Coupling Bifunctional Nanozyme-Mediated Catalytic Signal Amplification and Label-Free SERS with Immunoassays for Ultrasensitive Detection of Pathogens in Milk Samples

Multifunctional nanozymatic biosensors: Awareness, regulation and pathogenic bacteria detection

It is estimated that approximately 700,000 fatalities occur annually due to infections attributed to various pathogens, which are capable of dissemination via multiple environmental vectors, including air, water, and soil. Consequently, there is an urgent need to enhance and refine rapid detection technologies for pathogens to prevent and control the spread of associated diseases. This review focuses on applying nanozymes in constructing biosensors, particularly their advancement in detecting pathogenic bacteria. Nanozymes, which are nanomaterials exhibiting enzyme-like activity, combine unique magnetic, optical, and electronic properties with structural diversity. This blend of characteristics makes them highly appealing for use in biocatalytic applications. Moreover, their nanoscale dimensions facilitate effective contact with pathogenic bacteria, leading to efficient detection and antibacterial effects. This article briefly summarizes the development, classification, and strategies for regulating the catalytic activity of nanozymes. It primarily focuses on recent advancements in constructing biosensors that utilize nanozymes as probes for sensitively detecting pathogenic bacteria. The discussion covers the development of various optical and electrochemical biosensors, including colorimetric, fluorescence, surface-enhanced Raman scattering (SERS), and electrochemical methods. These approaches provide a reliable solution for the sensitive detection of pathogenic bacteria. Finally, the challenges and future development directions of nanozymes in pathogen detection are discussed.

An enzyme-free multi-stage hybridization chain reaction for the electrochemiluminescence detection of MRSA using MoS2 NF@AuNPs catalyst

Methicillin-resistant Staphylococcus aureus (MRSA) is a ubiquitous foodborne pathogen capable of causing food poisoning and producing enterotoxins in foodstuffs, which ultimately results in various illnesses, such as vomiting, diarrhea, and pneumonia. In this study, we present a MoS2 NF@AuNPs enhanced electrochemiluminescence (ECL) biosensor for MRSA detection based on a DNA branching tree structure formed via enzyme-free hybridization chain reaction (HCR) amplification. This approach integrates bacterial aptamers with multistage HCR amplification to achieve highly sensitive and specific target recognition. Furthermore, MoS2 NF@AuNPs act as a synergistic catalyst for Ru(bpy)32+ molecules, which in turn substantially enhances the signal readout of the biosensor. The biosensor exhibits a robust linear correlation for MRSA detection over a concentration range of 100 to 107 cfu/mL, with a detection limit of 1 cfu/mL. In addition, the biosensor demonstrates excellent selectivity and high sensitivity when applied to real samples such as water, juice, and milk.

Two birds with one stone: colorimetric and photothermal dual-mode biosensor based on CoOOH nanorings for detecting β-galactosidase activity and Escherichia coli

Pathogenic bacterial infections are a serious global public health threats, creating an urgent requirement for the rapid, sensitive, and reliable detection of bacteria. Herein, a multi-colorimetric and portable photothermal dual-mode biosensor with cross-references and self-calibration was established for the analysis of β-galactosidase (β-Gal) and Escherichia coli (E. coli).

Nanozyme-based biosensors for food contaminants detection: advances, challenges, and prospects

The presence of food contaminants poses a growing threat to public health. Developing advanced and reliable biosensing methods with high sensitivity, specificity, and reproducibility for detecting food contaminants is an urgent requirement for food safety control. Nanozymes, recognized for their enzyme-mimicking catalytic activities and the unique physicochemical properties of nanomaterials, have been extensively utilized in the development of diverse biosensors for food safety assays. Recent years have witnessed an exponential surge in relevant publications, garnering considerable research interest. This review summarizes recent advancements in the catalytic mechanisms of peroxidase- and oxidase-like nanozymes and provides a comprehensive discussion on the construction, sensing mechanisms, and practical applications of nanozymes-based biosensors developed for detecting food contaminants over the past five years. These biosensors include colorimetric, fluorescence, chemiluminescent, electrochemical, surface-enhanced Raman scattering, multi-modal, and other types, used for detecting food contaminants such as mycotoxins, pathogens, pesticides, veterinary drugs, illegal additives, and heavy metals. The review also addresses current challenges and prospects in this field, aiming to summarize advancements and promote further exploration of nanozyme-based sensing platforms to guarantee food safety.

