Nanozyme-Enhanced Electrochemical Biosensors: Mechanisms and Applications.

Nanozymes, as innovative materials, have demonstrated remarkable potential in the field of electrochemical biosensors. This article provides an overview of the mechanisms and extensive practical applications of nanozymes in electrochemical biosensors. First, the definition and characteristics of nanozymes are introduced, emphasizing their significant role in constructing efficient sensors. Subsequently, several common categories of nanozyme materials are delved into, including metal-based, carbon-based, metal-organic framework, and layered double hydroxide nanostructures, discussing their applications in electrochemical biosensors. Regarding their mechanisms, two key roles of nanozymes are particularly focused in electrochemical biosensors: selective enhancement and signal amplification, which crucially support the enhancement of sensor performance. In terms of practical applications, the widespread use of nanozyme-based electrochemical biosensors are showcased in various domains. From detecting biomolecules, pollutants, nucleic acids, proteins, to cells, providing robust means for high-sensitivity detection. Furthermore, insights into the future development of nanozyme-based electrochemical biosensors is provided, encompassing improvements and optimizations of nanozyme materials, innovative sensor design and integration, and the expansion of application fields through interdisciplinary collaboration. In conclusion, this article systematically presents the mechanisms and applications of nanozymes in electrochemical biosensors, offering valuable references and prospects for research and development in this field.

Photosensitive Peptide Enabling Molecular Recognition Tandem Covalent Biosensing for Evaluating and Preventing Venous Thromboembolism in Dravet Syndrome.

Venous thromboembolism (VTE) is a complication of Dravet syndrome, accounting for many unexpected deaths. To control VTE more tightly and to prevent such tragedies, a reliable and low-cost risk evaluation assay is urgently needed, so that the daily routine of VTE risk evaluation can be established. In this work, we have developed such an assay combining the photocatalytic activity of Bengal red to trigger the target-specific self-splicing of a peptide probe and subsequent cross-linking with P-selectin. Following this protocol, a robust and one-step detection can be achieved, without using any costly enzymes, antibodies, or nanomaterials, but the same level of sensitivity and robustness can be attained. Specifically, the effect of epilepsy on elevating platelet P-selectin can be observed by using the proposed assay. This may in the near future promise a new method for evaluating the side effects of P-selectin through relatively noninvasive peripheral blood sampling.

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.

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.

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.

Highly ordered binary assembly of silica mesochannels and surfactant micelles for extraction and electrochemical analysis of trace nitroaromatic explosives and pesticides.

The rapid and sensitive detection of nitroaromatic compounds is of great significance for human health, the environment, and public security. The present work reports on the extraction and electrochemical analysis of trace nitroaromatic compounds, such as explosives and organophosphate pesticides (OPs), using the indium tin oxide (ITO) electrodes modified with a highly ordered and aligned binary assembly of silica mesochannels and micelles (BASMM). With a pore diameter of ca. 2-3 nm, silica mesochannels (SMs) perpendicularly oriented to the ITO electrode surface can provide hard and robust supports to confine the soft cylindrical micelles formed by the aggregation of cationic surfactants, namely, cetyltrimethylammonium bromide (CTAB). Due to the organized self-assembly of hydrocarbon tails of CTAB surfactants, each micelle has a hydrophobic core, which acts as an excellent adsorbent for rapid extraction and preconcentration of trace nitroaromatic compounds from aqueous solutions via the hydrophobic effect. Furthermore, the cylindrical micelles are directly in contact with the underlying electrode surface, to which extracted compounds can freely diffuse and then be reduced therein, thus allowing their determination by means of voltammetry. Using the BASMM/ITO sensor, electrochemical analysis of trace nitroaromatic explosives, including 2,4,6-trinitrotoluene (TNT), 2,4,6-trinitrophenol, 2,6-dinitrotoluene, 3-nitrophenol, and nitrobenzene, and OPs, such as paraoxon, methyl parathion, and fenitrothion, was achieved with a fast response, wide linear range, high sensitivity, and low detection limit at the ppb level. TNT and paraoxon in real apple, tea, and water samples were also determined. By combining the heterogeneous extraction and determination in one ordered binary nanostructure, the BASMM sensor provides a very simple, rapid, and cost-effective way for analysis of nitroaromatic compounds and can be extended to a wide range of lipophilic yet redox-active analytes.

Vertically oriented silica mesochannels as the template for electrodeposition of polyaniline nanostructures and their electrocatalytic and electroanalytical applications.

