In Situ Visualizing Oxidase-Mimicking Activity of Single MnOOH Nanotubes with Mie Scattering-Based Absorption Microscopy.

Imaging the catalytic activity at the single-particle level can greatly promote the screening and rational design of highly efficient nanozymes, but conventional techniques are based on ensemble analysis. Here, we present a new absorption microscopy for in situ visualizing oxidase-mimicking activity of single MnOOH nanotubes. The particle with a size more than 700 nm roughly equally scatters all wavelengths of visible light via Mie scattering, and the scattering light is collected by dark-field optical microscopy. When the particles absorb a single color of the scattering light, each individual nanoparticle shows its complementary color, enabling a form of absorption microscopy that we name Mie scattering-based absorption microscopy. We find that MnOOH nanotubes can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate polyTMB nanowires at their tips. There are multiple active sites on the surface of the individual nanotube, and the nanozyme activity shows a large heterogeneity as well as pH-dependent characteristic.

Design of γ-AlOOH, γ-MnOOH, and α-Mn2O3 nanorods as advanced antibacterial active agents.

In the current study, γ-AlOOH, γ-MnOOH, and α-Mn2O3 nanorods (NRs) were easily synthesized and applied as advanced antibacterial materials. γ-AlOOH NRs with 20 nm width, [100] crystal plane, and 200 nm length were fabricated through a surfactant-directed solvothermal method. γ-MnOOH NRs with 20 nm width, [101] crystal direction and 500 nm length were fabricated through a hydrothermal method. The prepared γ-MnOOH NRs were calcinated (for 5 h) at 700 °C to produce α-Mn2O3 NRs with 20 nm average width and increased surface area. The NRs' structures were confirmed through FT-IR, XRD, XPS, FESEM, and FETEM. The antibacterial activity of the NRs was studied against different Gram-negative and Gram-positive bacterial strains and yeast. The three NRs exhibited antibacterial activity against all of the used strains. Biological studies indicated that the NRs' antimicrobial activity increased in the order of γ-MnOOH < γ-AlOOH < α-Mn2O3 NRs. The α-Mn2O3 NRs exhibited the lowest MIC value (39 µg mL-1) against B. subtilis, B. pertussis, and P. aeruginosa. The prepared NRs exhibited a higher antimicrobial potential toward Gram-positive bacteria than Gram-negative bacteria. The higher antimicrobial activity of the α-Mn2O3 NRs is highlighted based on their larger surface area and smaller diameter. Consequently, uniform NR architectures, single crystallinity, small nanoscale diameters, and more highly exposed [110] Mn-polar surfaces outwards are promising structures for α-Mn2O3 antibacterial agents. These NRs adhered firmly to the bacterial cells causing cell wrapping and morphology disruption, and microbial death. The designed NRs provide a great platform for microbial growth inhibition.

Biosynthesis and characterization of magnesium oxide and manganese dioxide nanoparticles using Matricaria chamomilla L. extract and its inhibitory effect on Acidovorax oryzae strain RS-2.

Bacterial brown stripe (BBS) is one of the most economically important diseases of rice caused by Acidovorax oryzae (Ao). In order to ensure food security and safe consumption, the use of non-chemical approach is necessary. In this study, MgO and MnO2 were synthesized using chamomile flower extract. The synthesized MgO and MnO2 nanoparticles were characterized by UV-Visible spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, transmission/scanning electron microscopy. The sizes were 18.2 and 16.5 nm for MgO and MnO2 nanoparticles, respectively. The MgO and MnO2 nanoparticles reduced the growth of Ao strain RS-2 by 62.9 and 71.3%, respectively. Also, the biofilm formation and swimming motility were significantly reduced compared to the control. The antibacterial mechanisms of MgO and MnO2 nanoparticles against RS-2 reveals that MgO and MnO2 nanoparticles penetrated the cells and destroyed the cell membrane leading to leakage of cytoplasmic content. Also, the flow cytometry observation reveals that the apoptotic cell ratio of RS-2 increased from 0.97% to 99.52 and 99.94% when treated with MgO and MnO2 nanoparticles, respectively. Altogether, the results suggest that the synthesized MgO and MnO2 nanoparticles could serve as an alternative approach method for the management of BBS.

