A Comprehensive Review of Detection Methods for Escherichia coli O157:H7

Exploring the Complexities of Seafood: From Benefits to Contaminants

Seafood plays a vital role in human diets worldwide, serving as an important source of high-quality protein, omega-3 fatty acids, and essential vitamins and minerals that promote health and prevent various chronic conditions. The health benefits of seafood consumption are well documented, including a reduced risk of cardiovascular diseases, improved cognitive function, and anti-inflammatory effects. However, the safety of seafood is compromised by multiple hazards that can pose significant health risks. Pathogenic microorganisms, including bacteria, viruses, and parasites, in addition to microbial metabolites, are prominent causes of the foodborne diseases linked to seafood consumption, necessitating reliable detection and monitoring systems. Molecular biology and digital techniques have emerged as essential tools for the rapid and accurate identification of these foodborne pathogens, enhancing seafood safety protocols. Additionally, the presence of chemical contaminants such as heavy metals (e.g., mercury and lead), microplastics, and per- and polyfluoroalkyl substances (PFASs) in seafood is of increasing concern due to their potential to accumulate in the food chain and adversely affect human health. The biogenic amines formed during the microbial degradation of the proteins and allergens present in certain seafood species also contribute to food safety challenges. This review aims to address the nutritional value and health-promoting effects of seafood while exploring the multifaceted risks associated with microbial contamination, chemical pollutants, and naturally occurring substances. Emphasis is placed on enhanced surveillance, seafood traceability, sustainable aquaculture practices, and regulatory harmonization as effective strategies for controlling the risks associated with seafood consumption and thereby contributing to a safer seafood supply chain.

Extracellular nucleic acid-triggered precision responsive antibacterial strategy

AIMS

The emergence of antibiotic-resistant bacteria in recent years has underscored the urgent need for novel, precision-targeted antibacterial strategies. To address this critical challenge, our study designed a responsive antibacterial system that achieves precise bacterial eradication by conjugating antibacterial agents to nucleic acid probes wherein drug release is specifically triggered by extracellular nucleic acids.

METHODS AND RESULTS

This innovative design utilizes toehold-mediated strand displacement to enable single-nucleotide precision targeting of bacterial sequences, thereby ensuring highly specific and quantitative drug release. And drug release is specifically triggered by extracellular nucleic acids. Comprehensive evaluations, including bacterial growth inhibition curves, inhibition zone measurements, and fluorescence staining assays, demonstrated the exceptional stability and selectivity. Furthermore, the practicality of this strategy was validated in spiked environmental water samples, where significant antibacterial efficacy was observed, highlighting its real-world applicability.

CONCLUSIONS

The assembly, identification, and drug release process of this new antibacterial strategy have been thoroughly verified, showing excellent stability and selectivity, and also having excellent effects on the actual environment.

Review of the detection of pathogenic Escherichia coli based-microchip technology

Escherichia coli (E. coli) is a pathogen that has generated global concern due to the public health challenges it has created. Therefore, the rapid and accurate detection of E. coli is important to public health safety. Microchips have become a popular analytical technique for detecting E. coli due to their automation, high analytical efficiency, and low analyte consumption. Therefore, this paper highlights multiple microchip-based strategies for the detection of E. coli, reviews their limitations, and provides strategies and future perspectives for analyzing E. coli..

Kirkendall Effect-Mediated Transformation of ZIF-67 to NiCo-LDH Nanocages as Oxidase Mimics for Multicolor Point-of-Care Testing of β-Galactosidase Activity and Escherichia coli

Early and portable detection of pathogenic bacteria is crucial for ensuring food safety, monitoring product quality, and tracing the sources of bacterial infections. Moving beyond traditional plate-culture counting methods, the analysis of active bacterial components offers a rapid means of quantifying bacteria. Here, metal-organic framework (MOF)-derived NiCo-layered double hydroxide nanosheets (LDHs), synthesized via the Kirkendall effect, were employed as highly effective oxidase mimics to generate reactive oxygen species (ROS). These ROS quickly etched gold nanobipyramids (Au NBPs), producing a vivid multicolormetric response. Experimental results and theoretical calculations indicated that the exceptional oxidase-like activity of NiCo-LDHs stemmed from the presence of bimetallic active sites and oxygen vacancies modulating the local electronic structure of LDHs. Additionally, β-galactosidase (β-Gal), a biomarker of Escherichia coli, reacted with p-aminophenyl-β-d-galactopyranoside (PAPG) to form p-aminophenol (PAP), a reducing agent which consumes ROS, thereby inhibiting the etching of Au NBPs. Furthermore, a three-dimensional (3D)-printed point-of-care testing (POCT) shell was designed as a portable device to visually detect β-Gal and E. coli in conjugation with smartphones. This study not only provides a novel approach to the rational design of nanozymes but also establishes a vivid and portably visual biosensing platform for detecting β-Gal activity and pathogenic bacteria.

