Block-Polymer-Restricted Sub-nanometer Pt Nanoclusters Nanozyme-Enhanced Immunoassay for Monitoring of Cardiac Troponin I

Nanozyme mediated Raman-NLISA dual-modal immunosensor for accurate and sensitive detection of microcystin-LR

A Raman scattering and nanozyme-linked immunosorbent assay (NLISA) dual modal immunosensor, was constructed by mesoporous SiO2/Au-Pt nanozymes (m-SAP) and nanobodies (A2.3-SBP). Oxidized TMB served as Raman and ELISA signals in a competitive binding assay. Under optimized conditions, an inverse correlation was established between the Microcystin-LR (MC-LR) concentration and the signals, spanning Raman and ELISA ranges of 0.1-100 μg L-1 and 1.0-500 μg L-1, with limit of detections (LODs, 3σ/S) of 0.015 μg L-1 and 0.12 μg L-1, respectively. The LODs showed over 90 times and 11 times higher sensitivity than that of traditional ELISA (t-ELISA, LOD, 1.36 μg L-1). The immunosensor exhibited excellent accuracy in practical samples, can be integrated together for the detection of MC-LR within 45 min, which greatly short the detection time of t-ELISA (>2 h). This method displayed potential for detecting other toxins by simply changing the nanobodies.

Efficient fluorescence and electrochemiluminescence dual-signal au nanoclusters-based portable antibiotic testing platform with super-wide detection range

The convenient detection of tetracycline (TC) residues has attracted considerable attention because irrational use of TC causes food pollution damaging the human health. Herein, a point-of-care testing (POCT) platform is established for the sensitive and specific determination of TC in a polydopamine-functionalised Eppendorf tube. In particular, TC can be efficiently recognised by an aptamer-antibody chimera to trigger visual fluorescence (FL) and electrochemiluminescence (ECL) 'dual-signal' response of gold nanoclusters. Consequently, the biosensor exhibits a wide detection range spanning from 5 fM to 1 μM, with low detection limits of 73 fM (visual FL) and 2.3 fM (ECL). Hence, it can be said that the POCT platform is superior to the enzyme-linked immunosorbent assay. The strategy utilises the strength of FL, i.e. visualisation, and that of ECL, i.e. high sensitivity, providing a guiding approach for the development of POCT in food security and environmental monitoring.

A three-stage amplified pressure bioassay for sensitive detection of cardiac troponin

Cardiac troponin I (cTnI) level in human blood is a key biomarker associated with acute myocardial infarction (AMI). Rapid, convenient, inexpensive and highly sensitive point-of-care (POC) bioassays for cTnI in home and community are of great importance in saving the lives of AMI patients. Herein, we present a three-stage amplified pressure-sensing bioassay system for highly sensitive detection of cTnI. Specifically, the magnetic bead-cTnI-Pt nanoclusters protein complex formed by the immunoconjugation of antigen and antibody can be conveniently subjected to magnetic separation to reduce background interference and achieve first-stage amplification. Then, the Pt nanoclusters in the complex can effectively catalyze the decomposition of H2O2 into O2, thus achieving the secondary amplification of the pressure signal. Finally, the biotin and streptavidin cross-linked Pt nanoclusters significantly increase the amount of catalyst, enabling the tertiary amplification of the bioassay. The method has good linearity in the range of 10 to 1 × 104 pg/mL for quantitative detection, and the detection limit of the method was calculated to be 3.8 pg/mL (in water), which is 30 times more sensitive than the original secondary amplification detection system. In addition, the results of clinical samples tested with the developed method were consistent with those tested with commercial kits. Given the automation, rapid response and miniaturization of pressure-based sensors, our bioassay is expected to be a powerful tool for home and community-based POC diagnosis of patients with various acute diseases in the future.

Inhibition effect-involved colorimetric sensor array based on PtBi aerogel nanozymes for discrimination of antioxidants

Nanozymes, as superior alternatives to natural enzymes, frequently employ the inhibition effect in turn-off sensors for analyte detection. However, limited attention has been paid to the inhibition mechanisms between analytes and nanozymes, limiting advancements in nanozyme-based sensing. Benefiting from the synergistic effects between three-dimensional network structure of aerogel and ligand effect triggered electronic regulation, Pt100Bi2 aerogel nanozymes (Pt100Bi2 ANs) exhibit superior peroxidase-like activity (293.48 U/mg). We found that antioxidants are able to inhibit the peroxidase-like activity of Pt100Bi2 ANs. The inhibition type (gallic acid as model) is reversible mixed-inhibition with the inhibition constants (Ki and Ki') of 0.213 mM and 0.108 mM. The inhibition effect-involved colorimetric sensor arrays were developed to overcome the "lock-key" limitation of traditional sensors, enabling distinguish five antioxidants via principal component analysis, with detection limit below 2 μM. This work provides new perspective on the inhibition mechanisms of nanozymes and optimization strategies for high-performance nanozyme-based sensors.

Harnessing bifunctional nanozyme with potent catalytic and signal amplification for innovating electrochemical immunoassay

Nanozyme-based electrochemical biosensors have emerged as an alternative to enzyme-based biosensors for next-generation bioanalysis. However, potential antibody modifications limit the catalytic sites of the nanozyme, thereby reducing sensor sensitivity. Here, a sensitive method for determining carcinoembryonic antigen (CEA) was developed. It involved coupling a cascade enzyme - enzyme - like catalytic reaction using Fe - Co Prussian blue analog nanozymes with high peroxidase - like activity (79.42 U mg-1). Briefly, the transduction of biological signals to chemical signals was achieved through the strategy centered on catalytic electroactive probes. Thereafter, with the assistance of the microelectrochemical workstation, the output of signals was realized. The platform exhibited an ultra-wide range of 0.020-100 ng mL-1 and a detection limit of 0.013 ng mL-1 CEA, which was mainly attributed to the excellent peroxidase activity, good conductivity, and synergistic amplification of current signals of synthesized nanozymes. In addition, the modification-free features greatly reduced the complexity of the bioassay and significantly improves its portability and cost-effectiveness. Overall, this study advances the development of nanozymes and their electrochemical biosensing applications and is expected to extend to the development of miniaturized devices in direct detection environments.

Dual-metal CuFe/Fe cube nanozyme with Prussian blue analogue for highly efficient colorimetric immunoassay

Due to unique framework structures, Prussian blue analogs (PBAs) have long been of considerable interest in biosensing. However, the predominantly cubic morphology of most PBAs, along with their inherent elemental and structural limitations, restricts their catalytic performance as the nanozymes. Herein, we designed a dual-metal CuFe/Fe PBA nanozyme composite (CuFe/Fe DMPBA) exhibiting excellent peroxidase (POD)-like activity. The synthesized FePBA was prismatically loaded along the inner core CuFe PBA to build an epitaxially deposited structure. This unique architecture resulted in a substantial enhancement of the POD-like activity of the composite nanozyme compared to its individual components, FePBA and CuFe PBA. Leveraging the superior catalytic performance of the synthesized CuFe/Fe DMPBA, we further developed a highly sensitive and selective colorimetric immunoassay platform for the detection of human epidermal growth factor receptor 2 (HER2), a crucial biomarker of cancer. Under optimized conditions, this nanozyme-based immunoassay platform achieved a limit of detection (LOD) of 0.007 ng mL-1 and a linear range from 0.01 to 10 ng mL-1 for HER2 detection. This work not only presents a novel strategy for synthesizing high-performance PBA-based nanozymes, but also provides insights for the rational design and application of PBA materials in bioanalytical sensing.

Dual Z-scheme In2S3/Bi2S3/ZnS heterojunction with broad-spectrum response as a photoactive material for ultrasensitive detection of environmental Pollutant tetracycline

Herein, a novel dual Z-scheme heterojunction In2S3/Bi2S3/ZnS (IBZS) with core-shell structure was prepared to establish a photoelectrochemical (PEC) biosensor for ultrasensitive detection of tetracycline (TC) referred to environmental pollution. Compared with the traditional single Z-scheme heterojunction with low PEC response, the dual Z-scheme heterojunction exhibited a strong PEC response due to its broad-spectrum response and highly efficient carrier migration. Furthermore, a redesigned target-triggered entropy-driven DNA reaction (TEDR) was implemented to mitigate spontaneous transient strand dissociation (breathing effect) in DNA duplexes, thereby effectively suppressing nonspecific background noise and enhancing the detection sensitivity of the biosensor. Hence, the PEC biosensor achieved an ultrasensitive detection of TC from 1.0 fM to 10 nM with a detection limit of 0.54 fM, which was far beyond the current TC detection methods. This strategy provided a new avenue for designing high-performance PEC photoactive materials, which was expected to be used to analyze antibiotics in environmental pollution monitoring and food quality control.

