showed linear electrochemical responses over the concentration range of 0.1 nM to 0.01 mM identified through the calibration curve, which is known as the linear dynamic range. The sensor analytical performance sensitivity (88.16 µA µM−1 cm−2) and detection limit (92.67 ± 4.63 pM) were calculated from the slope of the calibration curve. The proposed Mn2+ ion sensor based on CuO–PMMA–SWCNT (2%) NCs/binder/GCE was found satisfactory in terms of reproducibility, linear dynamic range detection limit, sensitivity, stability, and response time. In real environmental samples, it also showed substantial performances during detection. This methodology can be inferred safely as a unique approach to develop metal ion sensors using inorganic-carbon NCs on GCE.

Functionalized-AgNPs for Long-Term Stability and Its Applicability in the Detection of Manganese Ions

In this study, silver nanoparticles (AgNPs) were functionalized by various molecules, including sodium borohydride (NaBH4), polyhexamethylene biguanide hydrochloride (PHMB), and Tween 80 to investigate the long-term stabilization of AgNPs in an aqueous dispersion. PHMB-functionalized silver nanoparticles (AgNPs/PHMB) exhibited better stability than others and could be stored at ambient temperature for at least 180 days. In addition to creating stabilization based on the electrostatic repulsion, the use of PHMB helped to increase the degree of stability of the colloidal AgNPs for a long time owing to strong interactions between Ag atoms on AgNPs with nitrogen (N) positions in PHMB molecules. The formed bond led to improving maintenance ability of the electrostatic repulsion layer among independent nanoparticles. The applicability of the as-prepared AgNPs/PHMB was also examined for Mn2+ detection via a colorimetric approach. The calibration curve was found to be linear over the range of 0–100 mM with a correlation coefficient of 0.97. The amine groups of PHMB brought out a cooperative effect to form of ion-templated chelation with Mn2+, which caused the aggregation of AgNPs/PHMB. This suggested that the AgNPs/PHMB could be used as a potential probe in the detection of Mn2+ ions. More importantly, the long-term stability of AgNPs/PHMB paved a great promising path to provide many further solutions for the producer in practical applications.

Enhanced oxidation of arsenite to arsenate using tunable K+ concentration in the OMS-2 tunnel

Cryptomelane-type octahedral molecular sieve manganese oxide (OMS-2) possesses high redox potential and has attracted much interest in its application for oxidation arsenite (As(III)) species of arsenic to arsenate (As(V)) to decrease arsenic toxicity and promote total arsenic removal. However, coexisting ions such as As(V) and phosphate are ubiquitous and readily bond to manganese oxide surface, consequently passivating surface active sites of manganese oxide and reducing As(III) oxidation. In this study, we present a novel strategy to significantly promote As(III) oxidation activity of OMS-2 by tuning K+ concentration in the tunnel. Batch experimental results reveal that increasing K+ concentration in the tunnel of OMS-2 not only considerably improved As(III) oxidation kinetics rate from 0.027 to 0.102 min−1, but also reduced adverse effect of competitive ion on As(III) oxidation. The origin of K+ concentration effect on As(III) oxidation was investigated through As(V) and phosphate adsorption kinetics, detection of Mn2+ release in solution, surface charge characteristics, and density functional theory (DFT) calculations. Experimental results and theoretical calculations confirm that by increasing K+ concentration in the OMS-2 tunnel not only does it improve arsenic adsorption on K+ doped OMS-2, but also accelerates two electrons transfers from As(III) to each bonded Mn atom on OMS-2 surface, thus considerably improving As(III) oxidation kinetics rate, which is responsible for counteracting the adverse adsorption effects by coexisting ions.