Development of an in-situ signal amplified electrochemical assay for detection of Listeria monocytogenes with label-free strategy

Hybridization-driven synchronous regeneration of biosensing interfaces for Listeria monocytogenes based on recognition of fullerol to single- and double-stranded DNA

A novel sensitive and reusable electrochemical biosensor for Listeria monocytegenes DNA has been constructed based on the recognition of water-soluble hydroxylated fullerene (fullerol) to single- and double-stranded DNA. First, the fullerol was electrodeposited on glassy carbon electrode (GCE), acting as a matrix for non-covalent adsorption of single-stranded probe DNA. Upon hybridization with the target DNA, the double helix structure was formed and desorbed from the electrode surface, driving synchronous regeneration of the biosensing interfaces. The biosensor showed a probe DNA loading density of 144 pmol∙cm-2 with the hybridization efficiency of 72.2%. The biosensor is applicable for the analysis of target DNA in actual milk samples with recoveries between 101.0% and 104.0%. This sensing platform provides a simple method for the construction of sensitive and reusable biosensor to monitor Listeria monocytogenes-related food pollution.

Advances in DNA-based electrochemical biosensors for the detection of foodborne pathogenic bacteria

The detection of foodborne pathogenic bacteria is critical in preventing foodborne diseases. DNA-based electrochemical biosensors, with the merits of high sensitivity and short detection time, provide an effective detecting method for foodborne pathogens, attracting significant interest for the past few years. This review mainly describes the important research progress of DNA-based electrochemical biosensors for the detection of foodborne pathogenic bacteria through four perspectives: representative foodborne pathogens detection using electrochemical approaches, DNA immobilization strategies of aptamers, DNA-based signal amplification strategies used in electrochemical DNA sensors, and functional DNA used in electrochemical DNA sensors. Finally, perspectives and challenges are presented in this field. This review will contribute to DNA-based electrochemical biosensor in enhancing the nucleic acid signal amplification.

Recent progress on DNAzyme-based biosensors for pathogen detection

Pathogens endanger food safety, agricultural productivity, and human health. Those pathogens are spread through direct/indirect contact, airborne transmission and food/waterborne transmission, and some cause severe health consequences. As the population grows and global connections intensify, the transmission of infectious diseases expands. Traditional detection methods for pathogens still have some shortcomings, such as time-consuming procedures and high operational costs. To fulfil the demands for simple and effective detection, numerous biosensors have been developed. DNAzyme, a unique DNA structure with catalytic activity, is gradually being applied in the field of pathogen detection owing to its ease of preparation and use. In this review, we concentrated on the two main types of DNAzyme, hemin/G-quadruplex DNAzyme (HGD) and RNA-cleaving DNAzyme (RCD), explaining their research progress in pathogen detection. Furthermore, we introduced two additional novel DNAzymes, CLICK 17 DNAzyme and Supernova DNAzyme, which showed promising potential in pathogen detection. Finally, we summarize the strengths and weaknesses of these four DNAzymes and offer feasible recommendations for the development of biosensors.

RuZn NPs with electroactivity and oxidase-like property for dual-mode anti-cancer drug monitoring

6-mercaptopurine (6-MP) as the effective anti-cancer drug was used for the treatment of Crohn's disease and acute lymphoblastic leukaemia, but the response to maintenance therapy was variable with individual differences. In order to control the dosage and decrease the side effects of 6-MP, a sensitive and stable assay was urgently needed for 6-MP monitoring. Herein, RuZn NPs with electrochemical oxidation property and oxidase-like activity was proposed for dual-mode 6-MP monitoring. Burr-like RuZn NPs were prepared and explored to not only exhibit an electrochemical oxidation signal at 0.78 V, but also displayed excellent oxidase-like performances. RuZn NPs were utilized for the dual-mode monitoring of 6-MP, attributing to the formation of Ru-SH covalent bonding. The colorimetric method showed good linearity from 10 μM to 5 mM with the limit of detection (LOD) of 300 nM, while the electrochemical method provided a higher sensitivity with the LOD of 37 nM in range from 100 nM to 200 μM. This work provided a new way for the fabrication of dual-functional nanotags with electroactivity and oxidase-like property, and opened a dual-mode approach for the 6-MP detection applications with complementary and satisfactory results.

