One-pot synthesis of AuPt@FexOy nanoparticles with excellent peroxidase-like activity for development of ultrasensitive colorimetric lateral flow immunoassay of cardiac troponin I

Electrochemiluminescence lateral flow immunosensor using luminol-labeled silver nanoparticles for highly sensitive and quantitative detection of cardiac troponin I

Cardiac troponin I (cTnI) is a highly specific biomarker of cardiomyocyte injury, released during cell disintegration and necrosis, and is the gold standard for diagnosing acute myocardial infarction (AMI). At the onset of AMI, cTnI appears in very low concentrations (pg/mL level), necessitating the development of highly sensitive and rapid detection sensors. In this study, an electrochemiluminescence lateral flow immunosensor (ECL-LFI) was designed using luminol-labeled silver nanoparticles (luminol@AgNPs) for the sensitive and quantitative detection of cTnI. A screen-printed electrode (SPE) was integrated beneath the nitrocellulose (NC) membrane with plastic plates of the same thickness applied on both sides of the SPE to ensure a smooth flow surface. Upon addition of cTnI and the luminol-H2O2 system, sandwich immune complexes formed by antibody-functionalized luminol@AgNPs on the strips generated electrochemiluminescent (ECL) signals. The ECL-LFI exhibited a broad linear detection range from 5 pg/mL to 100 ng/mL, with a detection limit as low as 1.6 pg/mL. Additionally, the results show excellent correlation with clinical tests, demonstrating that the ECL-LFI provides a promising point-of-care tool for the early diagnosis of AMI and other diseases.

Troponin I biomarker sensing from clinical patient samples using molecularly imprinted polymer nanoparticles for advancing healthcare approaches in cardiovascular disease

Cardiac troponin I (cTnI) is a critical protein biomarker for heart attack diagnosis. This study presents a thorough analysis of a novel biosensing device utilizing molecularly imprinted polymer nanoparticles (nanoMIPs) for detecting cTnI in clinical patient serum samples post myocardial infarction. The methodology, based on the heat-transfer method approach, offers faster measurements times than the current gold standard and sample volumes equivalent to a single blood drop. Biomarker binding shows performance comparable to a high-sensitivity ELISA, accurately identifying patients with elevated cTnI levels (R2 = 0.893). The cTnI peak concentration time variations are attributed to heterogeneous serum complexes, with different troponin complex sizes potentially generating differing thermal insulation levels. Comparison with an established patient database demonstrates robust correlations between our cTnI concentrations and clinical parameters (R2 = 0.855). This underscores the potential of nanoMIP sensors for sensitive cTnI detection, providing insights into post-heart attack biomarker levels. Furthermore, our methodology presents the additional benefits of being low cost and portable enabling measurements at time and place of patients. Consequently, it holds the potential to become a vital part of the diagnostic pathway for heart attack treatment, ultimately reducing healthcare costs and improving patient outcomes.

A novel fluorometric and colorimetric dual-mode sensor for AMI early diagnosis based on an ultrathin Fe-MOF-74 nanosheet with peroxidase mimic activity and fluorescence properties

BACKGROUND

Cardiac troponin I (cTnI) is a crucial diagnosis biomarker for acute myocardial infarction (AMI). Early accurate determination of the concentration of cTnI significantly decreases the death rate of AMI. Compared with classic methods, dual-mode sensors for cTnI determination could help reduce the false positive rate.

RESULT

In this work, an ultrathin Fe-MOF-74 nanosheet with fluorescence properties and peroxidase mimic activity was synthesized for the first time. Applying this nanosheet, a novel dual-mode sensor was developed to quantify cTnI in human serum. The ultrathin Fe-MOF-74 nanosheets catalyze the decomposition of hydrogen peroxide produced by glucose oxidase (GOx)-triggered enzyme-linked immunosorbent assay (ELISA) applying cTnI as an antigen target, to generate reactive oxygen species (ROS). 3,3',5,5'-tetramethylbenzidine (TMB) can be oxidized by the generated free radicals, which simultaneously lead to the fluorescence quench of Fe-MOF-74 due to the inner filter effect (IFE). The correlation between the morphology of Fe-MOF-74 and its fluorescence intensity and peroxidase mimic activity was also investigated.