Photonic sensor based on surface imprinted polymers for enhanced point-of-care diagnosis of bacterial urinary tract infections

Effective bacterial detection is crucial for health diagnostics, particularly for the detection of pathogenic species like Escherichia coli (E. coli), which is responsible for up to 90% of urinary tract infections (UTIs), is especially crucial. Current detection methods are time-consuming, often delaying diagnosis and treatment. This study introduces an innovative approach for rapid E. coli detection using porous silicon (PSi) substrates combined with Surface Imprinted Polymers (SIPs) for photoluminescence-based (PL-based) E. coli detection. The PSi/SIP substrates offer high sensitivity, selectivity, and a low limit of detection (LOD) without the need for natural recognition elements. These substrates, fabricated via metal-assisted chemical etching (MACE) and PDMS-based E. coli imprinting, demonstrate reliable repeatability and a fast detection. Real-time detection experiments in phosphate-buffered saline (PBS) and urine showed consistent stair-like quenching of the PL signal with increasing E. coli concentrations, achieving theoretical LODs of approximately 13 ± 2 CFU/mL in PBS and 17 ± 3 CFU/mL in urine. The substrates exhibited excellent selectivity, differentiating E. coli from other species such as Cronobacter sakazakii (C. sakazakii) and Listeria monocytogenes. The high sensitivity and reproducibility of PSi/SIP substrates, along with the ease of use and rapid detection capabilities of the resulting sensor, highlight the potential of this novel platform for point-of-care (PoC) applications in clinical diagnostics.

Electrochemical and optical biosensors for the detection of E. Coli

E. coli is a common pathogenic microorganism responsible for numerous food and waterborne illnesses. Traditional detection methods often require long, multi-step processes and specialized equipment. Electrochemical and optical biosensors offer promising alternatives due to their high sensitivity, selectivity, and real-time monitoring capabilities. Recent advancements in sensor development focus on various techniques for detecting E. coli, including optical (fluorescence, colorimetric analysis, surface-enhanced Raman spectroscopy, surface plasmon resonance, localized surface plasmon resonance, chemiluminescence) and electrochemical (amperometric, voltammetry, impedance, potentiometric). Herein, the latest advancements in optical and electrochemical biosensors created for identifying E. coli with an emphasis on surface modifications employing nanomaterials and biomolecules are outlined in this review. Electrochemical biosensors exploit the unique electrochemical properties of E. coli or its specific biomolecules to generate a measurable signal. In contrast, optical biosensors rely on interactions between E. coli and optical elements to generate a detectable response. Moreover, optical detection has been exploited in portable devices such as smart phones and paper-based sensors. Different types of electrodes, nanoparticles, antibodies, aptamers, and fluorescence-based systems have been employed to enhance the sensitivity and specificity of these biosensors. Integrating nanotechnology and biorecognition (which bind to a specific region of the E. coli) elements has enabled the development of portable and miniaturized devices for on-site and point-of-care (POC) applications. These biosensors have demonstrated high sensitivity and offer low detection limits for E. coli detection. The convergence of electrochemical and optical technologies promises excellent opportunities to revolutionize E. coli detection, improving food safety and public health.

Electrochemical and Optical Multi-Detection of Escherichia coli Through Magneto-Optic Nanoparticles: A Pencil-on-Paper Biosensor

Escherichia coli (E. coli) detection suffers from slow analysis time and high costs, along with the need for specificity. While state-of-the-art electrochemical biosensors are cost-efficient and easy to implement, their sensitivity and analysis time still require improvement. In this work, we present a paper-based electrochemical biosensor utilizing magnetic core-shell Fe2O3@CdSe/ZnS quantum dots (MQDs) to achieve fast detection, low cost, and high sensitivity. Using electrochemical impedance spectroscopy (EIS) as the detection technique, the biosensor achieved a limit of detection of 2.7 × 102 CFU/mL for E. coli bacteria across a concentration range of 102-108 CFU/mL, with a relative standard deviation (RSD) of 3.5781%. From an optical perspective, as E. coli concentration increased steadily from 104 to 107 CFU/mL, quantum dot fluorescence showed over 60% lifetime quenching. This hybrid biosensor thus provides rapid, highly sensitive E. coli detection with a fast analysis time of 30 min. This study, which combines the detection advantages of electrochemical and optical biosensor systems in a graphite-based paper sensor for the first time, has the potential to meet the needs of point-of-care applications. It is thought that future studies that will aim to examine the performance of the production-optimized, portable, graphite-based sensor system on real food samples, environmental samples, and especially medical clinical samples will be promising.

Establishment of LAMP-CRISPR/Cas12a for rapid detection of Escherichia coli O157:H7 and one-pot detection

Escherichia coli O157:H7 is a pathogenic serotype of Escherichia coli. Consumption of food contaminated with E. coli O157:H7 could cause a range of diseases. Therefore, it is of great importance to establish rapid and accurate detection methods for E. coli O157:H7 in food. In this study, based on LAMP and combined with the CRISPR/cas12a system, a sensitive and specific rapid detection method for E. coli O157:H7 was established, and One-Pot detection method was also constructed. The sensitivity of this method could stably reach 9.2 × 10° CFU/mL in pure culture, and the whole reaction can be completed within 1 h. In milk, E. coli O157:H7 with an initial contamination of 7.4 × 10° CFU/mL only needed to be cultured for 3 h to be detected. The test results can be judged by the fluorescence curve or by visual observation under a UV lamp, eliminating instrument limitations and One-Pot detection can effectively prevent the problem of false positives. In a word, the LAMP-CRISPR/cas12a system is a highly sensitive and convenient method for detecting E. coli O157:H7.