Evolving trends in nanozyme-based SERS systems for food contaminant monitoring: A review

The integration of nanozyme and SERS shows promising prospects in monitoring contaminants by leveraging its enzyme-mimic activities and Raman enhancement. These characteristics facilitate signal amplification and sensitivity, thus enhancing contaminant analytical performance. In this review, recent research focusing on food contaminant detection through nanozyme-based SERS systems are summarized. Firstly, principles and strategies for contaminant monitoring using nanozyme-based SERS systems have been provided comprehensively. These techniques primarily involve analytes acting as reactants or reactant consumers, enzyme activity modulating, SERS signal modulating, and nanozymes integrating with other elements for targets. Moreover, various applications of nanozyme-based SERS sensors in metal ions, pesticide and veterinary drug residues, pathogens, toxins, and other pollutants monitoring have been presented. Finally, current challenges and future outlooks for more practical applications based on nanozyme-SERS systems are discussed. This review aims to not only offer guidance for constructing new nanozyme-based SERS sensors but also explore broader applications of SERS sensing.

Dual enzyme-mimicking bimetallic MOF for selective SERS detection of L-DOPA in human serum based on cascade catalytic reaction

Surface-enhanced Raman scattering (SERS) in conjunction with nanozymes has emerged as a powerful technique for bioanalysis due to their signal conversion and amplification effect. However, clinical applications continue to encounter challenges such as inadequate selectivity. Herein, we proposed a novel approach for the selective SERS detection of L-DOPA in human serum with dual enzyme-mimicking MOF-919(Fe-Cu). This material exhibits both catechol oxidase-like and peroxidase-like activities, enabling it to catalyze catecholic compounds to o-quinones and subsequently oxidize 3,3',5,5'-tetramethylbenzidine (TMB) molecules into SERS-active ox-TMB. Ultrasonic-assisted synthesis ensures uniform and dense loading of AgNPs within MOF-919(Fe-Cu), thereby enhancing SERS activity. A sensitive and selective method for SERS detection of L-DOPA was developed. The catechol oxidase-like activity of MOF-919(Fe-Cu) provides ideal selectivity and anti-interference to L-DOPA, while the cascade catalytic system transforms weak SERS signals of L-DOPA into amplified SERS signals of ox-TMB. The mechanism of dual enzyme-mimicking activity was further discussed. The detection process was optimized to achieve high sensitivity towards L-DOPA with a linear range 0.5-100 μmol/L and low limit of detection (LOD) of 0.16 μmol/L. Furthermore, it has been applied in serum sample of Parkinson's patients, demonstrating excellent recovery and low relative error compared to HPLC-UV. This approach offers an economical, efficient and accurate strategy for the detection of L-DOPA and provides valuable insights for the integration of selective multifunctional nanozyme and sensitive SERS detection method.

Metal and metal oxide nanoparticle-assisted molecular assays for the detection of Salmonella

This paper provides a comprehensive overview of the diverse applications and innovations of nanoparticles in the detection of Salmonella. It encompasses a comprehensive range of novel methods, including efficient enrichment, nucleic acid extraction, immunoassays, nucleic acid tests, biosensors, and emerging strategies with the potential for future applications. The surface modification of specific antibodies or ligands enables nanoparticles to achieve highly selective capture of Salmonella, while optimizing the nucleic acid extraction process and improving detection efficiency. The employment of nanoparticles in immunological and nucleic acid tests markedly enhances the specificity and sensitivity of the reaction, thereby optimizing the determination of detection results. Moreover, the distinctive physicochemical properties of nanoparticles enhance the sensitivity, selectivity, and stability of biosensors, thereby facilitating the rapid advancement of bio-detection technologies. It is particularly noteworthy that there has been significant advancement in the application and innovative research of nanozymes in molecular assays. This progress has not only resulted in enhanced detection efficiency but has also facilitated innovation and improvement in detection technologies. As nanotechnologies continue to advance, the use of metal and metal oxide nanoparticles in Salmonella detection is likely to become a more promising and reliable strategy for ensuring food safety and public health.

Recent Advances in Surface-Enhanced Raman Scattering for Pathogenic Bacteria Detection: A Review

Bacterial infection is one of the common infectious diseases in clinical practice, and the research on efficient detection of bacteria has attracted much attention in recent years. Currently, the traditional detection methods of bacteria are mainly based on cell culturing, microscopic examination, and molecular biology techniques, all of which have the disadvantages of complex operation and time-consuming. Surface-enhanced Raman spectroscopy (SERS) technology has shown prominent advantages in bacterial detection and identification because of the merit of high-sensitivity, fast detection and unique molecular fingerprint spectrum. This paper mainly investigates and discusses the application of SERS in bacterial detection, and systematically reviews the progress of SERS applications, including nano-enhanced dielectric materials of SERS, signal amplification of SERS labeled molecules, and the integration of SERS with microfluidic technology. Finally, the paper analyzes the challenges associated with the application of SERS in bacterial detection and offers insights into future development trends.

