Insights on catalytic mechanism of CeO2 as multiple nanozymes

A Self-Circulated Microenvironment-Adaptive Nanozyme for Wound Healing Acceleration

Nanozyme-mediated reactive oxygen species (ROS) homeostasis regulation in vivo is a promising strategy for accelerating the healing of pathogen-infected wounds. It is detrimental in nanozyme preparation to strike a balance between ROS production and scavenging, being adaptive to the wound microenvironment, especially to overcome the irreversible and inevitable inactivation caused by the enzymatic active center loss. Herein, with adjusting ligands and metal charge transfer, we prepared a nanozyme with a regenerated Fe(II) active center, which endowed cyclic and continuous oxidoreductase reactions of peroxidase, superoxide dismutase, catalase, and oxidase under the same neutral pH environment. The versatile enzymatic activity could be easily triggered with oxygen/ROS and cascaded into controllable and reversible ROS generation and scavenging, as well as oxygen release for acceleration of sterilization during infected wound recovery. Under ultralow dosage of Fe-DHB, remarkable effectiveness against 1.0 × 106 drug-resistant bacteria and a wound-healing rate of around 6.3 mm2 per day were realized. Our work presents a key breakthrough in nanozyme-based wound healing strategy design.

Insights into the molecular mechanism on high salt tolerance of electroactive microorganisms collaborated by biochar supported cerium dioxide

Electroactive microorganisms are a promising approach for treating high-salinity organic wastewater, however, they are highly susceptible to salt stress, which can compromise their metabolic activity. In this paper, biochar supported nano-cerium dioxide catalyst (BC-CeO2) was prepared to strengthen electroactive microorganisms in high salt environment. It was found that BC-CeO2 significantly improved the bioelectrochemical and metabolic activity of microorganisms in high salt environment (600 mM NaCl) compared with the Control. At the initial stage of the reaction, the maximum power density of microbial fuel cells (MFCs) reached 343.21 mW/m2, and the degradation efficiency of norfloxacin (NOR) was 64.8 %, which was 1.7 times that of the Control. The analysis of microbial antioxidant properties demonstrated that BC-CeO2 could significantly increase the activities of superoxide dismutase (SOD) and catalase (CAT), effectively enhancing the ability of microorganisms to scavenge reactive oxygen species produced by salt stress. Metagenomic analysis revealed that the abundance of KEGG pathways conducive to microbial growth and metabolism under BC-CeO2 was relatively high, such as biosynthesis of amino acids (ko01230), microbial metabolism in diverse environments (ko01120) and so on. The enrichment of salt tolerant genes further illustrated the strengthening effect of BC-CeO2 on microbial adaptation to high salt environment, including genes related to NADH ubiquinone oxidoreductase, Na+/H+ antiporter, intracellular small molecule compatible substance synthesis and transport related enzyme system and K+ transporter related genes. Furthermore, the activity changes of Na+/K+-ATPase, which regulates cell permeability, in different environments also confirmed this point. This paper provides an effective strategy for enhancing the treatment of high-salt organic wastewater by electroactive microorganisms.

Polydopamine-mediated biointerfacial nanozyme as probiotic protective coating for IBD therapy

Probiotics offer a promising strategy to address the dysfunction of the intestinal mucosal barrier and dysregulation of the gut microbiota in inflammatory bowel disease (IBD). However, the low viability and poor adhesion of probiotics in complex gastrointestinal environments pose significant challenges. To tackle these issues, we designed a specialized protective nano-coating (PDA@CeO2) using biointerfacial phenolic assembly combined with nanozymes for Bifidobacterium bifidum (B.B.). Characteristic peaks of CeO2 nanoparticles were detected on B.B. via XRD analysis, while SEM and TEM images confirmed the successful attachment of CeO2 nanoparticles to the probiotic surface. The nano-coating (PDA@CeO2) simultaneously provides B.B. with high adhesion in the intestine, strong tolerance in complex gastrointestinal environments, and the ability to scavenge excess reactive oxygen species (ROS) due to its excellent mucoadhesive ability and high nanozyme activity. Specifically, the protection provided by nano-coating against simulated gastric fluid (SGF, pH 1.2) resulted in cell survival rates approximately 9.4 times higher than those of unprotected B.B. after 1 h of exposure. In IBD mouse models, the combination of PDA@CeO2 and B.B. demonstrated excellent therapeutic effects, promoting gut barrier repair. Additionally, an increase in Muribaculaceae and Prevotellaceae_UCG-001 and a decrease in Desulfovibrionaceae reshaped the intestinal flora, reducing recurrence. This study highlights the potential of enhancing probiotic functionality through targeted design of protective nano-coatings for IBD therapy.

Interactions of metal-based nanozymes with aptamers, from the design of nanozyme to its application in aptasensor: Advances and perspectives

Nanozymes, characterized by enzyme-like activity, have been extensively used in quantitative analysis and rapid detection due to their small size, batch fabrication, and ease of modification. Researchers have combined aptamers, an emerging molecular probe, with nanozymes for biosensing to address the limited reaction specificity of nanozymes. Nanozyme aptasensors are currently experiencing significant growth, offering a promising solution to the lack of rapid detection methods across various fields. Unlike traditional nanozyme research, the development of nanozyme aptasensors is challenging as it requires the design of highly active nanozymes as well as the establishment of efficient and agile interactions between aptamers and nanozymes. Therefore, this review summarizes the active species and catalytic mechanisms of various nanozymes along with classical design options, discussing the future development of nanozyme aptasensors. It is anticipated that this review will inspire researchers in this domain, leading to the design of more enzymatically active nanozymes and advanced nanozyme aptasensors.

Bioinspired O2-Evolution Catalysts with Proton-Coupled Electron Transfer Pathway for Portable Oxygen Generation

Producing high-purity oxygen (O2) has a wide range of applications across diverse sectors, such as medicine, tunnel construction, the chemical industry, and fermentation. However, current O2 production methods are burdened by complexity, heavy equipment, high energy consumption, and limited adaptability to harsh environments. Here, to address this grand challenge, the de novo design of Ru-doped metal hydroxide is proposed to serve as bioinspired O2-evolution catalysts with proton-coupled electron transfer (PCET) pathway for low-energy, environmentally friendly, cost-effective, and portable O2 generation. The comprehensive studies confirm that the lattice H species in Ru-Co(OH)x-based O2-evolution catalyst can trigger a PCET pathway to optimize Ru-oxygen intermediates interactions, thus ultimately reducing reaction energy barriers and improving the activities and durabilities. Consequently, the prepared Ru-Co(OH)x-loaded membrane catalysts exhibit rapid and long-term stable O2 production capabilities. Furthermore, the proposed material design strategy of lattice H-species shows remarkable universality and adaptability to broad Ru-doped metal hydroxides. This efficient, portable, and cost-effective O2 generation technique is suggested to ensure an uninterrupted O2 supply during emergencies and in regions with limited O2 availability or air pollution, thus offering significant societal benefits in broad applications.

Unveiling the Role of Intracellular Dissolution Equilibria in the Antioxidant Mechanism of Ceria Nanoparticles

It is well-known that ceria nanoparticles (CNPs) exhibit significant antioxidant activity, offering potential applications in the treatment of ROS-related pathologies. This activity of CNPs as a nanozyme is typically interpreted by considering Ce(III)/Ce(IV) equilibria on the nanoparticles' surface. However, the validity of this mechanism has never been directly proven in a biological context. Furthermore, it is often overlooked that after endocytosis, CNPs are compartmentalized within endolysosomes, while ROS are primarily located in the cytoplasm, making their direct interaction difficult. This study presents chemical and biological evidence supporting an alternative mechanism of action. By utilizing synchrotron μXRF and μXANES analysis on individual cells, the study shows that the amount of Ce(III), the species responsible for the antioxidant activity, increases linearly with time within the endolysosomes, where CNPs are accumulated, and in their vicinity. Such an increase can be explained by the release of Ce3+ ions resulting from a partial reductive dissolution of CNPs in the acidic environment of the endolysosomes. The Ce3+ ions can then cross the endolysosomal membrane, reaching the cytosol, where they can exert their reducing activity on ROS. In fact, neutralizing the acidic endolysosomal pH results in a complete inhibition of the CNP activity. Consequently, CNP antioxidant activity should be regarded as the result of redox processes that extend beyond the nanoparticles surface but involve complex dissolution equilibria.