Phage-induced "one-to-many" FRET sensor for highly sensitive detection of Escherichia coli O157:H7

As a foodborne pathogen capable of causing severe illnesses, early detection of Escherichia coli O157:H7 (E. coli O157:H7) is crucial for ensuring food safety. While Förster resonance energy transfer (FRET) is an efficient and precise detection technique, there remains a need for amplification strategies to detect low concentrations of E. coli O157:H7. In this study, we presented a phage (M13)-induced "one to many" FRET platform for sensitively detecting E. coli O157:H7. The aptamers, which specifically recognize E. coli O157:H7 were attached to magnetic beads as capture probes for separating E. coli O157:H7 from food samples. The peptide O157S, which specifically targets E. coli O157:H7, and streptavidin binding peptide (SBP), which binds to streptavidin (SA), were displayed on the P3 and P8 proteins of M13, respectively, to construct the O157S-M13K07-SBP phage as a detection probe for signal output. Due to the precise distance (≈3.2 nm) between two neighboring N-terminus of P8 protein, the SA-labeled FRET donor and acceptor can be fixed at the Förster distance on the surface of O157S-M13K07-SBP via the binding of SA and SBP, inducing FRET. Moreover, the P8 protein, with ≈2700 copies, enabled multiple FRET (≈605) occurrences, amplifying FRET in each E. coli O157:H7 recognition event. The O157S-M13K07-SBP-based FRET sensor can detect E. coli O157:H7 at concentration as low as 6 CFU/mL and demonstrates excellent performance in terms of selectivity, detection time (≈3 h), accuracy, precision, practical application, and storage stability. In summary, we have developed a powerful tool for detecting various targets in food safety, environmental monitoring, and medical diagnosis.

Recent Progress in Nanomaterial-Based Surface-Enhanced Raman Spectroscopy for Food Safety Detection

Food safety has recently become a widespread concern among consumers. Surface-enhanced Raman scattering (SERS) is a rapidly developing novel spectroscopic analysis technique with high sensitivity, an ability to provide molecular fingerprint spectra, and resistance to photobleaching, offering broad application prospects in rapid trace detection. With the interdisciplinary development of nanomaterials and biotechnology, the detection performance of SERS biosensors has improved significantly. This review describes the advantages of nanomaterial-based SERS detection technology and SERS's latest applications in the detection of biological and chemical contaminants, the identification of foodborne pathogens, the authentication and quality control of food, and the safety assessment of food packaging materials. Finally, the challenges and prospects of constructing and applying nanomaterial-based SERS sensing platforms in the field of food safety detection are discussed with the aim of early detection and ultimate control of foodborne diseases.

Fast and sensitive detection of viable Escherichia coli O157:H7 using a microwell-confined and propidium monoazide-assisted digital CRISPR microfluidic platform

Escherichia coli O157:H7 is a major foodborne pathogen that poses a significant threat to food safety and human health. Rapid and sensitive detection of viable Escherichia coli O157:H7 can effectively prevent food poisoning. Here, we developed a microwell-confined and propidium monoazide-assisted digital CRISPR microfluidic platform for rapid and sensitive detection of viable Escherichia coli O157:H7 in food samples. The reaction time is significantly reduced by minimizing the microwell volume, yielding qualitative results in 5 min and absolute quantitative results in 15 min. With the assistance of propidium monoazide, this platform can eliminate the interference from 99% of dead Escherichia coli O157:H7. The direct lysis method obviates the need for a complex nucleic acid extraction process, offering a limit of detection of 3.6 × 101 CFU mL-1 within 30 min. Our results demonstrated that the platform provides a powerful tool for rapid detection of Escherichia coli O157:H7 and provides reliable guidance for food safety testing.

An ultrasensitive smartphone-assisted bicolor-ratiometric fluorescence sensing platform based on a "noise purifier" for point-of-care testing of pathogenic bacteria in food

Non-specific binding in fluorescence resonance energy transfer (FRET) remains a challenge in foodborne pathogen detection, resulting in interference of high background signals. Herein, we innovatively reported a dual-mode FRET sensor based on a "noise purifier" for the ultrasensitive quantification of Escherichia coli O157:H7 in food. An efficient FRET system was constructed with polymyxin B-modified nitrogen-sulfur co-doped graphene quantum dots (N, S-GQDs@PMB) as donors and aptamer-modified yellow carbon dots (Y-CDs@Apt) as acceptors. Magnetic multi-walled carbon nanotubes (Fe@MWCNTs) were employed as a "noise purifier" to reduce the interference of the fluorescence background. Under the background purification mode, the sensitivity of the dual-mode signals of the FRET sensor has increased by an order of magnitude. Additionally, smartphone-assisted colorimetric analysis enabled point-of-care detection of E. coli O157:H7 in real samples. The developed sensing platform based on a "noise purifier" provides a promising method for ultrasensitive on-site testing of trace pathogenic bacteria in various foodstuffs.

An integrated magnetic separation enzyme-linked colorimetric sensing platform for field detection of Escherichia coli O157: H7 in food

An intelligent colorimetric sensing platform integrated with in situ immunomagnetic separation function was developed for ultrasensitive detection of Escherichia coli O157: H7 (E. coli O157: H7) in food. Captured antibody modified magnetic nanoparticles (cMNPs) and detection antibody/horseradish peroxidase (HRP) co-functionalized AuNPs (dHAuNPs) were firstly synthesized for targeted enrichment and colorimetric assay of E. coli O157: H7, in which remarkable signal amplification was realized by loading large amounts of HRP on the surface of AuNPs. Coupling with the optical collimation attachments and embedded magnetic separation module, a highly integrated optical device was constructed, by which in situ magnetic separation and high-quality imaging of 96-well microplates containing E. coli O157: H7 was achieved with a smartphone. The concentration of E. coli O157: H7 could be achieved in one-step by performing digital image colorimetric analysis of the obtained image with a custom-designed app. This biosensor possesses high sensitivity (1.63 CFU/mL), short detecting time (3 h), and good anti-interference performance even in real-sample testing. Overall, the developed method is expected to be a novel field detection platform for foodborne pathogens in water and food as well as for the diagnosis of infections due to its portability, ease of operation, and high feasibility.