Three in one: A multifunctional oxidase-mimicking Ag/Mn3O4 nanozyme for colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria

A multifunctional oxidase-mimicking Ag/Mn3O4 was prepared, catalyzing the 3, 3', 5, 5'-tetramethylbenzidine (TMB) chromogenic reaction. Six foodborne pathogenic bacteria species, including Escherichia coli, Staphylococcus aureus, Salmonella enterica, Listeria monocytogenes, Bacillus cereus, and Cronobacter sakazakii, were observed to differentially inhibit its oxidase-like activity, resulting in decelerating the TMB chromogenic reaction. Owing to these properties, the following achievements were achieved: colorimetric determination of these bacteria with high sensitivity can be achieved using Ag/Mn3O4 + TMB reaction system; precise identification of these bacteria at different concentrations, including individual bacterium, binary mixtures, and even multivariate mixtures, can be effectively realized by combining the Ag/Mn3O4-based colorimetric sensor array with principal component analysis (PCA); broad-spectrum inactivation of these bacteria can be remarkably realized through catalyzation of Ag/Mn3O4 to generate superoxide anion free radicals. Therefore, our proposed Ag/Mn3O4 holds significant application potential in the colorimetric determination, precise identification, and broad-spectrum inactivation of foodborne pathogenic bacteria.

Advances and Future Trends in Nanozyme-Based SERS Sensors for Food Safety, Environmental and Biomedical Applications

Nanozymes, a kind of nanoparticles with enzyme-mimicking activities, have attracted considerable attention due to their robust catalytic properties, ease of preparation, and resistance to harsh conditions. By combining nanozymes with surface-enhanced Raman spectroscopy (SERS) technology, highly sensitive and selective sensors have been developed. These sensors are capable of detecting a wide range of analytes, such as foodborne toxins, environmental pollutants, and biomedical markers. This review provides an overview of recent advancements in the synthesis and surface modification of nanozymes, highlighting their ability to mimic multiple enzymes and enhance catalytic performance. In addition, we explore the development and applications of nanozyme-based SERS sensors in food contaminants, environmental pollutants, and biomedical markers. The review concludes with perspectives and challenges facing the field, involving the need for deeper understanding of nanozyme principles and mechanisms, development of standardized systems for characterization, and the engineering of nanozymes with tailored properties for specific applications. Finally, we discuss the potential for integrating various techniques with nanozymes to create multi-modal detection platforms, paving the way for the next generation of analytical tools in the fields of food safety, environmental monitoring, and biomedical diagnostics.

SERS Detection of Hydrophobic Molecules: Thio-β-Cyclodextrin-Driven Rapid Self-Assembly of Uniform Silver Nanoparticle Monolayers and Analyte Trapping

High-sensitivity and repeatable detection of hydrophobic molecules through the surface-enhanced Raman scattering (SERS) technique is a tough challenge because of their weak adsorption and non-uniform distribution on SERS substrates. In this research, we present a simple self-assembly protocol for monolayer SERS mediated by 6-deoxy-6-thio-β-cyclodextrin (β-CD-SH). This protocol allows for the rapid assembly of a compact silver nanoparticle (Ag NP) monolayer at the oil/water interface within 40 s, while entrapping analyte molecules within hotspots. The proposed method shows general applicability for detecting hydrophobic molecules, exemplified as Nile blue, Nile red, fluconazole, carbendazim, benz[a]anthracene, and bisphenol A. The detection limits range from 10-6to 10-9 M, and the relative standard deviations (RSDs) of signal intensity are less than 10%. Moreover, this method was used to investigate the release behaviors of a hydrophobic pollutant (Nile blue) adsorbed on the nanoplastic surface in the water environment. The results suggest that elevated temperatures, increased salinities, and the coexistence of fulvic acid promote the release of Nile blue. This simple and fast protocol overcomes the difficulties related to hotspot accessibility and detection repeatability for hydrophobic analytes, holding out extensive application prospects in environmental monitoring and chemical analysis.