Dual-Mode Detection of Glyphosate Based on DNAzyme-Mediated Click Chemistry and DNAzyme-Regulated CeO2 Peroxidase-like Activity

In this article, a dual-signal sensor for the fluorescence and colorimetric detection of glyphosate (Gly) is developed based on DNAzyme-mediated click chemistry and DNAzyme-regulated CeO2 peroxidase-like activity. DNAzyme can bind to Cu+, triggering a click chemistry reaction between 3-Azido-7-hydroxycoumarin (AHC) and 3-ethyn-1-ol (BOL), thus generating a strong fluorescence signal at 475 nm. Due to the strong coordination between Gly and Cu2+, the amount of reduced Cu+ decreases, resulting in a weakening of the fluorescence. In addition, Gly can inhibit the catalytic site of CeO2 enzyme activity, while DNAzyme, which does not participate in the click chemistry reaction, can be adsorbed by CeO2, further inhibiting the enzyme activity and reducing the oxidation color change of 3,3',5,5'-tetramethylbenzidine (TMB). The fluorescence detection limit of this dual-mode sensing platform is 0.15 μg/mL, and the colorimetric detection limit is 0.19 μg/mL. This method has been successfully applied to the detection of Gly in tap water and soybeans, which has a promising application in pesticide residue detection.

Nonwoven fabric coated with cerium oxide nanoparticles for viral inactivation and transmission Inhibition

Studies on virus inactivation by metal nanoparticles indicate that antiviral activity is influenced by the stabilizer on the particle surface. Additionally, cerium oxide nanoparticles stabilized with boric acid (BA-CeO2) exhibit potent antiviral activity. However, previous studies utilized BA-CeO2 dispersed in liquid form and did not fully account for the practical application of antiviral materials in real-world environments. We investigated the antiviral activity of nonwoven fabric coated with BA-CeO2 (NC-NWF). When a medium containing viruses was placed on NC-NWF, the titers of mouse hepatitis virus (MHV), influenza A virus, and feline calicivirus were reduced by > 99% within 2 h. Furthermore, the transmission of MHV was assessed in cages lined with NC-NWF. The cages were divided into two compartments using a mesh and NC-NWF, housing infected and uninfected mice on either side. The results indicated a significantly lower antibody titer against MHV in naïve mice with the NC-NWF partition than in the control partition. Additionally, placing infected mice in NC-NWF cages for 2 h, followed by naïve mice for 24 h, resulted in lower antibody titers against MHV than those in the control fabric. These findings suggest that NC-NWF exhibits antiviral activity and retains efficacy in living environments, such as rearing cages.

Improving Nanozyme-Based Colorimetric Assays through Medium Composition Optimization in Nanozyme-Substrate Reaction

Nanozymes, while promising alternatives to natural peroxidases in colorimetric assays, are often hindered by lower catalytic efficiencies. Although numerous approaches have been developed to improve signal intensity in nanozyme-based assays, optimization of the reaction medium in which the nanozyme interacts with the substrate remains a significantly underexplored area. The vast majority of studies rely on standard sodium acetate buffers or commercially sourced reagents optimized for horseradish peroxidase, neglecting the unique catalytic properties of different nanozymes. This work presents a systematic optimization of 3,3',5,5'-tetramethylbenzidine (TMB)-based reaction medium composition for four common nanozymes: iron oxide, LaNiO3, Mn-doped CeO2, and platinum nanoparticles. Our findings reveal that while sodium acetate buffer is suitable for LaNiO3, alternative buffers significantly enhance signal intensity (41-68%) for the other nanozymes. Further optimization of ionic strength, organic cosolvent type and concentration, and TMB/H2O2 concentrations yielded improvements in signal intensity, analytical sensitivity, and assay time. This study also identifies common pitfalls encountered during optimization of reaction conditions and proposes potential solutions. We posit that reaction medium should be a standard optimization step in the development of nanozyme-based assays, and the use of commercially sourced reagents with undisclosed compositions should be avoided.

Copper-based biomimetic nanozymes with multi-enzyme activity for phosphate detection

Nanozymes are nanoparticles with enzymatic activity, which are widely used in environmental and antibacterial research. Herein, we designed and synthesized novel amorphous nanozyme Cu-Im NPs with multiple enzyme-mimicking activities. Cu-Im NPs have the same active sites as natural laccase. In addition, the active center is similar to that of carbonic hydrolase, replacing the zinc ions with copper ions. Meanwhile, Cu-Im NPs also possess peroxidase-like activity. We reveal the multi-enzyme catalytic mechanisms of Cu-Im NPs. Notably, phosphate inhibits the laccase-like and peroxidase-like activities of Cu-Im NPs while activating their hydrolase activity. Based on these findings, we have developed a sensitive and selective method for detecting phosphate anions.

Iridium(III) complex functionalized ZIF-8 as a novel POD-like nanozyme for visual assay of triazine pesticides

Due to the unique advantages of mimicking natural enzymes, nanozymes have received ever-growing interest in a wide range of fields including analytical chemistry in the past two decades. Exploring novel kinds of nanozymes with efficient active sites has always been one of the most important and hot topics in nanozyme-related research so far, especially in portable monitors. Herein, zeolitic imidazolate framework-8 (ZIF-8) incorporated with an organometallic iridium(III) complex as a new active site denoted as Irppy-ZIF-8 obtained via a one-pot coordination reaction between the iridium solvent complex and 2-methylimidazole is reported as an efficient peroxidase (POD)-like nanozyme. Importantly, due to the specific inhibition effects of triazine pesticides on the POD-like activities of this novel nanozyme, a portable acetylcholinesterase (AChE)-free colorimetric sensor via a smartphone apart from a UV-vis spectrometer to detect triazine pesticides in real vegetable sample analysis is further successfully proposed in this work. It should be noted that this work could not only open up a new avenue to explore novel kinds of nanozymes from organometallic complexes as active sites, but also promote the progress in emerging applications of nanozymes in visual and portable sensors in the future.

Cerium-based nanohydrolase for fast catalytic hydrolysis of β-lactam antibiotics in wastewater effluents

To defuse risks of antibiotic residues in effluent to achieve safe wastewater reuse, direct hydrolysis of the functional group responsible for the antibacterial activity, such as the of β-lactam ring in β-lactam antibiotics, has been recognized as an efficient and cost-effective strategy. However, the instability of natural hydrolases limits their use in treating antibiotic-containing wastewater. Herein, inspired by the active site of natural hydrolase, a Ce-based nanohydrolase was created for rapid hydrolysis of β-lactam antibiotics. The typical β-lactam antibiotic, penicillin G (PG), could be totally removed by the nanohydrolase within 2 min with a hydrolysis efficiency of 44%, and the hydrolysis efficiency could reach 98% within 10 min. It revealed that Ce(IV) in the nanohydrolase adsorbed PG via Lewis acid-Lewis base interaction to activate the β-lactam ring, while the -OH on Ce(III) served as nucleophile to attack the β-lactam ring, thereby promoting the hydrolysis of PG. The Ce-based nanohydrolase also showed good catalytic hydrolysis performance towards other commonly used β-lactam antibiotics and structurally related chemicals, implying its substrate universality. In addition to having high hydrolytic activity similar to that of natural hydrolases, this nanohydrolase exhibited extraordinary reusability and potential for practical applications that natural hydrolases do not possess. This work offers an innovative strategy to eliminate the risks of hydrolysable micropollutants in wastewater effluents and also provides reference for designing better nanohydrolase.