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly mediated cyclic signal amplification strategy for the reliable determination of E. coli O157:H7

A ratiometric SERS aptasensor based on catalytic hairpin self-assembly (CHA) mediated cyclic signal amplification strategy was developed for the rapid and reliable determination of Escherichia coli O157:H7. The recognition probe was synthesized by modifying magnetic beads with blocked aptamers, and the SERS probe was constructed by functionalizing gold nanoparticles (Au NPs) with hairpin structured DNA and 4-mercaptobenzonitrile (4-MBN). The recognition probe captured E. coli O157:H7 specifically and released the blocker DNA, which activated the CHA reaction on the SERS probe and turned on the SERS signal of 6-carboxyl-x-rhodamine (ROX). Meanwhile, 4-MBN was used as an internal reference to calibrate the matrix interference. Thus, sensitive and reliable determination and quantification of E. coli O157:H7 was established using the ratio of the SERS signal intensities of ROX to 4-MBN. This aptasensor enabled detection of 2.44 × 102 CFU/mL of E. coli O157:H7 in approximately 3 h without pre-culture and DNA extraction. In addition, good reliability and excellent reproducibility were observed for the determination of E. coli O157:H7 in spiked water and milk samples. This study offered a new solution for the design of rapid, sensitive, and reliable SERS aptasensors.

A New SPQC Biosensor for the Detection of a New Target of Escherichia/Shigella Genera Based on a Novel Method of Synthesizing Long-Range DNA

The rapid and sensitive detection of Escherichia/Shigella genera is crucial for human disease and health. This study introduces a novel series of piezoelectric quartz crystal (SPQC) sensors for detecting Escherichia/Shigella genera. In this innovative biosensor, we propose a new target and novel method for synthesizing long-range DNA. The method relies on the amplification of two DNA probes, referred to as H and P amplification (HPA), resulting in the products of long-range DNA named Sn. The new target was screened from the 16S rRNA gene and utilized as a biomarker. The SPQC sensor operates as follows: the Capture probe is modified on the electrodes. In the presence of a Displace probe and target, the Capture can form a complex with the Displace probe. The resulting complex hybridizes with Sn, bridging the gap between the electrodes. Finally, silver wires are deposited between the electrodes using Sn as a template. This process results in a sensitive response from the SPQC. The detection limit of the SPQC sensor is 1 CFU/mL, and the detection time is within 2 h. This sensor would be of great benefit for food safety monitoring and clinical diagnosis.

A Dual-mode platform for the rapid detection of Escherichia coli O157:H7 based on CRISPR/Cas12a and RPA

Escherichia coli O157:H7 (E. coli O157:H7) is a foodborne pathogenic microorganism that is commonly found in the environment and poses a significant threat to human health, public safety, and economic stability worldwide. Thus, early detection is essential for E. coli O157:H7 control. In recent years, a series of E. coli O157:H7 detection methods have been developed, but the sensitivity and portability of the methods still need improvement. Therefore, in this study, a rapid and efficient testing platform based on the CRISPR/Cas12a cleavage reaction was constructed. Through the integration of recombinant polymerase amplification and lateral flow chromatography, we established a dual-interpretation-mode detection platform based on CRISPR/Cas12a-derived fluorescence and lateral flow chromatography for the detection of E. coli O157:H7. For the fluorescence detection method, the limits of detection (LODs) of genomic DNA and E. coli O157:H7 were 1.8 fg/µL and 2.4 CFU/mL, respectively, within 40 min. Conversely, for the lateral flow detection method, LODs of 1.8 fg/µL and 2.4 × 102 CFU/mL were achieved for genomic DNA and E. coli O157:H7, respectively, within 45 min. This detection strategy offered higher sensitivity and lower equipment requirements than industry standards. In conclusion, the established platform showed excellent specificity and strong universality. Modifying the target gene and its primers can broaden the platform's applicability to detect various other foodborne pathogens.

A Fully Integrated Handheld Electrochemical Sensing Platform for Point-of-Care Testing of Escherichia coli O157:H7

Fully integrated devices that enable full functioning execution without or with minimum external accessories or equipment are deemed to be one of the most desirable and ultimate objectives for modern device design and construction. Escherichia coli O157:H7 (E. coli O157:H7) is often linked to outbreaks caused by contaminated water and food. However, the sensors that are currently used for point-of-care E. coli O157:H7 (E. coli O157:H7) detection are often large and cumbersome. Herein, we demonstrate the first example of a handheld and pump-free fully integrated electrochemical sensing platform with the capability to point-of-care test E. coli O157:H7 in the actual samples of E. coli O157:H7-spiked tap water and E. coli O157:H7-spiked watermelon juice. This platform was made possible by overcoming major engineering challenges in the seamless integration of a microfluidic module for pump-free liquid sample collection and transportation, a sensing module for efficient E. coli O157:H7 testing, and an electronic module for automatically converting and wirelessly transmitting signals into a single and compact electrochemical sensing platform that retains its inimitable stand-alone, handheld, pump-free, and cost-effective feature. Although our primary emphasis in this study is on detecting E. coli O157:H7, this pump-free fully integrated handheld electrochemical sensing platform may also be used to monitor other pathogens in food and water by including specific antipathogen antibodies.

