Browse
Submit Data
Databases
API
Help

Dataset Information

32 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Chemical and Colloidal Dynamics of MnO₂ Nanosheets in Biological Media Relevant for Nanosafety Assessment.

ABSTRACT: Many layered crystal phases can be exfoliated or assembled into ultrathin 2D nanosheets with novel properties not achievable by particulate or fibrous nanoforms. Among these 2D materials are manganese dioxide (MnO₂ ) nanosheets, which have applications in batteries, catalysts, and biomedical probes. A novel feature of MnO₂ is its sensitivity to chemical reduction leading to dissolution and Mn²⁺ release. Biodissolution is critical for nanosafety assessment of 2D materials, but the timing and location of MnO₂ biodissolution in environmental or occupational exposure scenarios are poorly understood. This work investigates the chemical and colloidal dynamics of MnO₂ nanosheets in biological media for environmental and human health risk assessment. MnO₂ nanosheets are insoluble in most aqueous phases, but react with strong and weak reducing agents in biological fluid environments. In vitro, reductive dissolution can be slow enough in cell culture media for MnO₂ internalization by cells in the form of intact nanosheets, which localize in vacuoles, react to deplete intracellular glutathione, and induce cytotoxicity that is likely mediated by intracellular Mn²⁺ release. The results are used to classify MnO₂ nanosheets within a new hazard screening framework for 2D materials, and the implications of MnO₂ transformations for nanotoxicity testing and nanosafety assessment are discussed.

SUBMITTER: Gray EP

PROVIDER: S-EPMC7461694 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Chemical Dissolution Pathways of MoS2 Nanosheets in Biological and Environmental Media.

Project description:Material stability and dissolution in aqueous media are key issues to address in the development of a new nanomaterial intended for technological application. Dissolution phenomena affect biological and environmental persistence; fate, transport, and biokinetics; device and product stability; and toxicity pathways and mechanisms. This article shows that MoS2 nanosheets are thermodynamically and kinetically unstable to O2-oxidation under ambient conditions in a variety of aqueous media. The oxidation is accompanied by nanosheet degradation and release of soluble molybdenum and sulfur species, and generates protons that can colloidally destabilize the remaining sheets. The oxidation kinetics are pH-dependent, and a kinetic law is developed for use in biokinetic and environmental fate modeling. MoS2 nanosheets fabricated by chemical exfoliation with n-butyl-lithium are a mixture of 1T (primary) and 2H (secondary) phases and oxidize rapidly with a typical half-life of 1-30 days. Ultrasonically exfoliated sheets are in pure 2H phase, and oxidize much more slowly. Cytotoxicity experiments on MoS2 nanosheets and molybdate ion controls reveal the relative roles of the nanosheet and soluble fractions in the biological response. These results indicate that MoS2 nanosheets will not show long-term persistence in living systems and oxic natural waters, with important implications for biomedical applications and environmental risk.

| S-EPMC5217159 | biostudies-literature

Wet/Sono-Chemical Synthesis of Enzymatic Two-Dimensional MnO2 Nanosheets for Synergistic Catalysis-Enhanced Phototheranostics.

Project description:2D nanomaterials have attracted broad interest in the field of biomedicine owing to their large surface area, high drug-loading capacity, and excellent photothermal conversion. However, few studies report their "enzyme-like" catalytic performance because it is difficult to prepare enzymatic nanosheets with small size and ultrathin thickness by current synthetic protocols. Herein, a novel one-step wet-chemical method is first proposed for protein-directed synthesis of 2D MnO2 nanosheets (M-NSs), in which the size and thickness can be easily adjusted by the protein dosage. Then, a unique sono-chemical approach is introduced for surface functionalization of the M-NSs with high dispersity/stability as well as metal-cation-chelating capacity, which can not only chelate 64 Cu radionuclides for positron emission tomography (PET) imaging, but also capture the potentially released Mn2+ for enhanced biosafety. Interestingly, the resulting M-NS exhibits excellent enzyme-like activity to catalyze the oxidation of glucose, which represents an alternative paradigm of acute glucose oxidase for starving cancer cells and sensitizing them to thermal ablation. Featured with outstanding phototheranostic performance, the well-designed M-NS can achieve effective photoacoustic-imaging-guided synergistic starvation-enhanced photothermal therapy. This study is expected to establish a new enzymatic phototheranostic paradigm based on small-sized and ultrathin M-NSs, which will broaden the application of 2D nanomaterials.

| S-EPMC6587182 | biostudies-literature

Colloidal Synthesis of NbS2 Nanosheets: From Large-Area Ultrathin Nanosheets to Hierarchical Structures.