Iron chelators loaded on myocardiocyte mitochondria-targeted nanozyme system for treating myocardial ischemia-reperfusion injury in mouse models

Ferroptosis plays a critical role in myocardial ischemia-reperfusion injury (MIRI), posing a significant clinical challenge. Nanoenzymes like cerium oxide (CeO2) hold promise for mitigating oxidative damage and inhibiting ferroptosis, but their delivery efficiency and biological activity require optimization. This study aims to develop a targeted nanozyme delivery system for MIRI treatment by integrating CeO2 with mesoporous polydopamine (mPDA) and dexrazoxane (DXZ) to achieve synergistic therapeutic effects. A biomineralization technique was used to synthesize CeO2 nanoparticles (2-3 nm) within mPDA, forming ~ 130 nm composite nanoparticles (Ce@mPDA). Surface modifications with cardiac homing peptide (CHP) and triphenylphosphine (TPP) enabled hierarchical targeting to injured myocardium and mitochondria. DXZ-loaded Ce@mPDA-C/P nanoparticles (D/Ce@mPDA-C/P) were evaluated in vitro and in a MIRI mouse model for their effects on oxidative stress, ferroptosis, apoptosis, inflammation, and cardiac function. D/Ce@mPDA-C/P nanoparticles exhibited robust ROS scavenging, sustained DXZ release, and efficient myocardial and mitochondrial targeting. The D/Ce@mPDA-C/P system significantly reduced oxidative stress, upregulated GPX4 expression, inhibited ferroptosis, and modulated the inflammatory microenvironment. Long-term studies in a MIRI mouse model demonstrated reductions in myocardial fibrosis and improvements in cardiac function, including enhanced fractional shortening and ejection fraction. This hierarchical targeting delivery system effectively combines the antioxidant properties of CeO2 with the iron-chelating effects of DXZ, providing a promising therapeutic strategy for MIRI. This approach may expand the clinical use of DXZ and advance nanomedicine-based interventions for myocardial repair.

Microbe-mediated synthesis of defect-rich CeO2 nanoparticles with oxidase-like activity for colorimetric detection of L-penicillamine and glutathione

To enhance production efficiency, curtail costs, and minimize environmental impact, developing simple and sustainable nanozyme synthesis methods has been the focus of relevant research. In this report, graphite-coated CeO2 nanoparticles (CeO2 NPs) with multiple defects (Ce3+ defects, oxygen vacancies and carbon defects) were synthesized via the culture filtrate of the extremely radioresistant bacterium Deinococcus wulumuqiensis R12 (D. wulumuqiensis R12). The as-prepared CeO2 NPs exhibit remarkable oxidase (OXD)-like activity, efficiently catalyzing the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) to form oxTMB, even in the absence of H2O2. The electron-rich bioactive substances in the supernatant were demonstrated to modulate the electronic state of the Ce atom and played a key role in the formation of multiple defects, thereby enhancing the OXD-like activity of CeO2 NPs. Based on the inhibitory effect of sulphydryl groups (-SH) on the TMB-CeO2 system, a colorimetric strategy for the detection of both L-penicillamine (L-PA) and glutathione (GSH) was devised and successfully applied in real sample analysis. The linear ranges of L-PA and GSH detection were found to be 10-500 μM and 9-200 μM with the limits of detection (LODs) at 8.53 and 5.19 μM, respectively. This work provides a straightforward, eco-friendly and nontoxic method for the synthesis and defect construction of CeO2 NPs with OXD-like activity.

Ascorbate-loaded MgFe layered double hydroxide for osteomyelitis treatment

Bacterial infections evoke considerable apprehension in orthopedics. Traditional antibiotic treatments exhibit cytotoxic effects and foster bacterial resistance, thereby presenting an ongoing and formidable obstacle in the realm of therapeutic interventions. Achieving bacterial eradication and osteogenesis are critical requirements for bone infection treatment. Herein, we design and fabricate a nanoenzyme-mimicking drug through the co-precipitation process, integrating MgFe layered double hydroxide with ascorbic acid (AA@LDH), to facilitate the simultaneous presence of these two unique functionalities. Within a bacterial acidic milieu, the degradation of the AA@LDH nanosystem prompts ascorbic acid to undergo a pro-oxidative transformation, generating an abundance of reactive oxygen species (ROS). These ROS overwhelm bacterial cellular processes, including nucleic acid replication, cell wall construction, virulence factor production, biosynthetic pathways, and energy generation. This disruption culminates in substantial bacterial mortality, as substantiated by RNA sequencing data. Hence, the AA@LDH nano system exhibits an in vitro antibacterial rate of approximately 100 % and 99 %, against S.aureus and E. coli, respectivaly. Additionally, the AA@LDH could directly accelerate osteogenic differentiation in vitro, evidenced by a 50 % increase in alkaline phosphatase activity and a 270 % improvement in extracellular matrix mineralization capability. Moreover, it enhances osteointegration process in vivo by favorably reshaping the osteogenic immune microenvironment. This innovative nanosystem for delivery offers new strategies that concurrently combat bacterial infections, mitigate inflammation, and induce tissue regeneration, marking a significant advancement in the realm of advanced materials and its applications.

A methotrexate labelled dual metal oxide nanocomposite for long-lasting anti-cancer theranostics

We explored the feasibility of a self-assembled chitosan nanocomposite incorporating cerium oxide/nanoceria and superparamagnetic iron oxide nanoparticles (Chit-IOCO NPs), conjugated with methotrexate (MTX) and Cy5 dye, as an integrated cancer theranostic nanosystem (Chit-IOCO-MTX-Cy5). In this system, nanoceria serves as an anti-cancer agent, while the superparamagnetic iron oxide nanoparticles function as a negative contrast agent for MR imaging. This dual metal oxide nanocomposite is conjugated with MTX which is a structural analogue of folate, serving both as a targeting mechanism for folate receptors on cancer cells and as a chemotherapeutic drug. Chit-IOCO-MTX-Cy5 exhibited exceptional negative contrast in T2 and T2∗-weighted MRI, achieving a high relaxivity of 409.5 mM⁻1 s⁻1 which is superior to clinically approved agents. The nanocomposite demonstrated both pro-oxidative and antioxidative properties, significantly increasing reactive oxygen species (ROS) production in U87MG cells (1.4-fold change), which triggered apoptosis in these cancer cells. Simultaneously, it exhibited ROS scavenging activity in non-malignant endothelial cells (0.8-fold change). Intravenous infusion of Chit-IOCO-MTX-Cy5 (5 mg/kg MTX) led to significant tumor growth inhibition, indicating a synergistic enhancement of anti-cancer effects when combining MTX and nanoceria, compared to free MTX or nanoceria without MTX conjugation. Importantly, after treatment cessation, tumours in the nanocomposite group did not re-grow, while those in the free MTX group rapidly did. In vivo MR and fluorescence imaging revealed improved uptake and retention of Chit-IOCO-MTX-Cy5 in tumours compared to nanoceria without MTX. Notably, biosafety and biochemical analyses in mice showed no significant differences between the Chit-IOCO-MTX-Cy5 treatment group and control groups.

Collaboration in Contradiction: Self-Adaptive Synergistic ROS Generation and Scavenge Balancing Strategies Used for the Infected Wounds Treatment

The rational utilization of ROS is key to treating infected wounds. Exogenous ROS can destroy bacterial structures, quickly kill bacteria, and inhibit secondary infections. However, excess ROS at the wound will cause a secondary inflammatory response. Acute infections exacerbate this damage by increasing endogenous ROS, complicating the maintenance of ROS homeostasis. Therefore, regulating the balance of ROS production and scavenging in wounds has emerged as a promising strategy for wound treatment. Conventional ROS balancing platforms are mostly based on the " all for one" strategy of functional superposition and lack self-adaptability and integration. To subvert this conventional strategy, this study proposes a "one for all" self-adaptive integrated photodynamic therapy (PDT)-antioxidant model to actively regulate the ROS balance. A gelatin-hyaluronic acid hydrogel embedded with Se-modified cerium dioxide nanoparticles (Gel-HA-Se@CeO2 NPs) is designed for treating infected wounds. The Se@CeO2 NPs serve both as nanoenzymes and photosensitizers(PS). As nanoenzymes, they exhibit catalase and superoxide dismutase activities, converting hydrogen peroxide and superoxide anions into oxygen. As a PS, it synergizes with oxygen under NIR irradiation to rapidly produce singlet oxygen. Additionally, Se modification enhances the PDT effects by disrupting bacterial antioxidant systems. In vitro and in vivo experiments revealed that the ROS balance platform polarizes M1-type macrophages to M2-type macrophages, altering the wound microenvironment from proinflammatory to prohealing. RNA sequencing revealed that this hydrogel accelerated the reconstruction of the vascular network of the wound by activating the PI3K/AKT pathway and increasing VEGF secretion.This strategy is believed to be beneficial not only for infected wounds but also for treating other conditions that involve the regulation of reactive oxygen species, such as tumors and bacterial infections.