UV-induced oxidase activity of carbon dots in visible UVA dosage, Escherichia coli quantification and bacterial typing

Ultraviolet (UV) light and foodborne pathogenic bacteriais are an important risk to the environment's safety. They endanger human health, and also lead to outbreaks of infectious disease, posing great threats to global public health security, national economy, and social stability. The appearance of carbon dot (CD) nanozymes offers a new perspective to solve the problems of detection of UV light and pathogenic bacteria in environment. This paper reports the preparation of CDs with dual enzyme-like activities (superoxide dismutase activity and UV-induced oxidase activity). The product can catalyze the oxidation of the substrate 3, 3', 5, 5'-tetramethylbenzidine (TMB) under UV light (365 nm) to achieve rapid color development. Based on the excellent fluorescence properties of CDs, the colorimetric-fluorescence dual-channel real-time detection of UVA dose was realized, the mechanism underlying the catalytic oxidation of TMB by UV-induced oxidase CDs was also investigated. Furthermore, a portable CDs-TMB-PA hydrogel was prepared which could realize the real-time monitoring of UV in outdoor environment with the assistance of smartphone. Based on the pH dependency of the CD nanozymes and specific glycolytic response of the pathogenic bacteria Escherichia coli (E. coli) O157:H7, the direct, simple, quick, and sensitive typing and detection have been realized. This research offers new perspectives for studying CD nanozymes and their applications in UV and bacterial detection, demonstrating the remarkable potential of CD nanozymes in detecting environmental hazards.

Key steps for improving bacterial SERS signals in complex samples: Separation, recognition, detection, and analysis

Rapid and reliable detection of pathogenic bacteria is absolutely essential for research in environmental science, food quality, and medical diagnostics. Surface-enhanced Raman spectroscopy (SERS), as an emerging spectroscopic technique, has the advantages of high sensitivity, good selectivity, rapid detection speed, and portable operation, which has been broadly used in the detection of pathogenic bacteria in different kinds of complex samples. However, the SERS detection method is also challenging in dealing with the detection difficulties of bacterial samples in complex matrices, such as interference from complex matrices, confusion of similar bacteria, and complexity of data processing. Therefore, researchers have developed some technologies to assist in SERS detection of bacteria, including both the front-end process of obtaining bacterial sample data and the back-end data processing process. The review summarizes the key steps for improving bacterial SERS signals in complex samples: separation, recognition, detection, and analysis, highlighting the principles of each step and the key roles for SERS pathogenic bacteria analysis, and the interconnectivity between each step. In addition, the current challenges in the practical application of SERS technology and the development trends are discussed. The purpose of this review is to deepen researchers' understanding of the various stages of using SERS technology to detect bacteria in complex sample matrices, and help them find new breakthroughs in different stages to facilitate the detection and control of bacteria in complex samples.

Dual-mode colorimetric and fluorescence biosensors for the detection of foodborne bacteria

Due to the growing demand for detection technologies, there has been significant interest in the development of integrated dual-modal sensing technologies, which involve combining two signal transduction channels into a single technique, particularly in the context of food safety. The integration of two detection signals not only improves diagnostic performance by reducing assumptions, but also enhances diagnostic functions with increased application flexibility, improved accuracy, and a wider detection linear range. The top two output signals for emerging dual-modal probes are fluorescent and colorimetric, due to their exceptional advantages for real-time sensitive sensing and point-of-care applications. With the rapid progress of nanotechnology and material chemistry, the integrated colorimetric/fluorimetric dual-mode systems show immense potential in sensing foodborne pathogenic bacteria. In this comprehensive review, we present a detailed summary of various colorimetric and fluorimetric dual-modal sensing methods, with a focus on their application in detecting foodborne bacteria. We thoroughly examine the sensing methodologies and the underlying principles of the signal transduction systems, and also discuss the challenges and future prospects for advancing research in this field.

An intelligent readable and capture-antibody-independent lateral flow immunoassay based on Cu2-xSe nanocrystals for point-of-care detection of Escherichia coli O157:H7

Escherichia coli (E. coli) O157:H7 is a common foodborne pathogen which can cause serious harm. It is particularly important to establish a simple and portable method to achieve on-site pathogen detection. In this study, a capture-antibody-independent lateral flow immunoassay (LFIA) was constructed based on Cu2-xSe nanocrystals (Cu2-xSe NCs) for rapid detection of E. coli O157:H7. Cu2-xSe NCs can not only be regarded as the "nano-antibody" for the recognition of E. coli O157:H7 through electrostatic adsorption, but also as nanozymes that show good peroxidase-like catalytic activity. The formed compound of E. coli O157:H7 and Cu2-xSe NCs would be captured by a detection antibody on the T line due to the specific recognition of the antibody and E. coli O157:H7. Then, Cu2-xSe NCs could catalyze the oxidation of TMB by H2O2 to generate oxTMB, thereby generating blue bands. Meanwhile, we developed a mobile app for rapid data analysis. Under the optimal reaction conditions, E. coli O157:H7 could be detected within 70 min. The detection limit of this method was 2.65 × 105 CFU mL-1 with good specificity and stability. Additionally, it could achieve on-site rapid detection of E. coli O157:H7 in environmental water samples, providing a promising biosensor for portable pathogen detection.