Prepared Sandwich structure WS2/ag@MIP composite for ultrasensitive SERS detection of trace 17β-estradiol in food

17β-E2 is used in animal growth regulation and agricultural fertilizer, and even ng L-1 mass concentration levels can show biological effects. In this work, Ag NPs was used as surface-enhanced Raman spectroscopy (SERS) source and WS2 was synthesized by a simple method to provide a uniform distribution platform for Ag NPs. The MIP was the shell, which can selectively enrich the target molecule, pull the distance between the target molecule and SERS source, and protect Ag NPs. A cyclable SERS substrate with high sensitivity for detecting 17β-E2 in food was constructed. The optimized WS2/Ag@MIP as SERS substrate has the advantages of high Enhanced Factor (EF = 2.78 × 109), low detection limit (LOD = 0. 0958 pM), strong anti-interference ability, and good recycling performance. Moreover, the detection of 17β-E2 in real samples still has good accuracy. This work provides a new possibility for the trace detection of 17β-E2 in food.

Rapid Dynamic Surface-Enhanced Raman Spectroscopy Detection of Amoxicillin-Mediated Morphological Changes in a Pathogen for Diagnosis of Clinical Urine Samples

The swift and stable detection of pathogens in urine samples holds significant implications for the immediate clinical diagnosis and treatment of urinary tract infections (UTIs). In this study, we propose a detection strategy utilizing a hybrid substrate composed of graphene oxide (GO) and silver nanoparticles (Ag NPs) for the detection of pathogens subjected to amoxicillin-mediated (amo-mediated) treatment. This strategy employs dynamic surface-enhanced Raman spectroscopy (D-SERS) for stable and rapid detection, capturing signal variations induced by amo-mediated changes in pathogen morphology. During the 5 min D-SERS detection time window, stable SERS signals were detected for three types of pathogens and four types of pathogens were successfully distinguished using principal component analysis (PCA). In comparison to conventional nanosubstrates, the GO/Ag NP hybrid substrate exhibits outstanding stability and enhancement effects. This approach enables the dual detection of the pathogen cell structure and metabolites, facilitating specific identification of pathogens in the urinary tract, with a detection limit for Escherichia coli reaching 1 × 104 colony-forming units (CFU)/mL, meeting the clinical microbiology laboratory diagnostic standards for UTIs (105 CFU/mL). Testing of 188 clinically collected urine samples using this strategy yielded a sensitivity (SENS) of 86.4% and a specificity (SPC) of 89.7%. This introduces a novel method for diagnosing UTIs, offering broad applications in the field of clinical pathogen detection.

Rational design of monodispersed Au@Pt core-shell nanostructures with excellent peroxidase-mimicking activity for colorimetric detection of Cr(VI)

Cr(VI) is one of the most typical heavy metal contaminants and rapid detection of Cr(VI) is highly important in food control and public health. Herein, a core-shell Au@Pt nanozyme-based colorimetric assay was developed for the rapid and sensitive detection of Cr(VI). The monodispersed Au@Pt core-shell nanoparticles exhibited high peroxidase-mimicking activity and can catalyze colorless TMB into blue-colored oxidized oxTMB. After the addition of Cr(VI), the oxTMB molecules can be reduced into colorless TMB. The ultrathin Pt shell can prevent the Pt component from aggregation, thus improving the catalytic activity of Au@Pt nanozyme. These Au@Pt nanozyme-based Cr(VI) assays exhibited high sensitivity and selectivity and displayed satisfactory recoveries in practical samples. Our work highlights opportunities for the development of core-shell nanozymes with extensive applications in food safety, biomedicine, and environmental monitoring.

Bifunctional MoO3-x/CuS Heterojunction Nanozyme-Driven "Turn-On" SERS Signal for the Sensitive Detection of Cerebral Infarction Biomarker S100B