Tumor microenvironment-regulated nanoplatform for enhanced chemotherapy, cuproptosis and nonferrous ferroptosis combined cancer therapy

Therapeutic approaches combining various treatments have attracted intensive interests for tumor therapy. Nevertheless, these strategies still face many obstacles, such as overexpressed GSH and hypoxia, owing to the intricate tumor microenvironment (TME). Herein, a versatile nanoplatform, CeO2@CuO2@DOX-RSL3@HA (CCDRH), was initially constructed for promoting the antitumor efficiency via regulation of the TME. The CCDRH was prepared taking mixed valence CeO2 as the nanocarrier, followed by the attachment of CuO2 nanodots, DOX and RSL3 and the camouflaging of hyaluronic acid. The CuO2 could disassemble in the acidic TME to release Cu2+ and H2O2. The POD- and CAT-mimicking activities of CeO2 could convert H2O2 to ˙OH and O2, leading to the enhancement of chemo-chemodynamic therapy. Meanwhile, RSL3 could effectively suppress GPX4 expression, and the overloaded Cu2+ and Ce4+ could deplete excess GSH, resulting in an intensive accumulation of LPO and significant nonferrous ferroptosis. Additionally, Cu+ induces the oligomerization of lipoylated DLAT and downregulates iron-sulfur cluster proteins, resulting in potent cellular cuproptosis. The experimental results revealed that CCDRH exhibited high performance in tumor inhibition, which is attributed to the combined effect of enhanced chemotherapy, ferroptosis and cuproptosis. The study provides a new approach for improving anticancer efficiency via regulation of the TME.

Bioinspired mineralization of ultra-small ceria on cellulose nanofiber enables biocompatible and efficient nanozyme

The escalating threat of antibiotic-resistant bacteria necessitates the exploration of alternative therapeutic strategies. Mimicking natural enzymes with artificial nanomaterials to release reactive oxygen species offers an attractive approach but is still challenged by limited catalytic activity, high production costs, and compromised biocompatibility. This work develops a bioinspired mineralization strategy for immobilizing high-density and ultra-small ceria nanoparticles onto cellulose nanofibers. The high surface-to-volume ratio of as-prepared nanoceria coupled with the aqueous processing environment facilitates the incorporation of a high Ce3+ content, significantly enhancing the peroxidase-like activity. The resulting ceria nanozyme demonstrates efficient antibacterial activity with negligible cytotoxicity. The utilization of bio-based resources and a sustainable mineralization procedure allows for the cost-effective, facile preparation of eco-friendly nanozyme products under mild conditions. This study presents a promising strategy for the rational design and large-scale fabrication of high-performance and low-cost bio-based catalysts applicable to diverse targeted catalytic applications.

The Electrochemical Detection of Bisphenol A and Catechol in Red Wine

The use of nanozymes for electrochemical detection in the food industry is an intriguing area of research. In this study, we synthesized a laccase mimicking the MnO2@CeO2 nanozyme using a simple hydrothermal method, which was characterized by modern analytical methods, such as transmission electron microscope (TEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX), etc. We found that the addition of MnO2 significantly increased the laccase-like activity by 300% compared to CeO2 nanorods. Due to the excellent laccase-like activity of the MnO2@CeO2 nanozyme, we developed an electrochemical sensor for the detection of hazardous phenolic compounds such as bisphenol A and catechol in red wines by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). We used the MnO2@CeO2 nanozyme to develop an electrochemical sensor for detecting harmful phenolic compounds like bisphenol A and catechol in red wine due to its excellent laccase-like activity. The MnO2@CeO2 nanorods could be dispersion-modified glassy carbon electrodes (GCEs) by polyethyleneimine (PEI) to achieve a rapid detection of bisphenol A and catechol, with limits of detection as low as 1.2 × 10-8 M and 7.3 × 10-8 M, respectively. This approach provides a new way to accurately determine phenolic compounds with high sensitivity, low cost, and stability.

Lipid Coating Modulates Effects of Nanoceria on Oxidative Metabolism in Human Embryonic Lung Fibroblasts: A Case of Cardiolipin

The unique redox properties of nanoscale cerium dioxide determine its diverse application in biology and medicine as a regulator of oxidative metabolism. Lipid modifiers of the nanoparticle surface change their biochemical properties and bioavailability. Complexes with lipids can be formed upon contact of the nanoparticles with the membrane. The effects of lipid coating on nanoceria have not been studied yet. Here, we assessed the effect of bare and cardiolipin-coated CeO2 on the expression of oxidative metabolism genes in human embryonic lung fibroblasts. Cell viability, mitochondrial activity, intracellular reactive oxygen species, NOX4, NRF2, and NF-κB expression, oxidative DNA damage/repair, autophagy, and cell proliferation were studied. We used an MTT assay, fluorescence microscopy, real-time reverse transcription polymerase chain reaction, and flow cytometry. At a concentration of 1.5 μM, bare and cardiolipin-coated nanoceria penetrated into cells within 1-3 h. Cell survival, mitochondrial activity, and the proliferative effect were similar for bare and cardiolipin-coated nanoceria. Intracellular ROS, activation of NOX4, NRF2, and NF-kB, DNA oxidative damage, and DNA break/repair were different. Cardiolipin-coated nanoceria induced intracellular oxidative stress and short-term activation of these genes and DNA damage/break/repair. Unlike bare nanoceria, cardiolipin-coated nanoceria induced autophagy. Thus, the effects of cardiolipin-coated nanoceria are determined by both the nanoceria itself and cardiolipin. Presumably, the differences in properties are due to lipid peroxidation of cardiolipin. This effect needs to be taken into account when developing nanoceria-based drugs targeting mitochondria.

Cerium oxide-modified Pd nanosheets encapsulated by red blood cell membranes for high-efficiency RONS scavenging in depression treatment

Depression, a common and high-morbidity mental illness, can cause severe physical and psychiatric disorder. Recently, elevated levels of reactive oxygen and nitrogen species (RONS) have been recognized as a potential pathogenesis of depression. Unfortunately, available therapies provide limited outcomes in treating RONS-related depression symptoms. In addition, the low blood-brain barrier (BBB) penetration efficiency of some drugs is another major barrier to depression treatment. This study developed cerium oxide-modified Pd (Pd-CeO2) nanosheets with outstanding antioxidant activities for depression therapy. Under physiological conditions, Pd-CeO2 exhibited significant O2˙- and H2O2 clearance through their superoxide dismutase (SOD) and catalase (CAT) activities. Meanwhile, Pd-CeO2 also displayed the ability to scavenge ˙OH and reactive nitrogen radicals (RNS). What's more, when incorporated with biocompatible red blood cell (RBC) membranes, Pd-CeO2@RBC could overcome the BBB and protect brain tissues from oxidative damage caused by RONS. As a result, Pd-CeO2@RBC therapy reduced the proliferation of microglia and astrocytes and alleviated neuroinflammation and depression-like behaviors. This research not only provides a novel strategy for the effective treatment of depression, but also paves the way for new therapeutic options of nanozymes in neurological disorders.

Phytic acid-based nanomedicine against mTOR represses lipogenesis and immune response for metabolic dysfunction-associated steatohepatitis therapy

Metabolic dysfunction-associated steatohepatitis (MASH) is one of the most common chronic liver diseases and is mainly caused by metabolic disorders and systemic inflammatory responses. Recent studies have indicated that the activation of the mammalian (or mechanistic) target of rapamycin (mTOR) signaling participates in MASH progression by facilitating lipogenesis and regulating the immune microenvironment. Although several molecular medicines have been demonstrated to inhibit the phosphorylation or activation of mTOR, their poor specificity and side effects limit their clinical application in MASH treatment. Phytic acid (PA), as an endogenous and natural antioxidant in the liver, presents significant anti-inflammatory and lipid metabolism-inhibiting functions to alleviate MASH. In this study, considering the unique phosphate-rich structure of PA, we developed a cerium-PA (CePA) nanocomplex by combining PA with cerium ions possessing phosphodiesterase activity. CePA intervened in the S2448 phosphorylation of mTOR through the occupation effect of phosphate groups, thereby inhibiting the inflammatory response and mTOR-sterol regulatory element-binding protein 1 (SREBP1) regulation axis. The in vivo experiments suggested that CePA alleviated MASH progression and fat accumulation in high-fat diet-fed mice. Mechanistic studies validated that CePA exerts a liver-targeted mTOR repressive function, making it a promising candidate for MASH and other mTOR-related disease treatments.