Molecular Engineering Powered Dual-Readout Point-of-Care Testing for Sensitive Detection of Escherichia coli O157:H7

Escherichia coli O157:H7 (E. coli O157:H7) has become one of the major threats to public health and food safety. However, the culture method as a gold standard for the detection of E. coli O157:H7 requires laborious operations and a long processing time. Herein, we developed a dual-readout aggregation-induced emission nanoparticle-based lateral flow immunoassay (LFIA) for sensitive detection of E. coli O157:H7 to achieve a qualitative and quantitative assay for satisfying the applications under varying scenarios. 2,3-Bis(4-(bis(4-(tert-butyl)phenyl)amino)phenyl)fumaronitrile (BAPF), an aggregation-induced emission luminogen, was designed to achieve a strong molar extinction coefficient (3.0 × 104 M-1 cm-1) and high quantum yield (33.28%), which was further verified by a large rotation angle and low energy gap. Subsequently, BAPFs were integrated into a nanostructured system to form excellent water-soluble nanoparticles (BAPFNPs) for the detection of E. coli O157:H7 with colorimetric and fluorescent readout. The designed BAPFNPs-based LFIA (BAPFNPs-LFIA) exhibited nearly qualitative ability with gold nanoparticles-LFIA (AuNPs-LFIA) and a 9 times enhancement compared with quantum beads-LFIA (QBs-LFIA) in quantitative aspect. Especially, FL-BAPFNPs-LFIA could detect E. coli O157:H7 earlier than QBs-LFIA and AuNPs-LFIA when samples with low E. coli O157:H7 concentrations were cultured. Overall, the proposed strategy revealed that versatile BAPFNPs have great potential as reporters for dual-readout ability and enhancing detection sensitivity for rapid and accurate pathogenic bacteria assay.

Nanomaterial-based biosensors for the detection of foodborne bacteria: a review

Ensuring food safety is a critical concern for the development and well-being of humanity, as foodborne illnesses caused by foodborne bacteria have increasingly become a major public health concern worldwide. Traditional food safety monitoring systems are expensive and time-consuming, relying heavily on specialized equipment and operations. Therefore, there is an urgent need to develop low-cost, user-friendly and highly sensitive biosensors for detecting foodborne bacteria. In recent years, the combination of nanomaterials with optical biosensors has provided a prospective future platform for the detection of foodborne bacteria. By harnessing the unique properties of nanomaterials, such as their high surface area-to-volume ratio and exceptional sensitivity, in tandem with the precision of optical biosensing techniques, a new prospect has opened up for the rapid and accurate identification of potential bacterial contaminants in food. This review focuses on recent advances and new trends of nanomaterial-based biosensors for the detection of foodborne pathogens, which mainly include noble metal nanoparticles (NMPs), metal organic frameworks (MOFs), graphene nanomaterials, quantum dot (QD) nanomaterials, upconversion fluorescent nanomaterials (UCNPs) and carbon dots (CDs). Additionally, we summarized the research progress of color indicators, nanozymes, natural enzyme vectors and fluorescent dye biosensors, focusing on the advantages and disadvantages of nanomaterial-based biosensors and their development prospects. This review provides an outlook on future technological directions and potential applications to help identify the most promising areas of development in this field.

Triazine-based covalent-organic framework embedded with cuprous oxide as the bioplatform for photoelectrochemical aptasensing Escherichia coli

A superior photoelectrochemical (PEC) aptasensor was manufactured for the detection of Escherichia coli (E. coli) based on a hybrid of triazine-based covalent-organic framework (COF) and cuprous oxide (Cu2O). The COF synthesized using 1,3,5-tris(4-aminophenyl)-benzene (TAPB) and 1,3,5-triformylphloroglucinol (Tp) as building blocks acted as a scaffold for encapsulated Cu2O nanoparticles (denoted as Cu2O@TAPB-Tp-COF), which then was employed as the bioplatform for anchoring E. coli-targeted aptamer. Cu2O@Cu@TAPB-Tp-COF demonstrated enhanced separation of the photogenerated carriers and photoabsorption ability and boosted photoelectric conversion efficiency. The developed Cu2O@TAPB-Tp-COF-based PEC aptasensor exhibited a lower detection limit of 2.5 CFU mL-1 toward E. coli within a wider range of 10 CFU mL-1 to 1 × 104 CFU mL-1 than most of reported aptasensors for determining foodborne bacteria, together with high selectivity, good stability, and superior ability and reproducibility. The recoveries of E. coli spiked into milk and bread samples ranged within 95.3-103.6% and 96.6-102.8%, accompanying with low RSDs of 1.37-4.48% and 1.74-3.66%, respectively. The present study shows a promising alternative for the sensitive detection of foodborne bacteria from complex foodstuffs and pathogenic bacteria-polluted environment.

Nanozyme-Mediated Catalytic Signal Amplification for Microfluidic Biosensing of Foodborne Bacteria

Early detection of foodborne bacteria is urgently needed to ensure food quality and to avoid the outbreak of foodborne bacterial diseases. Here, a kind of metal-organic framework (Zr-MOF) modified with Pt nanoparticles (Pt-PCN-224) was designed as a peroxidase-like signal amplifier for microfluidic biosensing of foodborne bacteria. Taking Escherichia coli (E. coli) O157:H7 as a model, a linear range from 2.93 × 102 to 2.93 × 108 CFU/mL and a limit of detection of 2 CFU/mL were obtained. The whole detection procedure was integrated into a single microfluidic chip. Water, milk, and cabbage samples were successfully detected, showing consistency with the results of the standard culture method. Recoveries were in the range from 90 to 110% in spiked testing. The proposed microfluidic biosensor realized the specific and sensitive detection of E. coli O157:H7 within 1 h, implying broad prospects of MOF with biomimetic enzyme activities for biosensing.