SIGNIFICANCE

The sensors exhibited linearity with the concentration of cTnI in 10-2000 pg mL-1 in both the fluorescence and visual mode with the detection limit of 6.4 pg mL-1 and 8.4 pg mL-1, respectively. It presenting good selectivity and anti-interference ability, can provide accurate and precise results in testing the concentration of cTnI in serum samples from patients in hospitals. It could be applied in the early diagnosis of AMI to reduce the incidence, disability, and mortality rates.

Poly(ionic liquid)-regulated green one-pot synthesis of Au@Pt porous nanospheres for the smart detection of acid phosphatase and organophosphorus inhibitor

Here, a green poly(ionic liquid)-regulated one-pot method is developed for the synthesis of Au@Pt core-shell nanospheres (PNSs) under mild reaction conditions in water. It is found that the poly(ionic liquid) poly[1-methyl-3-butyl (3-hydroxy) imidazole] chloride (PIL-Cl) is very vital to guide the construction of Au@Pt PNSs. The as-obtained Au@Pt-1 PNSs have perfect spherical outlines, porous core-shell structures and large specific surface area by which they exhibit excellent peroxidase-like activity in acidic media and can be used to develop a simple and reliable colorimetric sensing platform. It is shown that the colorimetric sensing platform constructed with Au@Pt-1 PNSs nanozyme can effectively evaluate ACP activity, achieving a wide linear detection range of 0.1-3.0 U/L and having a low limit of detection (LOD) of 0.047 U/L (S/N = 3). Based on the cascade reaction, the Au@Pt-1 PNSs nanozyme and ACP are integrated to develop a biosensor, which can detect organophosphate inhibitor of malathion with a wide linear detection range of 5-80 nM and low LOD of 1.96 nM (S/N = 3). More importantly, this detection method is also practically applied to detect both ACP activity in fetal bovine serum and malathion concentration in cucumber juice with satisfied results. This work presents a simple and green feature for the synthesis of nanozyme with high performance and establishes a biosensing platform based on Au@Pt-1 PNSs nanozyme to effectively monitor the ACP activity and the concentration of its organophosphate inhibitor malathion with high sensitivity, anti-interference capability and good recovery capability.

Nanozymes-Mediated Lateral Flow Assays for the Detection of Pathogenic Microorganisms and Toxins: A Review from Synthesis to Application

In today's context, there is an increasing awareness among individuals regarding the importance of healthy and safe food consumption. Consequently, there is a growing demand for food products that are safeguarded against the detrimental effects of pathogens and harmful microbial metabolites. Actually, these organisms and their associated toxins pose a significant risk to food safety and are recognized as a critical threat to human health because of their capacity to induce foodborne infections and intoxications. Consequently, in order to address such challenges, it is imperative to enhance recognizing systems comprising bio/nanosensors for detections, which are trustworthy, quick, beneficial and economical. The advent of digital color imaging technology has led to the gradual establishment of lateral flow assays (LFAs) as one of the most significant sensors for point-of-care applications. Unlike colloidal gold nanoparticles (AuNPs), nanozymes offer enhanced color intensity through target-induced precise enrichment of nanozymes at the test line. Additionally, they amplify the color signal by facilitating the catalytic oxidation of colorless substrates into colored products. This dual functionality presents significant potential for the development of well-organized LFAs. In light of this, significant attempts are dedicated to the development of nanozyme-based LFAs. This review aims to outline recent advancements in the synthesis and design of nanozymes with varying compositions that exhibit distinct activities, as well as the structure and employment of nanozyme-based LFAs for the detection of pathogenic microorganisms and their associated toxins. Furthermore, the existing challenges and prospective development directions are outlined to assist readers in advancing the nanozyme-based LFAs performance.