Propelling gold nanozymes: catalytic activity and biosensing applications

Recently, gold nanomaterials have been rapidly developed owing to their high stability, good biocompatibility, and multifunctionality. The unique catalytic activity of gold nanomaterials has driven the emergence of the concept for a "gold nanozyme." Understanding the characteristics of gold nanozymes is crucial for improving their catalytic performance as well as expanding their applications. In this review, we provide an overview of the intrinsic enzyme-like activities of gold nanozymes, including peroxidase-, catalase-, superoxide dismutase-, and glucose oxidase-like activities, and the catalytic mechanisms involved. In addition, strategies for modulating the catalytic activity of gold nanozymes and their applications in biosensing were discussed in detail. Moreover, we highlight the current challenges of gold nanozymes and look forward to attracting more attention for propelling the developments in this field.

An NIR-propelled janus nanomotor with enhanced ROS-scavenging, immunomodulating and biofilm-eradicating capacity for periodontitis treatment

Periodontitis is an inflammatory disease caused by bacterial biofilms, which leads to the destruction of periodontal tissue. Current treatments, such as mechanical cleaning and antibiotics, struggle to effectively address the persistent biofilms, inflammation, and tissue damage. A new approach involves developing a Janus nanomotor (J-CeM@Au) by coating cerium dioxide-doped mesoporous silica (CeM) with gold nanoparticles (AuNPs). This nanomotor exhibits thermophoretic motion when exposed to near-infrared (NIR) laser light due to the temperature gradient produced by the photothermal effects of asymmetrically distributed AuNPs. The NIR laser provides the energy for propulsion and activates the nanomotor's antibacterial properties, allowing it to penetrate biofilms and kill bacteria. Additionally, the nanomotor's ability to scavenge reactive oxygen species (ROS) can modulate the immune response and create a regenerative environment, promoting the healing of periodontal tissue. Overall, this multifunctional nanomotor offers a promising new approach for treating periodontitis by simultaneously addressing biofilm management and immune modulation with autonomous movement.

Nanozyme-based colorimetric sensor arrays coupling with smartphone for discrimination and "segmentation-extraction-regression" deep learning assisted quantification of flavonoids

Achieving rapid, cost effective, and intelligent identification and quantification of flavonoids is challenging. For fast and uncomplicated flavonoid determination, a sensing platform of smartphone-coupled colorimetric sensor arrays (electronic noses) was developed, relying on the differential competitive inhibition of hesperidin, nobiletin, and tangeretin on the oxidation reactions of nanozymes with a 3,3',5,5'-tetramethylbenzidine substrate. First, density functional theory calculations predicted the enhanced peroxidase-like activities of CeO2 nanozymes after doping with Mn, Co, and Fe, which was then confirmed by experiments. The self-designed mobile application, Quick Viewer, enabled a rapid evaluation of the red, green, and blue values of colorimetric images using a multi-hole parallel acquisition strategy. The sensor array based on three channels of CeMn, CeFe, and CeCo was able to discriminate between different flavonoids from various categories, concentrations, mixtures, and the various storage durations of flavonoid-rich Citri Reticulatae Pericarpium through a linear discriminant analysis. Furthermore, the integration of a "segmentation-extraction-regression" deep learning algorithm enabled single-hole images to be obtained by segmenting from a 3 × 4 sensing array to augment the featured information of array images. The MobileNetV3-small neural network was trained on 37,488 single-well images and achieved an excellent predictive capability for flavonoid concentrations (R2 = 0.97). Finally, MobileNetV3-small was integrated into a smartphone as an application (Intelligent Analysis Master), to achieve the one-click output of three concentrations. This study developed an innovative approach for the qualitative and simultaneous multi-ingredient quantitative analysis of flavonoids.

Transition-metal-based nanozymes for biosensing and catalytic tumor therapy

Nanozymes, as an emerging class of enzyme mimics, have attracted much attention due to their adjustable catalytic activity, low cost, easy modification, and good stability. Researchers have made great efforts in developing and applying high-performance nanozymes. Recently, transition-metal-based nanozymes have been designed and widely developed because they possess unique photoelectric properties and high enzyme-like catalytic activities. To highlight these achievements and help researchers to understand the research status of transition-metal-based nanozymes, the development of transition-metal-based nanozymes from material characteristics to biological applications is summarized. Herein, we focus on introducing six categories of transition-metal-based nanozymes and highlight their progress in biomarker sensing and catalytic therapy for tumors. We hope that this review can guide the further development of transition-metal-based nanozymes and promote their practical applications in cancer diagnosis and treatment.

Strain Effects on the Adsorption of Water on Cerium Dioxide Surfaces and Nanoparticles: A Modeling Outlook

Nanocrystalline ceria exhibits significant redox activity and oxygen storage capacity. Any factor affecting its morphology can tune such activities. Strain is a promising method for controlling particle morphology, whether as core@shell structures, supported nanoparticles, or nanograins in nanocrystalline ceria. A key challenge is to define routes of controlling strain to enhance the expression of more active morphologies and to maintain their shape during the lifespan of the particle. Here, we demonstrate a computational route to gain insights into the strain effects on particle morphology. We use density functional theory to predict surface composition and particle morphology of strained ceria surfaces, as a function of environmental conditions of temperature and partial pressure of water. We find that adsorbed molecular water is not sufficient to shift stability and as such under all compressive and tensile strains studied, the most stable particle is of octahedral shape, similarly to the unstrained case. When dissociative water is involved at the surfaces of the particle, then the most stable particle morphology changes under high water coverage and tensile strain to cuboidal or truncated cuboidal shapes. This shift in shape is due to strain effects that affect the strength of water adsorption.

AuCePt porous hollow cascade nanozymes targeted delivery of disulfiram for alleviating hepatic insulin resistance

As the pathophysiological basis of type 2 diabetes mellitus (T2DM), insulin resistance (IR) is closely related to oxidative stress (OS) and inflammation, while nanozymes have a good therapeutic effect on inflammation and OS by scavenging reactive oxygen species (ROS). Hence, AuCePt porous hollow cascade nanozymes (AuCePt PHNs) are designed by integrating the dominant enzymatic activities of three metallic materials, which exhibit superior superoxide dismutase/catalase-like activities, and high drug loading capacity. In vitro experiments proved that AuCePt PHNs can ultra-efficiently scavenge endogenous and exogenous ROS. Moreover, AuCePt PHNs modified with lactobionic acid (LA) and loaded with disulfiram (DSF), named as AuCePt PHNs-LA@DSF, can significantly improve glucose uptake and glycogen synthesis in IR hepatocytes by regulating the insulin signaling pathways (IRS-1/AKT) and gluconeogenesis signaling pathways (FOXO-1/PEPCK). Intravenous administration of AuCePt PHNs-LA@DSF not only showed high liver targeting efficiency, but also reduced body weight and blood glucose and improved IR and lipid accumulation in high-fat diet-induced obese mice and diabetic ob/ob mice. This research elucidates the intrinsic activity of AuCePt PHNs for cascade scavenging of ROS, and reveals the potential effect of AuCePt PHNs-LA@DSF in T2DM treatment.

The biomedical applications of nanozymes in orthopaedics based on regulating reactive oxygen species

Nanozymes, a category of nanomaterials with enzyme-like activity, have garnered growing interest in various biomedical contexts. Notably, nanozymes that are capable of regulating reactive oxygen species levels by emulating antioxidant or prooxidant enzymes within cells hold significant therapeutic potential for a range of disorders. Herein, we overview the catalytic mechanisms of four exemplary nanozymes within the orthopedic domain. Subsequently, we emphasize recent groundbreaking advancements in nanozyme applications in orthopaedics, encompassing osteoarthritis, osteoporosis, intervertebral disc degeneration, bone defects, spinal cord injury, gout, rheumatoid arthritis, osteosarcoma and bone infection. Furthermore, we discuss the emerging area's future prospects and several noteworthy challenges in biomedical application. This review not only fosters the ongoing development of nanozyme research but also fosters the emergence of more potent nanozymes for the treatment of orthopaedical diseases in the future.