Project description:Layered NbS2, a member of group-V transition metal dichalcogenides, was synthesized via a colloidal synthesis method and employed as a negative material for a supercapacitor. The morphologies of NbS2 can be tuned from ultrathin nanosheets to hierarchical structures through dynamics controls based on growth mechanisms. Electrochemical energy storage measurements present that the ultrathin NbS2 electrode exhibits the highest rate capability due to having the largest electrochemical surface area and its efficient ion diffusion. Meanwhile, the hierarchical NbS2 shows the highest specific capacitance at low current densities for small charge transfer resistance, displays 221.4 F g-1 at 1 A g-1 and 117.1 F g-1 at 10 A g-1, and cycling stability with 78.9% of the initial specific capacitance after 10,000 cycles. The aggregate or stacking of nanosheets can be suppressed effectively by constructing hierarchical structure NbS2 nanosheets.

| S-EPMC7154151 | biostudies-literature

Colloidal Monolayer β-In2Se3 Nanosheets with High Photoresponsivity.

Project description:We report a low-temperature colloidal synthesis of single-layer, five-atom-thick, β-In2Se3 nanosheets with lateral sizes tunable from ∼300 to ∼900 nm, using short aminonitriles (dicyandiamide or cyanamide) as shape controlling agents. The phase and the monolayer nature of the nanosheets were ascertained by analyzing the intensity ratio between two diffraction peaks from two-dimensional slabs of the various phases, determined by diffraction simulations. These findings were further backed-up by comparing and fitting the experimental X-ray diffraction pattern with Debye formula simulated patterns and with side-view high-resolution transmission electron microscopy imaging and simulation. The β-In2Se3 nanosheets were found to be indirect band gap semiconductors (Eg = 1.55 eV), and single nanosheet photodetectors demonstrated high photoresponsivity and fast response times.

| S-EPMC5942869 | biostudies-literature

MnO2-graphene nanosheets wrapped mesoporous carbon/sulfur composite for lithium-sulfur batteries.

Project description:MnO2-graphene nanosheets wrapped mesoporous carbon/sulfur (MGN@MC/S) composite is successfully synthesized derived from metal-organic frameworks and investigated as cathode for lithium-ion batteries. Used as cathode, MGN@MC/S composite possesses electronic conductivity network for redox electron transfer and strong chemical bonding to lithium polysulfides, which enables low capacity loss to be achieved. MGN@MC/S cathodes exhibit high reversible capacity of 1475 mA h g-1 at 0.1 C and an ultra-low capacity fading of 0.042% per cycle at 1 C over 450 cycles.

| S-EPMC5830778 | biostudies-literature

Self-assembly of 2D MnO2 nanosheets into high-purity aerogels with ultralow density.

Project description:Self-assembling inorganic nanoparticles (NPs) into macroscopic three dimensional (3D) architectures often requires the assistance of organic components, leaving residual organics in the resultant. In this work, organic-free MnO2 aerogels with ultralow density have been achieved by the self-assembly of two dimensional (2D) MnO2 nanosheets via an ice-templating approach. To the authors' best knowledge, it is the first reported case of constructing a high-purity inorganic aerogel from preformed NPs without using any functionalization or stabilization agents. Moreover, it has been demonstrated that an ultralight MnO2 aerogel with a density as low as ∼0.53 mg cm-3, which is the lightest metal oxide aerogel to date, can be well obtained by such an approach. The successful formation of the aerogel can be attributed to the enhanced van der Waals force between the 2D building blocks that have been more orderly arranged by the squeezing of ice crystals during the freezing process. Hence, this work shows a pioneering example of assembling inorganic NPs into aerogels relying only on the weak interactions between NPs (e.g. van der Waals forces). It has also been demonstrated that the obtained MnO2 aerogel can function as an effective absorbent for toxic reducing gas, owing to its strong oxidation ability and high porosity. The strategy presented herein holds good potential to be applied to the fabrication of other high-purity inorganic aerogels, especially those with 2D building blocks readily available.

| S-EPMC5966798 | biostudies-literature

Valence-Change MnO2-Coated Arsenene Nanosheets as a Pin1 Inhibitor for Hepatocellular Carcinoma Treatment.