Multiplex analysis of ovarian cancer patients using glycan microarray

Investigation of tumor-associated glycan antigens (TAGs) could be helpful for the development of sensitive cancer diagnostics and novel therapies. Glycan microarrays are effective methods for analyzing glycans and anti-glycan antibodies, which are immobilized arrays of oligo- or poly-saccharides on different substrates, making them a promising class of oncological biomarkers. Blood serum samples from patients (n = 203) with ovarian cancer (OvaCan) and healthy volunteers were analyzed using a glycan microarray containing 63 immobilized glycans to determine changes in anti-glycan IgG and IgM antibody profiles in OvaCan. Levels of anti-glycan IgG and IgM antibodies in OvaCan statistically differed from levels in healthy donors: the most prominent statistically significant difference for anti-glycan IgG antibodies was found for 6-O-su-Lec (AUC = 0.657, Se = 48.0 %, and Sp = 73.3 %). The AUC values for certain glycans investigated in diagnosing OvaCan indicated a fingerprint consisting of IgM antibodies to specific glycans, and the most specific anti-glycan IgM antibodies were Ley (AUC = 0.625, Se = 98.0 % and Sp = 45.0 %). The potential of these serological biomarkers to distinguish between OvaCan and other malignancies is still an unresolved issue that requires more large-scale studies to confirm and validate the use of these biomarkers in the diagnosis of different types of cancer.

Transcriptional regulation of tumor suppressor gene RASSF1A by HBx

INTRODUCTION

The occurrence of liver cancer in China is primarily attributed to chronic hepatitis B virus (HBV) infection. HBV X protein (HBx) has emerged as a significant carcinogenic driver in HBV-related liver cancer. However, the underlying mechanism by which HBx contributes to liver cancer development is not fully understood.

METHODS

This study investigated HBx's role in regulating the tumor-suppressor gene RASSF1A. Firstly, the RASSF1A plasmid was constructed using a luciferase reporter system. The dual luciferase assay system detected HBx's effect on RASSF1A promoter activity. Western blotting and quantitative PCR methods measured HBx's impact on RASSF1A protein and mRNA expression. Chip was used to test the binding of HBx and SP1. CCK8, transwell, flow cytometry were used to detect the effect of RASSF1A on HCC proliferation. Methylation-specific PCR analyzed HBx's effect on RASSF1A methylation.

RESULTS

Our results show that HBx significantly enhances RASSF1A promoter activity in an SP1 binding site-dependent manner. When only one SP1 binding site remained, HBx's effect was abolished. RASSF1A can inhibit HCC proliferation. Both mRNA and protein expression levels of RASSF1A were lower in HBx-expressing THLE-2 cells than in control cells, correlating with higher RASSF1A promoter methylation.

CONCLUSION

These findings suggest HBx enhances RASSF1A promoter activity and upregulates transcription via SP1, potentially preceding RASSF1A promoter methylation. This study provides new insights into HBx's regulation of the tumor suppressor gene RASSF1A in HBV-related liver cancer.

Target-induced nanoparticle assemblies: a comprehensive review of strategies for nucleic acid functionalization, biosensing, and drug delivery applications

Fundamental studies on nanoparticle superstructures or core-satellite assemblies and their interactions with biomolecules have led to advancements in nanobiotechnology. Consequently, some novel nucleic acid (NA) biosensing, diagnostics, and imaging approaches have been developed by functionalizing the surface of nanoparticles with target-specific analytes. For functionalization, multivalent nanoparticles are chosen over monovalent ones because they can enhance the concentration of probes on the nanoparticle surface and simultaneously bind to multiple target sites, leading to specific and sensitive detection, primarily in the case of target NAs with low-abundance target. Selection of appropriate satellite (shell) and core nanoparticles is crucial for building assemblies that can improve the resistance of DNA against serum degradation and nuclease activity by several folds compared with those of un-assembled particles. Structural modification of NPs via covalent ligation with DNA or miRNA using synthetic click chemistry approaches resulted in the formation of dimers/tetramers, which could ease the delivery of DNA-intercalating drugs and simultaneously sense target biomarkers in the cellular environment, showing the synergistic applications of multivalent assemblies. This review provides an overview of the design strategies and chemistries involved in the loading of nucleic acid probes onto the NP surface, synthesis of PEG ligands, and purification and characterization techniques for assemblies (dimer, trimer, and multimer). In addition, the applications of NP assemblies in biosensing miRNA, strategies and challenges involved in the intracellular detection of miRNA, colorimetric, SERS, and electrochemical techniques for bacterial/virus detection, and drug delivery applications are discussed. Finally, the advantages, challenges, and future perspectives in commercializing this technology are comprehensively elucidated.

Inflammatory microenvironment-responsive electrochemical biosensing for cancer cell discrimination using PtZnCd-anchored multi-walled carbon nanotubes

The quantification of intracellular hydrogen peroxide (H2O2) serves as a critical biomarker for characterizing cellular physiological states, providing essential insights into metabolic regulation and signaling pathways. This analytical paradigm not only advances our understanding of pathological mechanisms but also contributes to the development of novel diagnostic approaches and precision therapeutic interventions. Herein, we established an innovative electrochemical microsensing platform capable of discriminating between malignant and normal cells through their distinct inflammatory responses under external stimulation. This innovative methodology integrates three critical technical advancements: (i) optimization of a one-pot microwave synthesis protocol for fabricating high-performance PtZnCd nanoparticles anchored on multi-walled carbon nanotubes (MWCNTs), which serve as the core sensing element; (ii) systematic electrochemical characterization coupled with density functional theory (DFT) calculations demonstrating that this hybrid architecture significantly reduces interfacial charge-transfer resistance while enhancing heterogeneous electron transfer kinetics; (iii) comprehensive biocompatibility evaluations confirming the composite material's favorable cytotoxicity profile and biological safety, supporting its potential for cellular classification applications. Through real-time monitoring of dynamic metabolic fluctuations and intracellular inflammatory microenvironment changes in response to ascorbic acid (AA) and dehydroascorbic acid (DHA) stimulation, we established distinct response signatures that effectively differentiate neoplastic cells from their healthy counterparts. This study introduces an innovative electrochemical sensing paradigm that synergistically combines biocompatible nanocatalysts with inflammatory microenvironment dynamics, establishing a robust platform for dual discrimination between cancerous and normal cells, with significant implications for biomedical research and clinical diagnostics.

From population-based to personalized laboratory medicine: continuous monitoring of individual laboratory data with wearable biosensors

Monitoring individuals' laboratory data is essential for assessing their health status, evaluating the effectiveness of treatments, predicting disease prognosis and detecting subclinical conditions. Currently, monitoring is performed intermittently, measuring serum, plasma, whole blood, urine and occasionally other body fluids at predefined time intervals. The ideal monitoring approach entails continuous measurement of concentration and activity of biomolecules in all body fluids, including solid tissues. This can be achieved through the use of biosensors strategically placed at various locations on the human body where measurements are required for monitoring. High-tech wearable biosensors provide an ideal, noninvasive, and esthetically pleasing solution for monitoring individuals' laboratory data. However, despite significant advances in wearable biosensor technology, the measurement capacities and the number of different analytes that are continuously monitored in patients are not yet at the desired level. In this review, we conducted a literature search and examined: (i) an overview of the background of monitoring for personalized laboratory medicine, (ii) the body fluids and analytes used for monitoring individuals, (iii) the different types of biosensors and methods used for measuring the concentration and activity of biomolecules, and (iv) the statistical algorithms used for personalized data analysis and interpretation in monitoring and evaluation.

Construction of Biomimetic Nanochannel, Property Regulation, and Biomarker Detection

The significance of biomimetic nanochannel in the field of biosensors is gaining increasing recognition. The controllable construction of biomimetic nanochannels and their performance modulation have demonstrated great importance and obtained wide interest. The nanochannels offer high sensitivity, enabling sensors to swiftly identify target biomarkers in complex biological samples, with detection limits reaching the picomolar level. Furthermore, they demonstrate exceptional selectivity and reproducibility, making them ideal tools for biomarker detection. In recent years, biosensors utilizing biomimetic nanochannel have shown remarkable performance in detecting a wide range of biomarkers. This review aims to explore the opportunities and challenges associated with biomimetic nanochannel technology in biosensor applications, focusing on the construction and performance modulation of these nanochannels, as well as their applications in detecting nucleic acids, proteins, organisms, and small molecules. Providing forward-looking insights into this cutting-edge field is aspired, with particular emphasis on technological advancements, addressing current challenges, and discussing future trends.