Hollow CeO2-Based Nanozyme with Self-Accelerated Cascade Reactions for Combined Tumor Therapy

Nanozymes have obvious advantages in improving the efficiency of cancer treatment. However, due to the lack of tissue specificity, low catalytic efficiency, and so on, their clinical applications are limited. Herein, the nanoplatform CeO2@ICG@GOx@HA (CIGH) with self-accelerated cascade reactions is constructed. The as-prepared nanozyme shows the superior oxidase (OXD)-like, superoxide dismutase (SOD)-like, catalase (CAT)-like and peroxidase (POD)-like activities. At the same time, under 808 nm near-infrared (NIR) irradiation, the photodynamic and photothermal capabilities are also significantly enhanced due to the presence of indocyanine green (ICG). We demonstrate that the nanozyme CIGH can efficiently accumulate in the tumor and exhibit amplified cascade antitumor effects with negligible systemic toxicity through the combination of photodynamic therapy (PDT), photothermal therapy (PTT), chemodynamic therapy (CDT) and starvation therapy. The nanozyme prepared in this study provides a promising candidate for catalytic nanomedicines for efficient tumor therapy.

Light-Controlled Regulation of Dual-Enzyme Properties in YbGd-Carbon Quantum Dots Nano-Hybrid for Advanced Biosensing

Compared to nanozymes with single enzyme activity, those with multiple enzyme activities possess broader application potential due to their diversified enzymatic functionalities. However, the multienzyme nanozymes currently face challenges of interference among different enzymatic activities during practical applications. In this study, we report the synthesis of a light-responsive YbGd-carbon quantum dots nano-hybrid, termed YbGd-CDs, which exhibits controllable enzyme-mimicking activities. This light-responsive behavior enables selective control of the enzymatic activities. Under visible light irradiation, YbGd-CDs demonstrate robust oxidase-like activity. Conversely, under dark conditions, they primarily exhibit peroxidase-like activity. Leveraging the dual-enzyme-mimicking capabilities of YbGd-CDs, we developed colorimetric assays for sensitive detection of total antioxidant capacity (TAC) in both normal and cancer cells as well as d-amino acids in human saliva. This study not only advances the synthesis of carbon-based nanozymes but also highlights their potential in biosensing applications.

Spatially Decoupled H2O2 Activation Pathways and Multi-Enzyme Activities in Rod-Shaped CeO2 with Implications for Facet Distribution

CeO2, particularly in the shape of rod, has recently gained considerable attention for its ability to mimic peroxidase (POD) and haloperoxidase (HPO). However, this multi-enzyme activities unavoidably compete for H2O2 affecting its performance in relevant applications. The lack of consensus on facet distribution in rod-shaped CeO2 further complicates the establishment of structure-activity correlations, presenting challenges for progress in the field. In this study, the HPO-like activity of rod-shaped CeO2 is successfully enhanced while maintaining its POD-like activity through a facile post-calcination method. By studying the spatial distribution of these two activities and their exclusive H2O2 activation pathways on CeO2 surfaces, this study finds that the increased HPO-like activity originated from the newly exposed (111) surface at the tip of the shortened rods after calcination, while the unchanged POD-like activity is attributed to the retained (110) surface in their lateral area. These findings not only address facet distribution discrepancies commonly reported in the literature for rod-shaped CeO2 but also offer a simple approach to enhance its antibacterial performance. This work is expected to provide atomic insights into catalytic correlations and guide the design of nanozymes with improved activity and reaction specificity.

Alleviation of arsenic stress in pakchoi by foliar spraying of engineered nanomaterials

Addressing heavy metal contamination in leafy vegetables is critically important due to its adverse effects on human health. In this study, we investigated the inhibitory effects of foliar spraying with four nanoparticles (CeO2, ZnO, SiO2, and S NPs) on arsenic (As) stress in pakchoi (Brassica rapa var. Chinensis). The findings reveal that foliar application of ZnO NPs at 1 ~ 2.5 mg plant-1 and CeO2 NPs at 5 mg plant-1 significantly reduces As in shoots by 40.9 ~ 47.3% and 39.4%, respectively. Moreover, 5 mg plant-1 CeO2 NPs increased plant height by 6.06% and chlorophyll a (Chla) content by 30.2% under As stress. Foliar spraying of CeO2 NPs at 0.2-5 mg plant-1 also significantly enhanced superoxide dismutase (SOD) activity in shoots by 9.4 ~ 13.9%, lowered H2O2 content by 42.4 ~ 53.25%, and increased root protein contents by 79 ~ 109.2%. CeO2 NPs regulate the As(III)/As(V) ratio, aiding in As efflux from roots and thereby reducing As toxicity to plants. In vitro digestion experiments reveal that the consumption of CeO2 NPs carries the lowest health risk of As. In addition, foliar spraying of ZnO NPs at 1 ~ 2.5 mg plant-1 can suppress plant As uptake by modulating enzyme activity, reducing leaf damage, and enhancing chlorophyll content. The study demonstrates that high CeO2 NP concentrations and suitable ZnO NP concentrations can alleviate As toxicity in pakchoi, consequently reducing human health risks.

Improvement in ORR Durability of Fe Single-Atom Carbon Catalysts Hybridized with CeO2 Nanozyme

FeNC catalysts are considered one of the most promising alternatives to platinum group metals for the oxygen reduction reaction (ORR). Despite the extensive research on improving ORR activity, the undesirable durability of FeNC is still a critical issue for its practical application. Herein, inspired by the antioxidant mechanism of natural enzymes, CeO2 nanozymes featuring catalase-like and superoxide dismutase-like activities were coupled with FeNC to mitigate the attack of reactive oxygen species (ROS) for improving durability. Benefiting from the multienzyme-like activities of CeO2, ROS generated from FeNC is instantaneously eliminated to alleviate the corrosion of carbon and demetallization of metal sites. Consequently, FeNC/CeO2 exhibits better ORR durability with a decay of only 5 mV compared to FeNC (18 mV) in neutral electrolyte after 10k cycles. The FeNC/CeO2-based zinc-air battery also shows minimal voltage decay over 140 h in galvanostatic discharge-charge cycling tests, outperforming FeNC and commercial Pt/C.

Multienzyme Active Nanozyme for Efficient Sepsis Therapy through Modulating Immune and Inflammation Inhibition

Sepsis, a life-threatening condition caused by a dysregulated immune response to infection, leads to systemic inflammation, immune dysfunction, and multiorgan damage. Various oxidoreductases play a very important role in balancing oxidative stress and modulating the immune response, but they are stored inconveniently, environmentally unstable, and expensive. Herein, we develop multifunctional artificial enzymes, CeO2 and Au/CeO2 nanozymes, exhibiting five distinct enzyme-like activities, namely, superoxide dismutase, catalase, glutathione peroxidase, peroxidase, and oxidase. These artificial enzymes have been used for the biocatalytic treatment of sepsis via inhibiting inflammation and modulating immune responses. These nanozymes significantly reduce reactive oxygen species and proinflammatory cytokines, achieving multiorgan protection. Notably, CeO2 and Au/CeO2 nanozymes with enzyme-mimicking activities can be particularly effective in restoring immunosuppression and maintaining homeostasis. The redox nanozyme offers a promising dual-protective strategy against sepsis-induced inflammation and organ dysfunction, paving the way for biocatalytic-based immunotherapies for sepsis and related inflammatory diseases.

Elucidating the catalytic mechanism of Prussian blue nanozymes with self-increasing catalytic activity

Although Prussian blue nanozymes (PBNZ) are widely applied in various fields, their catalytic mechanisms remain elusive. Here, we investigate the long-term catalytic performance of PBNZ as peroxidase (POD) and catalase (CAT) mimetics to elucidate their lifespan and underlying mechanisms. Unlike our previously reported Fe3O4 nanozymes, which exhibit depletable POD-like activity, the POD and CAT-like activities of PBNZ not only persist but slightly enhance over prolonged catalysis. We demonstrate that the irreversible oxidation of PBNZ significantly promotes catalysis, leading to self-increasing catalytic activities. The catalytic process of the pre-oxidized PBNZ can be initiated through either the conduction band pathway or the valence band pathway. In summary, we reveal that PBNZ follows a dual-path electron transfer mechanism during the POD and CAT-like catalysis, offering the advantage of a long service life.

