Recent Development of Copper-Based Nanozymes for Biomedical Applications.

Copper (Cu), an indispensable trace element within the human body, serving as an intrinsic constituent of numerous natural enzymes, carrying out vital biological functions. Furthermore, nanomaterials exhibiting enzyme-mimicking properties, commonly known as nanozymes, possess distinct advantages over their natural enzyme counterparts, including cost-effectiveness, enhanced stability, and adjustable performance. These advantageous attributes have captivated the attention of researchers, inspiring them to devise various Cu-based nanomaterials, such as copper oxide, Cu metal-organic framework, and CuS, and explore their potential in enzymatic catalysis. This comprehensive review encapsulates the most recent advancements in Cu-based nanozymes, illuminating their applications in the realm of biochemistry. Initially, it is delved into the emulation of typical enzyme types achieved by Cu-based nanomaterials. Subsequently, the latest breakthroughs concerning Cu-based nanozymes in biochemical sensing, bacterial inhibition, cancer therapy, and neurodegenerative diseases treatment is discussed. Within this segment, it is also explored the modulation of Cu-based nanozyme activity. Finally, a visionary outlook for the future development of Cu-based nanozymes is presented.

A novel two-dimensional NiCl2O8 lattice with negative Poisson's ratio and magnetic modulation.

Two-dimensional (2D) materials with simultaneous magnetic semiconducting properties and a negative Poisson's ratio are crucial for fabricating multifunctional electronic devices. However, progress in this area has been generally constrained. Based on first-principles calculations, we engineered a 2D Ni-based oxyhalide with a honeycomb lattice structure. It was observed that the NiCl2O8 monolayer exhibits both high- and low-buckling states in its geometry, along with intrinsic magnetic semiconductor properties in its electronic structure. Importantly, we demonstrated that the magnetic ordering of the NiCl2O8 lattice is susceptible to applied strain, which resulted in a phase transition from paramagnetic to ferromagnetic under biaxial strain. The Curie temperature was also evaluated using Monte Carlo simulations within the Ising model. Additionally, our research uncovered that the 2D NiCl2O8 lattice chain displays a negative Poisson's ratio (NPR) along the z-direction. The triangular hinge structure in its centrosymmetric configuration was identified as the origin of this unique phenomenon. The coexistence of NPR and magnetic phase transition properties in the NiCl2O8 lattice makes it quite promising for applications in nanoelectronic and spintronic devices.

Inverted Lowest Singlet and Triplet Excitation Energy Ordering of Graphitic Carbon Nitride Flakes.

In organic light-emitting diodes (OLEDs), only 25% of electrically generated excitons are in a singlet state, S1, and the remaining 75% are in a triplet state, T1. In thermally activated delayed fluorescence (TADF) chromophores the transition from the nonradiative T1 state to the radiative S1 state can be thermally activated, which improves the efficiency of OLEDs. Chromophores with inverted energy ordering of S1 and T1 states, S1 < T1, are superior to TADF chromophores, thanks to the absence of an energy barrier for the transition from T1 to S1. We benchmark the performance of time-dependent density functional theory using different exchange-correlation functionals and find that scaled long-range corrected double-hybrid functionals correctly predict the inverted singlet-triplet gaps of N-substituted phenalene derivatives. We then show that the inverted energy ordering of S1 and T1 is an intrinsic property of graphitic carbon nitride flakes. A design strategy of new chromophores with inverted singlet-triplet gaps is proposed. The color of emitted light can be fine-tuned through flake size and amine substitution on flake vertices.

Piezoelectric Effect Modulates Nanozyme Activity: Underlying Mechanism and Practical Application.