Review of Detection Limits for Various Techniques for Bacterial Detection in Food Samples

Foodborne illnesses can be infectious and dangerous, and most of them are caused by bacteria. Some common food-related bacteria species exist widely in nature and pose a serious threat to both humans and animals; they can cause poisoning, diseases, disabilities and even death. Rapid, reliable and cost-effective methods for bacterial detection are of paramount importance in food safety and environmental monitoring. Polymerase chain reaction (PCR), lateral flow immunochromatographic assay (LFIA) and electrochemical methods have been widely used in food safety and environmental monitoring. In this paper, the recent developments (2013-2023) covering PCR, LFIA and electrochemical methods for various bacterial species (Salmonella, Listeria, Campylobacter, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli)), considering different food sample types, analytical performances and the reported limit of detection (LOD), are discussed. It was found that the bacteria species and food sample type contributed significantly to the analytical performance and LOD. Detection via LFIA has a higher average LOD (24 CFU/mL) than detection via electrochemical methods (12 CFU/mL) and PCR (6 CFU/mL). Salmonella and E. coli in the Pseudomonadota domain usually have low LODs. LODs are usually lower for detection in fish and eggs. Gold and iron nanoparticles were the most studied in the reported articles for LFIA, and average LODs were 26 CFU/mL and 12 CFU/mL, respectively. The electrochemical method revealed that the average LOD was highest for cyclic voltammetry (CV) at 18 CFU/mL, followed by electrochemical impedance spectroscopy (EIS) at 12 CFU/mL and differential pulse voltammetry (DPV) at 8 CFU/mL. LOD usually decreases when the sample number increases until it remains unchanged. Exponential relations (R2 > 0.95) between LODs of Listeria in milk via LFIA and via the electrochemical method with sample numbers have been obtained. Finally, the review discusses challenges and future perspectives (including the role of nanomaterials/advanced materials) to improve analytical performance for bacterial detection.

Development and application of a visualization method for identification of Panax species with LAMP and a DNAzyme

Panax ginseng and Panax quinquefolium are two valuable Chinese herbal medicines that should not be mixed because they differ in drug properties and efficacy. The traditional identification method is easily affected by subjective factors and cannot effectively distinguish between ginseng products. This study aimed to develop a new chemical analysis method to visually identify P. ginseng and P. quinquefolium. In this method, a large number of sequences containing G-quadruplex were generated by loop-mediated isothermal amplification, and the combination of G-quadruplex and hemin was used to form deoxyribozyme, which catalyzed the color change of H2O2. Artificial simulation of adulteration experiments revealed that this method could detect more than 20% adulterated P. quinquefolium. Compared with the traditional identification methods, this technology was simpler and more efficient, providing a reference for developing rapid visual identification methods and reagents for P. ginseng and P. quinquefolium.

Visual isothermal amplification detection of ASFV based on trimeric G-quadruplex cis-cleavage activity of Cas-12a

African swine fever virus (ASFV) is a kind of DNA virus and can infect both domestic pigs and wild boars with fatality up to 100%. The contaminated meat products mainly led to the worldwide transmission of ASFV. The outbreak of ASF greatly affects the supply stability of meat products as well as the development of the global pig industry. In this study, a visual isothermal amplification detection assay for ASFV based on trimeric G-quadruplex cis-cleavage activity of Cas12a was developed. The introduction of Cas12a could discriminate the specific amplification from the non-specific amplification and improve the sensitivity. The detection limit was as low as 0.23 copies/μL. This assay had good potential in the detection of ASFV and would be helpful for the stability of meat production and supply.

