Fe-N-C single-atom nanozymes based sensor array for dual signal selective determination of antioxidants

Manganese-doped carbon nanospheres with robust peroxidase-like activity for the colorimetric detection of total antioxidant capacity

Total antioxidant capacity (TAC) assessment is vital for evaluating food nutritional quality, yet conventional methods face limitations in complex matrices, efficiency, and environmental robustness. To address this, we synthesized manganese-doped porous carbon nanospheres (Mn@CNS), which feature a high density of uniformly distributed diverse catalytic sites, creating an efficient peroxidase-like nanozyme for sensitive colorimetric detection of TAC. Kinetic analysis revealed that Mn@CNS had strong affinities for both 3,3',5,5'-tetramethylbenzidine and H2O2 substrates, with Km values of 0.15 mM and 14.63 mM, respectively. This allowed us to establish an effective colorimetric detection platform for the rapid and sensitive identification of ascorbic acid with a low detection limit of 0.17 μM. Furthermore, we used cysteine, glutathione, ferulic acid, caffeic acid, quercetin and (+)-α-tocopherol to validate the efficacy of Mn@CNS in antioxidant assessment. This assay has successfully evaluated TAC in real samples, highlighting its potential for the rapid, cost-effective, on-site detection of TAC.

Rapid identification of multiplexed pathogens via a two-step dual-channel fluorescence turn-on array

Bacterial infections have been an increasingly serious threat to human health. However, the rapid identification of multiplexed bacteria remains challenging due to their intricate composition. Herein, we developed a two-step, dual-channel fluorescence "turn-on" sensor array that sequentially amplifies signals via Indicator Displacement Analysis (IDA) and Aggregation-Induced Emission (AIE). Three weakly fluorescent, positively charged conjugated fluorophores (A1-A3) with AIE properties were designed to form electrostatic complexes (C1-C3) with negatively charged graphene oxide (GO). Upon addition of bacteria, fluorophores were released from the electrostatic complexes via IDA, resulting in fluorescence turn-on. These fluorophores then aggregated on the bacterial surface, further enhancing fluorescence. This array accurately differentiated among 10 distinct bacterial strains, achieving 98.3 % classification accuracy within 30 s. Finally, the approach facilitated semi-quantitative bacterial analysis, multiplex identification, and robust differentiation in artificial urine samples, presenting a promising method for early infectious disease diagnosis.

Colorimetric - Fluorescence - Photothermal tri-mode sensor array combining the machine learning method for the selective identification of sulfonylurea pesticides

Though cholinesterase-based method could detect two types of pesticides (organophosphorus and carbamate), they had weak sensing on sulfonylurea pesticides. In our previous work, the peroxidase-like reaction system of nanozyme - H2O2 - TMB showed selective detection of sulfonylurea pesticides, but the single-signal output sensing platform was easily affected by complex matrix background, cross-contamination and human error. Therefore, this work used colorimetric, photothermal, and fluorescent signals of the nanozyme reaction as sensing units for the detection of pesticides. This is the first time that photothermal signals have been used to construct a sensor array. When the concentration of interfering substances was 25 times that of pesticides, the method was still unaffected and had excellent selectivity and anti-interference performance. Meanwhile, a concentration-independent differentiation mode was established based on the K-nearest neighbor (KNN) algorithm. The pesticides were detected and distinguished with 100% accuracy. This work contributed to the detection of sulfonylurea pesticides in complex environmental/food matrices, bridging the gap of existing pesticide detection methods and providing an effective method for food safety detection.

Site-Defined High-Loading Tellurium Single-Atom Nanozymes Anchored on Checkerboard-Patterned Graphyne for Sensor Array Construction

Single-atom nanozymes exhibit unique enzymatic activity due to their active centers, which resemble those of natural metalloenzymes. The design of the anchoring sites of single-atom active centers is an important factor that affects the loading capacity and catalytic activity. Herein, para-nitrogen-doped graphyne with diamond cavity is used as support, and single-atom tellurium atoms are then anchored in the nitrogen-containing graphyne cavities, akin to chess pieces placed on a chessboard grid. Due to the pre-designed regular anchoring sites, the site-defined tellurium single-atom nanozyme (Te SAN) achieves a high Te loading of 19.21 wt.%. Therefore, Te SAN shows good peroxidase-like activity. To explain the enhanced peroxidase-like activity, density functional theory calculations are performed and the results demonstrate that Te doping enhances catalytic activity by lower Gibbs free energy barrier for formation of •OH, a key intermediate in peroxidase-like activity. Finally, based on the inhibitory effect of bisphenols on nanozyme activity, the Te SAN-based sensor array successfully identifies five bisphenols, holding potential for on-site food safety monitoring. The design of the anchoring sites of single atoms in this work provides new ideas for precisely controlling the synthesis of nanozymes, exploring their action mechanisms, and enhancing their activities.

Graphyne-supported manganese single-atom nanozyme sensor array for bisphenol identification

Bisphenols, as common industrial raw materials, are widely used in food packaging such as plastics. However, their migration and residue may affect the hormone secretion of the human body and then lead to health problems. Therefore, a low-cost, rapid and simple detection method that can simultaneously detect multiple bisphenols is very necessary. In this work, two types of manganese single-atom nanozymes with excellent peroxidase-like activity were synthesized with graphyne as a support. A high-throughput colorimetric sensor array was constructed using three types of nanozymes (Mn-GY, Mn-GY-2N, GY-2N) to distinguish various bisphenols. Due to the absorption of bisphenol molecules on the surface of nanozymes, the activity of nanozymes decreases differently, when different bisphenols are added to the catalytic system. The results proved that the prepared sensor had good linear relationships at both low and high concentrations for determination of five bisphenols. The LODs of BPA, BPS, BPF, BPAF, and Diphenolic Acid were 0.443, 0.280, 0.277, 0.424, and 0.326 μM respectively. Compared with traditional sensors, the sensor array can simultaneously detect multiple analytes with high throughput, showing great advantage in dealing with complex samples. Combined with machine learning algorithms, five bisphenols can be successfully identified by the obtained array data. The sensor array also demonstrated excellent performance in the detection of both mixed samples and real samples. This high-throughput colorimetric sensor array achieves accurate and sensitive detection of bisphenol substances, providing new means and ideas for enhancing food safety. At the same time, the simple and rapid identification of structurally similar compounds demonstrates its potential for more precise analysis, providing possibilities for future development.