Nanozyme activity relies on surface electron transfer processes. Notably, the piezoelectric effect plays a vital role in influencing nanozyme activity by generating positive and negative charges on piezoelectric materials' surfaces. This article comprehensively reviews the potential mechanisms and practical applications of regulating nanozyme activity through the piezoelectric effect. The article first elucidates how the piezoelectric effect enables nanozymes to exhibit catalytic activity. It is highlighted that the positive and negative charges produced by this effect directly participate in redox reactions, leading to the conversion of materials from an inactive to an active state. Moreover, the piezoelectric field generated can enhance nanozyme activity by accelerating electron transfer rates or reducing binding energy between nanozymes and substrates. Practical applications of piezoelectric nanozymes are explored in the subsequent section, including water pollutant degradation, bacterial disinfection, biological detection, and tumor therapy, which demonstrate the versatile potentials of the piezoelectric effect in nanozyme applications. The review concludes by emphasizing the need for further research into the catalytic mechanisms of piezoelectric nanozymes, suggesting expanding the scope of catalytic types and exploring new application areas. Furthermore, the promising direction of synergistic catalytic therapy is discussed as an inspiring avenue for future research.

Structurally diverse polycyclic polyprenylated acylphloroglucinols with protective effect on human vein endothelial cells injured by high-glucose from Hypericum acmosepalum N. Robson.

Hyperacmotone A, a polycyclic polyprenylated acylphloroglucinol (PPAP) with an unprecedented skeleton, along with five undescribed congeners and eleven reported ones, was isolated from Hypericum acmosepalum. Hyperacmotone A possesses a unique monocyclic ring skeleton based on a cyclopent-4-ene-1,3-dione acylphloroglucinol core. Their structures were elucidated by extensive analysis of HRESIMS, NMR, biogenetic pathway, and quantum-chemical calculations. In addition, hypercohone G exhibited significant protective effects on high-glucose-injured HUVECs.

A Molybdenum Disulfide Nanozyme with Charge-Enhanced Activity for Ultrasound-Mediated Cascade-Catalytic Tumor Ferroptosis.

The deficient catalytic activity of nanozymes and insufficient endogenous H2 O2 in the tumor microenvironment (TME) are major obstacles for nanozyme-mediated catalytic tumor therapy. Since electron transfer is the basic essence of catalysis-mediated redox reactions, we explored the contributing factors of enzymatic activity based on positive and negative charges, which are experimentally and theoretically demonstrated to enhance the peroxidase (POD)-like activity of a MoS2 nanozyme. Hence, an acidic tumor microenvironment-responsive and ultrasound-mediated cascade nanocatalyst (BTO/MoS2 @CA) is presented that is made from few-layer MoS2 nanosheets grown on the surface of piezoelectric tetragonal barium titanate (T-BTO) and modified with pH-responsive cinnamaldehyde (CA). The integration of pH-responsive CA-mediated H2 O2 self-supply, ultrasound-mediated charge-enhanced enzymatic activity, and glutathione (GSH) depletion enables out-of-balance redox homeostasis, leading to effective tumor ferroptosis with minimal side effects.

Stem Cell Membrane-Encapsulated Zeolitic Imidazolate Framework-8: A Targeted Nano-Platform for Osteogenic Differentiation.

Mesenchymal stem cells (MSCs) have been recognized as one of the most promising pharmaceutical multipotent cells, and a key step for their wide application is to safely and efficiently regulate their activities. Various methods have been proposed to regulate the directional differentiation of MSCs during tissue regeneration, such as nanoparticles and metal ions. Herein, nanoscale zeolitic imidazolate framework-8 (ZIF-8), a Zn-based metal-organic framework, is modified to direct MSCs toward an osteoblast lineage. Specifically, ZIF-8 nanoparticles are encapsulated using stem cell membranes (SCMs) to mimic natural molecules and improve the biocompatibility and targeted ability toward MSCs. SCM/ZIF-8 nanoparticles adjust the sustained release of Zn2+ , and promote their specific internalization toward MSCs. The internalized SCM/ZIF-8 nanoparticles show excellent biocompatibility, and increase MSCs' osteogenic potentials. Moreover, RNA-sequencing results elucidate that the activated cyclic adenosine 3,5-monophosphate (cAMP)-PKA-CREB signaling pathway can be dominant in accelerating osteogenic differentiation. In vivo, SCM/ZIF-8 nanoparticles greatly promote the formation of new bone tissue in the femoral bone defect detected by 3D micro-CT, hematoxylin and eosin staining, and Masson staining after 4 weeks. Overall, the SCM-derived ZIF-8 nanostructures achieve the superior targeting ability, biocompatibility, and enhanced osteogenesis, providing a constructive design for tissue repair.