Development of a Novel Phagomagnetic-Assisted Isothermal DNA Amplification System for Endpoint Electrochemical Detection of Listeria monocytogenes

The hitherto implemented Listeria monocytogenes detection techniques are cumbersome or require expensive non-portable instrumentation, hindering their transposition into on-time surveillance systems. The current work proposes a novel integrated system resorting to loop-mediated isothermal amplification (LAMP), assisted by a bacteriophage P100-magnetic platform, coupled to an endpoint electrochemical technique, towards L. monocytogenes expeditious detection. Molybdophosphate-based optimization of the bacterial phagomagnetic separation protocol allowed the determination of the optimal parameters for its execution (pH 7, 25 °C, 32 µg of magnetic particles; 60.6% of specific capture efficiency). The novel LAMP method targeting prfA was highly specific, accomplishing 100% inclusivity (for 61 L. monocytogenes strains) and 100% exclusivity (towards 42 non-target Gram-positive and Gram-negative bacteria). As a proof-of-concept, the developed scheme was successfully validated in pasteurized milk spiked with L. monocytogenes. The phagomagnetic-based approach succeeded in the selective bacterial capture and ensuing lysis, triggering Listeria DNA leakage, which was efficiently LAMP amplified. Methylene blue-based electrochemical detection of LAMP amplicons was accomplished in 20 min with remarkable analytical sensitivity (1 CFU mL^-1). Hence, the combined system presented an outstanding performance and robustness, providing a 2.5 h-swift, portable, cost-efficient detection scheme for decentralized on-field application.

Bioinspired CRISPR-Mediated Cascade Reaction Biosensor for Molecular Detection of HIV Using a Glucose Meter

HIV molecular detection plays a significant role in early diagnosis and antiretroviral therapy for HIV patients. CRISPR technology has recently emerged as a powerful tool for highly sensitive and specific nucleic acid based molecular detection when used in combination with isothermal amplification. However, it remains a challenge to improve the compatibility of such a multienzyme reaction system for simple and sensitive molecular detection. Inspired by the multicompartment structures in a living cell, we present a nanoporous membrane-separated (compartmentalized), artificial, cascade reaction system to improve the compatibility of a CRISPR-mediated multienzyme reaction. We further integrated the multienzyme cascade reaction system with a microfluidic platform and glucose biosensing technology to develop a bioinspired, CRISPR-mediated cascade reaction (CRISPR-MCR) biosensor, enabling HIV molecular detection by a simple glucose meter, analogous to diabetes home testing. We applied the bioinspired CRISPR-MCR biosensor to detect HIV DNA and HIV RNA, achieving a detection sensitivity of 43 copies and 200 copies per test, respectively. Further, we successfully validated the bioinspired biosensor by testing clinical plasma samples of HIV, demonstrating its great application potential for point-of-care testing of HIV virus and other pathogens at home or in resource-limited settings.

Design and 3D printing of an electrochemical sensor for Listeria monocytogenes detection based on loop mediated isothermal amplification

The aim of this work is the design and 3D printing of a new electrochemical sensor for the detection of Listeria monocytogenes based on loop mediated isothermal amplification (LAMP). The food related diseases involve a serious health issue all over the world. Listeria monocytogenes is one of the major problems of contaminated food, this pathogen causes a disease called listeriosis with a high rate of hospitalization and mortality. Having a fast, sensitive and specific detection method for food quality control is a must in the food industry to avoid the presence of this pathogen in the food chain (raw materials, facilities and products). A point-of-care biosensor based in LAMP and electrochemical detection is one of the best options to detect the bacteria on site and in a very short period of time. With the numerical analysis of different geometries and flow rates during sample injection in order to avoid bubbles, an optimized design of the microfluidic biosensor chamber was selected for 3D-printing and experimental analysis. For the electrochemical detection, a novel custom gold concentric-3-electrode consisting in a working electrode, reference electrode and a counter electrode was designed and placed in the bottom of the chamber. The LAMP reaction was optimized specifically for a primers set with a limit of detection of 1.25 pg of genomic DNA per reaction and 100% specific for detecting all 12 Listeria monocytogenes serotypes and no other Listeria species or food-related bacteria. The methylene blue redox-active molecule was tested as the electrochemical transducer and shown to be compatible with the LAMP reaction and very clearly distinguished negative from positive food samples when the reaction is measured at the end-point inside the biosensor.