The use of nanozymes has become a promising auxiliary approach to "turn on" surface-enhanced Raman scattering (SERS) signals for the label-free detection of disease markers. Nevertheless, there are still major challenges to develop bifunctional nanomaterials with both excellent enzyme-like activity and high SERS performance. To this end, a novel Z-scheme MoO3-x/CuS heterojunction was first constructed as a powerful "two-in-one" substrate, which can not only catalyze leucomalachite green (LMG) to SERS-active malachite green (MG) but also serve as an efficient substrate to amplify the SERS signal of catalysate. Due to the strong interfacial coupling effect between the MoO3-x and CuS nanomaterial, which promoted the separation and transport of carriers in the heterojunction, the MoO3-x/CuS heterojunction showed higher peroxidase-like activity compared to individual components and the previously reported heterojunction nanozymes. Inspired by these results, a sandwich-type SERS immunoassay for the detection of the cerebral infarction biomarker S100 calcium-binding protein (S100B) was proposed based on the output signal of MG at 1620 cm-1. Furthermore, introducing the antifouling material chitosan on the surface of the MoO3-x/CuS heterojunction can effectively resist nonspecific protein adsorption and significantly improve the detection accuracy of the immunoassay. Therefore, the SERS immunoassay based on the MoO3-x/CuS heterojunction realized highly sensitive and selective detection of S100B in the concentration range of 0.001 to 100 ng/mL, with a low limit of detection of 0.47 pg/mL. The developed method has been successfully used for the accurate detection of S100B in clinical serum. The results showed that the level of S100B in the serum of cerebral infarction patients can be distinguished from those of healthy individuals and intracranial tumor patient controls. In addition, the acquired values of S100B in the serum of cerebral infarction patients based this strategy were well consistent with the results of electrochemiluminescence (ECL) detection with a relative error of less than ±7.3. It is expected that this work may open up a paradigm for improving detection sensitivity and accuracy for the early diagnosis and treatment monitoring of cerebral infarction in the clinic.

A nano-biosensing platform based on CuS-BSA for label-free fluorescence detection of Escherichia coli

Bacterial contamination is a serious issue for public health and food safety. In this work, a simple and label-free fluorescence detection nanoplatform for Escherichia coli (E. coli) was established on the basis of the competitive relationship for the reduction of Cu2+ in CuS-BSA between E. coli and O-phenylenediamine (OPD). OPD could be directly oxidized by Cu2+ to produce 2,3-diaminophenazine (ox OPD) with fluorescence properties. When OPD was introduced into an aqueous solution containing CuS-BSA and E. coli, the oxidation of OPD was inhibited owing to the reduction of Cu2+ to Cu+/Cu0 by NADH-2 dehydrogenase in the bacterial copper homeostasis mechanism, thus decreasing the fluorescence response signal of the system. Meanwhile, our strategy exhibited a satisfactory performance with a broad linear response to E. coli ranging from 12 to 1.2 × 107 CFU mL-1, and the limit of detection was 9 CFU mL-1. The practicability of the developed fluorescence biosensing platform in real samples was evaluated by successful determination of E. coli in drinking water and orange juice. These findings provide a new sensing strategy for analyzing other foodborne bacteria and ensuring food safety assessment.

Development of a Colorimetric and SERS Dual-Signal Platform via dCas9-Mediated Chain Assembly of Bifunctional Au@Pt Nanozymes for Ultrasensitive and Robust Salmonella Assay

Timely screening for harmful pathogens is a great challenge in emergencies where traditional culture methods suffer from long assay time and alternative methods are limited by poor accuracy and low robustness. Herein, we present a dCas9-mediated colorimetric and surface-enhanced Raman scattering (SERS) dual-signal platform (dCas9-CSD) to address this challenge. Strategically, the platform used dCas9 to accurately recognize the repetitive sequences in amplicons produced by loop-mediated isothermal amplification (LAMP), forming nucleic acid frameworks that assemble numerous bifunctional gold-platinum (Au@Pt) nanozymes into chains on the surface of streptavidin-magnetic beads (SA-MB). The collected Au@Pt converted colorless 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB) via its Pt shell and then enhanced the Raman signal of oxTMB by its Au core. Therefore, the presence of Salmonella could be dexterously converted into cross-validated colorimetric and SERS signals, providing more reliable conclusions. Notably, dCas9-mediated secondary recognition of amplicons reduced background signal caused by nontarget amplification, and two-round signal amplification consisting of LAMP reaction and Au@Pt catalysis greatly improved the sensitivity. With this design, Salmonella as low as 1 CFU/mL could be detected within 50 min by colorimetric and SERS modes. The robustness of dCas9-CSD was further confirmed by various real samples such as lake water, cabbage, milk, orange juice, beer, and eggs. This work provides a promising point-of-need tool for pathogen detection.