Research progress and applications of iron-based nanozymes in colorimetric sensing of agricultural pollutants

Natural enzymes are highly valued for their efficient specificity and catalytic activity. However, their poor stability, environmental sensitivity, and costly preparation restrict their practical applications. Nanozymes are nanomaterials with superior catalytic properties that compensate for natural enzyme deficiencies. As one of the earliest developed nanozymes, iron-based nanozymes have diverse morphological structures and different simulated catalytic properties, showing promising potential for agricultural pollutant sensing. Compared with traditional detection methods, the colorimetric method based on nanozymes has the characteristics of simplicity, rapidity, and visualization, which can be used for immediate and rapid on-site detection. In this review, the catalytic types of iron-based nanozymes, such as peroxidase-like, oxidase-like, catalase-like, and superoxide dismutase-like activities, and the corresponding catalytic mechanisms are presented. The classification of iron-based nanozymes based on various structures is then discussed. Furthermore, this review focuses on the current status of iron-based nanozymes for the colorimetric detection of common agricultural pollutants, including heavy metal ions, nonmetal ions, pesticides, and pharmaceutical and personal care products. Finally, the current research status and development direction of iron-based nanozymes in sensing applications are summarized and prospected.

Single-Probe Sensing Array Based on Au Nanozyme for Simple, Rapid, and Low-Cost Colorimetric Identification of Antioxidants

Identification of biological antioxidants is of vital importance because of the essential role of antioxidants in keeping the balance of various diseases. Here, we designed a simple, rapid, and low-cost nanozyme sensing array for colorimetric identification of multiple antioxidants based on Au nanoparticles (Au NPs) synthesized via a facile and green aqueous phase method. In the presence of H2O2, Au NPs possessed peroxidase-like catalytic activity and could effectively catalyze the color-less 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxidized product with comparable enzyme kinetics parameters. The function of the colorimetric sensing array was based on the inhibitory effect of diverse antioxidants on the chromogenic system to varying degrees under different pH conditions, resulting in various "turn-off" colorimetric signal responses. Based on the developed sensing array, four kinds of antioxidants with various concentrations and different proportions of the mixtures were successfully discriminated from each other with the aid of principal component analysis. Moreover, the sensing array showed good performance in differentiating antioxidants in human serum samples, which broaden the analytical application of Au NPs. Compared with the existing sensing array, the single Au NP-based sensing array significantly simplified the sensing element and detection process, opening a new avenue for biological molecule identification in real complex samples.

Sensing array based on imidazole-regulated Cu@MOFs nanozymes with enhanced laccase-like activity for the discrimination of phenolic pollutants

BACKGROUND

Phenolic pollutants with high toxicity and low biodegradability can disrupt environmental balance and severely affect human health, whereas existing methods are difficult to implement the rapid and high-throughput detection of multiple phenolic pollutants.

RESULTS

Herein, we developed a four-dimensional colorimetric sensor array based on imidazole-modulated Cu@MOFs for distinguishing and determining phenolic pollutants. Wherein, four Cu@MOFs (ATP@Cu, ADP@Cu, AMP@Cu, and GMP@Cu) nanozyme with laccase-like activity were firstly prepared, and a novel strategy of imidazole-containing molecules-regulated was proposed to improve the laccase-like activity of Cu@MOFs nanozymes. Interestingly, imidazole (IM) exhibited the strongest enhancing effects on the laccase-like activity of the four Cu@MOFs by accelerating electron transfer on the surface of laccase nanozymes and producing more reactive oxygen species. Subsequently, by using Cu@MOFs@IM as the recognition elements of the sensor array, a colorimetric sensor array based on imidazole-modulated Cu@MOFs was developed, and differentiation and classification of phenolic pollutants were carried out using LDA and HCA methods. More importantly, the proposed sensor array could accomplish the identification of 6 phenolic pollutants and their mixtures.

SIGNIFICANCE

Additionally, the designed sensor array was applied to identify these phenolic pollutants in real water samples, further highlighting the potentials for assessing water pollution.

Regulation of the coordination number of Zn single atoms to boost electrochemical sensing of H2O2

Compared with transition metals with partially occupied 3d orbitals, Zn has a filled 3d10 configuration, which severely restricts electron mobility and hence usually renders Zn2+ intrinsically inactive for electrochemical sensing. Metal single-atom catalysts are a new kind of sensing material. Owing to their unique coordination structure and high atomic utilization rate, metal single-atom catalysts show unique properties, which makes them promising for use in the field of electrochemical sensing. However, whether Zn single atoms are active sites remains to be elucidated. In this study, we prepared nitrogen-doped carbon (NC) materials by pyrolyzing ZIF-8 at high temperatures and reported that when the pyrolysis temperature was 800 °C, many Zn single atoms with Zn-N4 coordination structures remained in the NC material. Even when the pyrolysis temperature is increased to 1000 °C, a small number of Zn single atoms remain, and the coordination structure changes from Zn-N4 to Zn-N3. Furthermore, unexpectedly, both residual Zn single atoms showed electrocatalytic activity for H2O2 reduction. In particular, the electrocatalytic activity was significantly enhanced after the coordination structure was changed from Zn-N4 to Zn-N3. Density functional theory (DFT) calculations indicate that the coordination structure of Zn-N3 optimizes the adsorption and desorption strength of oxygen-containing species in the electrocatalytic reaction process, which lowers the energy barrier of the rate-determining step and increases the detection sensitivity of H2O2 nearly 4.1 times. This study revealed new properties of Zn single atoms for the electrocatalytic reduction of H2O2 and developed a strategy to increase the electrocatalytic activity of metal single-atom catalysts through coordination number regulation, which lays the foundation for the use of Zn single atoms in the field of electrochemical sensing and provides ideas for the design of new highly active sensing materials.

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.