Covalent organic frameworks assisted for food safety analysis

Food safety incidents threaten human health and life safety. It is an effective method to prevent and control the occurrence of food safety events by enhancing the rapid and sensitive detection of food contaminants. Emerging porous materials provide for the development of efficient and stable detection methods. Covalent organic frameworks (COFs) are favored by researchers for their highly ordered pore structure, large specific surface area, and good structural and functional designability. Especially in the sensing field, COFs play the roles of carriers, conductors, quenchers, and reporters, and have broad application prospects. To better understand COFs-based sensing studies, this review briefly introduces the characteristics and different functional roles of COFs in food safety analysis, focusing on the applications of COFs in the detection of various food contaminants (including foodborne pathogens, mycotoxins, pesticides, antibiotics, heavy metals, and others). Finally, the challenges and opportunities for COFs-based sensing are discussed to facilitate further applications and development of COFs in food safety.

Simultaneous and rapid screening of live and dead E. coli O157:H7 with three signal outputs: An all-in-one biosensor using phage-apoferritin@CuO2 signal tags on MXenes-modified electrode platform

Simultaneous detection of live and dead bacteria is a huge challenge for food safety. To solve this issue, an all-in-one biosensor for bacteria was developed using the phage-apoferritin@CuO₂ (phage-Apo@CP) probe on an antimicrobial peptide (AMP)/MXenes-modified detection platform. With the specific recognition of AMP and phage-Apo@CP, the biosensor for the target Escherichia coli O157:H7 (E. coli O157:H7) presented multi-mode (bioluminescent, colorimetric, and electrochemical) signals to simultaneously measure live and dead bacteria. The bioluminescent signal caused by the adenosine triphosphate (ATP) from the bacteria was used to quantify live bacteria. The colorimetric and voltammetric signals triggered by ·OH and Cu²⁺ from the probe with the assistance of acid could rapidly screen and quantitative determination of total E. coli O157:H7 concentration. Thus, the dead one was obtained according to the total and live ones. All three signals could be mutually corrected to improve the accuracy. The biosensor was successfully used for on-site measurement of live and dead E. coli O157:H7 in food samples with the limit of detection of 30 CFU/mL for live ones and 6 CFU/mL for total bacteria within 50 min. This work presents a novel pathway for rapid and simultaneous quantification of both live and dead bacteria.

Dual-mode immunochromatographic assay based on dendritic gold nanoparticles with superior fluorescence quenching for ultrasensitive detection of E. coli O157:H7

We presented a colorimetric/fluorescent dual-mode immunochromatographic assay (ICA) for the sensitive detection of Escherichia coli O157:H7. The use of polydopamine (PDA)-modified gold nanoparticles (AuNPs) with broadband absorption allowed for excellent colorimetry signals for the ICA detection. Moreover, the absorption spectrum of PDA-AuNPs significantly overlaps with the excitation and emission spectra of ZnCdSe/ZnS quantum dots (QDs), resulting in effective quenching of the QDs fluorescence due to the inner filter effect. The fluorescence intensity changes induced by PDA-AuNPs were utilized for the sensitive detection of E. coli O157:H7, achieving a detection limit of 9.06 × 10¹ CFU/mL, which was 46-fold lower than that of traditional AuNPs-based immunoassay. The proposed immunosensor exhibited the recovery rate between 80.12% and 114.69% in detecting actual samples, indicating its reliability and satisfactory accuracy. This study provides insights into dual-mode signal outputs and the ICA development for food safety applications.

Nanostructured biosensing platforms for the detection of food- and water-borne pathogenic Escherichia coli

Pathogenic bacterial infection is one of the principal causes affecting human health and ecosystems. The accurate identification of bacteria in food and water samples is of significant interests to maintain safety and health for humans. Culture-based tests are practically tedious and may produce false-positive results, while viable but non-culturable microorganisms (NCMs) cannot be retrieved. Thus, it requires fast, reliable, and low-cost detection strategies for on-field analysis and point-of-care (POC) monitoring. The standard detection methods such as nucleic acid analysis (RT-PCR) and enzyme-linked immunosorbent assays (ELISA) are still challenging in POC practice due to their time-consuming (several hours to days) and expensive laboratory operations. The optical (surface plasmon resonance (SPR), fluorescence, and surface-enhanced Raman scattering (SERS)) and electrochemical-based detection of microbes (early stage of infective diseases) have been considered as alternative routes in the emerging world of nanostructured biosensing since they can attain a faster and concurrent screening of several pathogens in real samples. Moreover, optical and electrochemical detection strategies are opening a new route for the ability of detecting pathogens through the integration of cellphones, which is well fitted for POC analysis. This review article covers the current state of sensitive mechanistic approaches for the screening and detection of Escherichia coli O157:H7 (E. coli) pathogens in food and water samples, which can be potentially applied in clinical and environmental monitoring.

NIR II light response-based PDA/AuPt@CuS composites: Simultaneous readout of temperature and pressure sensing strategy for portable detection of pathogenic bacteria

In this study, we developed a simultaneous readout of pressure and temperature dual-signals platform based on the second near-infrared (NIR II) light response-based polydopamine (PDA)-functionalized-AuPt nanoparticles (NPs)@CuS nanosheets (PDA/AuPt@CuS NS) composite. Due to the excellent NIR photothermal performance of PDA/AuPt@CuS NS, it contribute to the decomposition of H₂O₂ and NH₄HCO₃ to generate gases (including O₂, CO₂, and NH₃₎ can be promoted, which can amplify the pressure signals in a sealed container. A sandwich mode is formed between Fe₃O₄ NPs and PDA/AuPt@CuS NS based on the dual-aptamer when target pathogenic bacteria is present. And, it is possible to convert the molecular recognition signals between the dual-aptamers into amplified pressures and temperatures, which can be read out by a portable pressure meter and smartphones simultaneously. It may offer the possibility for quantitative POCT analysis of Pathogenic Bacteria. Moreover, because of the high photothermal efficiency of this method, the developed dual-mode method can achieve that following the detection of bacteria and killing them immediately. As a result, secondary contamination is eliminated and bacterial transmission is avoided. The developed dual-signal sensing platform is also inexpensive, simple to operate and rapidly, indicating that it can be used for food safety analysis, clinical applications, and environmental monitoring.