A Titanium Nitride Nanozyme for pH-Responsive and Irradiation-Enhanced Cascade-Catalytic Tumor Therapy.

Nanozyme-based catalytic tumor therapy is an emerging therapeutic method with high reactivity in response to tumor microenvironments (TMEs). To overcome the current limitations of deficient catalytic activity of nanozymes, we studied the contributing factors of enzymatic activity based on non-metallic-atom doping and irradiation. Nitrogen doping significantly enhanced the peroxidase activity of Ti-based nanozymes, which was shown experimentally and theoretically. Based on the excellent NIR-adsorption-induced surface plasmon resonance and photothermal effect, the enzymatic activity of TiN nanoparticles (NPs) was further improved under NIR laser irradiation. Hence, an acidic TME-responsive and irradiation-mediated cascade nanocatalyst (TLGp) is presented by using TiN-NP-encapsulated liposomes linked with pH-responsive PEG-modified glucose oxidase (GOx). The integration of pH-responsive GOx-mediated H2 O2 self-supply, nitrogen-doping, and irradiation-enhanced enzymatic activity of TiN NPs and mild-photothermal therapy enables an effective tumor inhibition by TLGp with minimal side effects in vivo.

Heterojunction of Vertically Arrayed MoS2 Nanosheet/N-Doped Reduced Graphene Oxide Enabling a Nanozyme for Sensitive Biomolecule Monitoring.

Enzymes are still indispensable for bio-assaying methods in biomolecule detection by far. The unsatisfied long-term instability, high cost, and susceptibility to the physical environment of natural enzymes are obvious weak points. Here, we developed peroxidase-like heterostructured nanozyme, vertically arraying molybdenum disulfide nanosheets on a substrate layer of nitrogen-doped reduced graphene oxide (MoS2/N-rGO), with a well-pleasing stability that is characterized by the retained enzymatic activity and maintained structure after 2 years of casual storage at ambient temperatures or 80 cycles of catalytic reaction. The catalytic kinetics of the as-prepared heterostructured nanozyme was superior to some reported nanozymes and even horse radish peroxidase, which was demonstrated due to the defect-rich MoS2 with Mo and S vacancies and nitrogen-doped rGO experimentally and theoretically. The vertically heterostructured nanozyme exhibited adequate analytical performance in sensitive and quantitative detection of glucose and glutathione (GSH), with a large dynamic sensing range and extremely low limit of detection (0.02 and 0.12 µM (3σ/slope) for glucose and GSH, respectively). We hope this inspired artificial nanozyme will contribute to the future development in sensitive detection of other biomolecules in physiological conditions.

Full Solar-Spectrum-Driven Antibacterial Therapy over Hierarchical Sn3 O4 /PDINH with Enhanced Photocatalytic Activity.

Antibacterial photocatalytic therapy (APCT) is considered to be a potential treatment for administrating antibiotic-resistant bacteria. However, due to the low photocatalytic efficiency and weak ability to capture bacteria, it is not practically applied. In this work, an organic-metal oxide hybrid semiconductor heterostructure is fabricated for the photocatalytic generation of reactive oxygen species (ROS) to kill the drug-resistant bacteria. The organic semiconductor, perylene diimide (PDI), can self-assemble on Sn3 O4 nanosheets to form a "hook-and-loop" sticky surface that can capture bacteria, via large numbers of hydrogen bonding and π-π stacking interactions, which are not possible in inorganic semiconductors. This easy-to-fabricate hybrid semiconductor also possesses improved photocatalytic activity, which is owing to the formation of heterostructure that achieves full-spectrum absorption, and the reduction of the photocarrier recombination rate to produce more reactive oxygen species. It has a good promoting effect on the wounds of mice infected by Staphylococcus aureus. This work shows new ideas for fabricating smart full-spectrum inorganic-organic hybrid adhesive heterostructure photocatalysts for antibacterial photocatalytic therapy.