Optical Methods for Label-Free Detection of Bacteria

Pathogenic bacteria are the leading causes of food-borne and water-borne infections, and one of the most serious public threats. Traditional bacterial detection techniques, including plate culture, polymerase chain reaction, and enzyme-linked immunosorbent assay are time-consuming, while hindering precise therapy initiation. Thus, rapid detection of bacteria is of vital clinical importance in reducing the misuse of antibiotics. Among the most recently developed methods, the label-free optical approach is one of the most promising methods that is able to address this challenge due to its rapidity, simplicity, and relatively low-cost. This paper reviews optical methods such as surface-enhanced Raman scattering spectroscopy, surface plasmon resonance, and dark-field microscopic imaging techniques for the rapid detection of pathogenic bacteria in a label-free manner. The advantages and disadvantages of these label-free technologies for bacterial detection are summarized in order to promote their application for rapid bacterial detection in source-limited environments and for drug resistance assessments.

Portable sensor based on magnetic separation and enzyme-mediated immune nanomaterials for point-of-care testing of Listeria monocytogenes in food

Listeria monocytogenes (L. monocytogenes), a typical foodborne pathogen, poses a serious threat to public health safety. This stimulates to develop a point-of-care testing (POCT) method to achieve rapid, sensitive detection of L. monocytogenes. In this study, polyethylene glycol (PEG) mediated ampicillin functionalized magnetic beads (Amp-PEG-MBs) was prepared successfully and it achieved high efficiency (>90%) and rapid (5 min) capture for L. monocytogenes at room temperature. The innovative combination of antibody (Ab), glucose oxidase (GOD) and graphene oxide (GO) prepared Ab@GO@GOD for the specific recognition of L. monocytogenes. Finally, Amp-PEG-MBs and Ab@GO@GOD were successfully assembled into Amp-PEG-MBs@L. monocytogenes-Ab@GO@GOD sandwich structure which could catalyze the glucose, and the final detection results were recorded by a blood glucose meter (BGM). Magnetic separation (MS) combined with enzyme-catalyzed sensor (MS-Ab@GO@GOD-BGM) was successfully established to achieve the detection of L. monocytogenes in artificially contaminated juice within 66 min with the limit of detection was 10¹ CFU/mL. This sensor has potential for other pathogens detection by modifying specific antibodies.

Novel integrating polymethylene blue nanoparticles with dumbbell hybridization chain reaction for electrochemical detection of pathogenic bacteria

Pathogenic bacteria infections pose a major threat to human health which can be found in contaminated food and infected humans. Herein, an electrochemical sensor was developed for pathogenic bacteria assay using a dual amplification strategy of polymethylene blue nanoparticles (pMB NPs) and dumbbell hybridization chain reaction (DHCR). The strong binding ability of aptamer to targets endowed outstanding performance in identifying Staphylococcus aureus (S. aureus) among other typical bacteria. The released T strands were hybridized with capture DNA on electrode surface which triggered DHCR in the presence of two dumbbell-shaped helper DNA, leading to the formation of extended and tight dsDNA polymers. In combination with pMB NPs (redox indicators), S. aureus was quantitatively detected in a range of 10-10⁸ CFU/mL and the detection limit reached 1 CFU/mL. Moreover, this sensor was successfully applied for S. aureus detection in human serum and foods, demonstrating the reliability in practical applications.