Nanozyme-based visual diagnosis and therapeutics for myocardial infarction: The application and strategy

BACKGROUND

Myocardial infarction (MI) is a heart injury caused by ischemia and low oxygen conditions. The occurrence of MI lead to the activation of a large number of neutrophils and macrophages, inducing severe inflammatory injury. Meanwhile, the inflammatory response produces much more free radicals, further exacerbating the inflammatory response and tissue damage. Efforts are being dedicated to developing antioxidants and enzymes, as well as small molecule drugs, for treating myocardial ischemia. However, poor pharmacokinetics and potential side effects limit the clinical application of these drugs. Recent advances in nanotechnology have paved new pathways in biomedical and healthcare environments. Nanozymes exhibit the advantages of biological enzymes and nanomaterials, including with higher catalytic activity and stability than natural enzymes. Thus, nanozymes provide new possibilities for the diagnosis and treatment of oxidative stress and inflammation-related diseases.

AIM OF REVIEW

We describe the application of nanozymes in the diagnosis and therapy of MI, aiming to bridge the gap between the diagnostic and therapeutic needs of MI.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We describe the application of nanozymes in the diagnosis and therapy of MI, and discuss the new strategies for improving the diagnosis and treatment of MI. We review in detail the applications of nanozymes to achieve highly sensitive detection of biomarkers of MI. Due to their unique enzyme catalytic capabilities, nanozymes have the ability to sensitively detect biomolecules through colorimetric, fluorescent, and electrochemical assays. In addition, nanozymes exhibit excellent antioxidase-mimicking activity to treat MI by modulating reduction/oxidation (REDOX) homeostasis. Nanozymes can also passively or actively target MI tissue sites, thereby protecting ischemic myocardial tissue and reducing the infarct area. These innovative applications of nanozymes in the field of biomedicine have shown promising results in the diagnosis and treatment of MI, offering a novel therapeutic strategy.

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.

Smartphone-assisted colorimetric sensor arrays based on nanozymes for high throughput identification of heavy metal ions in salmon

The rapid, precise, and high-throughput identification of multiple heavy metals ions holds immense importance in ensuring food safety and promoting public health. This study presents a novel smartphone-assisted colorimetric sensor array for the rapid and precise detection of multiple heavy metals ions. The sensor array is based on three signal recognition elements (AuPt@Fe-N-C, AuPt@N-C, and Fe-N-C) and the presence of different heavy metal ions affects the nanozymes-chromogenic substrate (TMB) catalytic color production, enabling the differentiation and quantification of various heavy metal ions. Combined with a smartphone-based RGB mode, the colorimetric sensor array can successfully identify five different heavy metal ions (Hg2+, Pb2+, Co2+, Cr6+, and Fe3+) as low as 0.5 μM and different ratios of binary and ternary mixed heavy metal ions in just 5 min. The sensor array successfully tested seawater and salmon samples with a total heavy metal content of 10 μM in the South China Sea (Haikou and Wenchang). Overall, this study highlights the potential of smartphone-assisted colorimetric sensor arrays for the rapid and precise detection of multiple heavy metal ions, which could significantly contribute to food safety and public health monitoring.

Research progress on detection of foodborne pathogens: The more rapid and accurate answer to food safety

In recent years, foodborne diseases have posed a serious threat to human health, and rapid detection of foodborne pathogens is particularly crucial for the prevention and control of such diseases. This article offers a detailed overview of the development of detection techniques for foodborne pathogens, transitioning from traditional microbiological culture methods to the current array of techniques, including immunological, molecular biological, and biosensor-based methods. It summarizes the technical principles, advantages, disadvantages, and research progress of these diverse methods. Furthermore, the article demonstrates that the combination of different methods enhances the efficiency and accuracy of pathogens detection. Specifically, the article focuses on the application and advantages of combining CRISPR/Cas systems with other detection methods in the detection of foodborne pathogens. CRISPR/Cas systems, with their high specificity, sensitivity, and ease of operation, show great potential in the field of foodborne pathogens detection. When integrated with other detection techniques such as immunological detection techniques, molecular biology detection techniques, and biosensors, the accuracy and efficiency of detection can be further improved. By fully utilizing these tools, early detection and control of foodborne diseases can be achieved, enhancing public health and preventing disease outbreaks. This article serves as a valuable reference for exploring more convenient, accurate, and sensitive field detection methods for foodborne pathogens, promoting the application of rapid detection techniques, and ensuring food safety and human health.