Joint-detection of Salmonella typhimurium and Escherichia coli O157:H7 by an immersible amplification dip-stick immunoassay

To explore the superiority of multifunctional nanocomposites and realize the joint-detection of foodborne pathogens, an immersible amplification dip-stick immunoassay (DSIA) was exploited for the sensitive detection of Salmonella typhimurium (S. typhi) and Escherichia coli O157:H7 (E. coli O157:H7). Saving for the basic colorimetric performance, the reporter molecule of CoFe₂O₄ (CFO) possesses multivalent elements (Co^2+/3+, Fe^2+/3+) as well as multifunction of superior catalase-like activity and magnetic properties. By dint of the catalytic activity of CFO, a directly immersible amplification can be simply achieved to endure the DSIA with an intensive signal and a dual-visible mode for the determination of S. typhi and E. coli O157:H7. In virtue of the magnetic separation and enrichment capability of the CFO, the DSIA can perform a matrix-interference-free detection and obtain a dynamic detection range of 10²-10⁸ CFU/mL and a low assay limit of 10² CFU/mL. Moreover, the DSIA has reasonable recovery rates for contamination monitoring of two target bacteria in milk and beef samples. Our research provides a persuasive supplement for the application of multifunctional nanocomposites in the ongoing dip-stick immunoassay and an alternative strategy for the efficient detection of foodborne pathogens.

A novel ADA-coated UCNPs@NB sensing platform combined with nucleic acid amplification for rapid detection of Escherichia coli

In this study, we reported a novel sensing platform based on fluorescence quenching composed of alendronic acid (ADA) coated upconversion nanoparticles (UCNPs) and Nile Blue (NB) combined with polymerase chain reaction (PCR) for rapid, sensitive, and specific detection of Escherichia coli (E. coli). As a fluorescence acceptor, NB has a broad absorption band and can quench upconversion fluorescence intensity at 544 nm and 658 nm based on IFE. PCR is a double-stranded DNA (dsDNA) amplification technique with high specificity. The NB-dsDNA complex can be formed by intercalation of NB between base pairs and groove of dsDNA, leading to upconversion fluorescence recovery. The ADA-coated UCNPs@NB sensing platform achieved to detect E. coli in 1.5 h, with a lower limit of detection (33 CFU mL^-1). In addition, the sensitivity of the ADA@UCNPs-NB fluorescence sensor under different PCR cycle numbers was discussed. The results showed that the proposed sensor could effectively shorten the assay time (1.0 h) while maintaining excellent sensitivity. This study demonstrated a rapid and sensitive analytical method for detecting E. coli in chicken, providing a reference for constructing PCR fluorescence sensors.

Colorimetric and handheld pH meter dual-signal readout platform for E. coli detection based on a cascade reaction

A dual-signal readout has been designed detecting platform based on a cascade reaction for Escherichia coli (E. coli) detection by using colorimetric approach and a handheld pH meter. The immunoreaction was conducted using polydopamine@copper ferrite-Ag nanoparticles (PDA@CuFe₂O₄-Ag NP) and a glucose oxidase (GOD)-conjugated graphene oxide-gold nanosheet composite (GOD-GO/Au NS) to synthesize a sandwich complex mode between targets. Together with the formation of immune complexes, the GOD-GO/Au NS can catalyze glucose to produce gluconic acid and hydrogen peroxide (H₂O₂). The gluconic acid produced altered the pH of the detection solution. Since the PDA@CuFe₂O₄-Ag NP have good peroxidase-like activity, they can catalyze the oxidation of TMB to the blue product oxTMB once H₂O₂ is produced in the reaction system, and the absorbance change of oxTMB at 652 nm can be recorded using ultraviolet-visible (UV-Vis) spectroscopy. Interestingly, the PDA@CuFe₂O₄-Ag NP composites can consume the generated H₂O₂, and can create a reaction cycle that promotes glucose oxidation. Under optimal conditions, the proposed dual-channel signal platform is proportional to the logarithm of the E. coli concentration within a range of 10²-10⁷ cfu mL^-1. Additionally, the devised approach was successfully used to detect E. coli at the required levels in real samples. This dual-mode detection method notably enhances the accuracy and diversity of detection, and curbs the false negative and positive rates.

Recent Advances in PLA-Based Antibacterial Food Packaging and Its Applications

In order to reduce environmental pollution and resource waste, food packaging materials should not only have good biodegradable ability but also effective antibacterial properties. Poly(lactic acid) (PLA) is the most commonly used biopolymer for food packaging applications. PLA has good physical properties, mechanical properties, biodegradability, and cell compatibility but does not have inherent antibacterial properties. Therefore, antibacterial packaging materials based on PLA need to add antibacterial agents to the polymer matrix. Natural antibacterial agents are widely used in food packaging materials due to their low toxicity. The high volatility of natural antibacterial agents restricts their application in food packaging materials. Therefore, appropriate processing methods are particularly important. This review introduces PLA-based natural antibacterial food packaging, and the composition and application of natural antibacterial agents are discussed. The properties of natural antibacterial agents, the technology of binding with the matrix, and the effect of inhibiting various bacteria are summarized.