The Identification of Oral Cariogenic Bacteria through Colorimetric Sensor Array Based on Single-Atom Nanozymes

Effective identification of multiple cariogenic bacteria in saliva samples is important for oral disease prevention and treatment. Here, a simple colorimetric sensor array is developed for the identification of cariogenic bacteria using single-atom nanozymes (SANs) assisted by machine learning. Interestingly, cariogenic bacteria can increase oxidase-like activity of iron (Fe)─nitrogen (N)─carbon (C) SANs by accelerating electron transfer, and inversely reduce the activity of Fe─N─C further reconstruction with urea. Through machine-learning-assisted sensor array, colorimetric responses are developed as "fingerprints" of cariogenic bacteria. Multiple cariogenic bacteria can be well distinguished by linear discriminant analysis and bacteria at different genera can also be distinguished by hierarchical cluster analysis. Furthermore, colorimetric sensor array has demonstrated excellent performance for the identification of mixed cariogenic bacteria in artificial saliva samples. In view of convenience, precise, and high-throughput discrimination, the developed colorimetric sensor array based on SANs assisted by machine learning, has great potential for the identification of oral cariogenic bacteria so as to serve for oral disease prevention and treatment.

Colorimetric sensor array for identifying antioxidants based on pyrolysis-free synthesis of Fe-N/C single-atom nanozymes

Iron-anchored nitrogen/doped carbon single-atom nanozymes (Fe-N/C), which possess homogeneous active sites and adjustable catalytic environment, represent an exemplary model for investigating the structure-function relationship and catalytic activity. However, the development of pyrolysis-free synthesis technique for Fe-N/C with adjustable enzyme-mimicking activity still presents a significant challenge. Herein, Fe-N/C anchored three carrier morphologies were created via a pyrolysis-free approach by covalent organic polymers. The peroxidase-like activity of these Fe-N/C nanozymes was regulated via the pores of the anchored carrier, resulting in varying electron transfer efficiency due to disparities in contact efficacy between substrates and catalytic sites within diverse microenvironments. Additionally, a colorimetric sensor array for identifying antioxidants was developed: (1) the Fe-N/C catalytically oxidized two substrates TMB and ABTS, respectively; (2) the development of a colorimetric sensor array utilizing oxTMB and oxABTS as sensing channels enabled accurate discrimination of antioxidants such as ascorbic acid (AsA), glutathione (GSH), cysteine (Cys), gallic acid (GA), and caffeic acid (CA). Subsequently, the sensor array underwent rigorous testing to validate its performance, including assessment of antioxidant mixtures and individual antioxidants at varying concentrations, as well as target antioxidants and interfering substances. In general, the present study offered valuable insights into the active origin and rational design of nanozyme materials, and highlighting their potential applications in food analysis.

Advances in machine learning-enhanced nanozymes

Nanozymes, synthetic nanomaterials that mimic the catalytic functions of natural enzymes, have emerged as transformative technologies for biosensing, diagnostics, and environmental monitoring. Since their introduction, nanozymes have rapidly evolved with significant advancements in their design and applications, particularly through the integration of machine learning (ML). Machine learning (ML) has optimized nanozyme efficiency by predicting ideal size, shape, and surface chemistry, reducing experimental time and resources. This review explores the rapid advancements in nanozyme technology, highlighting the role of ML in improving performance across various bioapplications, including real-time monitoring and the development of chemiluminescent, electrochemical and colorimetric sensors. We discuss the evolution of different types of nanozymes, their catalytic mechanisms, and the impact of ML on their property optimization. Furthermore, this review addresses challenges related to data quality, scalability, and standardization, while highlighting future directions for ML-driven nanozyme development. By examining recent innovations, this review highlights the potential of combining nanozymes with ML to drive the development of next-generation diagnostic and detection technologies.

Non-pyrolytic synthesis of laccase-like iron based single-atom nanozymes for highly efficient dual-mode colorimetric and fluorescence detection of epinephrine

Single-atom nanozymes have garnered significant attention due to their exceptional atom utilization and ability to establish well-defined structure-activity relationships. However, conventional pyrolytic synthesis methods pose challenges such as high energy consumption and random local environments at the active sites, while achieving non-pyrolytic synthesis of single-atom nanozymes remains a formidable technical hurdle. The present study focuses on the synthesis of laccase-like iron-based single-atom nanozymes (Fe-SAzymes) using a non-pyrolysis method facilitated by microwave irradiation. Under low iron loading conditions, Fe-SAzymes exhibited significantly enhanced laccase activity (12.1 U/mg), surpassing that of laccase by 24-fold. Moreover, Fe-SAzymes demonstrated efficient catalytic oxidation of epinephrine (EP), enabling its colorimetric detection. Owing to the remarkable laccase activity of Fe-SAzymes, the conventional nanozymes EP detection time was reduced from 60 min to 20 min, with an impressive low detection limit as low as 2.95 μM. In addition, an ultra-sensitive fluorescence method for EP detection was developed using the internal filter effect of EP oxidation products and CDs combined with carbon dots probe. The detection limit of fluorescence method was only 0.39 μM. Therefore, an visual, fast, and highly sensitive dual-mode EP detection strategy has great potential in the clinical diagnostic industry.

Accelerated and precise identification of antioxidants and pesticides using a smartphone-based colorimetric sensor array

The integration of smartphones with conventional analytical approaches plays a crucial role in enhancing on-site detection platforms for point-of-care testing. Here, we developed a simple, rapid, and efficient three-channel colorimetric sensor array, leveraging the peroxidase (POD)-like activity of polydopamine-decorated FeNi foam (PDFeNi foam), to identify antioxidants using both microplate readers and smartphones for signal readouts. The exceptional catalytic capacity of PDFeNi foam enabled the quick catalytic oxidation of three typical peroxidase substrates (TMB, OPD and 4-AT) within 3 min. Consequently, we constructed a colorimetric sensor array with cross-reactive responses, which was successfully applied to differentiate five antioxidants (i.e., glycine (GLY), glutathione (GSH), citric acid (CA), ascorbic acid (AA), and tannic acid (TAN)) within the concentration range of 0.1-10 μM, quantitatively analyze individual antioxidants (with AA and CA as model analytes), and assess binary mixtures of AA and GSH. The practical application was further validated by discriminating antioxidants in serum samples with a smartphone for signal readout. In addition, since pesticides could be absorbed on the surface of PDFeNi foam through π-π stacking and hydrogen bonding, the active sites were differentially masked, leading to featured modulation on POD-like activity of PDFeNi foam, thereby forming the basis for pesticides discrimination on the sensor array. The nanozyme-based sensor array provides a simple, rapid, visual and high-throughput strategy for precise identification of various analytes with a versatile platform, highlighting its potential application in point-care-of diagnostic, food safety and environmental surveillance.