Spin-Gapless States in Two-Dimensional Molecular Ferromagnet Fe2(TCNQ)2.

Two-dimensional van der Waals magnetic atomic crystals have provided unprecedented access to magnetic ground states due to a quantum confinement effect. Here, using first-principles calculations, we demonstrate a spin-gapless molecular ferromagnet, namely, Fe2(TCNQ)2, with superior mechanical stability and a remarkable linear Dirac cone, which can be exfoliated from its already-synthesized van der Waals crystal. Especially, Young's modulus has values of 175.28 GPa·nm along the x- and y-directions with a Poisson's ratio of 0.29, while the Curie temperature within the Ising model is considerably higher than room temperature. Furthermore, spin-orbit coupling can open a band gap at the Dirac point, leading to topologically nontrivial electronic states characterized by an integer value of the Chern number and the edge states of its nanoribbon. Our results offer versatile platforms for achieving plastic spin filtering or a quantum anomalous Hall effect with promising applications in spintronics devices.

Acmoxanthones A-E, New Lavandulated Xanthones from Hypericum acmosepalum N. Robson.

Acmoxanthones A-E (1-5), five new lavandulylated xanthones, were isolated from the aerial parts of Hypericum acmosepalum, together with four known xanthones. Their structures with absolute configurations were elucidated on the basis of analysis of MS, NMR and chiroptical properties. A bioassay against high glucose-induced damage on human umbilical vein endothelial cells (HUVECs) showed ananixanthone (6) and osajaxanthone (7) had potential antioxidative damage activity with EC50 values of 10.5 µg/mL and 7.6 µg/mL, respectively, while 3-hydroxy-2,4-dimethoxyxanthone (8) exhibited cytotoxic effect on the damaged cells with IC50 values of 7.1 µg/mL.

Structurally diverse polyprenylated acylphloroglucinols from Hypericum uralum Buch.-Ham. ex D. Don.

Uralins A - D, four undescribed polycyclic polyprenylated acylphloroglucinols (PPAPs) featuring an unprecedented fused hexacyclic architecture, a unique monocyclic tetra-seco-tetranor-b-PPAP, an oxidative b-PPAP and a rare norspiroindane-type m-PPAP, respectively, were isolated from the aerial parts of Hypericum uralum, along with ten known PPAPs. Their structures and absolute configurations were elucidated by extensive spectroscopic techniques (MS, NMR, [α]D, CD), conceivable biogenetic pathways and time-dependent density functional theory-based electronic circular dichroism (TDDFT-ECD) calculations. Biological assays showed three b-PPAPs had moderate antioxidative damage activities, while spiroindanes exhibited moderate cytotoxic effects.

CeO2 Nanocrystal Decorated TiO2 Nanobelt with Enhanced Photocatalytic Performance.

In this work, CeO2 nanocrystal-decorated TiO2 nanobelt for forming a CeO2@TiO2 heterostructure. CeO2 plays a dual role in improving photocatalytic activity, not only by promoting the separation and transfer of photogenerated charge carriers, but also by increasing visible light absorption of the photocatalyst as a photosensitizer. The as-prepared CeO2@TiO2 heterostructure demonstrates the performance of organic degradation and H2 production (about 17 µmol/h/g, which is about 2.5 times higher than that of pure TiO2 nanobelts). Our work provides a facile and controllable synthesis method for high performance photocatalyst, which will have potential applications in synthesis clean/solar fuel, and photocatalytic water treatment.

Defect-Rich Adhesive Molybdenum Disulfide/rGO Vertical Heterostructures with Enhanced Nanozyme Activity for Smart Bacterial Killing Application.