Project description:The heterogeneity of hepatocellular carcinoma (HCC) can prevent effective treatment, emphasizing the need for more effective therapies. Herein, we employed arsenene nanosheets coated with manganese dioxide and polyethylene glycol (AMPNs) for the degradation of Pin1, which is universally overexpressed in HCC. By employing an "AND gate", AMPNs exhibited responsiveness toward excessive glutathione and hydrogen peroxide within the tumor microenvironment, thereby selectively releasing AsxOy to mitigate potential side effects of As2O3. Notably, AMPNs induced the suppressing Pin1 expression while simultaneously upregulation PD-L1, thereby eliciting a robust antitumor immune response and enhancing the efficacy of anti-PD-1/anti-PD-L1 therapy. The combination of AMPNs and anti-PD-1 synergistically enhanced tumor suppression and effectively induced long-lasting immune memory. This approach did not reveal As2O3-associated toxicity, indicating that arsenene-based nanotherapeutic could be employed to amplify the response rate of anti-PD-1/anti-PD-L1 therapy to improve the clinical outcomes of HCC patients and potentially other solid tumors (e.g., breast cancer) that are refractory to anti-PD-1/anti-PD-L1 therapy.

| S-EPMC11311233 | biostudies-literature

Synthesis and Characterization of MnO2@Cellulose and Polypyrrole-Decorated MnO2@Cellulose for the Detection of Chemical Warfare Agent Simulant.

Project description:Chemical warfare agents (CWAs) have been threatening human civilization and its existence because of their rapid response, toxic, and irreversible nature. The hybrid nanostructured composites were synthesized by the hydrothermal process to detect the dimethyl methyl phosphonate (DMMP), a simulant of G-series nerve agents, especially sarin. Cellulose (CE), manganese oxide cellulose (MnO2@CE), and MnO2@CE/polypyrrole (PPy) exhibited a frequency shift of 0.4, 4.8, and 8.9 Hz, respectively, for a DMMP concentration of 25 ppm in the quartz crystal microbalance (QCM). In surface acoustic wave (SAW) sensor, they exhibited 187 Hz, 276 Hz, and 78 Hz, respectively. A comparison between CE, MnO2@CE, and MnO2@CE/PPy demonstrated that MnO2@CE/PPy possesses excellent linearity with a coefficient of determination (COD or R2) of 0.992 and 0.9547 in the QCM and SAW sensor. The hybrid composite materials showed a reversible adsorption and desorption phenomenon in the reproducibility test. The response and recovery times indicated that MnO2@CE/PPy showed the shortest response (~23 s) and recovery times (~42 s) in the case of the QCM sensor. Hence, the pristine CE and its nanostructured composites were compared to analyze the sensing performance based on sensitivity, selectivity, linearity, reproducibility, and response and recovery times to detect the simulant of nerve agents.

| S-EPMC9606964 | biostudies-literature

The critical role of point defects in improving the specific capacitance of δ-MnO2 nanosheets.

Project description:3D porous nanostructures built from 2D δ-MnO2 nanosheets are an environmentally friendly and industrially scalable class of supercapacitor electrode material. While both the electrochemistry and defects of this material have been studied, the role of defects in improving the energy storage density of these materials has not been addressed. In this work, δ-MnO2 nanosheet assemblies with 150 m2 g-1 specific surface area are prepared by exfoliation of crystalline KxMnO2 and subsequent reassembly. Equilibration at different pH introduces intentional Mn vacancies into the nanosheets, increasing pseudocapacitance to over 300 F g-1, reducing charge transfer resistance as low as 3 Ω, and providing a 50% improvement in cycling stability. X-ray absorption spectroscopy and high-energy X-ray scattering demonstrate a correlation between the defect content and the improved electrochemical performance. The results show that Mn vacancies provide ion intercalation sites which concurrently improve specific capacitance, charge transfer resistance and cycling stability.

| S-EPMC5331340 | biostudies-literature

Metabolomics analysis of MnO2 nanosheets CDT for breast cancer cells and mechanism of cytotoxic action.

Project description:Chemodynamic therapy (CDT) has received more and more attention as an emerging therapeutic strategy, especially transition metals with Fenton or Fenton-like activity have good effects in CDT research, manganese dioxide nanosheets (MnO2 NSs) and their complexes have become one of the most favored nanomaterials in CDT of tumors. CDT is mainly based on the role of reactive oxygen species (ROS) in tumor treatment, which have clear chemical properties and produce clear chemical reactions. However, their mechanism of interaction with cells has not been fully elucidated. Here, we performed CDT on mouse breast cancer cells (4T1) based on MnO2 NSs, extracted the metabolites from the 4T1 cells during the treatment, and analyzed the differences in metabolites by using high-resolution liquid chromatography-mass spectrometry (LC-MS). Untargeted metabolomics studies were conducted using the relevant data. This study mainly explored the changes in MnO2 NSs on the metabolite profile of 4T1 cells and their potential impact on tumor therapy, in order to determine the mechanism of action of MnO2 NSs in the treatment of breast cancer. The results of the study showed the presence of 11 different metabolites in MnO2 NSs CDT for 4T1 tumor cells, including phosphoserine, sphingine, phosphocholine, and stearoylcarnitine. These findings provide a deeper understanding of breast cancer treatment, and are beneficial for the further research and clinical application of CDT.

| S-EPMC10481133 | biostudies-literature