Elevating nanomaterial optical sensor arrays through the integration of advanced machine learning techniques for enhancing visual inspection of food quality and safety

Food quality and safety problems caused by inefficient control in the food chain have significant implications for human health, social stability, and economic progress and optical sensor arrays (OSAs) can effectively address these challenges. This review aims to summarize the recent applications of nanomaterials-based OSA for food quality and safety visual monitoring, including colourimetric sensor array (CSA) and fluorescent sensor array (FSA). First, the fundamental properties of various advanced nanomaterials, mainly including metal nanoparticles (MNPs) and nanoclusters (MNCs), quantum dots (QDs), upconversion nanoparticles (UCNPs), and others, were described. Besides, the diverse machine learning (ML) and deep learning (DL) methods of high-dimensional data obtained from the responses between different sensing elements and analytes were presented. Moreover, the recent and representative applications in pesticide residues, heavy metal ions, bacterial contamination, antioxidants, flavor matters, and food freshness detection were comprehensively summarized. Finally, the challenges and future perspectives for nanomaterials-based OSAs are discussed. It is believed that with the advancements in artificial intelligence (AI) techniques and integrated technology, nanomaterials-based OSAs are expected to be an intelligent, effective, and rapid tool for food quality assessment and safety control.

Green synthesis of iron-doped graphene quantum dots: an efficient nanozyme for glucose sensing

Single-atom nanozymes with well-defined atomic structures and electronic coordination environments can effectively mimic the functions of natural enzymes. However, the costly and intricate preparation processes have hindered further exploration and application of these single-atom nanozymes. In this study, we presented a synthesis technique for creating Fe-N central single-atom doped graphene quantum dot (FeN/GQDs) nanozymes using a one-step solvothermal process, where individual iron atoms form strong bonds with graphene quantum dots through nitrogen coordination. Unlike previous studies, this method significantly simplifies the synthesis conditions for single-atom nanozymes, eliminating the need for high temperatures and employing environmentally friendly precursors derived from pineapple (ananas comosus) leaves. The resulting FeN/GQDs exhibited peroxidase-like catalytic activity and kinetics comparable to that of natural enzymes, efficiently converting H2O2 into hydroxyl radical species. Leveraging their excellent peroxide-like activity, FeN/GQDs nanozymes have been successfully applied to construct a colorimetric biosensor system characterized by remarkably high sensitivity for glucose detection. This achievement demonstrated a promising approach to designing single-atom nanozymes with both facile synthesis procedures and high catalytic activity, offering potential applications in wearable sensors and personalized health monitoring.

Construction and Application of Nanozyme Sensor Arrays

Compared with traditional "lock-key mode" biosensors, a sensor array consists of a series of sensing elements based on intermolecular interactions (typically hydrogen bonds, van der Waals forces, and electrostatic interactions). At the same time, sensor arrays also have the advantages of fast response, high sensitivity, low energy consumption, low cost, rich output signals, and imageability, which have attracted widespread attention from researchers. Nanozymes are nanomaterials which own enzyme-like properties. Because of the adjustable activity, high stability, and cost effectiveness of nanozymes, they are potential candidates for construction of sensor arrays to output different signals from analytes through the chemoresponse of colorants, which solves the shortcomings of traditional sensors that they cannot support multiple detection and lack universality. Recently, a sensor array based on nanozymes as nonspecific recognition receptors has attracted much more attention from researchers and has been applied to precise recognition of proteins, bacteria, and heavy metals. In this perspective, attention is given to nanozymes and the regulation of their enzyme-like activity. Particularly, the building principles and methods for sensor arrays based on nanozymes are analyzed, and the applications are summarized. Finally, the approaches to overcome the challenges and perspectives are also presented and analyzed for facilitating further research and development of nanozyme sensor arrays. This perspective should be helpful for gaining insight into research ideas within the field of nanozyme sensor arrays.

Transition-Metal-Based Nanozymes: Synthesis, Mechanisms of Therapeutic Action, and Applications in Cancer Treatment

Cancer, as one of the leading causes of death worldwide, drives the advancement of cutting-edge technologies for cancer treatment. Transition-metal-based nanozymes emerge as promising therapeutic nanodrugs that provide a reference for cancer therapy. In this review, we present recent breakthrough nanozymes for cancer treatment. First, we comprehensively outline the preparation strategies involved in creating transition-metal-based nanozymes, including hydrothermal method, solvothermal method, chemical reduction method, biomimetic mineralization method, and sol-gel method. Subsequently, we elucidate the catalytic mechanisms (catalase (CAT)-like activities), peroxidase (POD)-like activities), oxidase (OXD)-like activities) and superoxide dismutase (SOD)-like activities) of transition-metal-based nanozymes along with their activity regulation strategies such as morphology control, size manipulation, modulation, composition adjustment and surface modification under environmental stimulation. Furthermore, we elaborate on the diverse applications of transition-metal-based nanozymes in anticancer therapies encompassing radiotherapy (RT), chemodynamic therapy (CDT), photodynamic therapy (PDT), photothermal therapy (PTT), sonodynamic therapy (SDT), immunotherapy, and synergistic therapy. Finally, the challenges faced by transition-metal-based nanozymes are discussed alongside future research directions. The purpose of this review is to offer scientific guidance that will enhance the clinical applications of nanozymes based on transition metals.

Development and performance of NLISA for C-reactive protein detection based on Prussian blue nanoparticle conjugates

Prussian blue nanoparticles (PBNPs), also called nanozymes, are very attractive as an alternative to horseradish peroxidase in immunoassay development due to their simple and low-cost synthesis, stability and high catalytic activity. Today, there is a method for highly effective PBNP synthesis based on the reduction of an FeCl3/K3[Fe(CN)6] mixture by hydrogen peroxide. However, there is a lack of research showcasing the use of these highly effective PBNPs for specific target detection in clinical settings, as well as a lack of comprehensive comparisons with conventional methods. To address this gap, we prepared diagnostic reagents based on highly effective PBNPs by modifying them using gelatin and attaching anti-C-reactive protein (CRP) monoclonal antibodies through cross-linking with glutaraldehyde. As a result, a solid-phase colorimetric immunoassay in a sandwich format (nanozyme-linked immunosorbent assay [NLISA]) using highly effective PBNPs as a label for CRP detection has been demonstrated for the first time. The assay demonstrated a detection limit of 21.8 pg/mL, along with acceptable selectivity, precision (CV < 25%) and accuracy (the recovery index was within acceptable limits (75-125%) for LLOQ /ULOQ range. The analytical performance of this method is on par with sensitive assays developed in the last 5 years. Notably, the results obtained from NLISA align with those from an immunofluorescence assay conducted by a certified clinical laboratory. Furthermore, this study underscores the technological challenges involved in constructing an analysis that necessitate further exploration.

