Nanozymes for foodborne microbial contaminants detection: Mechanisms, recent advances, and challenges

Current research development on food contaminants, future risks, regulatory regime and detection technologies: A systematic literature review

Food contaminants pose serious threats to public health, with profound negative impacts on the economy, society, and environment. However, there is a lack of timely and comprehensive reviews on the latest developments in food contaminants and effective measures to prevent contamination, particularly through novel intelligent detection technologies and regulatory regimes. This study addresses this knowledge gap by presenting a timely review of the literature, focusing on current types of food contaminants, advances in detection technologies, emerging risks, and the latest developments in regulatory frameworks. The study reviewed 116 relevant articles published between 2019 and 2024 and conducted a thematic analysis. The food contaminants were classified into three categories: biological, chemical, and physical. The study identified six key drivers of current and future food safety risks: demographic change, economic factors, environmental conditions, geopolitical shifts, consumer priorities, and technological advancements. Findings reveal the uneven understanding of contaminants of emerging concern, future drivers of contaminants of emerging concern, and their impact on the food system, the environment, and human health. These findings highlight the need for future research on systematically identifying and validating the regional differences in food contamination prevention measures and assessing the extent to which these differences impact the effectiveness of prevention, mitigation, and control efforts. The findings also call for more international cooperation in food contamination research and the active involvement of technology partners to facilitate the application of cutting-edge technologies in food contamination detection and control.

Recent advances in metallic and metal oxide nanoparticle-assisted molecular methods for the detection of Escherichia coli

The detection of E. coli is of irreplaceable importance for the maintenance of public health and food safety. In the field of molecular detection, metal and metal oxide nanoparticles have demonstrated significant advantages due to their unique physicochemical properties, and their application in E. coli detection has become a cutting-edge focus of scientific research. This review systematically introduces the innovative applications of these nanoparticles in E. coli detection, including the use of magnetic nanoparticles for efficient enrichment of bacteria and precise purification of nucleic acids, as well as a variety of nanoparticle-assisted immunoassays such as enzyme-linked immunosorbent assays, lateral flow immunoassays, colorimetric methods, and fluorescence strategies. In addition, this paper addresses the application of nanoparticles used in nucleic acid tests, including amplification-free and amplification-based assays. Furthermore, the application of nanoparticles used in electrochemical and optical biosensors in E. coli detection is described, as well as other innovative assays. The advantages and challenges of the aforementioned technologies are subjected to rigorous analysis, and a prospective outlook on the future direction of development is presented. In conclusion, this review not only illustrates the practical utility and extensive potential of metal and metal oxide nanoparticles in E. coli detection, but also serves as a scientific and comprehensive reference for molecular diagnostics in food safety and public health.

Nanozyme-based colorimetric and smartphone imaging advanced sensing platforms for tetracycline detection and removal in food

The presence of antibiotic residues poses a significant threat to food assurance, triggering widespread concerns. Therefore, the prompt and accurate detection and removal of antibiotic residues are essential for ensuring food safety. In this study, an aptmer modified triple-metal nanozyme (apt-TMNzyme) sensor was developed, which achieved a portable, visual, intelligent, and fast determination for tetracycline (TET). The proposed apt-TMNzyme exhibited willow leaf-like morphology, high specific surface area and excellent TET adsorption and removal properties. The experiments showed that the apt-TMNzyme had outstanding peroxidase activity and could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to produce a blue product in the presence of H2O2, which provided a visual response signal to TET. This sensor was capable of quantifying TET within a concentration range of 0.2 nM-70 μM, achieving a detection limit of 7.1 nM under optimal conditions. When tested on real food samples, our sensor produced results that closely paralleled those achieved through high-performance liquid chromatography. To improve accessibility and user-friendliness, we also designed a colorimetric testing paper integrated with a smartphone application for intuitive and intelligent detection of TET, which enables the quantitative determination of TET in the concentration range of 0.003-60 μM, the detection limit was 5.1 μM. This integrated portable sensor not only streamlines the testing process, saving time and costs, but also offers a promising solution for rapid and sensitive detection of antibiotic residues.