Kiwi-Inspired Rational Nanoarchitecture with Intensified and Discrete Magneto-Fluorescent Functionalities for Ultrasensitive Point-of-Care Immunoassay

Fluorescent lateral flow immunoassays (FLFIA) is a well-established rapid detection technique for quantitative analysis. However, achieving accurate analysis of biomarkers at the pg mL-1 level using FLFIA still poses challenges. Herein, an ultrasensitive FLFIA platform is reported utilizing a kiwi-type magneto-fluorescent silica nanohybrid (designated as MFS) that serves as both a target-enrichment substrate and an optical signal enhancement label. The spatially-layered architecture comprises a Fe3O4 core, an endocarp-fibers like dendritic mesoporous silica, seed-like quantum dots, and a kiwi-flesh like silica matrix. The MFS demonstrates heightened fluorescence brightness, swift magnetic response, excellent size uniformity, and dispersibility in water. Through liquid-phase capturing and fluorescence-enhanced signal amplification, as well as magnetic-enrichment sample amplification and magnetic-separation noise reduction, the MFS-based FLFIA is successfully applied to the detection of cardiac troponin I that achieved a limit of detection at 8.4 pg mL-1, tens of times lower than those of previously published fluorescent and colorimetric lateral flow immunoassays. This work offers insights into the strategic design of magneto-fluorescent synergetic signal amplification on LFIA platform and underscores their prospects in high-sensitive rapid and on-site diagnosis of biomarkers.

Near-infrared light-enhanced colorimetric signal amplification strategy for tumor marker detection based on MoS2/CuO/Au nanocomposite

A novel signal amplification strategy was developed by combining near-infrared light with MoS2/CuO/Au nanocomposite for building a colorimetric immunoassay. First, MoS2/CuO/Au nanocomposite was synthesized by precipitation and photoreduction methods and characterized by scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). MoS2/CuO/Au nanocomposite has oxidase-like activity and can oxidize TMB to form a blue product (TMBox). Further, the catalytic oxidation of TMB was accelerated under near-infrared (NIR) laser radiation. The sandwich-type colorimetric immunoassay was constructed using MoS2/CuO/Au nanocomposite. Under the enhancement of near-infrared light, carcinoembryonic antigen (CEA) was sensitively detected in the range 0.1 to 40 ng/mL with the limit of detection of 0.03 ng/mL. Moreover, the immunosensor has excellent selectivity and anti-interference, good repeatability, and stability.

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

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

"Cave Effect" Induces Self-Assembled Bimetallic Hollow Structure for Three-in-One Lateral Flow Immunoassay

Bimetallic hollow structures have attracted much attention due to their unique properties, but they still face the problems of nonuniform alloys and excessive etching leading to structural collapse. Here, uniform bimetallic hollow nanospheres are constructed by pore engineering and then highly loaded with hemin (Hemin@MOF). Interestingly, in the presence of polydopamine (PDA), the competitive coordination between anionic polymer (γ-PGA) and dimethylimidazole does not lead to the collapse of the external framework but self-assembly into a hollow structure. By constructing the Hemin@MOF immune platform and using E. coli O157:H7 as the detection object, we find that the visual detection limits can reach 10, 3, and 3 CFU/mL in colorimetric, photothermal, and catalytic modes, which is 4 orders of magnitude lower than the traditional gold standard. This study provides a new idea for the morphological modification of the metal-organic skeleton and multifunctional immunochromatography detection.