Neutral pH photoenzymatic activity of Au-doped g-C3N4 nanosheet for colorimetric detection of total antioxidant capacity in food samples

Total antioxidant capacity (TAC) is vital for food quality evaluation. The emergence of various nanozymes with TMB as substrate offered a new avenue for TAC detection due to simple operation and fast response, but a long-standing challenge is its low activity at physiological pH, which may account for the discrepancy between the measured TAC and the actual antioxidant capacity in vivo. Herein, Au doping was explored to break the pH limitation of g-C3N4 nanosheets (CNNS) photozyme. The catalytic activities of Au@CNNS at pH 4.0 and 7.4 were 14.9- and 6.2-fold higher than that of CNNS at pH 4. The neutral pH photozymatic activity (photosensitized oxidation of TMB, oxidase mimic) of Au@CNNS was explored for sensitivity TAC detection (LOD: 1.0 μM TE), which featured more convenient operations and higher sensitivity over the DPPH assay. The proposed Au@CNNS-based photozymatic colorimetric method was explored for accurate detection of TAC in drinks and juices.

Current Advances on the Single-Atom Nanozyme and Its Bioapplications

Nanozymes, a class of nanomaterials mimicking the function of enzymes, have aroused much attention as the candidate in diverse fields with the arbitrarily tunable features owing to the diversity of crystalline nanostructures, composition, and surface configurations. However, the uncertainty of their active sites and the lower intrinsic deficiencies of nanomaterial-initiated catalysis compared with the natural enzymes promote the pursuing of alternatives by imitating the biological active centers. Single-atom nanozymes (SAzymes) maximize the atom utilization with the well-defined structure, providing an important bridge to investigate mechanism and the relationship between structure and catalytic activity. They have risen as the new burgeoning alternative to the natural enzyme from in vitro bioanalytical tool to in vivo therapy owing to the flexible atomic engineering structure. Here, focus is mainly on the three parts. First, a detailed overview of single-atom catalyst synthesis strategies including bottom-up and top-down approaches is given. Then, according to the structural feature of single-atom nanocatalysts, the influence factors such as central metal atom, coordination number, heteroatom doping, and the metal-support interaction are discussed and the representative biological applications (including antibacterial/antiviral performance, cancer therapy, and biosensing) are highlighted. In the end, the future perspective and challenge facing are demonstrated.

A signal "switch-on" photoelectrochemical sensor based on a 3D-FM/BiOI heterostructure for the sensitive detection of l-ascorbic acid

A highly efficient 3D flower MoS2 (3D-FM)-based heterostructure photocatalyst (3D-FM/BiOI) was successfully obtained via a simple hydrothermal synthesis strategy. 3D-FM/BiOI showed prominent photoelectrochemical performance, distinguished stability and good selectivity. The introduction of 3D-FM, by promoting the photoelectric property attributed to it, facilitated the separation of photogenerated electron-hole pairs. Since the redox process of l-ascorbic acid (l-AA) resulted in an increasing photocurrent of 3D-FM/BiOI, a signal "switch-on" photoelectrochemical sensor (PECS) was designed to sensitively determine l-AA for the first time. Under optimized conditions, the 3D-FM/BiOI PECS worked over a wide range from 1 μM to 0.8 mM with a low detection limit of 0.05 μM (S/N = 3). The PECS was successfully exploited for l-AA sensing in human urine with excellent accuracy and applicability, demonstrating its practical precision and superb serviceability. Furthermore, the 3D-FM/BiOI PECS exhibited satisfactory selectivity and stability, providing a great potential platform for the construction of an l-AA sensor in various practical samples and complicated environments.

A colorimetric sensor array based on nanoceria crosslinked and heteroatom-doped graphene oxide nanoribbons for the detection and discrimination of multiple pesticides

Nanozymes have demonstrated high potential in constructing colorimetric sensor array for pesticides. However, rarely array for pesticides constructed without bio-enzyme were reported. Herein, nanoceria crosslinked graphene oxide nanoribbons (Ce-GONRs) and heteroatom-doped graphene oxide nanoribbons (Ce-BGONRs and Ce-NGONRs) were prepared, demonstrating excellent peroxidase-like activities. A colorimetric sensor array was developed based on directly inhibiting the peroxidase-like activities of the above three nanozymes, which realized the discrimination and quantitative analysis of six pesticides. In the presence of pesticides including carbaryl (Car), fluroxypyr-mepthyl (Flu), thiophanate-methyl (Thio), thiram (Thir), diafenthiuron (Dia) and fomesafen (Fom), the peroxidase-like activities of three nanozymes were inhibited to different degrees, resulting in different fingerprint responses. The six pesticides in the concentration range of 0.1-50 μg/mL and two pesticides mixtures at varied ratios could be detected and discriminated, and minimum detection limit for pesticides was 0.022 μg/mL. In addition, this sensor array has been successfully applied for pesticides discrimination in lake water and apple samples. This work provided a new strategy of constructing simple and sensitive colorimetric sensor array for pesticides based on directly inhibiting the catalytic activities of nanozymes.

Transition Metal High-Entropy Nanozyme: Multi-Site Orbital Coupling Modulated High-Efficiency Peroxidase Mimics

Strong substrate affinity and high catalytic efficiency are persistently pursued to generate high-performance nanozymes. Herein, with unique surface atomic configurations and distinct d-orbital coupling features of different metal components, a class of highly efficient MnFeCoNiCu transition metal high-entropy nanozymes (HEzymes) is prepared for the first time. Density functional theory calculations demonstrate that improved d-orbital coupling between different metals increases the electron density near the Fermi energy level (EF ) and shifts the position of the overall d-band center with respect to EF , thereby boosting the efficiency of site-to-site electron transfer while also enhancing the adsorption of oxygen intermediates during catalysis. As such, the proposed HEzymes exhibit superior substrate affinities and catalytic efficiencies comparable to that of natural horseradish peroxidase (HRP). Finally, HEzymes with superb peroxidase (POD)-like activity are used in biosensing and antibacterial applications. These results suggest that HEzymes have great potential as new-generation nanozymes.