Synergistic Oxygen Generation and Reactive Oxygen Species Scavenging by Manganese Ferrite/Ceria Co-decorated Nanoparticles for Rheumatoid Arthritis Treatment.

Poor O2 supply to the infiltrated immune cells in the joint synovium of rheumatoid arthritis (RA) up-regulates hypoxia-inducible factor (HIF-1α) expression and induces reactive oxygen species (ROS) generation, both of which exacerbate synovial inflammation. Synovial inflammation in RA can be resolved by eliminating pro-inflammatory M1 macrophages and inducing anti-inflammatory M2 macrophages. Because hypoxia and ROS in the RA synovium play a crucial role in the induction of M1 macrophages and reduction of M2 macrophages, herein, we develop manganese ferrite and ceria nanoparticle-anchored mesoporous silica nanoparticles (MFC-MSNs) that can synergistically scavenge ROS and produce O2 for reducing M1 macrophage levels and inducing M2 macrophages for RA treatment. MFC-MSNs exhibit a synergistic effect on O2 generation and ROS scavenging that is attributed to the complementary reaction of ceria nanoparticles (NPs) that can scavenge intermediate hydroxyl radicals generated by manganese ferrite NPs in the process of O2 generation during the Fenton reaction, leading to the efficient polarization of M1 to M2 macrophages both in vitro and in vivo. Intra-articular administration of MFC-MSNs to rat RA models alleviated hypoxia, inflammation, and pathological features in the joint. Furthermore, MSNs were used as a drug-delivery vehicle, releasing the anti-rheumatic drug methotrexate in a sustained manner to augment the therapeutic effect of MFC-MSNs. This study highlights the therapeutic potential of MFC-MSNs that simultaneously generate O2 and scavenge ROS, subsequently driving inflammatory macrophages to the anti-inflammatory subtype for RA treatment.

One step green synthesis of larvicidal, and azo dye degrading antibacterial nanoparticles by response surface methodology.

The present study explored the one step extracellular green synthesis of Iron oxide (FexOy) and manganese oxide nanoparticles (MnNPs) using aqueous extract of Acorus calamus rhizome. The organic chemicals including polyphenol compounds responsible for bio-reduction and stabilization from the polyphenol enriched microwave irradiated aqueous extract of Acorus calamus were studied using GC-MS analysis. Further, their synthesis conditions were optimized using response surface methodology (RSM) and central composite design (CCD) using three variables. The green synthesized Iron oxide and Manganese oxide NPs were characterized by UV, FTIR, XRD, TEM and SEM. Results indicated that the Iron oxide NPs and mixture of iron and manganese NPs showed photocatalytic excellent activities in reducing dyes like methylene blue (0.1%) and Congo red (0.25%) at 0.03% NPs. However, Mn NPs showed moderate activity. On a contrary, manganese showed better larvicidal activity compared to Iron oxide NPs against the phytopathogens commonly affecting the vegetable crops. The present finding showed that high mortality rate at 30 µg/ml concentration of manganese NPs was comparatively interesting. In addition, NPs overall had appreciable activity with P. aeruginosa being more sensitive to Iron oxide NPs (22 ±â€¯2 mm zone of inhibition) and manganese NPs (13 ±â€¯2 mm zone of inhibition) and Iron oxide NPs completely inhibited the growth of A. flavus at 40 µg/ml concentration.

Integration of Polymerization and Biomineralization as a Strategy to Facilely Synthesize Nanotheranostic Agents.

Integration of biological macromolecules with inorganic materials via biomineralization has demonstrated great potential for development of nanotheranostic agents. To produce multifunctionality, integration of multiple components in the biomineralized theranostic agents is required; however, how to efficiently and reproducibly implement this is challenging. In this report, a universal biomineralization strategy is developed by incorporation of oxidization polymerization into albumin-templated biomineralization for facile synthesis of nanotheranostic agents. A series of biomineralized polymers and manganese dioxide hybrid nanoparticles (PMHNs) can be synthesized via the polymerization of various monomers, including dopamine (DA), epigallocatechin (EGC), pyrrole (PY), and diaminopyridine (DP), along with the reduction of KMnO4 and formation of manganese dioxide nanoparticles in albumin templates. These biomineralized PMHNs demonstrate ultrahigh MRI (longitudinal relaxivity up to 38 mM-1 s-1) and ultrasonic (US) imaging contrasting capabilities and have excellent photothermal therapy efficacy with complete ablation of orthotopic tumors. Moreover, these biomineralized hybrid nanoparticles can be effectively excreted through the kidneys, avoiding potential systemic toxicity. Thus, integration of polymerization into biomineralization presents a strategy for the fabrication of hybrid nanomaterials, allowing the production of multifunctional and biocompatible nanotheranostic agents via a facile one-pot method.