Nanomaterials with intrinsic enzyme-like activities, namely "nanozymes," are showing increasing potential as a new type of broad-spectrum antibiotics. However, their feasibility is still far from satisfactory, due to their low catalytic activity, poor bacterial capturing capacity, and complicated material design. Herein, a facile synthesis of a defect-rich adhesive molybdenum disulfide (MoS2 )/rGO vertical heterostructure (VHS) through a one-step microwave-assisted hydrothermal method is reported. This simple, convenient but effective method for rapid material synthesis enables extremely uniform and well-dispersed MoS2 /rGO VHS with abundant S and Mo vacancies and rough surface, for a performance approaching the requirements of practical application. It is demonstrated experimentally and theoretically that the as-prepared MoS2 /rGO VHS possesses defect and irradiation dual-enhanced triple enzyme-like activities (oxidase, peroxidase, and catalase) for promoting free-radical generation, owing to much more active edge sites exposure. Meanwhile, the VHS-achieved rough surface exhibits excellent capacity for bacterial capture, with elevated reactive oxygen species (ROS) destruction through local topological interactions. As a result, optimized efficacy against drug-resistant Gram-negative and Gram-positive bacteria can be explored by such defect-rich adhesive nanozymes, demonstrating a simple but powerful way to engineered nanozymes for alternative antibiotics.

A Microorganism Bred TiO2/Au/TiO2 Heterostructure for Whispering Gallery Mode Resonance Assisted Plasmonic Photocatalysis.

The TiO2/Au nanostructure has been acknowledged as one of the most classic visible-light active photocatalysts due to the surface plasmon resonance (SPR) of Au nanoparticles. In many cases, the SPR effect only features weak visible light absorption in conventional TiO2/Au nanostructures. Here, we demonstrate a design of TiO2/Au/TiO2 with a combination of whispering gallery mode (WGM) resonances and SPR for efficient visible-light-driven photocatalysis. Escherichia coli (E. coli) were used as natural reactants as well as a template to construct an E. coli-like TiO2/Au/TiO2 nanostructure. Using numerical simulations, we show that the E. coli-like TiO2 capsule acts as the WGM resonator to interplay with the SPR effect of the Au NPs on TiO2 surface, which leads to a significant increase of visible light absorption and the local field enhancement at the Au-TiO2 interface. Accordingly, with the synergistic effect of WGM and SPR, the E. coli-like TiO2/Au/TiO2 nanostructure exhibits enhanced photocatalytic activity in the visible range. Our work reveals a promising bioapproach to a design highly visible light active plasmonic photocatalyst.

Recycling of titanium-coagulated algae-rich sludge for enhanced photocatalytic oxidation of phenolic contaminants through oxygen vacancy.

In the 21st century, sludge disposal and resource recycling are global issues. Titanium coagulation has received increasing attention due its strong coagulation capability and sludge recycling. Titanium coagulation is highly efficient for the treatment of algae-laden micro-polluted surface water; however, the safe disposal of titanium-coagulated algae-rich sludge remains a challenge. Here, we report on the recycling of titanium-coagulated algae-rich sludge for the production of functional TiO2 nanoflowers (TNFs) through a simple hydrothermal and calcination process. Anatase TNFs (particle size of 10-15 nm) with petal-like structures (mesoporous), relatively high specific surface areas, i.e. 299.4 m2g-1, and low band gaps, i.e. 2.67 eV (compared to P-25), were obtained. Additionally, oxygen vacancy (OV) was generated on the surface of the recycled TNFs based on electron paramagnetic resonance (EPR) results, which were verified by the first-principles calculations within density-functional theory. These TNFs display high photocatalytic performance for the degradation of diverse phenolic organic contaminants, such as bisphenol A, diphenyl phenol, p-tert-butyl phenol, and resorcinol, i.e. > 95%, under mild ultraviolet light irradiation and without any sacrificial reagents. Formation of OV on TNFs not only efficiently inhibited the recombination of photo-generated electrons and holes but also facilitated contaminant adsorption and photo-generated electron transfer on the surface of the recycled TNFs, thereby promoting the generation of holes and hydroxyl and superoxide radicals which were regarded as the reactive oxygen species for attacking contaminants in the reactions. This study proposes a new perspective on recycling chemical-coagulated sludge for producing functional nanomaterials as photocatalysts.