Fabrication of a hierarchical PtIr@Rh hollow trimetallic nanozyme with a higher specific activity than that of HRP for sensitive colorimetric detection

Nanozymes have emerged as promising alternatives to natural enzymes in various fields, owing to their advantages in terms of stability, cost-effectiveness, and multifunctionality. However, their relatively low catalytic activity compared to natural enzymes remains a major challenge for practical applications. Here, we developed hierarchical PtIr@Rh hollow trimetallic nanorods, where Rh served as the substrate and the surface was decorated with numerous Pt nanoparticles doped with a small amount of Ir. The resulting nanorods exhibited remarkable peroxidase-like activity, with a specific activity of 2287 U mg-1, surpassing that of horseradish peroxidase (HRP). Additionally, the maximum reaction velocity (Vmax) was 1.024 × 10-6 M s-1, and the Michaelis-Menten constant (Km) was 1.706 mM. The enhanced catalytic performance was attributed to the unique hierarchical structure and the small amount of Ir doping, as supported by density functional theory (DFT) calculations. The PtIr@Rh nanozyme was successfully applied for the colorimetric detection of L-ascorbic acid, achieving a rapid detection with a limit of detection (LOD) of 0.12 μM. This study introduces a novel nanozyme with superior specific activity compared to natural enzymes, highlighting its potential for colorimetric sensing applications.

Development of novel poly(1,4-benzenedithiol) nanoparticles@AuNPs lateral flow immunochromatographic test strips

In this study, we successfully developed a novel lateral flow immunochromatography (LFIA) strip that utilizes poly(1,4-benzenedithiol) (PBDT) nanoparticles loaded with gold nanoparticles (PBDT@AuNPs), characterized by a particle size of 147 nm and a spherical morphology, as labeling materials to enhance the sensitivity of colloidal gold. PBDT@AuNPs exhibit a higher loading capacity and molar extinction coefficient compared to traditional markers, with an approximately 22-fold increase in molar extinction coefficient relative to colloidal gold immunochromatography, significantly improving detection sensitivity. Cardiac troponin I (cTnI) was employed as a model to assess the detection efficiency and reliability of PBDT@AuNPs LFIA strips. A calibration curve was established using a four-parameter logistic function to fit the relationship between colloidal gold colorimetric strength and cTnI concentration, covering a range of 0.06 to 500 ng mL-1, with a detection limit of 0.03 ng mL-1 as calculated by the International Union of Pure and Applied Chemistry (IUPAC). A chemical comparison of various cTnI concentrations in human serum samples, conducted using Passing-Bablok regression, confirmed the equivalence of the PBDT@AuNPs LFIA strips with a commercial fluorescent cTnI LFIA kit, revealing no significant systematic or proportional bias. The spike recovery ranged from 91.92% to 108.70%, and the relative standard deviation (RSD) ranged from 5.29% to 5.85%, underscoring the high precision of the PBDT@AuNPs LFIA strips in quantifying cTnI in human serum samples.

Signal "Off-On Model'' for Colorimetric Sensing Proanthocyanidin B2 Achieved by the Organic Solvent-Processed Amorphous BiVO4 Nanozyme

Here, we report a "off-on model"-based colorimetric sensor without the assistance of H2O2, achieved by organic solvent-processed amorphous BiVO4 nanoparticles favorable for large-scale manufacturing. The amorphous material beyond traditional crystalline nanozymes has both vanadium vacancy (Vv) and oxygen vacancy (Ov), as well as single oxidase-like activity with both hydroxyl radical (•OH) and superoxide anion (O2•-) as electron acceptors. Despite the high enzymatic performance, the dual-defect-rich amorphous BiVO4 preserves good long-term activity in either buffer solution or the solid state. The specially designed BiVO4 is capable of accelerating TMB oxidation in the presence of polyphenols, thus leading to an interesting signal-intensified colorimetric response. This is probably due to the coordination of the ortho dihydroxyl group in polyphenols with the catalyst by replacing the surface-adsorbed NO3-, which results in faster charge transfer between BiVO4 and substrate and, thus, more rapid depletion of radicals for TMB oxidation. Based on these findings, a sensor platform for proanthocyanidin (PAC) B2 is established with a limit of detection (LOD) as low as 65 nM and good specificity. The sensor shows higher sensitivity than the standard Porter method (LOD: 0.29 μM) and comparable accuracy when analyzing PAC B2 in commercially available grape seed capsules, with quantitative recoveries varying from 104.0 to 108.3% and relative standard deviations ranging from 1.7 to 5.7%. To date, this is the only nanozyme-based chemical sensor that is active for the signal "off-on model" for the detection of reducing polyphenols. Also, this method seems quite general, and it can be used for sensing of a series of specific polyphenols in addition to PAC B2.

Integrating Ferroelectric Fields with Active Sites for the Construction of Highly Efficient Nanozymes

Enhancing nanozymes' catalytic activity is challenging yet crucial for practical applications. Herein, inspired by the electrostatic preorganization effect in the catalytic process of natural protein enzymes, a nanozyme is constructed by decorating ferroelectric BaTiO3 nanoparticles (BTO) with hemin, which is often regarded as the active site of natural horseradish peroxidase (HRP). The Hemin-BTO nanozyme demonstrates excellent peroxidase-like (POD-like) activity with the catalytic constant (Kcat) up to 9.71 × 105 s-1 and 1.41 × 106 s-1 for TMB and H2O2 substrates, which is ca. 240-fold and 400-fold greater than that of HRP. Theoretical studies utilizing Density Functional Theory calculations revealed the underlying mechanism. The spontaneous polarization electric field of BTO adjusts the internal electrostatic field of the active site hemin, thereby enhancing the affinity between the Hemin-BTO nanozyme and the substrate. Simultaneously, the existence of hemin reduced the recombination of BTO charge carriers, accelerated electron transfer, and thus promoted the generation of reactive oxygen species, effectively enhancing its POD-like activity. In addition, Hemin-BTO has been successfully used to establish an immunoassay of human brain natriuretic peptide. This work presented a feasible strategy to construct nanozymes with highly catalytic activity by integrating the ferroelectric fields with the active site of natural enzymes.

Platinum Nanozyme-Loaded Dissolving Microneedles Scavenge ROS and Promote Lineage Progression for Androgenetic Alopecia Treatment

Androgenetic alopecia (AGA) is a prevalent issue affecting the physical and mental health of individuals but with fewer current treatments. Platinum nanozymes (PtNZs) are known for their excellent ability to reduce and modulate the high oxidative stress environment in AGA pathology. And microneedles are used to overcome the skin barrier due to the poor permeability of PtNZs. Herein, dissolving microneedles loaded with PtNZs (Pt-MNs) are designed and successfully induced hair regeneration in the AGA model. Pt-MNs possessed adequate mechanical strength to breach the skin barrier for effective PtNZs delivery. In vivo, PtNZs first reduced reactive oxygen species (ROS) to oxygen, which recovered the AGA pathological environment. And the oxygen then increased oxidative phosphorylation, promoting the differentiation of hair follicle stem cells to achieve hair regeneration. The group treated with Pt-MNs with a dosing frequency of once every three days achieved faster hair growth than the daily application of the positive drug minoxidil. Further safety experiments showed that the application of Pt-MNs locally opened temporary and recoverable skin channels, with no retention of Pt in major organs, indicating high safety. In conclusion, this study indicated the potential of Pt-MNs as an effective method for treating AGA.

Recent advances in MXene nanozyme-based optical and electrochemical biosensors for food safety analysis

The importance of nanotechnology is increasing every day in different fields and, especially, the application of nanomaterials has attracted considerable attention in food safety. Among different nanomaterials, MXenes, which are two-dimensional (2D) transition metal-based layered materials made of nitrides and carbides, have revolutionized various fields as a cutting-edge scientific discovery in nanotechnology. These materials have been widely used in the structure of biosensors and sensors due to their excellent metallic conductivity, mechanical stability, optical absorbance, good redox capability, and higher heterogeneous electron transfer rate. In particular, the application of MXenes as nanozymes has highlighted their high performance to a great extent in biosensor domains. The growing interest in these nanozymes is attributed to their specific physicochemical features. The key enzymatic features of these materials include activities similar to oxidase, peroxidase, catalase, and superoxide dismutase. In this review, initially, several common synthesis methods of MXenes are presented, emphasizing their significant role as nanozymes in constructing efficient sensors. Subsequently, several common applications of MXene nanozymes in food safety analysis are delved into, including the detection of bacteria, mycotoxins, antibiotic residues, and pesticide residues, along with their applications in different electrochemical and optical biosensors. In addition, the gap, limitation, and future perspective of these novel nanozymes in food safety are highlighted.