Burgeoning Single-Atom Nanozymes for Efficient Bacterial Elimination

To fight against antibacterial-resistant bacteria-induced infections, the development of highly efficient antibacterial agents with a low risk of inducing resistance is exceedingly urgent. Nanozymes can rapidly kill bacteria with high efficiency by generating reactive oxygen species via enzyme-mimetic catalytic reactions, making them promising alternatives to antibiotics for antibacterial applications. However, insufficient catalytic activity greatly limits the development of nanozymes to eliminate bacterial infection. By increasing atom utilization to the maximum, single-atom nanozymes (SAzymes) with an atomical dispersion of active metal sites manifest superior enzyme-like activities and have achieved great results in antibacterial applications in recent years. In this review, the latest advances in antibacterial SAzymes are summarized, with specific attention to the action mechanism involved in antibacterial applications covering wound disinfection, osteomyelitis treatment, and marine antibiofouling. The remaining challenges and further perspectives of SAzymes for practical antibacterial applications are also discussed.

Nitrogen-doped porous carbon nanomaterials synthesized using a magadiite template as efficient peroxidase mimics for colorimetric detection of ascorbic acid as an antioxidant

Nanomaterials with intrinsic enzyme-like activity have gained substantial scientific attention as viable substitutes to natural biological enzymes owing to their cheap price and great stability. Numerous artificial enzyme mimics have been employed effectively in sectors such as sensing, environmental processing, and cancer treatment. In this study, novel nitrogen-doped porous carbon nanomaterials (CPs) were produced by modifying polypyrrole with magadiite using chemical oxidative polymerization and calcination methods. The obtained nitrogen-doped porous carbon nanomaterials exhibited improved peroxidase-like activity, which catalyzed the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to produce colorful compounds. Kinetic investigation revealed that the affinity for TMB of nitrogen-doped porous carbon peroxidase mimics was higher than that of genuine horseradish peroxidase (HRP). In addition, a sensitive assay with encouraging performance for the colorimetric detection of ascorbic acid (AA) was successfully fabricated employing nitrogen-doped porous carbon nanomaterials as peroxidase mimics. The results were satisfactory and demonstrated its potential application in antioxidant detection.

Recent advances in the synthesis and applications of single-atom nanozymes in food safety monitoring

Nanozymes are synthetic compounds with enzyme-like tunable catalytic properties. The success of nanozymes for catalytic applications can be attributed to their small dimensions, cost-effective synthesis, appreciable stability, and scalability to molecular dimensions. The emergence of single atom nanozymes (SANzymes) has opened up new possibilities in bioanalytical applications. In this regard, this review outlines enzyme-mimicking features of SANzymes for food safety applications in relation to the key variables controlling their catalytic performance. The discussion is extended further to cover the applications of SANzymes for the monitoring of various compounds/biomaterials of significance with respect to food safety (e.g., pesticides, veterinary drug residues, foodborne pathogenic bacteria, mycotoxins/bacterial endotoxin, antioxidant residues, hydrogen peroxide residues, and heavy metal ions). Furthermore, the performance of SANzymes is evaluated in terms of various performance metrics such as limit of detection (LOD), linear dynamic range, and figure of merit (FoM). The challenges and future road map for the applications of SANzymes are also addressed along with their upscaling in the area of food safety.

Cascade Reaction Regulated Electrochemiluminescence via Dual-Atomic-Site Catalysts

Single-atom catalysts (SACs), a novel kind of electrocatalysts with full metal utilization, have been developed as unique signal amplifiers in several sensing platforms. Herein, based on theoretical prediction of the oxygen reduction reaction (ORR) mechanism on different atom sites, we constructed dual-atomic-site catalysts (DACs), Fe/Mn-N-C, to catalyze luminol-dissolved oxygen electrochemiluminescence (ECL). Computational simulation indicated that the weak adsorption of OH* on a single Fe site was overcome by introducing Mn as the secondary metallic active site, resulting in a synergic dual-site cascade mechanism. The superior catalytic activity of Fe/Mn-N-C DACs for the ORR was proven by the highly efficient cathodic luminol ECL, surpassing the performance of single-site catalysts (SACs), Fe-N-C and Mn-N-C. Furthermore, the ECL system, enhanced by a cascade reaction, exhibited remarkable sensitivity to ascorbic acid, with a detection limit of 0.02 nM. This research opens up opportunities for enhancing both the ECL efficiency and sensing performance by employing a rational atomic-scale design for DACs.

Discrimination and Quantification of Glutathione by Cu+-Based Nanozymes

Glutathione (GSH) is the most abundant low-molecular-weight biological thiol in vivo and has been linked to several diseases. The accurate quantification of GSH is therefore crucial for disease diagnosis and monitoring. In this study, we prepared self-assembled Cu(I)-Cys (cysteine) nanozymes through a two-step procedure. The Cu(I)-Cys nanoparticles exhibited peroxidase-mimicking activity. Upon the addition of H2O2, they were able to oxidize 3,3,5,5-tetramethylbenzidine (TMB) into oxTMB, resulting in a measurable increase in UV-Vis absorption at 655 nm. However, in the presence of GSH, oxTMB was reduced back to TMB, leading to a decrease in UV-Vis absorption at 655 nm. By utilizing these changes in the absorption intensity, we achieved the sensitive detection of GSH with a detection limit of 2.13 μM. Moreover, taking advantage of the different peroxidase-mimicking activities of Cu(I)-Cys nanoparticles at various pH values, a sensor array with Cu(I)-Cys nanoparticles at pH 4 and pH 5 was constructed. The discrimination of GSH among Cys and ascorbic acid was achieved and the practicability of the sensor array in human serum was validated. This novel approach holds significant promise for the precise discrimination and quantification of GSH and its potential applications in disease diagnosis and therapeutics.

