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Carbon-based nanomaterials (CNMs) have recently been found in humans raising a great concern over their adverse roles in the hosts. However, our knowledge of the in vivo behavior and fate of CNMs, especially their biological processes elicited by the gut microbiota, remains poor. Here, we uncovered the integration of CNMs (single-walled carbon nanotubes and graphene oxide) into the endogenous carbon flow through degradation and fermentation, mediated by the gut microbiota of mice using isotope tracing and gene sequencing. As a newly available carbon source for the gut microbiota, microbial fermentation leads to the incorporation of inorganic carbon from the CNMs into organic butyrate through the pyruvate pathway. Furthermore, the butyrate-producing bacteria are identified to show a preference for the CNMs as their favorable source, and excessive butyrate derived from microbial CNMs fermentation further impacts on the function (proliferation and differentiation) of intestinal stem cells in mouse and intestinal organoid models. Collectively, our results unlock the unknown fermentation processes of CNMs in the gut of hosts and underscore an urgent need for assessing the transformation of CNMs and their health risk via the gut-centric physiological and anatomical pathways.

We construct a D–A type fluorescent dye via modification of its structural engineering, and exhibit almost the same quantum yields with the increase of solvent polarity. Furthermore, it shows good emission efficiency in the solid state.

Targeting tumor hydrogen peroxide (H

As next-generation artificial enzymes, nanozymes have shown great promise for tumor catalytic therapy. In particular, their peroxidase-like activity has been employed to catalyze hydrogen peroxide (H2O2) to produce highly toxic hydroxyl radicals (•OH) to kill tumor cells. However, limited by the low affinity between nanozymes with H2O2 and the low level of H2O2 in the tumor microenvironment, peroxidase nanozymes usually produced insufficient •OH to kill tumor cells for therapeutic purposes. Herein, we present a pyrite peroxidase nanozyme with ultrahigh H2O2 affinity, resulting in a 4144- and 3086-fold increase of catalytic activity compared with that of classical Fe3O4 nanozyme and natural horseradish peroxidase, respectively. We found that the pyrite nanozyme also possesses intrinsic glutathione oxidase-like activity, which catalyzes the oxidation of reduced glutathione accompanied by H2O2 generation. Thus, the dual-activity pyrite nanozyme constitutes a self-cascade platform to generate abundant •OH and deplete reduced glutathione, which induces apoptosis as well as ferroptosis of tumor cells. Consequently, it killed apoptosis-resistant tumor cells harboring KRAS mutation by inducing ferroptosis. The pyrite nanozyme also exhibited favorable tumor-specific cytotoxicity and biodegradability to ensure its biosafety. These results indicate that the high-performance pyrite nanozyme is an effective therapeutic reagent and may aid the development of nanozyme-based tumor catalytic therapy.

A wide variety of nanomaterials possess peroxidase-like catalytic activities and show promise as cost-effective and versatile replacements for natural peroxidases. However, a universal tool for pre...

The substituent effects on the electronic structures and peroxidase-mimicking activities of γ-graphyne (GY) and Pd-doped GY are studied by density functional theory calculations. Both the inductive...

While gold compound have been approved for Rheumatoid arthritis treatment as it well suppresses inflammatory cytokines of patients, no such treatment is currently available for COVID-19 treatment

We present a facile route towards a dual single-atom nanozyme composed of Zn and Mo, which utilizes the non-covalent nano-assembly of polyoxometalates, supramolecular coordination complexes as the metal-atom precursor, and a macroscopic amphiphilic aerogel as the supporting substrate. The dual single-atoms of Zn and Mo have a high content (1.5 and 7.3 wt%, respectively) and exhibit a synergistic effect and a peroxidase-like activity. The Zn/Mo site was identified as the main active center by X-ray absorption fine structure spectroscopy and density functional theory calculation. The detection of versatile analytes, including intracellular H

A peroxidase catalyzes the oxidation of a substrate with a peroxide. The search for peroxidase-like and other enzyme-like nanomaterials (called nanozymes) mainly relies on trial-and-error strategies, due to the lack of predictive descriptors. To fill this gap, here we investigate the occupancy of eg orbitals as a possible descriptor for the peroxidase-like activity of transition metal oxide (including perovskite oxide) nanozymes. Both experimental measurements and density functional theory calculations reveal a volcano relationship between the eg occupancy and nanozymes’ activity, with the highest peroxidase-like activities corresponding to eg occupancies of ~1.2. LaNiO3-δ, optimized based on the eg occupancy, exhibits an activity one to two orders of magnitude higher than that of other representative peroxidase-like nanozymes. This study shows that the eg occupancy is a predictive descriptor to guide the design of peroxidase-like nanozymes; in addition, it provides detailed insight into the catalytic mechanism of peroxidase-like nanozymes.