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

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

"Four - in - one" platform based on multifunctional nanozyme for ultra - accurate detection and on - demand disinfection of Listeria monocytogenes

The inability to integrate detection and disinfection hindered building a unified pathogen monitoring platform, risking secondary contamination. Herein, a novel "four - in - one" platform for monitoring foodborne Listeria monocytogenes (L. monocytogenes) was presented. The magnetic daptomycin - functionalized Fe3O4 (Dap/Fe3O4) could selectively bind to L. monocytogenes, enhancing detection accuracy. The separated bacteria were captured by aptamers - functionalized Fe - doped - silica nanoparticles (Apt/Fe@SiNPs) for tri - mode detection. Besides fluorescence, the Apt/Fe@SiNPs converted 3,3',5,5' - tetramethylbenzidine (TMB) to oxidized TMB (oxTMB) via peroxidase activity, allowing colorimetric and subsequent photothermal detection upon irradiation, as low as 2.06 CFU/mL. Magnetic - induced aggregation of Apt/Fe@SiNPs generated toxic hydroxyl radicals around L. monocytogenes, achieving ∼99.6% disinfection. Furthermore, the biofilm of L. monocytogenes was effectively inhibited by the action of hydroxyl radicals. The platform might offer a promising prospect to control L. monocytogenes in food industries.

A two-dimensional coordination polymer with high laccase-like activity for sensitive colorimetric detection of thiram

In contrast to natural enzymes, nanozymes show promising advantages of low cost and high stability for analytical applications. The simple mix of L-phenylalanine (F) and Cu2+ produces two-dimensional nanosheets of a coordination polymer with a high surface area ratio and rich exposed active sites as a novel catalyst. As the mimetic of natural laccase, this nanozyme (F-Cu) can catalyze the oxidative coupling reaction of 2,4-dichlorophenol (2,4-DP) and 4-aminoantipyrine (4-AP) to produce a distinct red product, thus establishing an intuitive and simple method for the detection of thiram. In the range of 0-7.5 μM, the absorbance intensity was linearly related to the concentration of thiram, and the detection limit was 0.0845 μM. The F-Cu nanozyme was successfully applied to the colorimetric detection of thiram in real samples.

Applications of nanomaterials with enzyme-like activity for the detection of phytochemicals and hazardous substances in plant samples

Plants such as herbs, vegetables, fruits, and cereals are closely related to human life. Developing effective testing methods to ensure their safety and quantify their active components are of significant importance. Recently, nanomaterials with enzyme-like activity (known as nanozymes) have been widely developed in various assays, including colorimetric, fluorescence, chemiluminescence, and electrochemical analysis. This review presents the latest advances in analyzing phytochemicals and hazardous substances in plant samples based on nanozymes, including some active ingredients, organophosphorus pesticides, heavy metal ions, and mycotoxins. Additionally, the current shortcomings and challenges of the actual sample analysis were discussed.

Colorimetry/fluorescence dual-mode detection of Salmonella typhimurium based on a "three-in-one" nanohybrid with high oxidase-like activity for AIEgen

A colorimetry/fluorescence dual-mode assay based on the aptamer-functionalized magnetic covalent organic framework-supported CuO and Au NPs (MCOF-CuO/Au@apt) was developed for Salmonella typhimurium (S. typhimurium) biosensing. The nanohybrid combined three functions in one: good magnetic separation characteristic, excellent oxidase-mimic activity for tetrap-aminophenylethylene (TPE-4A), and target recognition capability. The attachment of MCOF-CuO/Au@apt onto the surface of S. typhimurium resulted in a significant reduction in the oxidase-mimicking activity of the nanohybrid, which could generate dual-signal of colorimetry and fluorescence through the catalytic oxidation of TPE-4A. Based on this, S. typhimurium could be specifically detected in the linear ranges of 102- 106 CFU·mL-1 and 101- 106 CFU·mL-1, with LODs of 7.6 and 2.1 CFU·mL-1, respectively in colorimetry/fluorescence modes. Moreover, the smartphone and linear discrimination analysis-based system could be used for on-site and portable testing. In addition, this platform showed applicability in detecting S. typhimurium in milk, egg liquid and chicken samples.

Engineering an enzyme-like catalytic sensor for on-site dual-mode evaluation of total antioxidant capacity

A novel Fe-MoOx nanozyme, engineered with enhanced peroxidase (POD)-like activity through strategic doping and the creation of oxygen vacancies, is introduced to catalyze the oxidation of TMB with high efficiency. Furthermore, Fe-MoOx is responsive to single electron transfer (SET) and hydrogen atom transfer (HAT) mechanisms related to antioxidants and can serve as a desirable nanozyme for total antioxidant capacity (TAC) determination. The TAC colorimetric platform can reach a low LOD of 0.512 μM in solution and 24.316 μM in the smartphone-mediated RGB hydrogel (AA as the standard). As proof of concept, the practical application in real samples was explored. The work paves a promising avenue to design diverse nanozymes for visual on-site inspection of food quality.