A mesoporous silica film (MSF) with vertically oriented mesochannels on a conductive substrate serves as a hard-template for electrodeposition of polyaniline (PANI). The PANI nanostructures thus prepared are orderly confined in silica mesochannels, eventually producing a robust hybrid film. The film displays a good electrocatalytic activity toward oxidation of ascorbic acid, and can be used for potentiometric pH sensing with a Nernstian response.

Gold nanoparticles confined in vertically aligned silica nanochannels and their electrocatalytic activity toward ascorbic acid.

A facile method of confining gold nanoparticles (AuNPs) in silica nanochannels aligned perpendicularly to an underlying electrode surface is reported. The nanochannel surface carrying a layer of (3-aminopropyl)triethoxy silane (APTS) displays a strong electrostatic interaction with AuCl4(-), eventually resulting in the confinement of AuNPs inside the nanochannels after chemical reduction. As-prepared AuNPs in APTS-modified mesoporous silica film (APTS-MSF) are highly dispersed with a narrow size distribution. Furthermore, these AuNPs are free of protecting ligands and exhibit a good electrochemical catalytic activity toward the oxidation of ascorbic acid.

Differential pulse voltammetry detection of dopamine and ascorbic acid by permselective silica mesochannels vertically attached to the electrode surface.

A thin film consisting of highly ordered and vertically oriented silica mesochannels (SMCs) was prepared on the indium tin oxide (ITO) coated glass electrode surface by chronopotentiometry. The mesochannel has a uniform pore size of 2-3 nm in diameter and a positively charged surface due to grafted ammonium groups. The electrostatic and steric effects resulted from control of the surface charge and the ionic buffer concentration make the SMCs permselective, favoring the mass transport of oppositely charged species and repelling that of similarly charged ones. By using differential pulse voltammetry (DPV), the SMCs with this charge selectivity can be employed for permselective detection of ascorbic acid (AA) and dopamine (DA) that are oppositely charged compounds. The obtained linear detection range was 49-2651 µM for AA and 20-226 µM for DA, respectively. AA and DA in real samples were also determined by the SMC film modified electrode.

Electrochemical sensing mechanisms of neonicotinoid pesticides and recent progress in utilizing functional materials for electrochemical detection platforms.

The excessive residue of neonicotinoid pesticides in the environment and food poses a severe threat to human health, necessitating the urgent development of a sensitive and efficient method for detecting trace amounts of these pesticides. Electrochemical sensors, characterized by their simplicity of operation, rapid response, low cost, strong selectivity, and high feasibility, have garnered significant attention for their immense potential in swiftly detecting trace target molecules. The detection capability of electrochemical sensors primarily relies on the catalytic activity of electrode materials towards the target analyte, efficient loading of biomolecular functionalities, and the effective conversion of interactions between the target analyte and its receptor into electrical signals. Electrode materials with superior performance play a crucial role in enhancing the detection capability of electrochemical sensors. With the continuous advancement of nanotechnology, particularly the widespread application of novel functional materials, there is paramount significance in broadening the applicability and expanding the detection range of pesticide sensors. This comprehensive review encapsulates the electrochemical detection mechanisms of neonicotinoid pesticides, providing detailed insights into the outstanding roles, advantages, and limitations of functional materials such as carbon-based materials, metal-organic framework materials, supramolecular materials, metal-based nanomaterials, as well as molecular imprinted materials, antibodies/antigens, and aptamers as molecular recognition elements in the construction of electrochemical sensors for neonicotinoid pesticides. Furthermore, prospects and challenges facing various electrochemical sensors based on functional materials for neonicotinoid pesticides are discussed, providing valuable insights for the future development and application of biosensors for simplified on-site detection of agricultural residues.

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.

Nitrogen Vacancy Modulation of Tungsten Nitride Peroxidase-Mimetic Activity for Bacterial Infection Therapy.