The activity of nanomaterials (NMs) in catalytically scavenging superoxide anions mimics that of superoxide dismutase (SOD). Although dozens of NMs have been demonstrated to possess such activity, the underlying principles are unclear, hindering the discovery of NMs as the novel SOD mimics. In this work, we use density functional theory calculations to study the thermodynamics and kinetics of the catalytic processes, and we develop two principles, namely, an energy level principle and an adsorption energy principle, for the activity. The first principle quantitatively describes the role of the intermediate frontier molecular orbital in transferring electrons for catalysis. The second one quantitatively describes the competition between the desired catalytic reaction and undesired side reactions. The ability of the principles to predict the SOD-like activities of metal-organic frameworks were verified by experiments. Both principles can be easily implemented in computer programs to computationally screen NMs with the intrinsic SOD-like activity., A general predicting theory for superoxide-dismutase mimicking nanomaterials is currently lacking. The present manuscript reports a density functional theory study on the superoxides dismutase-like activity of nanomaterials based on their electronic band structures and surface adsorption energies.

Spinel oxides are promising low-cost catalysts with manifold and controllable physicochemical properties. Trial and error strategies cannot achieve the effective screening of high-performance spinel catalysts. Therefore, unraveling the structure–performance relationship is the foundation for their rational design. Herein, the effects of cations in tetrahedral and octahedral sites on the electronic structures of spinels were systematically investigated using GGA + U calculations based on ACr2O4 (A = Mn, Fe, Co, Ni, and Zn) and Zn/LiB2O4 (B = Cr, Mn, Fe, Co and Ni). The results indicate that the octahedrally coordinated B cations have notable influence on the electronic structures of spinels. The Jahn–Teller active ions Fe2+, Ni2+, Mn3+, Ni3+, Cr4+ and Fe4+ can remarkably reduce the band gaps of spinels and even change their electroconductibilities. These results will provide theoretical insights into the electronic properties of 3d transition metal spinels.

Mussel foot proteins (MFPs) strongly adhere to both hydrophilic and hydrophobic surfaces under wet conditions. This water-resistant adhesion of MFP is ascribed to catechol (1,2-dihydroxybenzene) which is highly contained in the MFP. Currently, little is known about the molecular details of the underwater adhesion of catechol onto a nonpolar hydrophobic surface. By using the density functional theory, we investigate the adhesion of catechol onto a wet graphite surface. We unveil the molecular geometry and energy in the course of the wet adhesion of catechol. Catechol adheres through π-π stacking with the underlying graphite. The surrounding water molecules further strengthen the adhesion by forming hydrogen bonds with catechol. In addition, a significant charge transfer has been observed from wet graphite to the catechol. Consequently, catechol adheres onto the present hydrophobic surface as strongly as onto a hydrophilic silica surface.

Graphene-based nanomaterials, including graphene oxide (GO) and reduced graphene oxide (rGO), play key roles in the nanozyme field. GO and rGO carrying various oxygen-containing functional groups, including epoxy, hydroxyl, ether, endoperoxide, carbonyl, carboxyl, and ester, have been reported to display peroxidase mimicking activities. However, the active center and the underlying mechanism responsible for its peroxidase mimicking activities still remain unclear. Herein, taking the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 as the model reaction, we investigate the possible catalytic mechanisms using DFT calculations. The results indicate that the carbonyl groups are the active centers. The activation of the C[double bond, length as m-dash]O bond is the key step in the catalytic cycle. The results will help realize the rational design of carbon-based nanozymes.

SummarySARS-CoV-2 has emerged as a world public health threat. Herein, we report that the clinical approved auranofin could perfectly inhibit the activity of 3-chymotrypsin-like cysteine protease (Mpro or 3CLpro) of SARS-CoV-2. Gold cluster could significantly inhibit 3CLpro of SARS-COV-2. Phenyl isothiocyanate and Vitamin K3 could well suppress the activity of 3CLpro. For Mpro inhibition, IC50 of auranofin, Vitamin K3, phenyl isothiocyanate, gold cluster are about 0.51μM, 7.96μM, 10.13μM, 1.61μM, respectively. These compounds may be with potentials for treatment SARS-CoV-2 virus replication. Especially for FDA approved auranofin, it is an anti-inflammation drug in clinic, thus it may with strong potential to inhibit virus replication and suppress the inflammation damage in COVID-19 patients. Gold cluster is with better safety index and well anti-inflammation in vitro/vivo, therefore it is with potential to inhibit virus replication and suppress the inflammation damage caused by COVID-19 virus. As Au(I) ion is active metabolism specie derived from gold compounds or gold clusters in vivo, further computational studies revealed Au ion could tightly bind thiol group of Cys145 residue of 3CLpro thus inhibit enzyme activity. Also, phenyl isothiocyanate and Vitamin K3 may interact with thiol group of Cys145 via Michael addition reaction, molecular dynamic (MD) theory studied are applied to confirmed these small molecules are stable in the pocket and inhibit Mpro activity.