Nano-biosensor based on manganese dioxide nanosheets and carbon dots for dual-mode determination of Staphylococcus aureus

A ratiometric fluorescence and colorimetry dual-mode nano-biosensor has been established for Staphylococcus aureus (S. aureus) determination. The prepared approaches of Manganese dioxide nanosheets (MnO2 NSs) and carbon dots (BCDs) were facile, efficient and labor-saving and MnO2 NSs-mediated fluorescence quenching and oxidation could amplify detection signals. The dual-mode determination had a broad linear range of 37 ∼ 3.7 × 106 CFU/mL and low detection limits of 9 CFU/mL (ratiometric fluorescence) and 22 CFU/mL (colorimetry). Meanwhile, the method was applied in real samples with recovery ranging of 90 ∼ 102% and RSD < 4.44%, which was an insignificant difference with standard plate counting. The new dual-mode approach of S. aureus possesses the advantages of superior sensitivity, precision, accuracy and specificity. Moreover, the dual-mode nano-biosensor can be adopted in other foodborne pathogens determination by changing corresponding aptamers and provide an enlightenment in monitoring food safety.

The In Vitro Antibacterial Activity of Argirium SUNc against Most Common Pathogenic and Spoilage Food Bacteria

Foodborne diseases are one of the main issues for human health, and antibacterial packaging plays a major role in food security assurance. Silver ultra nanoparticles (Argirium SUNc) are antimicrobial agents that have a wide spectrum of action, including against pathogenic bacteria and spoilage fungi. The aim of the present study was to evaluate the antibacterial activity of Argirium SUNc on the bacteria most commonly found in food: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Listeria monocytogenes, and Salmonella typhimurium. In this regard, an in vitro study was carried out by assessing the Argirium SUNc effectiveness on different concentrations of each tested microbial strain and at different time intervals. The data showed that the antimicrobial activity of Argirium SUNc was directly related to the microbial concentration and varied depending on the microbial species. Moreover, a greater effectiveness against Gram-negative bacteria than Gram-positive bacteria was observed. These preliminary results provided important information on the silver nanoparticles spectrum of action, and this is an aspect that appears particularly promising for obtaining a viable alternative to traditional antimicrobials to be used against the pathogens and spoilage agents most commonly found in the food chain, harmful both to health and quality aspects.

Novel colorimetric detection of oxytetracycline in foods by copper nanozyme

In this study, copper nanozyme (CuNZs) possess good laccase-like activity were synthesized by grinding method with cupric chloride dihydrate as copper source, sodium borohydride as reducing agent and β-cyclodextrin as protective agent. The CuNZs can oxidize colorless 2,4-dinitrophenol (2,4-DP) to red product. When oxytetracycline (OTC) was added to the above three solutions, the color changed from red to orange and the absorbance increased again, indicating that OTC was also an affinity substrate for CuNZs. When CuNZs was mixed with OTC alone, the color changed from colorless to yellow, and the absorption intensity was related to OTC concentration. It has good selectivity and sensitivity, and had a good linear response to the concentration of OTC in the range of 50-500 μM, and the limit of detection was 0.148 μM. Thus, a fast and simple colorimetric assay for the determination of OTC was established by using the laccase-like activity of CuNZs, and it was applied successfully to detect OTC in food samples.

Immobilization of Enzyme Electrochemical Biosensors and Their Application to Food Bioprocess Monitoring

Electrochemical biosensors based on immobilized enzymes are among the most popular and commercially successful biosensors. The literature in this field suggests that modification of electrodes with nanomaterials is an excellent method for enzyme immobilization, which can greatly improve the stability and sensitivity of the sensor. However, the poor stability, weak reproducibility, and limited lifetime of the enzyme itself still limit the requirements for the development of enzyme electrochemical biosensors for food production process monitoring. Therefore, constructing sensing technologies based on enzyme electrochemical biosensors remains a great challenge. This article outlines the construction principles of four generations of enzyme electrochemical biosensors and discusses the applications of single-enzyme systems, multi-enzyme systems, and nano-enzyme systems developed based on these principles. The article further describes methods to improve enzyme immobilization by combining different types of nanomaterials such as metals and their oxides, graphene-related materials, metal-organic frameworks, carbon nanotubes, and conducting polymers. In addition, the article highlights the challenges and future trends of enzyme electrochemical biosensors, providing theoretical support and future perspectives for further research and development of high-performance enzyme chemical biosensors.