Rapid and sensitive determination of ascorbic acid based on label-free silver triangular nanoplates

In this study, a new method for the detection of ascorbic acid (AA) was proposed. It was based on the protective effect of AA on silver triangular nanoplates (Ag TNPs) against Cl- induced etching reactions. Cl- can attack the corners of Ag TNPs and etch them, causing a morphological shift from triangular nanoplates to nanodiscs. As a result, the solution changes color from blue to yellow. However, in the presence of AA, the corners of Ag TNPs can be protected from Cl- etching, and the blue color of the solution remains unchanged. Using this effect, a selective sensor was designed to detect AA in the range of 0-40.00 μM with a detection limit of 2.17 μM. As the concentration of AA varies in this range, color changes from yellow to blue can be easily observed, so the designed sensor can be used for colorimetric detection. This method can be used to analyze fruit juice samples.

Research Progress in Iron-Based Nanozymes: Catalytic Mechanisms, Classification, and Biomedical Applications

Natural enzymes are crucial in biological systems and widely used in biology and medicine, but their disadvantages, such as insufficient stability and high-cost, have limited their wide application. Since Fe₃O₄ nanoparticles were found to show peroxidase-like activity, researchers have designed and developed a growing number of nanozymes that mimic the activity of natural enzymes. Nanozymes can compensate for the defects of natural enzymes and show higher stability with lower cost. Iron, a nontoxic and low-cost transition metal, has been used to synthesize a variety of iron-based nanozymes with unique structural and physicochemical properties to obtain different enzymes mimicking catalytic properties. In this perspective, catalytic mechanisms, activity modulation, and their recent research progress in sensing, tumor therapy, and antibacterial and anti-inflammatory applications are systematically presented. The challenges and perspectives on the development of iron-based nanozymes are also analyzed and discussed.

Dual recognition elements for selective determination of progesterone based on molecularly imprinted electrochemical aptasensor

A novel molecularly imprinted electrochemical aptasensor (MIEAS) was constructed for selective progesterone (P4) detection based on SnO₂-graphene (SnO₂-Gr) nanomaterial and gold nanoparticles (AuNPs). SnO₂-Gr with a large specific area and excellent conductivity improved the adsorption capacity of P4. Aptamer, as biocompatible monomer, was captured by AuNPs on modified electrode through Au-S bond. An electropolymerized molecularly imprinted polymer (MIP) film consisted of p-aminothiophenol as chemical functional monomer and P4 as template molecule. Due to the synergetic effect of MIP and aptamer towards P4, this MIEAS exhibited better selectivity than the sensor with MIP or aptamer as single recognition element. The prepared sensor had a low detection limit of 1.73 × 10^-15 M in a wide linear range from 10^-14 M to 10^-5 M. Satisfactory recovery obtained in tap water and milk samples proved that this sensor had great potential in environmental and food analysis.

A molecularly imprinted electrochemical sensor with dual functional monomers for selective determination of gatifloxacin

A molecularly imprinted electrochemical sensor was designed for the selective determination of gatifloxacin (GTX) based on dual functional monomers. Multi-walled carbon nanotube (MWCNT) enhanced the current intensity and zeolitic imidazolate framework 8 (ZIF8) provided a large surface area to produce more imprinted cavities. In the electropolymerization of molecularly imprinted polymer (MIP), p-aminobenzoic acid (p-ABA) and nicotinamide (NA) were used as dual functional monomers, and GTX was the template molecule. Taking [Fe(CN)6]3-/4- as an electrochemical probe, an oxidation peak on the glassy carbon electrode was located at about 0.16 V (vs. saturated calomel electrode). Due to the diverse interactions among p-ABA, NA, and GTX, the MIP-dual sensor exhibited higher specificity towards GTX than MIP-p-ABA and MIP-NA sensors. The sensor had a wide linear range from 1.00 × 10-14 to 1.00 × 10-7 M with a low detection limit of 2.61 × 10-15 M. Satisfactory recovery between 96.5 and 105% with relative standard deviation from 2.4 to 3.7% in real water samples evidenced the potential of the method in antibiotic contaminant determination.

A colorimetric smartphone-based sensor for on-site AA detection in tropical fruits using Fe-P/NC single-atom nanoenzyme

Ascorbic acid is one of the important vitamins to maintain human life activities and plays an irreplaceable role in regulating human redox metabolism. Fresh fruit can provide plenty of AA to maintain human metabolic balance. Thus, it is great significant to develop a rapid and convenient method for detection of AA to evaluate the freshness and nutritional quality of fruits. In this work, Fe single-atom nanoenzyme (Fe-SAN) based colorimetric sensor assisted with smartphone was designed for rapid and on-site AA detection in tropical fruits. Firstly, Fe-SAN with high oxidase-mimicking activity was synthesized by using green tea leaves as sources of carbon and nitrogen and NaH₂PO₂ as P source to obtain Fe-P/NC SAN, in which P was used to reconstruct the distribution of electronic to enhance the oxidase-mimicking activity of Fe-SAN. Besides, the as-synthesized Fe-P/NC SAN with remarkable oxidase-like activities could oxidize 3,3́,5,5́-tetramethylbenzidine (TMB) to blue colored oxidized TMB. AA could inhibit the oxidation of TMB, leading to blue fading. Based on the above principle, colorimetric sensor integrated with smartphone RGB mode was fabricated and exhibited a good linear detection range (0.5-100 μM) and low detection limit of 0.315 μM for AA detection under optimal conditions. More importantly, the developed sensor could rapidly and accurately detect AA in real sample, such as pineapple, wax apple and mango. Therefore, this research provides a new cost-effective method for the efficient and exact detection of AA in tropical fruit, which has a broad application prospect.

Recent Progress in Sensor Arrays: From Construction Principles of Sensing Elements to Applications

The traditional sensors are designed based on the "lock-and-key" strategy with high selectivity and specificity for detecting specific analytes, which however are not suitable for detecting multiple analytes simultaneously. With the help of pattern recognition technologies, the sensor arrays excel in distinguishing subtle changes caused by multitarget analytes with similar structures in a complex system. To construct a sensor array, the multiple sensing elements are undoubtedly indispensable units that will selectively interact with targets to generate the unique "fingerprints" based on the distinct responses, enabling the identification among various analytes through pattern recognition methods. This comprehensive review mainly focuses on the construction strategies and principles of sensing elements, as well as the applications of sensor array for identification and detection of target analytes in a wide range of fields. Furthermore, the present challenges and further perspectives of sensor arrays are discussed in detail.