Synthesis of Ferromagnetic Fe0.6 Mn0.4 O Nanoflowers as a New Class of Magnetic Theranostic Platform for In Vivo T1 -T2 Dual-Mode Magnetic Resonance Imaging and Magnetic Hyperthermia Therapy.

Uniform wüstite Fe0.6 Mn0.4 O nanoflowers have been successfully developed as an innovative theranostic agent with T1 -T2 dual-mode magnetic resonance imaging (MRI), for diagnostic applications and therapeutic interventions via magnetic hyperthermia. Unlike their antiferromagnetic bulk counterpart, the obtained Fe0.6 Mn0.4 O nanoflowers show unique room-temperature ferromagnetic behavior, probably due to the presence of an exchange coupling effect. Combined with the flower-like morphology, ferromagnetic Fe0.6 Mn0.4 O nanoflowers are demonstrated to possess dual-modal MRI sensitivity, with longitudinal relaxivity r1 and transverse relaxivity r2 as high as 4.9 and 61.2 mm(-1) s(-1) [Fe]+[Mn], respectively. Further in vivo MRI carried out on the mouse orthotopic glioma model revealed gliomas are clearly delineated in both T1 - and T2 -weighted MR images, after administration of the Fe0.6 Mn0.4 O nanoflowers. In addition, the Fe0.6 Mn0.4 O nanoflowers also exhibit excellent magnetic induction heating effects. Both in vitro and in vivo magnetic hyperthermia experimentation has demonstrated that magnetic hyperthermia by using the innovative Fe0.6 Mn0.4 O nanoflowers can induce MCF-7 breast cancer cell apoptosis and a complete tumor regression without appreciable side effects. The results have demonstrated that the innovative Fe0.6 Mn0.4 O nanoflowers can be a new magnetic theranostic platform for in vivo T1 -T2 dual-mode MRI and magnetic thermotherapy, thereby achieving a one-stop diagnosis cum effective therapeutic modality in cancer management.

In vitro study on apoptotic cell death by effective magnetic hyperthermia with chitosan-coated MnFe2O4.

Magnetic nanoparticles (MNPs) have been widely investigated as a hyperthermic agent for cancer treatment. In this study, thermally responsive Chitosan-coated MnFe2O4 (Chitosan-MnFe2O4) nanoparticles were developed to conduct localized magnetic hyperthermia for cancer treatment. Hydrophobic MnFe2O4 nanoparticles were synthesized via thermal decomposition and modified with 2,3-dimercaptosuccinic acid (DMSA) for further conjugation of chitosan. Chitosan-MnFe2O4 nanoparticles exhibited high magnetization and excellent biocompatibility along with low cell cytotoxicity. During magnetic hyperthermia treatment (MHT) with Chitosan-MnFe2O4 on MDA-MB 231 cancer cells, the targeted therapeutic temperature was achieved by directly controlling the strength of the external AC magnetic fields. In vitro Chitosan-MnFe2O4-assisted MHT at 42 °C led to drastic and irreversible changes in cell morphology and eventual cellular death in association with the induction of apoptosis through heat dissipation from the excited magnetic nanoparticles. Therefore, the Chitosan-MnFe2O4 nanoparticles with high biocompatibility and thermal capability can be an effective nano-mediated agent for MHT on cancer.

Ultrasonic cavitation induced water in vegetable oil emulsion droplets--a simple and easy technique to synthesize manganese zinc ferrite nanocrystals with improved magnetization.

