Decomposition Of MnO2 Research Articles

Boosting Antitumor Immunity via a Tumor Microenvironment‐Responsive Transformable Trifecta Nanovaccine

AbstractIn situ tumor vaccines (ISTVs) hold great potential in tumor immunotherapy, however, three major obstacles, including inadequate endogenous antigen uptake by dendritic cells (DCs), weak T‐cell immune responses, and stubborn immunosuppressive tumor microenvironment (TME), still need to be fully addressed. Herein, a trifecta nanovaccine (TriNV) with TME‐responsive transformable ability is developed to tri‐boost antitumor immunity. First, sufficient endogenous tumor‐associated antigens (TAAs) are liberated in situ after immunogenic cell death is induced via TriNV‐based photoimmunotherapy. In the TME, soft‐transformed TriNV improves the uptake of TAAs by DCs to enhance acquired immunity. Second, the self‐adjuvating TriNV and the TME‐responsive released Mn2+ synergistically promote DC maturation and macrophage M1 polarization by augmenting the stimulator of interferon genes activation to further amplify T‐cell immune responses. Moreover, the decomposition of MnO2 within the core of TriNV exhausts glutathione and facilitates O2 release to alleviate hypoxia in the TME, thereby overcoming the chemical obstacles of the TME to further mitigate immunosuppression. Thus, TriNV remarkably eradicates primary tumors and inhibits distant metastasis, thus demonstrating great potential as a feasible and effective ISTV nanoplatform for combating poorly immunogenic solid tumors.

Mitochondria-targeted and multistage synergistic ROS-elevated drug delivery system based on surface decorated MnO2 with CeO2 for enhanced chemodynamic/chemotherapy

Mitochondria-targeted drug delivery nano-platform for the generation of endogenous reactive oxygen species (ROS) are envisioned as a promising strategy for inducing cytotoxicity and inhibiting tumor growth. However, how to induce excessive ROS in cancer cell remains a challenge. Herein, mitochondria-targeted combination therapy platform of chemodynamic (CDT)/chemotherapy was constructed for enhanced generation of ROS based on the multistage synergistic effect of MnO2/CeO2-meditated Fenton-like reaction and glutathione (GSH) depletion, as well as camptothecin (CPT). After accumulation in mitochondria via surface targeting molecule TPP, the MnO2 depleted over-expressed GSH to generate Mn2+, which can convert endogenous H2O2 to highly toxic hydroxyl radicals (·OH) based on Fenton-like reaction, and outside surface CeO2 can elevate the ·OH level by Fenton-like reaction. Besides, the gradual depletion of over-expressed GSH decreased the scavenging effect on the highly reactive ·OH, improving the CDT efficacy. Additionally, the released CPT accompanied by the decomposition of MnO2 would further stimuli ROS generation in mitochondria, resulting in the amplified ROS effect. In vivo experiments suggested that the combination therapy platform performed obvious inhibition to tumor based on the enhanced CDT/chemotherapy, which provide a novel approach for the ROS-based cancer combination therapy.

Natural ferruginous manganese ore for efficient immobilization of elemental mercury from coal combustion flue gas

Mercury emission from industrial activities poses a serious threat to the ecosystem. The development of cost-effective sorbents for mercury removal is a feasible method to alleviate this problem. In this study, natural ferruginous manganese ore (NFM) was adopted as a cost-effective sorbent for elemental mercury (Hg0) removal from flue gas. Samples characterization indicated that the pore stricture of NFM was deteriorated after calcination procedure. The secondary recrystallization of manganese oxides and decomposition of MnO2 into Mn2O3 also happened during calcination process. Raw NFM exhibited high Hg0 removal efficiency (ET > 80%) over a broad temperature range (100 °C–200 °C), whereas calcination procedure had negative effects on Hg0 removal performance. The effects of calcination temperature (450 °C–650 °C) and reaction temperature (100 °C–400 °C) on Hg0 removal performance were also explored. Under the simulated flue gas condition, both equilibrium mercury adsorption capacity and adsorption rate were superior to those of a commercial activated carbon specifically used for mercury emission reduction. The Hg0 removal mechanism was revealed by combining with Hg0 adsorption/oxidization behavior and XPS analysis. It was demonstrated that chemisorption dominated Hg0 removal process, where MnO2 could serve as active components for Hg0 capture. The results were affirmed by the mercury temperature programmed desorption experiments.

A thiamine-triggered fluormetric assay for acetylcholinesterase activity and inhibitor screening based on oxidase-like activity of MnO2 nanosheets

Acetylcholinesterase (AChE) plays an essential role in biological signal transmission, the aberrant expression of which could cause diverse neurodegenerative diseases. Herein, based on the oxidase-like activity of manganese dioxide nanosheets (MnO2 NSs), we found that MnO2 NSs could directly oxidize thiamine into intensely fluorescent thiochrome without the need of peroxides. When AChE was introduced, acetylthiocholine could be hydrolyzed to generate thiocholine, which efficiently triggered the reduction of MnO2 NSs into Mn2+, resulting in the decrease of fluorescence. Owing to the inhibiting effect of tacrine to the AChE activity, the decomposition of MnO2 was hindered, thus leading to the fluorescence recovery. According to the above mechanism, we constructed a simple, low-cost, label-free, facile and rapid synthetic fluorescent biosensor for highly sensitive and selective detection of AChE activity and screening of its inhibitor. This biosensor obtained a good linear range from 0.02 to 1 mU/mL and an extremely low detection limit of 15 μU/mL for AChE assay, as well as a sensitive screening for tacrine and an excellent applicability in human serum samples. These results suggested that our proposed method would be potentially applied in monitoring the disease progression.

A comparative study of MnO2 and composite MnO2–Ag nanostructures prepared by a hydrothermal technique on supercapacitor applications

Pure MnO2 and composite MnO2–Ag electrodes with four different structures were synthesized via a hydrothermal process. Tube, urchin, rod and wire/sphere-like structures were obtained from the addition of HCl, H2SO4, (NH4)2S2O8 or CO(NH2)2 reagents into potassium permanganate solutions, respectively. The crystal structure of the MnO2 particles was examined using X-ray diffraction and transmission electron microscopy, revealing an α-phase MnO2. Specific capacitance values of 74.5, 111.7, 103.4 and 204.1 F g−1 at a charge/discharge current density of 0.3 A g−1 were obtained for tube, urchin, rod and wire/sphere-like pure MnO2 structures, respectively. The wire/sphere-like structure delivered the highest specific capacitance owing to its largest specific surface area (164.60 m2 g−1). The specific capacitances were further increased to 96.6, 210.9 and 186.4 F g−1, respectively, for tube, urchin and rod-like structures after Ag addition. Additionally, the capacitance retention of the rod and wire/sphere-like composite MnO2–Ag films were also prolonged because Ag nanoparticles prevented the aggregation and/or decomposition of MnO2.