Bacterial infections claim millions of lives every year, with the escalating menace of microbial antibiotic resistance compounding this global crisis. Nanozymes, poised as prospective substitutes for antibiotics, present a significant frontier in antibacterial therapy, yet their precise enzymatic origins remain elusive. With the continuous development of nanozymes, the applications of elemental N-modulated nanozymes have spanned multiple fields, including sensing and detection, infection therapy, cancer treatment, and pollutant degradation. The introduction of nitrogen into nanozymes not only broadens their application range but also holds significant importance for the design of catalysts in biomedical research. The synergistic interplay between W and N induces pivotal alterations in electronic configurations, endowing tungsten nitride (WN) with a peroxidase-like functionality. Furthermore, the introduction of N vacancies augments the nanozyme activity, thus amplifying the catalytic potential of WN nanostructures. Rigorous theoretical modeling and empirical validation corroborate the genesis of the enzyme activity. The meticulously engineered WN nanoflower architecture exhibits an exceptional ability in traversing bacterial surfaces, exerting potent bactericidal effects through direct physical interactions. Additionally, the topological intricacies of these nanostructures facilitate precise targeting of generated radicals on bacterial surfaces, culminating in exceptional bactericidal efficacy against both Gram-negative and Gram-positive bacterial strains along with notable inhibition of bacterial biofilm formation. Importantly, assessments using a skin infection model underscore the proficiency of WN nanoflowers in effectively clearing bacterial infections and fostering wound healing. This pioneering research illuminates the realm of pseudoenzyme activity and bacterial capture-killing strategies, promising a fertile ground for the development of innovative, high-performance artificial peroxidases.

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.

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.

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.

catena-Poly[[triphenyl-tin(IV)]-µ-2-(2-picolinoylhydrazono)propanoato-κO:O].

In the title polymeric coordination compound, [Sn(C(6)H(5))(3)(C(9)H(8)N(3)O(3))](n), the Sn(IV) atom is in a distorted trigonal-bipyramidal geometry, being coordinated by two O atoms from two 2-(2-picolinoylhydrazono)propanoate ligands and three phenyl groups. Adjacent Sn atoms are bridged by the 2-(2-picolinoylhydrazono)propanoate ligand through one carbonyl O atom and one carboxyl-ate O atom, forming a chain structure propagating parallel to [100]. An intra-molecular N-H⋯O hydrogen bond is observed.

2,2'-[Pyridine-2,6-diylbis(carbonyl-hydrazono)]dipropanoic acid N,N-dimethyl-formamide disolvate.

The complete molecule of the title compound, C(13)H(13)N(5)O(6)·2C(3)H(7)NO, is generated by crystallographic twofold rotation with an N and a C atom lying on the axis. The structure is stabilized by inter-molecular O-H⋯O hydrogen bonds.

An "off-on" fluorescent sensor for copper ion using graphene quantum dots based on oxidation of l-cysteine.

A simple and highly efficient "off-on" fluorescent sensor based on grapheme quantum dots (GQDs) for Cu2+ was developed. In this sensing platform, the fluorescence of GQDs was quenched in the presence of 2,4-dinitrophenylcysteine (DNPC), which is the reaction product of 1-chloro-2,4-dinitrobenzene (CDNB) and l-cysteine, owing to the spectral overlap between the absorption of DNPC and the excitation of GQDs. In the presence of Cu2+, l-cysteine was catalytically oxidized to l-cystine by O2, resulting in the reduction of DNPC. Thus, the fluorescence of GQDs was recovery. Based on this, the fluorescent detection of Cu2+ could be achieved. The proposed sensing strategy offered a selective identification of Cu2+ with a detection limit of 4.5 nM. Additionally, the practical application of this assay for Cu2+ determination in real water samples was also demonstrated.

Fluorescent carbon dots nanosensor for label-free determination of vitamin B12 based on inner filter effect.

A simple and effective fluorescent assay for the determination of vitamin B12 was developed. In this study, carbon dots (CDs) were prepared by one-pot hydrothermal method and directly used as a fluorophore in the inner filter effect (IFE). Both of the maximum absorption peak of vitamin B12 and excitation maxima of CDs are located at 360nm, hence, the excited light of CDs can be absorbed by vitamin B12, resulting in the fluorescence reduction of CDs. And the fluorescence intensity of CDs decreases with the increasing concentration of vitamin B12. This IFE-based sensing strategy shows a good linear relationship between the normalized fluorescence intensity and the concentration of vitamin B12 ranging from 0 to 60µM, with a limit of detection (LOD) of 0.1µM at a signal-to-noise ratio of 3. Furthermore, this proposed approach was successfully applied to vitamin B12 sensing in injections. This IFE sensing platform based on various fluorescent nanomaterials has a high promise for the detection of other biomolecules due to its inherent convenience.

TiO2/TiN core/shell nanobelts for efficient solar hydrogen generation.

TiO2/TiN core/shell NBs are successfully synthesized, and used as highly efficient photocatalytic H2 evolution catalysts (120 µmol h-1 g-1) from methanol solution. The TiN shell plays dual roles by extending the light absorption range and also promoting the separation/transfer of photoexcited charge carriers as an electron collector.