An electrochemical biosensor using AuNPs-Ti3C2Tx and ARGET ATRP reactions as signal amplification strategies for ultra-sensitive detection of HER2 protein

Human epidermal growth factor receptor 2 (HER2) status is an important factor in evaluating the prognosis of breast cancer patients. Therefore, it is particularly important to develop a simple and sensitive method for the detection of HER2-positive breast cancer. Here, an ultra-sensitive electrochemical biosensor for detecting HER2-specific proteins was assembled using gold nanoparticles and Two-dimensional carbides (AuNPs-Ti3C2Tx) as a conducting substrate. The prepared AuNPs-Ti3C2Tx not only has good electrical conductivity and strong electrochemical signal output, but also provides a large number of active sites for the AuS bonds assembly aptamer. In addition, the antibodies-modified functionalized graphene oxide (GO) as a carrier platform, which provides an additional boost for the detection of trace targets with high sensitivity under optimal conditions. Afterwards,HER2 protein was detected by signal amplification effect of AuNPs-Ti3C2Tx and functionalized GO combined with Electron transfer activated regeneration catalyst atomic transfer radical polymerization (ARGET ATRP). In the range of 1 to 105 ng·mL-1, there was a good linear relationship between the HER2 concentration and the signal intensity, with a limit of detection of 0.19 pg·mL-1. Moreover, this method has good selectivity and stability, and then still maintains good detection performance and strong anti-interference ability in the complex environment of normal human serum, which is expected to be applied in clinical application.

Electrocatalysts for the Formation of Hydrogen Peroxide by Oxygen Reduction Reaction

Hydrogen peroxide (H2O2) is a widely used strong oxidant, and its traditional preparation methods, anthraquinone method, and direct synthesis method, have many drawbacks. The method of producing H2O2 by two-electron oxygen reduction reaction (2e- ORR) is considered an alternative strategy for the traditional anthraquinone method due to its high efficiency, energy saving, and environmental friendliness, but it remains a big challenge. In this review, we have described the mechanism of ORR and the principle of electrocatalytic performance testing, and have summarized the standard performance evaluation techniques for electrocatalysts to produce H2O2. Secondly, according to the theoretical calculation and experimental results, several kinds of efficient electrocatalysts are introduced. It is concluded that noble metal-based materials, carbon-based materials, non-noble metal composites, and single-atom catalysts are the preferred catalyst materials for the preparation of H2O2 by 2e- ORR. Finally, the advantages and novelty of 2e- ORR compared with traditional methods for H2O2 production, as well as the advantages and disadvantages of the above-mentioned high-efficiency catalysts, are summarized. The application prospect and development direction of high-efficiency catalysts for H2O2 production by 2e- ORR has been prospected, which is of great significance for promoting the electrochemical yield of H2O2 and developing green chemical production.

Multi-technique-based electrochemical sensing of lipoarabinomannan (LAM) antigen as a biomarker for early-stage tuberculosis diagnosis

Tuberculosis (TB) remains a pressing global health challenge, necessitating precise and reliable biomarkers for early detection. Lipoarabinomannan (LAM), an FDA-approved biomarker (Monoclonal Antibody-MBS320597), holds significant potential due to its association with theMycobacterium tuberculosiscell wall. This study systematically evaluates LAM concentrations ranging from 1 pg ml-1to 6 ng ml-1using square wave voltammetry analysis, achieving an exceptional limit of detection of 0.077 pg ml-1. A comprehensive review of current diagnostics highlights critical gaps, including limitations in speed and accuracy, underscoring the urgency for advanced methodologies. In this study, LAM's performance is assessed by analyzing spiked urine samples, demonstrating its high sensitivity, specificity, and reliability as an early-stage TB biomarker. By comparing findings with existing diagnostic tools and addressing identified limitations, this study emphasizes LAM's potential to transform TB diagnostic strategies. These results contribute to global efforts to improve early detection, enhance patient outcomes, and pave the way for future advancements in TB diagnostics.

Luteolin-Manganese Nanozyme Induces Apoptosis and Ferroptosis for Enhanced Cancer Therapy

Cancer presents a significant global public health challenge that impacts millions of individuals worldwide. The incorporation of natural products into cancer treatment has the potential to mitigate many of the side effects commonly associated with chemotherapy. This study builds on the advantages of enhancing the anticancer activity of natural flavonoids through metal chelation by synthesizing a natural antioxidant flavonoid complex, termed Lu-Mn nanozyme, which involves the chelation of luteolin with manganese ions. In vitro experiments demonstrated that Lu-Mn exhibits a strong affinity for hydrogen peroxide (H2O2) and effectively catalyzes the generation of hydroxyl radicals (•OH) from H2O2 within the tumor microenvironment. The administration of the Lu-Mn nanozyme not only induced apoptosis in tumor cells by upregulating the expression of cleaved caspase3 and caspase9 but also activated ferroptosis through downregulation of the NRF2-GPX4 signaling pathway. Furthermore, animal studies have shown that Lu-Mn possesses significant antitumor efficacy and a favorable safety profile. Collectively, these findings suggest that luteolin, through its chelation with metal ions, has considerable potential for application in cancer treatment.

Nanozyme-Enabled Biomedical Diagnosis: Advances, Trends, and Challenges

As nanoscale materials with the function of catalyzing substrates through enzymatic kinetics, nanozymes are regarded as potential alternatives to natural enzymes. Compared to protein-based enzymes, nanozymes exhibit attractive characteristics of low preparation cost, robust activity, flexible performance adjustment, and versatile functionalization. These advantages endow them with wide use from biochemical sensing and environmental remediation to medical theranostics. Especially in biomedical diagnosis, the feature of catalytic signal amplification provided by nanozymes makes them function as emerging labels for the detection of biomarkers and diseases, with rapid developments observed in recent years. To provide a comprehensive overview of recent progress made in this dynamic field, here an overview of biomedical diagnosis enabled by nanozymes is provided. This review first summarizes the synthesis of nanozyme materials and then discusses the main strategies applied to enhance their catalytic activity and specificity. Subsequently, representative utilization of nanozymes combined with biological elements in disease diagnosis is reviewed, including the detection of biomarkers related to metabolic, cardiovascular, nervous, and digestive diseases as well as cancers. Finally, some development trends in nanozyme-enabled biomedical diagnosis are highlighted, and corresponding challenges are also pointed out, aiming to inspire future efforts to further advance this promising field.

Onion-like carbon based single-atom iron nanozyme for photothermal and catalytic synergistic antibacterial application

Nanozymes with oxidase (OXD)-like activity have emerged as promising antibacterial agents due to their capability of catalyzing atmospheric O2 to generate highly active free radicals. However, the precise engineering of functional nanozyme at the atomic level for antibacterial therapy presents a challenge. Here, atomically dispersed Fe atoms were loaded onto onion-like carbon (OLC) through a ligand-assisted calcination strategy, yielding a single-atom nanozyme (FeSA-OLC) with enhanced oxidase-like activity. The FeSA-OLC could catalyze the decomposition of O2 to produce active hydroxyl radicals (·OH) owing to the fully exposed Fe atoms and a highly curved carbon shell. Density functional theory calculation revealed that the single-atom Fe sites facilitated the generation of free radical species by promoting the adsorption and cleavage of OO bond. Meanwhile, the FeSA-OLC exhibited a notable photothermal conversion efficiency of 66.48% under near-infrared laser irradiation. Furthermore, in vitro experimental results demonstrated a synergistic antibacterial effect towards Escherichia coli due to the photothermal-enhanced oxidase-like activity. Overall, this work introduced a strategy to develop OLC-based single-atom nanozyme, thereby offering new avenues for photothermal-augmented antibacterial therapy.

A comprehensive review of atomically precise metal nanoclusters with emergent photophysical properties towards diverse applications

Atomically precise metal nanoclusters (MNCs) composed of a few to hundreds of metal atoms represent an emerging class of nanomaterials with a precise composition. With the size approaching the Fermi wavelength of electrons, their energy levels are well-separated, leading to molecule-like properties, like discrete single electronic transitions, tunable photoluminescence (PL), inherent structural anisotropy, and distinct redox behavior. Extensive synthetic efforts and electronic structure revelation have expanded applicability of MNCs in catalysis, optoelectronics, and biology. This review highlights the intriguing photophysical and electrochemical behaviors of MNCs and their regulatory parameters and applications. Initially, we present a brief discussion on the evolution of MNCs from gas-phase naked metal clusters to monolayer ligand-protected MNCs along with representative studies on their electronic structure. Due to their quantized molecular orbitals, they often exhibit PL, which can be regulated based on their capping ligands, number of atoms, crystal packing, presence of heterometal, and surrounding environment. Apart from PL, the relaxation pathways of MNCs on an ultrafast time scale have been extensively studied, which significantly differ from that of plasmonic metal nanoparticles. Moreover, their interaction with high-intensity light results in unique non-linear optical properties. The synergy between MNCs in a hierarchical self-assembled structure has been exploited to enhance their PL by precisely tuning their non-covalent interactions. Moreover, several NC-based hybrids have been designed to exhibit efficient electron or energy transfer in the photoexcited state. In the next section, we briefly focus on the redox behavior of NCs and facile electron transfer to suitable substrates, which result in enzyme-like catalytic activity. Utilizing these photophysical and electrochemical behaviors, NCs are widely employed in catalysis, optical sensing, and light-harvesting applications, which are also discussed in this review. In the final section, conclusions and open questions for the NC research community are included. This review will provide a comprehensive view of the emerging physicochemical properties of MNCs, thereby enabling an understanding for their precise modulation in future.