Scalable synthesis of Au@CeO2 nanozyme for development of colorimetric lateral flow immunochromatographic assay to sensitively detect heart-type fatty acid binding protein

Nanozymes with core@shell nanostructure are considered promising biolabeling materials for their multifunctional properties. In this work, a simple one-pot strategy has been proposed for scalable synthesis of gold@cerium dioxide core@shell nanoparticles (Au@CeO2 NPs) with strong localized surface plasmon resonance (LSPR) absorption and high peroxidase-like catalytic activity by redox reactions of Ce3+ ions and AuCl4- ions in diluted ammonia solution under room temperature. A colorimetric lateral flow immunochromatographic assay (LFIA) has been successfully fabricated for sensitive detection of heart-type fatty acid binding protein (H-FABP, an early cardiac biomarker) by using the Au@CeO2 NPs as reporters. The as-developed LFIA with Au@CeO2 NP reporter (termed as Au@CeO2-LFIA) exhibits a dynamic range of nearly two orders of magnitude, and a limit of detection (LOD) as low as 0.35 ng mL-1 H-FABP with nanozyme-triggered 3,3',5,5'-tetramethylbenzidine (TMB) colorimetric amplification. Furthermore, the practicality of Au@CeO2-LFIA has been demonstrated by profiling the concentrations of H-FABP in 156 blood samples of acute myocardial infarction (AMI) patients, and satisfactory results are obtained.

Unveiling the role of inorganic nanoparticles in Earth's biochemical evolution through electron transfer dynamics

This article explores the intricate interplay between inorganic nanoparticles and Earth's biochemical history, with a focus on their electron transfer properties. It reveals how iron oxide and sulfide nanoparticles, as examples of inorganic nanoparticles, exhibit oxidoreductase activity similar to proteins. Termed "life fossil oxidoreductases," these inorganic enzymes influence redox reactions, detoxification processes, and nutrient cycling in early Earth environments. By emphasizing the structural configuration of nanoparticles and their electron conformation, including oxygen defects and metal vacancies, especially electron hopping, the article provides a foundation for understanding inorganic enzyme mechanisms. This approach, rooted in physics, underscores that life's origin and evolution are governed by electron transfer principles within the framework of chemical equilibrium. Today, these nanoparticles serve as vital biocatalysts in natural ecosystems, participating in critical reactions for ecosystem health. The research highlights their enduring impact on Earth's history, shaping ecosystems and interacting with protein metal centers through shared electron transfer dynamics, offering insights into early life processes and adaptations.

Graphene quantum dots on TiO2 nanotubes as a light-assisted peroxidase nanozyme

Hybrid nanozyme graphene quantum dots (GQDs) deposited TiO2 nanotubes (NTs) on titanium foil (Ti/TiO2 NTs-GQDs) were manufactured by bestowing the hybrid with the advantageous porous morphology, surface valence states, high surface area, and copious active sites. The peroxidase-like activity was investigated through the catalytic oxidation of chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2, which can be visualized by the eyes. TiO2 NTs and GQDs comprising oxygen-containing functional groups can oxidize TMB in the presence of H2O2 by mimicking peroxidase enzymes. The peroxidase-mimicking activity of hybrid nanozyme was significantly escalated by introducing light illumination due to the photosensitive features of the hybrid material. The peroxidase-like activity of Ti/TiO2 NTs-GQDs enabled H2O2 determination over the linear range of 7 to 250 μM, with a LOD of 2.1 µM. The satisfying peroxidase activity is possibly due to the unimpeded access of H2O2 to the catalyst's active sites. The porous morphology provides the easy channeling of reactants and products. The periodic structure of the material also gave rise to acceptable reproducibility. Without material functionalization, the Ti/TiO2 NTs-GQDs can be a promising substitute for peroxidases for H2O2 detection.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Fluorimetric determination of tetracycline antibiotics in animal derived foods using boron and nitrogen co-doped ceria-based nanoparticles

An innovative synthesis of boron and nitrogen co-doped ceria-based nanoparticles (B/N-CeFNPs) with bright blue fluorescence emission is reported using the hydrothermal method. Based on the aggregation-induced emission enhancement (AIEE) effect between B/N-CeFNPs and chlortetracycline (CTC), a rapid detection method for CTC through fluorescence enhancement was developed. In addition, through the electron transfer process (ET), fluorescence resonance energy transfer (FRET) effect and static quenching between B/N-CeFNPs and oxytetracycline (OTC), a ratio fluorescence strategy for detecting OTC was generated. The fluorescence of B/N-CeFNPs at 410 nm can be effectively quenched by OTC, and new fluorescence emission appears at a wavelength of 500 nm. B/N-CeFNPs showed good linear responses with CTC and OTC in the range 0.1-1 µM and 1-40 µM, respectively. This system was used to simultaneously detect the CTC and OTC in milk and honey, realizing multi-residues detection of TCs in actual samples by using the same ceria-based fluorescence nanomaterial.

Inorganic Fe-O and Fe-S oxidoreductases: paradigms for prebiotic chemistry and the evolution of enzymatic activity in biology

Oxidoreductases play crucial roles in electron transfer during biological redox reactions. These reactions are not exclusive to protein-based biocatalysts; nano-size (<100 nm), fine-grained inorganic colloids, such as iron oxides and sulfides, also participate. These nanocolloids exhibit intrinsic redox activity and possess direct electron transfer capacities comparable to their biological counterparts. The unique metal ion architecture of these nanocolloids, including electron configurations, coordination environment, electron conductivity, and the ability to promote spontaneous electron hopping, contributes to their transfer capabilities. Nano-size inorganic colloids are believed to be among the earliest 'oxidoreductases' to have 'evolved' on early Earth, playing critical roles in biological systems. Representing a distinct type of biocatalysts alongside metalloproteins, these nanoparticles offer an early alternative to protein-based oxidoreductase activity. While the roles of inorganic nano-sized catalysts in current Earth ecosystems are intuitively significant, they remain poorly understood and underestimated. Their contribution to chemical reactions and biogeochemical cycles likely helped shape and maintain the balance of our planet's ecosystems. However, their potential applications in biomedical, agricultural, and environmental protection sectors have not been fully explored or exploited. This review examines the structure, properties, and mechanisms of such catalysts from a material's evolutionary standpoint, aiming to raise awareness of their potential to provide innovative solutions to some of Earth's sustainability challenges.

Tuning oxidant and antioxidant activities of ceria by anchoring copper single-site for antibacterial application

The reaction system of hydrogen peroxide (H2O2) catalyzed by nanozyme has a broad prospect in antibacterial treatment. However, the complex catalytic activities of nanozymes lead to multiple pathways reacting in parallel, causing uncertain antibacterial results. New approach to effectively regulate the multiple catalytic activities of nanozyme is in urgent need. Herein, Cu single site is modified on nanoceria with various catalytic activities, such as peroxidase-like activity (POD) and hydroxyl radical antioxidant capacity (HORAC). Benefiting from the interaction between coordinated Cu and CeO2 substrate, POD is enhanced while HORAC is inhibited, which is further confirmed by density functional theory (DFT) calculations. Cu-CeO2 + H2O2 system shows good antibacterial properties both in vitro and in vivo. In this work, the strategy based on the interaction between coordinated metal and carrier provides a general clue for optimizing the complex activities of nanozymes.