The bio-antioxidant ability of nanoceria has been mainly ascribed to its ability to mimic superoxide dismutase (SOD) and catalase (CAT), and its mechanisms are thought to be analogous to those of the natural enzymes. Accordingly, nanoceria has been called a nanozyme, a nanomaterial mimicking enzymes. Because they overlook the real structural features of nanoceria, these hypothetical mechanisms cannot explain the important antioxidant experiments of nanoceria and have little predictive power. We hereby study the O2˙- and H2O2 scavenging mechanisms of nanoceria using first principles calculations, taking into account the role of oxygen vacancies that are practically abundant in nanoceria. The results reveal atomistic-level mechanisms responsible for the SOD and CAT mimetic activities of nanoceria. The newly created surface defect states in the electronic band structures of the shortly-lived intermediate species, called transient surface defect states (TSDSs), play critical roles in the enzyme mimetic catalysis and can serve as the bridge between computations and experiments at the atomistic level. The energy levels of TSDSs, which depend on the concentration and distribution of oxygen vacancies, determine whether the nanoceria is eligible for the catalysis. Besides the known enzyme mimicking mechanisms, the non-catalytic chemical reduction mechanisms are also responsible for the scavenging of O2˙- and H2O2, in which nanoceria serves as a reducing agent rather than a catalyst. The chemical reduction pathways poison the active sites of nanoceria which serve to mimic SOD and thus deteriorate its SOD mimetic activity. The results provide guidance for the engineering of nanoceria for bio-antioxidant applications. In particular, the proposed catalytic model can be generalized for the screening and design of high-performance nanozymes based on semiconductor nanomaterials.

Substitutional B and N doping is a powerful way to modulate the electronic properties of carbon π-conjugated materials. However, the B and N dopants in all the previously reported hybrid materials ...

Recently, two-dimensional layered materials have come forth as encouraging candidates for advanced electronic and optoelectronic applications. Anode materials with high energy-density and diffusion rate are fundamental features for the development of non-lithium ion batteries. Based on the density functional theory calculations, we propose a two-dimensional (2D) sheet of germanium selenide (GeSe) as a promising anode material for a sodium (Na) or potassium (K) ion battery. The phonon dispersion and formation energy verify the dynamic and thermal stability of the GeSe sheet. A substantial charge transfer from the alkali metal atoms to the GeSe sheet enhances the electrical conductivity of GeSe, favorable for an anode material. The Na or K diffusion on the GeSe sheet has a low energy barrier of 0.10 eV, giving a rapid charge/discharge rate without metal clustering. The GeSe sheet has a high theoretical capacity for both Na (707 mA h g−1) and K (530 mA h g−1) ion batteries. The GeSe sheet also gives a low and stable electrode potential comparable to that of a commercial anode material.

The small Sc3 N cluster has only been found in such small cages as C2n (2n=68, 78, 80, 82), whereas the large M3 N (M=Y, Gd, Tb, Tm) clusters choose those larger cages C2n (2n=82-88). Herein, concrete experimental evidence is presented to establish the size effect of the internal metallic cluster on selecting the outer cage of endohedral metallofullerenes (EMFs) by using a medium-sized metal, lutetium, which possesses an ionic radius between Sc and Gd. A series of lutetium-containing EMFs have been obtained and their structures are unambiguously determined as Lu3 N@Ih (7)-C80 , Lu3 N@D5h (6)-C80 , Lu3 N@C2v (9)-C82 , Lu3 N@Cs (51365)-C84 , Lu3 N@D3 (17)-C86 , and Lu3 N@D2 (35)-C88 by single-crystal X-ray diffraction crystallography. It was confirmed that the encaged Lu3 N cluster always adopts a planar geometry in Lu3 N@C80-88 isomers to ensure substantial metal-cage/metal-nitrogen interactions. As a result, the Lu3 N cluster selects the C2v (9)-C82 cage, which also encapsulates Sc3 N, instead of the Cs (39663)-C82 cage which is more suitable for M3 N (M=Y, Gd, Tb, Tm). However, different from Sc3 N, Lu3 N can also template the C84-88 cages which are absent for Sc3 N-containing EMFs, confirming clearly the size effect of the internal cluster on selecting the outer cage.

Nanozymes, the enzyme-mimicking nanomaterials, have been developed to overcome the low stability and high cost of natural enzymes. Unlike highly active and specific enzymes, however, the catalytic ...

The structural transformation and mechanical properties of fullerenes under high pressure have attracted a significant interest. However, the research data on the large-cage endohedral metallofulle...

A new Gd@C2v(9)-C82·2.5(S8)·0.5(CS2) co-crystal was prepared for the first time and characterized by single-crystal X-ray diffraction (XRD). The analysis clearly showed that, even though the C2v(9)-C82 cage is fully ordered, the endohedral Gd atoms are highly disordered. This result indicates the presence of highly delocalized endohedral Gd atoms, which has never been reported before. Density functional theory (DFT) calculations were used to rationalize the XRD results. The calculations reveal the presence of two local energy minima, a and b, with the latter existing as four conformers b1–b4. Whereas the energy difference between the two minima is calculated only ∼ 10 kcal/mol, their interconversion is almost impossible due to a high energy barrier, of up to 35.98 kcal/mol. This suggests the existence of multiple low-energy positions for the endohedral Gd atom. In addition, a remarkable electron transfer from the C2v(9)-C82 cage to the S8 moieties was demonstrated, which might result in a modified endohedral environment and further contribute to the occurrence of delocalized endohedral Gd atoms.