Quantitative Detection of Multiple Cardiovascular Biomarkers by an Antibody Microarray-Based Metal-Enhanced Fluorescence Assay

Accurate detection of multiple cardiovascular biomarkers is crucial for the timely screening of acute coronary syndrome (ACS) and differential diagnosis from acute aortic syndrome (AAS). Herein, an antibody microarray-based metal-enhanced fluorescence assay (AMMEFA) has been developed to quantitatively detect 7 cardiovascular biomarkers through the formation of a sandwich immunoassay on the poly(glycidyl methacrylate-co-2-hydroxyethyl methacrylate)-decorated GNR-modified slide (GNR@P(GMA-HEMA) slide). The AMMEFA exhibits high specificity and sensitivity, the linear ranges span 5 orders of magnitude, and the limits of detection (LODs) of cardiac troponin I (cTnI), heart-type fatty acid binding protein (H-FABP), C-reactive protein (CRP), copeptin, myoglobin, D-Dimer, and N-terminal pro-brain natriuretic peptide (NT-proBNP) reach 0.07, 0.2, 65.7, 0.6, 0.2, 8.3, and 0.3 pg mL-1, respectively. To demonstrate its practicability, the AMMEFA has been applied to quantitatively analyze 7 cardiovascular biomarkers in 140 clinical plasma samples. In addition, the expression levels of cardiovascular biomarkers were analyzed by the least absolute shrinkage and selector operator (LASSO) regression, and the area under receiver operator characteristic curves (AUCs) of healthy donors (HDs), ACS patients, and AAS patients are 0.99, 0.98, and 0.97, respectively.

Magnetic photoelectrochemical sensor array utilizing addressing sensing strategy for simultaneous detection of amyloid-β 42 and microtubule-associated protein tau

The accurate diagnosis of diseases can be improved by detecting multiple biomarkers simultaneously. This study presents the development of a magnetic photoelectrochemical (PEC) immunosensor array for the simultaneous detection of amyloid-β 42 (Aβ) and microtubule-associated protein (Tau), which are markers for neurodegenerative disorders. A metal-organic framework (MOF) derivative, Fe2O3@FeS2 magnetic composites with exceptional photoelectric and ferromagnetic properties was synthesized while preserving the original structure and advantages. Thus, the immunoassembly process of the sensor can be carried out in homogeneous solution and recovered by magnetic separation. For simultaneous detection, a chip is divided into multiple independent sensing sites, which have the same preparation and detection environment, allowing for the implementation of a self-calibration method. The sensor array demonstrates considerable detection ranges of 0.01-100 ng mL-1 for Aβ and 0.05-100 ng mL-1 for Tau, with low detection limits of 2.1 pg mL-1 for Aβ and 7.9 pg mL-1 for Tau. The PEC sensor array proposed in this study exhibits exceptional stability, selectivity, and reproducibility, providing a new method for detecting multiple markers.

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).

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

Noble-metal nanozymes have demonstrated great potential in various fields. However, aggregation of single-particle nanoparticles severely affects their exposed catalytically active sites to the extent of exhibiting weak enzyme-like activity. Here, we present an organic block surfactant (polyvinylpyrrolidone, PVP) to construct monodisperse water-stable Pt nanoclusters (Pt NCs) for an enhanced immunoassay of cardiac troponin I (cTnI). The PVP-modified Pt NC nanozyme exhibited up to 16.3 U mg-1 peroxidase-mimicking activity, which was mainly attributed to the ligand modification on the surface and the electron-absorbing effect of the ligand on the Pt NCs. The PVP-modified Pt NCs have a lower OH-transition potential, as determined by density functional theory. Under optimized experimental conditions, the enhanced nanozyme immunoassay strategy exhibited an ultrawide dynamic response range of 0.005-50 ng mL-1 for cTnI targets with a detection limit of 1.3 pg mL-1, far superior to some reported test protocols. This work provides a designable pathway for the design of artificial enzymes with high enzyme-like activity to further expand the practical range of enzyme alternatives.