Tailored Metal-Organic Framework-Based Nanozymes for Enhanced Enzyme-Like Catalysis

The global crisis of bacterial infections is exacerbated by the escalating threat of microbial antibiotic resistance. Nanozymes promise to provide ingenious solutions. Here, we reported a homogeneous catalytic structure of Pt nanoclusters with finely tuned metal-organic framework (ZIF-8) channel structures for the treatment of infected wounds. Catalytic site normalization showed that the active site of the Pt aggregates structure with fine-tuned pore modifications structure had a catalytic capacity of 14.903×105 min-1, which was 18.7 times higher than that of the Pt particles in monodisperse state in ZIF-8 (0.793×105 min-1). In situ tests revealed that the change from homocleavage to heterocleavage of hydrogen peroxide at the interface of the nanozyme was one of the key reasons for the improvement of nanozyme activity. Density-functional theory and kinetic simulations of the reaction interface jointly determine the role of the catalytic center and the substrate channel together. Metabolomics analysis showed that the developed nanozyme, working in conjunction with reactive oxygen species, could effectively block energy metabolic pathways within bacteria, leading to spontaneous apoptosis and bacterial rupture. This pioneering study elucidates new ideas for the regulation of artificial enzyme activity and provides new perspectives for the development of efficient antibiotic substitutes.

Nanozyme-based aptasensors for the detection of tumor biomarkers

A nanozyme-based aptasensor combines the unique properties of nanozymes with the specificity of aptamers for the detection of various biomolecules. Nanozymes are nanomaterials that possess enzyme-like properties, demonstrating substantial potential for enhancing the sensing capabilities of biosensors. In recent years, the incorporation of nanozymes into biosensors has opened new avenues for the detection of tumor biomarkers. The unique attributes of nanozymes and aptamers lead to biosensors characterized by high sensitivity, specificity, reproducibility and accuracy in analytical performance. This article reviews the research progress of nanozyme-based aptasensors in tumor biomarker detection over the past decade. We categorize these sensors based on their sensing modes and target types, and examine the properties and applications of the nanozymes employed in these devices, providing a thorough discussion of the strengths and weaknesses associated with each sensor type. Finally, the review highlights the strengths and challenges associated with nanozyme-based biosensors and envisions future developments and applications in this field. The objective is to provide insights for improving biosensor performance in tumor biomarker detection, thereby contributing to advancements in precision cancer diagnosis and treatment.

Single-atom nanozyme-based catalytic ROS clearance for efficiently alleviating eczema

Single-atom nanozymes (SAzymes) with excellent biological catalytic activity have emerged as promising candidates for advancing biomedical applications. Herein, we synthesized a RuN4-SAzyme by thermal decomposition. In in vitro experiments, the RuN4-SAzyme demonstrated exceptional catalytic efficiency in mimicking the activity of peroxidase, with a Michaelis-Menten constant (Km) for 3,3',5,5'-tetramethylbenzidine reaching 0.077 mM, reflecting a high substrate affinity. Moreover, the RuN4-SAzyme also exhibited catalase- and superoxide dismutase-like activities, as well as nicotinamide adenine dinucleotide oxidase-like activity, effectively neutralizing reactive oxygen species. Significantly, in vivo experiments demonstrated that RuN4-SAzymes can effectively alleviate eczema-like symptoms by clearing inflammatory factors, reducing oxidative stress, and promoting macrophage polarization from M1 to M2, showing comparable efficacy to the clinical drug tacrolimus.

A sensitive electrochemical biosensor based on Pd@PdPtCo mesoporous nanopolyhedras as signal amplifiers for assay of cardiac troponin I

Cardiac troponin I (cTnI) has been widely used in clinical diagnosis of acute myocardial infarction (AMI). Herein, a sensitive electrochemical biosensor for cTnI analysis was designed, in which the simple synthesized Pd@PdPtCo mesoporous nanopolyhedras (MNPs) were utilized as signal amplifiers. The mesoporous polyhedral structure of Pd@PdPtCo MNPs endows them with more specific surface area and more active sites, as well as the synergistic effect between multiple metal elements, all of which increase the electrocatalytic performance of Pd@PdPtCo MNPs in efficiently oxidizing hydroquinone (HQ) to benzoquinone (BQ). Experimental results showed that Pd@PdPtCo MNPs had better performance in oxidation of HQ to BQ compared with their corresponding monometallic and bimetallic nanomaterials. With the aid of the interaction between antigens and antibodies, the peak current of HQ to BQ showed an upward trend with increasing concentration of cTnI, thus the quantitative detection of cTnI could be achieved. Under optimal conditions, the biosensor prepared in this work has a wider linear range (1.0 × 10-4-200 ng mL-1) and a lower detection limit (0.031 pg mL-1) than other sensors reported in literatures, coupled by good stability and high sensitivity. More importantly, it also performed well in complex serum environment, proving that the electrochemical sensor has a practical application potential in this field.

Single-atom ruthenium nanozyme-induced signal amplification strategy in photoelectrochemical aptasensor for ultrasensitive detection of chloramphenicol

To develop ultrasensitive and rapid antibiotics residue detection method is crucial for ensuring food safety and protecting human health. Herein, a novel photoelectrochemical (PEC) aptasensor integrated with single-atom ruthenium (Ru) nanozyme-mediated catalytic precipitation as a valuable signal amplification strategy, have been established for ultrasensitive chloramphenicol (CAP) detection. Particularly, the exceptional peroxidase-mimicking activity of single-atom Ru nanozyme is responsible for accelerating the oxidation of 4-chloro-1-naphthol (4-CN) to produce insoluble precipitate on the electrode, which in turn causes a notable reduction in the photocurrent. Whereas, when CAP is present, the aptamer is liberated away the electrode because of its potent affinity with CAP, resulting in an elevation of the photocurrent signal, enhancing the detection sensitivity. Importantly, the signal amplification strategy combines the effective photoactive material of Au nanoparticles/CdS quantum dot/TiO2 composites, a PEC aptasensor for determination of CAP with an ultralow detection limit of 4.12 pM is achieved in a self-powered mode with great selectivity and accuracy. This work proposes a novel reasonable approach utilizing high-activity single-atom nanozyme to induce signal amplification strategy for the advancement of single-atom nanozyme in ultrasensitive PEC biosensor, and further creates new avenues for ultrasensitive detection beyond antibiotics residue.

Proximity ligation-triggered DNAzyme for selective fluorescent aptasensing of methicillin-resistant Staphylococcus aureus

There is an urgent need for novel strategies to accurately and reliably detect pathogenic bacteria to address the global epidemic of antibiotic resistance. This study proposes an innovative approach combining dual aptamer-based target recognition and proximity ligation assay (PLA) triggered DNAzyme recycling cleavage. This method allows for the precise identification and reliable detection of methicillin-resistant Staphylococcus aureus (MRSA). The fluorescence probe labeled with a fluorophore is modified on gold nanoparticles (AuNPs), resulting in the quenching of the fluorescent signal by the AuNPs. The interaction between MRSA and two aptamers leads to forming a Mg2+-dependent DNAzyme. The DNAzyme cleaves the fluorescence probe, causing the fluorescent fragment to detach from the surface of the AuNPs, in which the quenched fluorescence signal in the fluorescence probe reappears. The DNAzyme-assisted cleavage and rebinding process generates a processive strolling along the surface track of AuNPs. Consequently, the fluorescence intensity experiences a substantial recovery. A strong linear correlation is observed between the fluorescence intensity and MRSA concentration within 50 cfu/mL to 106 cfu/mL. We believe that implementing the novel integrated strategy will broaden the range of bacterial detection methods in the battlefield environment and stimulate the creation of potential new drugs in the future.

Enhanced photocurrents for photoelectrochemical immunoassay of alpha-fetoprotein with Pt-functionalized Bi2O2S nanoflowers

BACKGROUND

Designing heterojunctions with efficient electron-hole separation holds great promise for improving photoelectric response.