In the present investigation, synthesis of manganese zinc ferrite (Mn(0.5)Zn(0.5)Fe(2)O(4)) nanoparticles with narrow size distribution have been prepared using ultrasound assisted emulsion (consisting of rapeseed oil as an oil phase and aqueous solution of Mn(2+), Zn(2+) and Fe(2+) acetates) and evaporation processes. The as-prepared ferrite was nanocrystalline. In order to remove the small amount of oil present on the surface of the ferrite, it was subjected to heat treatment at 300 °C for 3h. Both the as-prepared and heat treated ferrites have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), TGA/DTA, transmission electron microscopy (TEM) and energy dispersion X-ray spectroscopy (EDS) techniques. As-prepared ferrite is of 20 nm, whereas the heat treated ferrite shows the size of 33 nm. In addition, magnetic properties of the as-prepared as well as the heat treated ferrites have also been carried out and the results of which show that the spontaneous magnetization (σ(s)) of the heat treated sample (24.1 emu/g) is significantly higher than that of the as-synthesized sample (1.81 emu/g). The key features of this method are avoiding (a) the cumbersome conditions that exist in the conventional methods; (b) usage of necessary additive components (stabilizers or surfactants, precipitants) and (c) calcination requirements. In addition, rapeseed oil as an oil phase has been used for the first time, replacing the toxic and troublesome organic nonpolar solvents. As a whole, this simple straightforward sonochemical approach results in more phase pure system with improved magnetization.

Electrochemical insertion of lithium in mechanochemically synthesized Zn2SnO4.

We studied the electrochemical insertion of Li in mechanochemically prepared Zn(2)SnO(4). The mechanism of the electrochemical reaction was investigated by using X-ray diffraction, nuclear magnetic resonance spectroscopy, and Mössbauer spectroscopy. Changes in the morphology of the Zn(2)SnO(4) particles were studied by in situ scanning electron microscopy. The results were compared with mixtures of SnO(2) + ZnO and with Zn(2)SnO(4) prepared by conventional solid-state synthesis and showed that the mechanochemically prepared Zn(2)SnO(4) exhibits the best cyclic stability of these samples.

Effect of palladium on the reducibility of Mn based materials: correlation with methane oxidation activity.

Mn-based oxide supports were synthesized using different procedures: (i) carbonate co-precipitation method, leading to the formation of a hexaaluminate crystallized solid (La(0.2)Sr(0.3)Ba(0.5)MnAl(11)O(19)) and (ii) solid-solid diffusion method, leading to the formation of a doped theta-Al(2)O(3) crystallized solid (nominal composition: 60 wt% La(0.2)Sr(0.3)Ba(0.5)MnAl(11)O(19) + 40 wt% Al(2)O(3)). Impregnation of 1.0 wt%Pd was carried out on both oxides. The solids were tested for the catalytic methane combustion up to 700 degrees C. It was observed that adding palladium resulted in an important increase in the catalytic activity. The combined use of H(2)-TPR and XPS techniques reveals that only Mn(3+)/Mn(2+) redox "couple" is present in the solids, whatever the synthesis procedure used. The fraction Mn(3+)/Mn is proportional to the total Mn content in the solid support, whatever the sample structure (hexaaluminate or doped theta-Al(2)O(3)) and its morphology (large crystals or aggregates of small particles, respectively). Pd impregnation and further calcination at 650 degrees C has no significant effect on the Mn(3+)/Mn fraction. However, some changes in Mn(3+) reduction profile are observed, depending on the solid structure. Indeed, palladium addition strongly affects the manganese reducibility with an important shift of the reduction process to lower temperatures (approximately 100 degrees C). On the basis of redox properties observed for the different catalysts, a Mars-van-Krevelen redox mechanism, with oxygen transfer from support oxides to palladium particles, is proposed to explain the difference in terms of catalytic conversion and stability with respect to a 1.0 wt%Pd/Al(2)O(3) reference sample.

Formation of a novel type of reverse microemulsion system and its application in synthesis of the nanostructured La0.95Ba0.05MnAl11O19 catalyst.

In the study, a novel microemulsion system, consisting of water, iso-propanol and n-butanol, was developed to synthesize the nanostructured La(0.95)Ba(0.05)MnAl(11)O(19) catalyst with high surface area and catalytic activity for methane combustion.