Multi-functional nanozyme-based colorimetric, fluorescence dual-mode assay for Salmonella typhimurium detection in milk

Rapid and high-sensitive Salmonella detection in milk is important for preventing foodborne disease eruption. To overcome the influence of the complex ingredients in milk on the sensitive detection of Salmonella, a dual-signal reporter red fluorescence nanosphere (RNs)-Pt was designed by combining RNs and Pt nanoparticles. After being equipped with antibodies, the immune RNs-Pt (IRNs-Pt) provide an ultra-strong fluorescence signal when excited by UV light. With the assistance of the H2O2/TMB system, a visible color change appeared that was attributed to the strong peroxidase-like catalytic activity derived from Pt nanoparticles. The IRNs-Pt in conjunction with immune magnetic beads can realize that Salmonella typhimurium (S. typhi) was captured, labeled, and separated effectively from untreated reduced-fat pure milk samples. Under the optimal experimental conditions, with the assay, as low as 50 CFU S. typhi can be converted to detectable fluorescence and absorbance signals within 2 h, suggesting the feasibility of practical application of the assay. Meanwhile, dual-signal modes of quantitative detection were realized. For fluorescence signal detection (emission at 615 nm), the linear correlation between signal intensity and the concentration of S. typhi was Y = 83C-3321 (R2 = 0.9941), ranging from 103 to 105 CFU/mL, while for colorimetric detection (absorbamce at 450 nm), the relationship between signal intensity and the concentration of S. typhi was Y = 2.9logC-10.2 (R2 = 0.9875), ranging from 5 × 103 to 105 CFU/mL. For suspect food contamination by foodborne pathogens, this dual-mode signal readout assay is promising for achieving the aim of convenient preliminary screening and accurate quantification simultaneously.

"Three-in-One" Plasmonic Au@PtOs Nanocluster Driven Lateral Flow Assay for Multimodal Cancer Exosome Biosensing

Exploiting the multiple properties of nanozymes for the multimode lateral flow assay (LFA) is urgently required to improve the accuracy and versatility. Herein, we developed a novel plasmonic Au nanostar@PtOs nanocluster (Au@PtOs) as a multimode signal tag for LFA detection. Based on the PtOs bimetallic nanocluster doping strategy, Au@PtOs can indicate both excellent SERS enhancement and nanozyme catalytic activity. Meanwhile, Au@PtOs displays a better photothermal effect than that of Au nanostars. Therefore, catalytic colorimetric/SERS/temperature three-mode signals can be read out based on the Au@PtOs nanocomposite. The Au@PtOs was combined with LFA and applied for breast cancer exosome detection. The detection limit for the colorimetric/SERS/temperature mode was 2.6 × 103/4.1 × 101/4.6 × 102 exosomes/μL, respectively, which was much superior to the common Au nanoparticles LFA (∼105 exosomes/μL). Moreover, based on the fingerprint molecular recognition ability of the SERS mode, exosome phenotypes derived from different breast cancer cell lines can be discriminated easily. Based on the convenient visual colorimetric mode and sensitive SERS/temperature quantitative modes, Au@PtOs driven LFA can satisfy the requirements of accurate and flexible multimodal sensing in different application scenarios.

Application and progress of nanozymes in antitumor therapy

Tumors remain one of the major threats to public health and there is an urgent need to design new pharmaceutical agents for their diagnosis and treatment. In recent years, due to the rapid development of nanotechnology, biotechnology, catalytic science, and theoretical computing, subtlety has gradually made great progress in research related to tumor diagnosis and treatment. Compared to conventional drugs, enzymes can improve drug distribution and enhance drug enrichment at the tumor site, thereby reducing drug side effects and enhancing drug efficacy. Nanozymes can also be used as tumor tracking imaging agents to reshape the tumor microenvironment, providing a versatile platform for the diagnosis and treatment of malignancies. In this paper, we review the current status of research on enzymes in oncology and analyze novel oncology therapeutic approaches and related mechanisms. To date, a large number of nanomaterials, such as noble metal nanomaterials, nonmetallic nanomaterials, and carbon-based nanomaterials, have been shown to be able to function like natural enzymes, particularly with significant advantages in tumor therapy. In light of this, the authors in this review have systematically summarized and evaluated the construction, enzymatic activity, and their characteristics of nanozymes with respect to current modalities of tumor treatment. In addition, the application and research progress of different types of nicknames and their features in recent years are summarized in detail. We conclude with a summary and outlook on the study of nanozymes in tumor diagnosis and treatment. It is hoped that this review will inspire researchers in the fields of nanotechnology, chemistry, biology, materials science and theoretical computing, and contribute to the development of nano-enzymology.