RESULTS

Herein, we reported a multifunctional Pt co-catalyst-modified Bi2O2S nanoflowers (BOS NFs) photocatalytic component for achieving an efficient photoelectric chemistry (PEC) immunosensor for alpha-fetoprotein (AFP). Briefly, the Pt co-catalyst improved the intrinsic band gap structure of BOS on the one hand, and on the other hand, it was able to achieve a rapid decomposition of hydrogen peroxide to hydroxyl radicals, which led to the improvement of electrochemical half-responses during the amplification of target immunosignals. In addition, Pt-functionalized BOS NFs (BOS-Pt) exhibited peroxidase-like enzymatic reaction activity and related properties. By enzyme-linked immunosorbent assay, a sandwich immuno-model in the presence of AFP catalyzed the production of hydrogen peroxide from the substrate glucose and the conversion of a sizable photoelectrochemical signal catalyzed by BOS-Pt. Following condition optimization, it was determined that the developed sensor exhibited a specific response to AFP over a wide linear range of 0.05-50 ng mL-1.

SIGNIFICANCE

This work provides a new strategy for developing efficient immunosensors from the perspective of modulating photoelectrochemical half-reactions.

Exploring Selective Fluorescence Turn-On Sensing of Caspase-3 with Molybdenum Disulfide Quenched Copper Nanoclusters: FRET Biosensor

Sensing caspase-3 activity is essential for understanding the role of apoptosis in cancer dynamics, controlling therapeutic strategies, and improving patient care in cancer treatment. In this study, we demonstrate a highly sensitive recombinant human caspase-3 (rhC3) detection technique in biological fluids. This technique uses a copper nanocluster stabilized with bovine serum albumin (BSA-CuNCs) as a metal-based fluorescent biosensor, conjugated with anti-human caspase-3 (ahC3). To turn its fluorescence off, molybdenum disulfide nanosheets (MoS2 NSs) are added; this partnership is termed ahC3@BSA-CuNCs/MoS2 nanocouple. In the presence of rhC3, the energy transfer process is affected by strong ahC3/rhC3 interactions. When in close proximity, the rhC3 molecules cause detachment of the nanocluster from the MoS2 NS surface by attracting the ahC3 component of the nanocluster. This increases the distance between the nanocluster and quencher with a consequent restoration of intensity. As the concentration of rhC3 increases, the fluorescence intensity of the system also increases. A proportional response is seen in the concentration between 0.1 and 1.3 ng/mL with a very low limit of detection of 2.75 pg/mL and a quantification limit of 8.60 pg/mL. A simple filter paper strip was made to visually identify the presence of rhC3 under UV light.

Dual-electrode signal amplification self-powered biosensing platform based on nanozyme boosting target-induced DNA nanospace array for ultrasensitive detection of sugarcane Pokkah Boeng disease pathogenic bacteria

Sugarcane is a crop with significant economic importance worldwide. However, pokkah boeng disease poses a serious threat to its production and the sustainable development. There is a pressing necessity for precise and portable detection methods. We develop a dual-electrode signal amplification biosensing platform, for highly sensitive detection of sugarcane pokkah boeng disease pathogenic bacteria. This innovative platform integrates highly catalytic AuNPs/Mn3O4 nanozymes with N-GDY, along with a target-induced development of DNA nanostructure arrays. AuNPs/N-GDY serves as dual electrode substrates, and AuNPs/Mn3O4 nanozymes are surface-loaded as the bioanode. The biocathode is constructed by introducing DNA nanospace arrays onto the electrode through target-induced methods. [Ru(NH3)6]3+ is embedded into the nucleic acid double-helix scaffold via electrostatic adsorption, generating an EOCV signal that is strongly correlated with the target concentration. To further enhance sensitivity, the detection platform is combined with a capacitor to amplify the detection signal, utilizing its high power density, which results in a 22.5-fold increase in sensitivity. The method offers a linear detection range of 0.0001 to 10,000 pM and an detection limit of 32.5 aM (S/N = 3). This method supplies a novel approach for real-time monitoring and competent oversight of pokkah boeng disease pathogenic bacteria.

Deep learning assisted quantitative detection of cardiac troponin I in hierarchical dendritic copper-nickel nanostructure lateral flow immunoassay

The rising demand for point-of-care testing (POCT) in disease diagnosis has made LFIA sensors based on dendritic metal thin film (HD-nanometal) and background fluorescence technology essential for rapid and accurate disease marker detection, thanks to their integrated design, high sensitivity, and cost-effectiveness. However, their unique 3D nanostructures cause significant fluorescence variation, challenging traditional image processing methods in segmenting weak fluorescence regions. This paper develops a deep learning method to efficiently segment target regions in HD-nanometal LFIA sensor images, improving quantitative detection accuracy. We propose an improved UNet++ network with attention and residual modules, accurately segmenting varying fluorescence intensities, especially weak ones. We evaluated the method using IoU and Dice coefficients, comparing it with UNet, Deeplabv3, and UNet++. We used an HD-nanoCu-Ni LFIA sensor for cardiac troponin I (cTnI) as a case study to validate the method's practicality. The proposed method achieved a 96.3% IoU, outperforming other networks. The R2 between characteristic quantity and cTnI concentration reached 0.994, confirming the method's accuracy and reliability. This enhances POCT accuracy and provides a reference for future fluorescence immunochromatography expansion.

Revolutionizing the capture efficiency of ultrasensitive digital ELISA via an antibody oriented-immobilization strategy

Bead-based digital ELISA, the most sensitive protein quantification method, has drawn much attention to exploring ultra-low abundance biomarkers in the life sciences and clinical applications. However, its major challenge refers to the low antigen capture efficiency in the immunoreaction process due to the low probability of collision between the deficient concentration of the analytes and the captured antibody-immobilized on the beads. Here, we achieved significantly improved reaction efficiency in the digital signal formation by fixing the orientation of antibodies and revealed the kinetic mechanism for the first time. A facile and fast antibody conjugation strategy that formed boronate ester complexes was designed to retain the uniform orientation of antibodies with controllable antibody density. Remarkably, the oriented immobilized antibody exhibited stronger antigen-binding capacity and faster antigen-binding speed compared to randomly immobilized antibodies, with capture efficiency increasing approximately 14-fold at 15 μg of antibody per 1 mg microbeads (0.035 antibody nm-2) under 0.5 h incubation. Combined with theoretical analysis, we verified that the improved capture efficiency of the oriented antibodies mainly originated from the considerable rise in the binding rate constant (kon) rather than the increase in antigen-binding sites, which further prominently decreased the limit of detection (LoD) in a shorter incubation time compared with the randomly immobilized antibody. In conclusion, the antibody oriented conjugation method effectively overcomes the low capture efficiency challenge of bead-based digital ELISA. It paves a promising way for further improving the digital immunoassay performance and promotes the early diagnosis of diseases by recognizing more ultra-low abundance significant biomarkers.

Probing trace of intracellularly-originated hydrogen peroxide based Pt-Cd bimetallic nanozyme on an enzyme-free electrochemical sensor

BACKGROUND

Measurement of endogenous cellular hydrogen peroxide (H2O2) can provide information on cellular status, and help to understand cellular metabolism and signaling processes, thus contributing to elucidation of disease mechanisms and new diagnostics/therapeutic approaches.

RESULTS

In this work, Pt-Cd bimetallic nanozyme was successfully prepared via the solvothermal synthetic method for sensitive detection of H2O2. The synthesized Pt-Cd bimetallic nanozyme could exhibited good electrochemical activity. Then, the materials were analyzed for the electrochemical properties and catalytic properties of H2O2 by cyclic voltammetry and chronoamperometry, respectively. Results indicated that the synthesized nanozyme had superior sensitivity (295 μA⸳mM-1⸳cm-2) and selectivity toward H2O2 with a detection limit of 0.21 μM. Further, the Pt-Cd bimetallic nanozyme displayed good electrochemical properties compared to platinum catalysts alone. The application was extended to determine the produced H2O2 from human hepatocellular carcinoma cells (HepG2) and normal hepatocyte (LO2) samples after ascorbic acid stimulation, thus enabling the early warning of cellular carcinogenesis.

SIGNIFICANCE

This strategy promises simple, rapid, inexpensive and effective electrochemical sensing and provides a new pathway for the synthesis of bimetallic nanozymes to construct an electrochemical sensor for the sensitive detection of H2O2.