Towards Development of Molecularly Imprinted Electrochemical Sensors for Food and Drug Safety: Progress and Trends

Due to their advantages of good flexibility, low cost, simple operations, and small equipment size, electrochemical sensors have been commonly employed in food safety. However, when they are applied to detect various food or drug samples, their stability and specificity can be greatly influenced by the complex matrix. By combining electrochemical sensors with molecular imprinting techniques (MIT), they will be endowed with new functions of specific recognition and separation, which make them powerful tools in analytical fields. MIT-based electrochemical sensors (MIECs) require preparing or modifying molecularly imprinted polymers (MIPs) on the electrode surface. In this review, we explored different MIECs regarding the design, working principle and functions. Additionally, the applications of MIECs in food and drug safety were discussed, as well as the challenges and prospects for developing new electrochemical methods. The strengths and weaknesses of MIECs including low stability and electrode fouling are discussed to indicate the research direction for future electrochemical sensors.

G-quadruplex based biosensors for the detection of food contaminants

G-quadruplex (G4) is a very interesting DNA structure, commonly associated with cancer and its treatment. With flexible binding ability, G4 has been extended as a significant component in biosensors. On account of its simple operation, high sensitivity and low cost, G4-based biosensors have attracted considerable interest for the detection of food contaminants. In this review, research published in recent 5 years is collated from a principle perspective, that is target recognition and signal transduction. Contaminants with G4 binding capacity are illustrated, emerging G4-based biosensors including colorimetric, electrochemical and fluorescent sensors are also elaborated. The current review indicates that G4 has provided an efficient and effective solution for the rapid detection of food contaminants. A distinctive feature of G4 as recognition unit is the simple composition, but the selectivity is still unsatisfactory. As signal reporter, G4/hemin DNAzyme has not only achieved amplified signals, but also enabled visualized detection, which offers great potential for on-site measurement. With improved selectivity and visualized signal, the combination of aptamer and G4 seems to be an ideal strategy. This promising combination should be developed for the real-time monitor of multiple contaminants in food matrix.

Development and Clinical Validation of a Potential Penside Colorimetric Loop-Mediated Isothermal Amplification Assay of Porcine Circovirus Type 3

Porcine circovirus type 3 (PCV3), a novel circovirus, imposes great burdens on the global pig industry. The penside tests for detecting PCV3 are critical for assessing the epidemiological status and working out disease prevention and control programs due to the unavailability of a commercial vaccine. A one-step molecular assay based on visual loop-mediated isothermal amplification (vLAMP) was developed for simple and rapid detection of PCV3. We compared its sensitivity and specificity with TaqMan quantitative real-time polymerase chain reaction (qPCR) and applied the developed assay in the epidemiological study of (n = 407) pooled swine sera collected from almost the entire mainland China during the years 2017–2018. We also explored the feasibility of the vLAMP assay for detecting raw samples without a prior DNA isolation step to expand its application capability. Results showed that the vLAMP assay could reliably detect the PCV3 cap gene with a detection limit of 10 DNA copies equal to that of the Taqman qPCR assay. In the epidemiological study, the PCV3 positive detection rate for 407 swine pooled sera detected by the vLAMP assay was 37.35% (152/407), whereas it was 39.01% (159/407) for Taqman qPCR. For the detection method without genome extraction, the results kept satisfactory specificity (100%) but displayed lower sensitivity (100% for CT < 32), indicating the direct detection is not sensitive enough to discriminate the samples with low viral loads. The one-step vLAMP is a convenient, rapid, and cost-effective diagnostic for penside detection and will enable the epidemiological surveillance of PCV3, which has widely spread in mainland China.

A Novel Photoelectrochemical Aptamer Sensor Based on CdTe Quantum Dots Enhancement and Exonuclease I-Assisted Signal Amplification for Listeria monocytogenes Detection

To achieve the rapid detection of Listeria monocytogenes, this study used aptamers for the original identification and built a photoelectrochemical aptamer sensor using exonuclease-assisted amplification. Tungsten trioxide (WO3) was used as a photosensitive material, was modified with gold nanoparticles to immobilize complementary DNA, and amplified the signal by means of the sensitization effect of CdTe quantum dots and the shearing effect of Exonuclease I (Exo I) to achieve high-sensitivity detection. This strategy had a detection limit of 45 CFU/mL in the concentration range of 1.3 × 101-1.3 × 107 CFU/mL. The construction strategy provides a new way to detect Listeria monocytogenes.