A novel electrochemical sensor based on an Fe–N–C/AuNP nanohybrid for rapid and sensitive gallic acid detection

An Fe–N–C/AuNP nanohybrid was combined with a glassy carbon electrode to construct a novel electrochemical sensor for rapid detection of gallic acid (GA). The sensor exhibited excellent performance to detect GA with a wide linear response range and low detection limit.

Atomic Dispersion of Zn2+ on N-Doped Carbon Materials: From Non-Activity to High Activity for Catalyzing Luminol-H2O2 Chemiluminescence

Fe and Co single-atom catalysts (SACs) have been widely explored in many fields, while Zn SACs are still in their infancy stage. Herein, we unexpectedly found that atomically dispersed Zn²⁺ on N-doped carbon material (Zn-N-C) exhibited high catalytic activity on luminol-H₂O₂ chemiluminescence (CL) reaction. The Zn-N-C SACs were readily prepared through simple pyrolyzation of the cheap precursors (dopamine and ZnCl₂). The mechanism of Zn SAC-catalyzed CL reaction of luminol-H₂O₂ was investigated in detail. The activity of Zn SACs originated from the Zn-N sites in the Zn-N-C structure. The monoatomic dispersion makes Zn²⁺ catalytic performance change from no activity to high activity in luminol-H₂O₂ CL reaction. This study demonstrated the particularity of the monatomic metal catalyst over the conventional metal ion. This work provides the unprecedented perspective for design of new metal SACs in CL reaction.

Emerging single-atom iron catalysts for advanced catalytic systems

Due to the elusive structure-function relationship, traditional nanocatalysts always yield limited catalytic activity and selectivity, making them practically difficult to replace natural enzymes in wide industrial and biomedical applications. Accordingly, single-atom catalysts (SACs), defined as catalysts containing atomically dispersed active sites on a support material, strikingly show the highest atomic utilization and drastically boosted catalytic performances to functionally mimic or even outperform natural enzymes. The molecular characteristics of SACs (e.g., unique metal-support interactions and precisely located metal sites), especially single-atom iron catalysts (Fe-SACs) that have a similar catalytic structure to the catalytically active center of metalloprotease, enable the accurate identification of active centers in catalytic reactions, which afford ample opportunity for unraveling the structure-function relationship of Fe-SACs. In this review, we present an overview of the recent advances of support materials for anchoring an atomic dispersion of Fe. Subsequently, we highlight the structural designability of support materials as two sides of the same coin. Moreover, the applications described herein illustrate the utility of Fe-SACs in a broad scope of industrially and biologically important reactions. Finally, we present an outlook of the major challenges and opportunities remaining for the successful combination of single Fe atoms and catalysts.

Switching on-off-on colorimetric sensor based on Fe-N/S-C single-atom nanozyme for ultrasensitive and multimodal detection of Hg2

Single-atom nanozymes (SAzymes) as a new class of efficient nanozymes have attracted extensive research interest due to their high catalytic activity and specificity. However, it is challenging to develop a novel nanoenzyme with high activity, good stability and reproducibility. In this paper, the nitrogen and sulfur coordinated Fe-N/S-C SAzymes were synthesized using peanuts shells as carbon, nitrogen and sulfur source. It shows high oxidase-like activities due to the doping of S induced geometric and electronic effects, which is further confirmed by density functional theory calculations. The prepared Fe-N/S-C SAzymes with the remarkable oxidase-mimicking activity could oxidize TMB to blue oxTMB, but the GSH can inhibit the oxidation of TMB resulting in blue fading. However, when Hg²⁺ is added into above system, Hg²⁺-SH complexes are generated attributed to a high affinity between GSH and Hg²⁺, ultimately leading to blue recovery. Based on this phenomenon, we constructed a novel "on-off-on" colorimetric sensor for the simultaneous detection of GSH (off) and Hg²⁺ (on), and the signal is acquired by various modes such as naked eye, UV-Vis spectrometer and smartphone. The colorimetric detection mode based on a smartphone showed a good linear response from 10 to 80 μM for GSH with a detection limit of 3.92 μM, and for Hg²⁺ with a linear range of 1 nM-10 μM and LOD of 0.17 nM, which is more suitable for routine laboratory applications. More importantly, the proposed colorimetric sensor has been successfully applied to the detection of GSH and Hg²⁺ in real samples with good analytical performance. This work not only provides a simple and cost-effective method to detect GSH and Hg²⁺ but also makes a certain contribution to environmental protection.

A nanozyme-based colorimetric sensor array as electronic tongue for thiols discrimination and disease identification

Thiol analysis is of vital significance due to the essential roles in disease diagnosis, while the highly similar structures of thiols are a major challenge in practical determination. Herein, a nanozyme-based colorimetric sensor array has been proposed as electronic tongue for excellent discrimination and sensitive quantitation of thiols. The sensing units are fabricated by integrating the terephthalic acid modified graphene quantum dots (TPA@GQDs) with three transition metal ions (Fe²⁺, Cu²⁺ and Zn²⁺) via coordination, respectively, which not only provide sufficient substrate binding sites but also form the metal ion-regulated catalytic active centers. In this way, disparate promotion degrees on the peroxidase-like catalytic activity have been achieved in different metal ion-TPA@GQD ensembles. Based on the strong binding affinity between metal ions and thiols, the catalytic active centers are removed from TPA@GQDs, which inhibits the catalytic activity of sensing unit to diverse degrees. Accordingly, using 3, 3', 5, 5'-tetramethylbenzidine (TMB) as chromogenic substrate in the presence of hydrogen peroxide (H₂O₂), each sensing unit can generate differential colorimetric signals (fingerprints) for six thiol analytes, which can be accurately discriminated through linear discriminant analysis (LDA) with a detection limit of 50 nM. In addition, the discrimination of the same thiol with different concentrations and thiol mixtures have also been achieved. Furthermore, inspired by the distinct levels of thiols in practical samples, the proposed sensor array enables the identification of thiol-associated diseases by means of machine learning algorithm, which makes a positive contribution to medical diagnosis.