Accelerating the Phosphatase-like Activity of Uio-66-NH2 by Catalytically Inactive Metal Ions and Its Application for Improved Fluorescence Detection of Cardiac Troponin I

Compared with natural enzymes, nanozymes usually exhibit much lower catalytic activities, which limit the sensitivities of nanozyme-based immunoassays. Herein, several metal ions without enzyme-like activities were engineered onto Uio-66-NH2 nanozyme through postsynthetic modification. The obtained Mn+@Uio-66-NH2 (Mn+ = Zn2+, Cd2+, Co2+, Ca2+and Ni2+) exhibited improved phosphatase-like catalytic activities. In particular, a 12-fold increase in the catalytic efficiency (kcat/Km) of Uio-66-NH2 was observed after the modification with Zn2+. Mechanism investigations indicate that both the amino groups and oxygen-containing functional groups in Uio-66-NH2 are the binding sites of Zn2+, and the modified Zn2+ ions on Uio-66-NH2 serve as the additional catalytic sites for improving the catalytic performance. Furthermore, the highly active Zn2+@Uio-66-NH2 was used as a nanozyme label to develop a fluorescence immunoassay method for the detection of cardiac troponin I (cTnI). Compared with pristine Uio-66-NH2, Zn2+@Uio-66-NH2 can widen the linear range by 1 order of magnitude (from 10 pg/mL-1 μg/mL to 1 pg/mL-1 μg/mL) and also lower the detection limit by 5 times (from 4.7 pg/mL to 0.9 pg/mL).

Bifunctional Mo2N Nanoparticles with Nanozyme and SERS Activity: A Versatile Platform for Sensitive Detection of Biomarkers in Serum Samples

The combined application of nanozymes and surface-enhanced Raman scattering (SERS) provides a promising approach to obtain label-free detection. However, developing nanomaterials with both highly efficient enzyme-like activity and excellent SERS sensitivity remains a huge challenge. Herein, we proposed one-step synthesis of Mo2N nanoparticles (NPs) as a "two-in-one" substrate, which exhibits both excellent peroxidase (POD)-like activity and high SERS activity. Its mimetic POD activity can catalyze the 3,3',5,5'-tetramethylbenzidine (TMB) molecule to SERS-active oxidized TMB (ox-TMB) with high efficiency. Furthermore, combining experimental profiling with theory, the mechanism of POD-like activity and SERS enhancement of Mo2N NPs was explored in depth. Benefiting from the outstanding properties of Mo2N NPs, a versatile platform for indirect SERS detection of biomarkers was developed based on the Mo2N NPs-catalyzed product ox-TMB, which acts as the SERS signal readout. The feasibility of this platform was validated using glutathione (GSH) and target antigens alpha-fetoprotein antigen (AFP) and carcinoembryonic antigen (CEA) as representatives of small molecules with a hydroxyl radical (·OH) scavenging effect and proteins with a low Raman scattering cross-section, respectively. The limits of detection of GSH, AFP, and CEA were as low as 0.1 μmol/L, 89.1, and 74.6 pg/mL, respectively. Significantly, it also showed application in human serum samples with recoveries ranging from 96.0 to 101%. The acquired values based on this platform were compared with the standard electrochemiluminescence method, and the relative error was less than ±7.3. This work not only provides a strategy for developing highly active bifunctional nanomaterials but also manifests their widespread application for multiple biomarkers analysis.

MOFs-derived Co3O4@MnO2@Carbon dots with enhanced nanozymes activity for photoelectrochemical detection of cancer cells in whole blood

Nanozymes have attracted widespread attention, and rationally designing high-activity nanozymes to improve their application performance are a long-term objective. Herein, taking metal-organic frameworks-derived Co3O4 polyhedron with large surface area and high porosity as nanoconfinement carriers, Co3O4@MnO2@CDs polyhedron was successfully synthesized by the room-temperature reduction of MnO4- ions and physical load of carbon dots (CDs). Through cancer cells-triggered double antibody sandwich strategy, the Co3O4@MnO2@CDs polyhedron were introduced to the TiO2 nanoparticle (NPs) modified electrode, leading to the decreased photocurrent. The Co3O4@MnO2@CDs polyhedron can not only quench the photocurrent of TiO2 NPs, also act as nanozymes to catalyze precipitates. Moreover, the precipitates can not only reduce the photoelectrochemical (PEC) response, also increase the quenching capacity of the Co3O4@MnO2@CDs polyhedron. Additionally, the steric hindrance effect of the Co3O4@MnO2@CDs-Ab conjugates further weaken the photocurrent. Based on the multifunctional Co3O4@MnO2@CDs polyhedron, the proposed PEC biosensor for the detection of A549 cancer cells exhibits a wide linear range from 102 to 106 cells/mL and a low detection limit of 11 cells/mL. Furthermore, this strategy can differentiate between lung cancer patients and healthy individuals. The designed multifunctional Co3O4@MnO2@CDs nanozymes provide a new horizon for PEC detection of cancer cells, and may have great potential in early clinical diagnosis and biomedical research.