High-throughput and specific detection of microorganisms by intelligent modular fluorescent photoelectric microbe detector

Food safety has emerged as a major global issue. Detecting foodborne pathogenic microorganisms and controlling them is vital to guard against foodborne diseases caused by microorganisms. However, the current detection methods need to meet the demand for real-time detection on the spot after a simple operation. Considering unresolved challenges, we developed an Intelligent Modular Fluorescent Photoelectric Microbe (IMFP) system containing a special detection reagent. This IMFP system can automatically monitor microbial growth in which the photoelectric detection, temperature control, fluorescent probe, and bioinformatics screen are integrated into one platform and employed to detect pathogenic microorganisms. Moreover, a specific culture medium was also developed, which matched the system platform for Coliform bacteria and Salmonella typhi. The developed IMFP system could attain a limit of detection (LOD) of about 1 CFU/mL for both bacteria, while the selectivity could reach 99%. In addition, the IMFP system was applied to detect 256 bacterial samples simultaneously. This platform reflects the high-throughput needs of fields for microbial identification and related requirements, such as the development of pathogenic microbial diagnostic reagents, antibacterial sterilization performance tests, and microbial growth kinetics. The IMFP system also confirmed the other merits, such as high sensitivity, high-throughput, and operation simplicity compared to conventional methods, and it has a high potential as a tool for application in the health and food security fields.

Nanozymes towards Personalized Diagnostics: A Recent Progress in Biosensing

This review highlights the recent advancements in the field of nanozymes and their applications in the development of point-of-care biosensors. The use of nanozymes as enzyme-mimicking components in biosensing systems has led to improved performance and miniaturization of these sensors. The unique properties of nanozymes, such as high stability, robustness, and surface tunability, make them an attractive alternative to traditional enzymes in biosensing applications. Researchers have explored a wide range of nanomaterials, including metals, metal oxides, and metal-organic frameworks, for the development of nanozyme-based biosensors. Different sensing strategies, such as colorimetric, fluorescent, electrochemical and SERS, have been implemented using nanozymes as signal-producing components. Despite the numerous advantages, there are also challenges associated with nanozyme-based biosensors, including stability and specificity, which need to be addressed for their wider applications. The future of nanozyme-based biosensors looks promising, with the potential to bring a paradigm shift in biomolecular sensing. The development of highly specific, multi-enzyme mimicking nanozymes could lead to the creation of highly sensitive and low-biofouling biosensors. Integration of nanozymes into point-of-care diagnostics promises to revolutionize healthcare by improving patient outcomes and reducing costs while enhancing the accuracy and sensitivity of diagnostic tools.

Prospects for the next generation of artificial enzymes for ensuring the quality of chilled meat: Opportunities and challenges

As living standards rise, the demand for high-quality chilled meat among consumers also grows. Researchers and enterprises have been interested in ensuring the quality of chilled meat in all links of the downstream industry. Nanozyme has shown the potential to address the aforementioned requirements. Reasons and approaches for the application of nanozymes in the freshness assessment or shelf life extension of chilled meat were discussed. The challenges for applying these nanozymes to ensure the quality of chilled meat were also summarized. Finally, this review examined the safety, regulatory status, and consumer attitudes toward nanozymes. This review revealed that the freshness assessment of chilled meat is closely related to mimicking the enzyme activities of nanozymes, whereas the shelf life changes of chilled meat are mostly dependent on the photothermal activities and pseudophotodynamic activities of nanozymes. In contrast, studies regarding the shelf life of chilled meat are more challenging to develop, as excessive heat or reactive oxygen species impair its quality. Notably, meat contains a complex matrix composition that may interact with the nanozyme, reducing its effectiveness. Nanopollution and mass manufacturing are additional obstacles that must be overcome. Therefore, it is vital to choose suitable approaches to ensure meat quality. Furthermore, the safety of nanozymes in meat applications still needs careful consideration owing to their widespread usage.