Inhibition effect of p-d orbital hybridized PtSn nanozymes for colorimetric sensor array of antioxidants

Rational design of peroxidase (POD)-like nanozymes with high activity and specificity still faces a great challenge. Besides, the investigations of nanozymes inhibitors commonly focus on inhibition efficiency, the interaction between nanozymes-involved catalytic reactions and inhibitors is rarely reported. In this work, we design a p-block metal Sn-doped Pt (p-d/PtSn) nanozymes with the selective enhancement of POD-like activity. The p-d orbital hybridization interaction between Pt and Sn can effectively optimize the electronic structure of PtSn nanozymes and thus selectively enhance POD-like activity. In addition, the antioxidants as nanozymes inhibitors can effectively inhibit the POD-like activity of p-d/PtSn nanozymes, which results in the fact that antioxidants absorbed on the p-d/PtSn surface can hinder the adsorption of hydrogen peroxide. The inhibition type (glutathione as a model molecule) is reversible mixed-inhibition with inhibition constants (Ki' and Ki) of 0.21 mM and 0.03 mM. Finally, based on the varying inhibition levels of antioxidant molecules, a colorimetric sensor array is constructed to distinguish and simultaneously detect five antioxidants. This work is expected to design highly active and specific nanozymes through p-d orbital hybrid engineering, and also provides insights into the interaction between nanozymes and inhibitors.

Two swords combination: Smartphone-assisted ratiometric fluorescent and paper sensors for dual-mode detection of glyphosate in edible malt

The long-term and excessive use of glyphosate (GLY) in diverse matrices has caused serious hazard to the human and environment. However, the ultrasensitive detection of GLY still remains challenging. In this study, the smartphone-assisted dual-signal mode ratiometric fluorescent and paper sensors based on the red-emissive gold nanoclusters (R-AuNCs) and blue-emissive carbon dots (B-CDs) were ingeniously designed accurate and sensitive detection of GLY. Upon the presence of GLY, it would quench the fluorescence of B-CDs through dynamic quenching effect, and strengthen the fluorescence response of R-AuNCs due to aggregation-induced enhancement effect. Through calculating the GLY-induced fluorescence intensity ratio of B-CDs to R-AuNCs by using a fluorescence spectrophotometer, low to 0.218 μg/mL of GLY could be detected in lab in a wide concentration range of 0.3-12 μg/mL with high recovery of 94.7-103.1% in the spiked malt samples. The smartphone-assisted ratiometric fluorescent sensor achieved in the 96-well plate could monitor 0-11 μg/mL of GLY with satisfactory recovery of 94.1-107.0% in real edible malt matrices for high-throughput analysis. In addition, a portable smartphone-assisted ratiometric paper sensor established through directly depositing the combined B-CDs/R-AuNCs probes on the test strip could realize on-site measurement of 2-8 μg/mL of GLY with good linear relationship. This study provides new insights into developing the dual-signal ratiometric sensing platforms for the in-lab sensitive detection, high-throughput analysis, and on-site portable measurement of more trace contaminants in foods, clinical and environmental samples.

Cu-MOFs@AuPtNPs nanozyme-based immunosorbent assay for colorimetric detection of alpha-fetoprotein

Accurate detection of tumor biomarkers in blood is crucial for diagnosing and treating tumor disease. In this study, a metal enzyme-linked immunosorbent assay (MeLISA) was fabricated for the ultrasensitive and naked-eye detection of tumor biomarker alpha-fetoprotein (AFP) in clinical serum samples. Herein, novel copper metal-organic frameworks and gold platinum nanoparticle composites (Cu-MOFs@AuPtNPs) were synthesized for the first time by an in situ method, which showed an enormous specific surface area and excellent peroxidase (POx) mimicking properties. Cu-MOFs@AuPtNPs linked with antibodies targeting AFP served as a signal nanoprobe to amplify the detection signal. Additionally, the specificity of MeLISA was significantly enhanced through a conventional antigen-antibody reaction and efficient blocking of non-specific sites with BSA. Under optimal conditions, the sandwich-type MeLISA exhibited a wide range from 0.001 to 1000 ng mL-1 (R2 = 0.997) and a low detection limit of 0.86 pg mL-1 (S/N = 3) with acceptable stability, selectivity, and reproducibility. It is noteworthy that the suggested MeLISA performed exceptionally well in detecting clinical serum samples, which were visible to the naked eye and did not require complex platforms. To sum up, the innovative MeLISA based on Cu-MOFs@AuPtNPs provides an alternative method for early cancer diagnosis, particularly in economically backward areas where simple diagnostic apparatus is extremely desirable.

Quercetin-Derived Platinum Nanomaterials Influence Particle Stability, Catalytic, and Antimicrobial Performance

Quercetin possesses high biological properties but low bioavailability, poor solubility, and rapid body clearance. Its structural modification is imperative for enhanced applications. Herein, we demonstrate the catalytic and antimicrobial characteristics of shape-dependent (cuboidal and peanuts) platinum nanoparticles. Modified quercetin, 4'-QP, was employed as the reducing and stabilizing agent for the aqueous synthesis of PtNPs without extraneous reagents. Monodispersed platinum nanocubes (C-PtNPs) and nanopeanuts (P-PtNPs) were produced by reacting 4'-QP and Pt ions in the ratios of 3:1 and 1:1, respectively. TEM characterization confirmed the formation of Pt nanocubes and Pt nanopeanuts, with their corresponding sizes of 39.1 ± 0.20 and 45.1 ± 0.24 nm. The shape-dependency of PtNPs on the nosocomial-causing bacteria, Citrobacter freundii ATCC 8090 (C. freundii) was determined by the Agar well-diffusion assay. Under the same particle size and dose treatments, C-PtNPs and P-PtNPs exhibited 16.28 ± 0.10 and 4.50 ± 0.15 mm zones of inhibition with minimum inhibitory concentrations of 25 and 45 μg/mL, respectively. SEM analysis of C-PtNPs treated C. freundii showed a damaged cell membrane and confirmed contact-killing as the antibacterial mechanism. The catalytic conversion of 4-nitrophenol (4-NP) to 4-amino phenol (4-AP) was tested using a shape-dependent PtNPs catalyst in the presence of sodium borohydride. The conversion rates (k) of C-PtNPs and P-PtNPs in wastewater samples from New Jersey were 0.0108 and 0.00607 s-1, respectively.

A Bioinspired Single-Atom Fe Nanozyme with Excellent Laccase-Like Activity for Efficient Aflatoxin B1 Removal

The applications of natural laccases are greatly restricted because of their drawbacks like poor biostability, high costs, and low recovery efficiency. M/NC single atom nanozymes (M/NC SAzymes) are presenting as great substitutes due to their superior enzyme-like activity, excellent selectivity and high stability. In this work, inspired by the catalytic active center of natural enzyme, a biomimetic Fe/NC SAzyme (Fe-SAzyme) with O2-Fe-N4 coordination is successfully developed, exhibiting excellent laccase-like activity. Compared with their natural counterpart, Fe-SAzyme has shown superior catalytic efficiency and excellent stability under a wide range of pH (3.0-9.0), temperature (4-80 °C) and NaCl strength (0-300 mm). Interestingly, density functional theory (DFT) calculations reveal that the high catalytic performance is attributed to the activation of O2 by O2-Fe-N4 sites, which weakened the O─O bonds in the oxygen-to-water oxidation pathway. Furthermore, Fe-SAzyme is successfully applied for efficient aflatoxin B1 removal based on its robust laccase-like catalytic activity. This work provides a strategy for the rational design of laccase-like SAzymes, and the proposed catalytic mechanism will help to understand the coordination environment effect of SAzymes on laccase-like catalytic processes.

DNA/RNA-based electrochemical nanobiosensors for early detection of cancers

Nucleic acids, like DNA and RNA, serve as versatile recognition elements in electrochemical biosensors, demonstrating notable efficacy in detecting various cancer biomarkers with high sensitivity and selectivity. These biosensors offer advantages such as cost-effectiveness, rapid response, ease of operation, and minimal sample preparation. This review provides a comprehensive overview of recent developments in nucleic acid-based electrochemical biosensors for cancer diagnosis, comparing them with antibody-based counterparts. Specific examples targeting key cancer biomarkers, including prostate-specific antigen, microRNA-21, and carcinoembryonic antigen, are highlighted. The discussion delves into challenges and limitations, encompassing stability, reproducibility, interference, and standardization issues. The review suggests future research directions, exploring new nucleic acid recognition elements, innovative transducer materials and designs, novel signal amplification strategies, and integration with microfluidic devices or portable instruments. Evaluating these biosensors in clinical settings using actual samples from cancer patients or healthy donors is emphasized. These sensors are sensitive and specific at detecting non-communicable and communicable disease biomarkers. DNA and RNA's self-assembly, programmability, catalytic activity, and dynamic behavior enable adaptable sensing platforms. They can increase biosensor biocompatibility, stability, signal transduction, and amplification with nanomaterials. In conclusion, nucleic acids-based electrochemical biosensors hold significant potential to enhance cancer detection and treatment through early and accurate diagnosis.