A Colorimetric/Fluorescent Dual-Mode Aptasensor for Salmonella Based on the Magnetic Separation of Aptamers and a DNA-Nanotriangle Programmed Multivalent Aptamer

Salmonella infection has emerged as a global health threat, causing death, disability, and socioeconomic disruption worldwide. The rapid and sensitive detection of Salmonella is of great significance in guaranteeing food safety. Herein, we developed a colorimetric/fluorescent dual-mode method based on a DNA-nanotriangle programmed multivalent aptamer for the sensitive detection of Salmonella. In this system, aptamers are precisely controlled and assembled on a DNA nanotriangle structure to fabricate a multivalent aptamer (NTri-Multi-Apt) with enhanced binding affinity and specificity toward Salmonella. The NTri-Multi-Apt was designed to carry many streptavidin-HRPs for colorimetric read-outs and a large load of Sybr green I in the dsDNA scaffold for the output of a fluorescent signal. Therefore, combined with the magnetic separation of aptamers and the prefabricated NTri-Multi-Apt, the dual-mode approach achieved simple and sensitive detection, with LODs of 316 and 60 CFU/mL for colorimetric and fluorescent detection, respectively. Notably, the fluorescent mode provided a self-calibrated and fivefold-improved sensitivity over colorimetric detection. Systematic results also revealed that the proposed dual-mode method exhibited high specificity and applicability for milk, egg white, and chicken meat samples, serving as a promising tool for real bacterial sample testing. As a result, the innovative dual-mode detection method showed new insights for the detection of other pathogens.

Fe(III)-incorporated porphyrin-based conjugated organic polymer as a peroxidase mimic for the sensitive determination of glucose and H2O2

Nanozymes, i.e., nanomaterials that possess intrinsic enzyme-like behaviour, have thrived over the past few decades owing to their advantages of superior stability and effortless storage. Such artificial enzymes can be a perfect alternative to naturally occurring enzymes, which have disadvantages of high cost and limited functionality. In this work, we present the fabrication of an Fe(III)-incorporated porphyrin-based conjugated organic polymer as a nanozyme for the efficient detection of glucose through its intrinsic peroxidase activity and the amperometric detection of hydrogen peroxide. The iron-incorporated porphyrin-based conjugated organic polymer (Fe-DMP-POR) possesses a spherical morphology with high chemical and thermal stability. Exploiting the peroxidase-mimicking activity of the material for the determination of glucose, a detection limit of 4.84 μM is achieved with a linear range of 0-0.15 mM. The Fe-DMP-POR also exhibits a reasonable recovery range for the detection of human blood glucose. The as-synthesized material can also act as an H2O2 sensor, with a sensitivity of 947.67 μA cm-2 mM-1 and a limit of detection of 3.16 μM.

Recent Advances in Nanozyme-Mediated Strategies for Pathogen Detection and Control

Pathogen detection and control have long presented formidable challenges in the domains of medicine and public health. This review paper underscores the potential of nanozymes as emerging bio-mimetic enzymes that hold promise in effectively tackling these challenges. The key features and advantages of nanozymes are introduced, encompassing their comparable catalytic activity to natural enzymes, enhanced stability and reliability, cost effectiveness, and straightforward preparation methods. Subsequently, the paper delves into the detailed utilization of nanozymes for pathogen detection. This includes their application as biosensors, facilitating rapid and sensitive identification of diverse pathogens, including bacteria, viruses, and plasmodium. Furthermore, the paper explores strategies employing nanozymes for pathogen control, such as the regulation of reactive oxygen species (ROS), HOBr/Cl regulation, and clearance of extracellular DNA to impede pathogen growth and transmission. The review underscores the vast potential of nanozymes in pathogen detection and control through numerous specific examples and case studies. The authors highlight the efficiency, rapidity, and specificity of pathogen detection achieved with nanozymes, employing various strategies. They also demonstrate the feasibility of nanozymes in hindering pathogen growth and transmission. These innovative approaches employing nanozymes are projected to provide novel options for early disease diagnoses, treatment, and prevention. Through a comprehensive discourse on the characteristics and advantages of nanozymes, as well as diverse application approaches, this paper serves as a crucial reference and guide for further research and development in nanozyme technology. The expectation is that such advancements will significantly contribute to enhancing disease control measures and improving public health outcomes.