Catalyzing Generation and Stabilization of Oxygen Vacancies on CeO2-x Nanorods by Pt Nanoclusters as Nanozymes for Catalytic Therapy

Although CeO2 nanomaterials have been widely explored as nanozymes for catalytic therapy, they still suffer from relatively low activities. Herein, the catalyzing generation and stabilization of oxygen vacancies on CeO2 nanorods by Pt nanoclusters via H2 gas reduction under mild temperature (350 °C) to obtain Pt/CeO2- x , which can serve as a highly efficient nanozyme for catalytic cancer therapy, is reported. The deposited Pt on CeO2 by the atomic layer deposition technique not only can serve as the catalyst to generate oxygen vacancies under mild temperature reduction through the hydrogen spillover effect, but also can stabilize the generated oxygen vacancies. Meanwhile, the oxygen vacancies also provide anchoring sites for Pt forming strong metal-support interactions and thus preventing their agglomerations. Importantly, the Pt/CeO2- x reduced at 350 °C (Pt/CeO2- x -350R) exhibits excellent enzyme-mimicking catalytic activity for generation of reactive oxygen species (e.g., ·OH) as compared to other control samples, including CeO2 , Pt/CeO2 , and Pt/CeO2- x reduced at other temperatures, thus achieving excellent performance for tumor-specific catalytic therapy to efficiently eliminate cancer cells in vitro and ablate tumors in vivo. The excellent enzyme-mimicking catalytic activity of Pt/CeO2- x -350R originates from the good catalytic activities of oxygen vacancy-rich CeO2- x and Pt nanoclusters.

Adenine phosphate-Cu nanozyme with multienzyme mimicking activity for efficient degrading phenolic compounds and detection of hydrogen peroxide, epinephrine and glutathione

BACKGROUND

With the development of nanotechnology, various nanomaterials with enzyme-like activity (nanozymes) have been reported. Due to their superior properties, nanozymes have shown important application potential in the fields of bioanalysis, disease detection, and environmental remediation. However, only a few nanomaterials with multi-enzyme mimicry activity have been reported. In this study, a novel multienzyme mimic was synthesized through a simple and rapid preparation protocol by coordinating copper ions with N3, N6 (amino), N7, and N9 on adenine phosphate.

RESULTS

The prepared adenine phosphate-Cu complex exhibits significant peroxidase, laccase, and oxidase mimicking activities. The Michaelis-Menten constant (Km) and the maximal velocity (Vmax) values of the peroxidase, laccase, and oxidase mimicking activities of AP-Cu nanozyme are 0.052 mM, 0.14 mM, and 2.49 mM; and 0.552 μM min-1, 6.70 μM min-1, and 2.24 μM min-1, respectively. Then, based on its laccase mimicking activity, the nanozyme was applied in the degradation of phenolic compounds. The calculated kinetic constant for the degradation of 2,4-dichlorophenol is 0.468 min-1 and the degradation efficiency of 2,4-dichlorophenol (0.1 mM) reaches 96.14% at 7 min. Finally, based on the multienzyme mimicking activity of adenine phosphate-Cu nanozyme, simple colorimetric sensing methods with high sensitivity and good selectivity were developed for the detection of hydrogen peroxide, epinephrine, and glutathione in the ranges of 20.0-200.0 μM (R2 = 0.9951), 5.0-100.0 μM (R2 = 0.9970), and 5.0-200.0 μM (R2 = 0.9924) with the limits of quantitation of 20.0 μM, 5.0 μM, and 5.0 μM, respectively.

SIGNIFICANCE

In short, the synthesis of nanozymes with multi-enzyme mimicry activity through coordination between copper ions and small molecule mimicry enzymes provides new ideas for the design and research of multi-enzyme mimics.

The Impressive Anti-Inflammatory Activity of Cerium Oxide Nanoparticles: More than Redox?

Cerium oxide nanoparticles (CNPs) are biocompatible nanozymes exerting multifunctional biomimetic activities, including superoxide dismutase (SOD), catalase, glutathione peroxidase, photolyase, and phosphatase. SOD- and catalase-mimesis depend on Ce3+/Ce4+ redox switch on nanoparticle surface, which allows scavenging the most noxious reactive oxygen species in a self-regenerating, energy-free manner. As oxidative stress plays pivotal roles in the pathogenesis of inflammatory disorders, CNPs have recently attracted attention as potential anti-inflammatory agents. A careful survey of the literature reveals that CNPs, alone or as constituents of implants and scaffolds, strongly contrast chronic inflammation (including neurodegenerative and autoimmune diseases, liver steatosis, gastrointestinal disorders), infections, and trauma, thereby ameliorating/restoring organ function. By general consensus, CNPs inhibit inflammation cues while boosting the pro-resolving anti-inflammatory signaling pathways. The mechanism of CNPs' anti-inflammatory effects has hardly been investigated, being rather deductively attributed to CNP-induced ROS scavenging. However, CNPs are multi-functional nanozymes that exert additional bioactivities independent from the Ce3+/Ce4+ redox switch, such as phosphatase activity, which could conceivably mediate some of the anti-inflammatory effects reported, suggesting that CNPs fight inflammation via pleiotropic actions. Since CNP anti-inflammatory activity is potentially a pharmacological breakthrough, it is important to precisely attribute the described effects to one or another of their nanozyme functions, thus achieving therapeutic credibility.

A comprehensive exploration of the latest innovations for advancements in enhancing selectivity of nanozymes for theranostic nanoplatforms

Nanozymes have captured significant attention as a versatile and promising alternative to natural enzymes in catalytic applications, with wide-ranging implications for both diagnosis and therapy. However, the limited selectivity exhibited by many nanozymes presents challenges to their efficacy in diagnosis and raises concerns regarding their impact on the progression of disease treatments. In this article, we explore the latest innovations aimed at enhancing the selectivity of nanozymes, thereby expanding their applications in theranostic nanoplatforms. We place paramount importance on the critical development of highly selective nanozymes and present innovative strategies that have yielded remarkable outcomes in augmenting selectivities. The strategies encompass enhancements in analyte selectivity by incorporating recognition units, refining activity selectivity through the meticulous control of structural and elemental composition, integrating synergistic materials, fabricating selective nanomaterials, and comprehensively fine-tuning selectivity via approaches such as surface modification, cascade nanozyme systems, and manipulation of external stimuli. Additionally, we propose optimized approaches to propel the further advancement of these tailored nanozymes while considering the limitations associated with existing techniques. Our ultimate objective is to present a comprehensive solution that effectively addresses the limitations attributed to non-selective nanozymes, thus unlocking the full potential of these catalytic systems in the realm of theranostics.

Calcein-Modified CeO2 for Intracellular ROS Detection: Mechanisms of Action and Cytotoxicity Analysis In Vitro

Cerium oxide nanoparticles (CeO2 NPs) are metal-oxide-based nanozymes with unique reactive oxygen species (ROS) scavenging abilities. Here, we studied new CeO2 NPs modified with calcein (CeO2-calcein) as an intracellular ROS inactivation/visualization theranostic agent. The molecular mechanisms of the CeO2-calcein intracellular activity, allowing for the direct monitoring of ROS inactivation in living cells, were studied. CeO2-calcein was taken up by both normal (human mesenchymal stem cells, hMSc) and cancer (human osteosarcoma, MNNG/Hos cell line) cells, and was easily decomposed via endogenous or exogenous ROS, releasing brightly fluorescent calcein, which could be quantitatively detected using fluorescence microscopy. It was shown that the CeO2-calcein has selective cytotoxicity, inducing the death of human osteosarcoma cells and modulating the expression of key genes responsible for cell redox status as well as proliferative and migration activity. Such cerium-based theranostic agents can be used in various biomedical applications.

Overview of nanozymes with phosphatase-like activity

Nanomaterials with intrinsic enzyme activity, referred to as nanozymes, have attracted substantial attention in recent years. Among them, phosphatase-mimicking nanozymes have become an increasingly important focus for future research, considering that phosphatase is not only one of key enzymes for phosphorous metabolism, which is essential for many biological processes (e.g., cellular regulation and signaling), but also one of extensively used biocatalytic labels in the enzyme-linked assays as well as a powerful tool enzyme in molecular biology laboratories. Nevertheless, compared with extensive oxidoreductase-mimicking nanozymes, there are a very limited number of nanozymes with phosphatase-like activity have been explored at present. The increasing demand of complex and individualized phosphatase-involved catalytic behaviors is pushing the development of more advanced phosphatase-mimicking nanozymes. Thus, we present an overview on recently reported phosphatase-like nanozymes, providing guidelines and new insights for designing more advanced phosphatase-mimicking nanozyme with superior properties.