Folic acid capping Bi3+-doped Ag quantum dots for enzyme-like dual-mode recognition of toxic S2- and visual sensing of NO2. Anal Chim Acta 2024;1319:342963. [PMID: 39122276 DOI: 10.1016/j.aca.2024.342963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

BACKGROUND

NO2- and S2- are two kinds of common toxic anions widely distributed in environmental water, soil and food products. Human beings have suffered a lot of diseases from intake of excessive NO2- or S2-, i.e., infantile methemoglobin, cancer and even to death. Although tremendous efforts have been afforded to monitor NO2- and S2-, most were high instrument-depended with complex processing procedures. To keep food safety and to protect human health, it will be a huge challenge to develop a convenient and efficient way to monitor S2- and NO2- in practice.

RESULTS

A kind of folic acid capping Bi3+-doped Ag quantum dots (FA@Bi3+-Ag QDs) was developed for the first time by one-pot homogeneous reduced self-assembly. Not only did FA@Bi3+-Ag QDs possess intrinsic fluorescent property, it expressed synergistic peroxidase-like activity to catalyze the redox of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 with Km/vmax of 0.087 mM/6.61 × 10-8 M s-1 and 6.42 mM/6.25 × 10-7 M s-1 respectively. Interestingly, trace S2- could exclusively alter its fluorescent property and peroxidase-like activity, exhibiting significant hypochromic and "turn-on" fluorescent effects. While trace NO2- could make FA@Bi3+-Ag QDs-TMB-H2O2 system hyperchromic. Under the optimized conditions, FA@Bi3+-Ag QDs were applied for dual-mode recognition of S2- and visual sensing of NO2- in real food samples with satisfactory recoveries, i.e., 100.7-107.9 %/95.8-104.7 % and 97.2-104.8 % respectively. The synergistic enzyme-mimic mechanism of FA@Bi3+-Ag QDs and its selective response mechanisms to S2- and NO2- were also proposed.

SIGNIFICANCE

This represents the first nanozyme-based FA@Bi3+-Ag QDs system for dual-mode recognition of S2- and visual sensing of NO2-, well meeting the basic requirement in drinking water set by WHO. It will offer a promising way for multi-mode monitoring of different pollution using the same nanozyme-based sensor.

Exploring Electrochemical Sensing for Fungicide Detection: Utilization of Newly Synthesized Oligomers

The determination of thiabendazole is crucial for ensuring food safety, environmental protection, and compliance with regulatory standards. Accurate detection helps prevent harmful exposure, ensuring the safety of agricultural products and safeguarding public health. Therefore, this study investigates the electrochemical sensing capabilities of newly synthesized oligo 3-amino-5-mercapto-1,2,4-triazole (oligo AMTa) using hydrogen tetrachloroaurate (III) (HAuCl4) as an oxidizing agent at room temperature for thiabendazole (TBZ) detection, employing a simple electrode fabrication process. The prepared oligo AMTa was thoroughly characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), Energy Dispersive X-ray Analysis (EDAX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution mass spectroscopy (HR-MS), and Fourier-transform infrared spectroscopy (FT-IR) to confirm its oligomerization structure and properties. The IR spectrum of oligo AMTa reveals a new peak at 1449 cm-1, indicating the conversion of -NH2 groups to -N=N- groups during oligomerization, unlike AMTa. Additionally, the disappearance of the -SH group peak at 2615 cm-1 in oligo AMTa suggests an S-S linkage involvement in the oligomerization process. In the oligo AMTa XPS spectrum, the presence of C=N is displayed by a small peak at 287.3 eV, and oligomerization via -NH and N=N is confirmed by the lack of a 284.0 eV peak for C-C or C=C. Gold nanoparticle formation is not demonstrated by the 84.8 eV peak, which implies that the gold atom is not in the Au0 state. The HR-MS spectrum of oligo AMTa shows a peak at m/z 564.08, indicating a chain of five monomers, and another peak at m/z 435.03, confirming the presence of a tetrameric form of AMTa. After that, the GC electrode was directly linked to the oligo AMTa by the potentiodynamic method. SEM, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were all employed to confirm the fabrication of oligo AMTa. The SEM image illustrates the formation of a particlelike structure with a uniform size of the oligomer after cycling in 0.1 M H2SO4. After electrocycling, the size of the oligomer was reduced from 2.6 μm to 30 nm. The oligo AMTa-modified electrode possesses the highest electroactive surface area and electrical conductivity due to several key factors. First, the presence of amino (-NH2) and thiol (-SH) functional groups in AMTa enhances the surface coverage and density of electroactive sites, increasing the electroactive surface area. Additionally, the conjugated structure of AMTa facilitates efficient electron transfer, resulting in enhanced electrical conductivity compared to unmodified electrodes. Eventually, the electrochemical oxidation of TBZ occurred using the fabricated electrodes. The GC/oligo AMTa electrode exhibited a four-fold increase in oxidation current for TBZ compared to unmodified GC electrodes. This enhancement is due to the improved surface properties from the oligo AMTa modification, which significantly boosts TBZ adsorption through strong interactions like hydrogen bonding and π-π stacking. These interactions, along with the increased surface area and catalytic properties, facilitate effective electron transfer, resulting in a higher oxidation current. As an outcome, the film was employed to determine the sensitivity level of TBZ, and a LOD of 1.8 × 10-11 M (S/N = 3) was found. The straightforward method's practical utility was proven by measuring TBZ in tap water, water spinach, and pear juice samples. The comprehensive characterization of oligo AMTa provided insights into its interaction mechanisms with thiabendazole, contributing to the development of a reliable, cost-effective, and efficient sensor.

Bimetallic Single-Atom Nanozyme-Based Electrochemical-Photothermal Dual-Function Portable Immunoassay with Smartphone Imaging

Rapid and accurate detection of human epidermal growth factor receptor 2 (HER2) is crucial for the early diagnosis and prognosis of breast cancer. In this study, we reported an iron-manganese ion N-doped carbon single-atom catalyst (FeMn-NCetch/SAC) bimetallic peroxidase mimetic enzyme with abundant active sites etched by H2O2 and further demonstrated unique advantages of single-atom bimetallic nanozymes in generating hydroxyl radicals by density functional theory (DFT) calculations. As a proof of concept, a portable device-dependent electrochemical-photothermal bifunctional immunoassay detection platform was designed to achieve reliable detection of HER2. In the enzyme-linked reaction, H2O2 was generated by substrate catalysis via secondary antibody-labeled glucose oxidase (GOx), while FeMn-NCetch/SAC nanozymes catalyzed the decomposition of H2O2 to form OH*, which catalyzed the conversion of 3,3',5,5'-tetramethylbenzidine (TMB) to ox-TMB. The ox-TMB generation was converted from the colorimetric signals to electrical and photothermal signals by applied potential and laser irradiation, which could be employed for the quantitative detection of HER2. With the help of this bifunctional detection technology, HER2 was accurately detected in two ways: photothermally, with a linear scope of 0.01 to 2.0 ng mL-1 and a limit of detection (LOD) of 7.5 pg mL-1, and electrochemically, with a linear scope of 0.01 to 10 ng mL-1 at an LOD of 3.9 pg mL-1. By successfully avoiding environmental impacts, the bifunctional-based immunosensing strategy offers strong support for accurate clinical detection.

A microfluidic chip platform based on Pt nanozyme and magnetized phage composite probes for dual-mode detecting and imaging pathogenic bacteria viability

The detection of pathogen viability is critically important to evaluate its infectivity. In the study, an integrated microfluidic chip based on dual-mode analytical strategy was developed to rapidly realize detection of bacteria activity (with Salmonella typhimurium, S.T, as a model analyte). Firstly, the composite probes, including deactivated phage modified magnetic beads and nano Pt-antimicrobial peptide (AMP) which can specifically recognize Gram-negative bacteria as nanozyme were prepared. When the composite probes are introduced into the chip together with target bacteria, after enrichment, oscillating and magnetic separation, they will conjugate with S.T and produce a magnetic sandwich complex. The complex can catalyze tetramethylbenzidine (TMB)-H2O2 to produce visible colorimetric signals which is correspondent to the total S.T content. Simultaneously, PtNPs in the complex can produce hydroxyl radical oxidation (∙OH) by decomposing H2O2. Under the synergistic action of ∙OH and AMP, the captured live S.T can be lysed to release ATP and emit bioluminescence signals which corresponds to the live S.T concentration. Therefore, the chip can simultaneously detect and image S.T at different viability in one test. The dual-mode assay demonstrated high sensitivity (≤33 CFU/mL), high specificity (identifying strain), signal amplification (5 folds) and short time (≤40min). The chip array can detect four samples in one test and exhibited advantages of high-integration, -sensitivity, -specificity and miniaturization, which are suitable to rapidly detect and image pathogen's viability in trace level. The replacement of phage probes can detect other bacteria. It has a wide prospect in pathogens screening.