NaGdF4:Yb/Er nanoparticles of different sizes for tracking mesenchymal stem cells and their effects on cell differentiation.

Mesenchymal stem cells (MSCs) hold great promise in the field of regenerative medicine, and great effort goes into investigating the mechanisms underlying their therapeutic effects. These investigations necessitate the development of sensitive and reliable methods of tracking stem cells. As the unique physicochemical properties of ß-NaGdF4:Yb/Er upconversion nanoparticles make them highly efficient fluorescent probes, they could be utilized to track stem cells through bio-imaging. However, their biocompatibility constitutes a major challenge to their use in biomedical applications. In this paper, we prepared ligand-free spherical ß- NaGdF4:Yb/Er nanoparticles of two different sizes (~15 and ~30 nm in diameter) and investigated their internalization into rat bone marrow-derived MSCs (rBMSCs), as well as their effects on cell proliferation, osteogenic and adipogenic differentiation. Even though particles of both sizes were efficiently taken up by the cells, the larger particles had a stronger fluorescence intensity but their proliferation was not significantly affected; this makes them superior for cell imaging. Analysis of multiple markers revealed that the nanoparticles, especially the larger ones, promoted the process of osteogenic differentiation. In contrast, adipogenesis was slightly hindered by the larger particles, whereas the smaller ones did not affect the process. As a whole, this study suggests that ligand-free spherical ß-NaGdF4:Yb/Er particles of appropriate size are compatible with stem cell proliferation and differentiation, which makes them promising agents for biomedical applications.

Enhanced Antibacterial Photocatalytic Activity of Porous Few-Layer C3N4.

Nowadays, antibacterial photocatalytic activity of semiconductors has attracted great attention due to its excellent stability, good biocompatibility and no disinfection byproducts. Herein, a porous few-layer C3N4 was successfully fabricated via a simple and low-cost bottom-up method. The asprepared porous few-layer C3N4 exhibits large specific surface areas, which is about 4.8 times than bulk C3N4. Under the light (<430 nm) irradiation, reactive oxygen species (ROS) (singlet oxygen (1O2), hydroxyl radicals (·OH), and superoxide (O·-2)) can be generated. The porous few-layer C3N4 was used as an antibacterial agent to kill gram-positive bacterium S. Aureus with an anibacterial efficiency up to 99.7%. The log removal rate of the porous few-layer C3N4 is more than 50 times than the bulk C3N4. The material shows a potential application in water purification and antibacterial photocatalytic therapy.

Highly-efficient overall water splitting in 2D Janus group-III chalcogenide multilayers: the roles of intrinsic electric filed and vacancy defects.

Two-dimensional (2D) van der Waals materials have been widely adopted as photocatalysts for water splitting, but the energy conversion efficiency remains low. On the basis of first-principles calculations, we demonstrate that the 2D Janus group-III chalcogenide multilayers: InGaXY, M2XY and InGaX2 (M = In/Ga; X, Y = S/Se/Te), are promising photocatalysts for highly-efficient overall water splitting. The intrinsic electric field enhances the spatial separations of photogenerated carriers and alters the band alignment, which is more pronounced compared with the Janus monolayers. High solar-to-hydrogen (STH) efficiency with the upper limit of 38.5% was predicted in the Janus multilayers. More excitingly, the Ga vacancy of InGaSSe bilayer effectively lowers the overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) to the levels provided solely by the photogenerated carriers. Our theoretical results suggest that the 2D Janus group-III chalcogenide multilayers could be utilized as highly efficient photocatalysts for overall water splitting without the needs of sacrificial reagents.