Recent Advancements in Nanobioassays and Nanobiosensors for Foodborne Pathogenic Bacteria Detection

Gold Nanoparticle-Based Plasmonic Detection of Escherichia coli, Salmonella enterica, Campylobacter jejuni, and Listeria monocytogenes from Bovine Fecal Samples

Current diagnostic methods for detecting foodborne pathogens are time-consuming, require sophisticated equipment, and have a low specificity and sensitivity. Magnetic nanoparticles (MNPs) and plasmonic/colorimetric biosensors like gold nanoparticles (GNPs) are cost-effective, high-throughput, precise, and rapid. This study aimed to validate the use of MNPs and GNPs for the early detection of Escherichia coli O157:H7, Salmonella enterica spp., Campylobacter jejuni, and Listeria monocytogenes in bovine fecal samples. The capture efficiency (CE) of the MNPs was determined by using Salmonella Typhimurium (ATCC_13311) adjusted at an original concentration of 1.5 × 108 CFU/mL. One (1) mL of this bacterial suspension was spiked into bovine fecal suspension (1 g of fecal sample in 9 mL PBS) and serially diluted ten-fold. DNA was extracted from Salmonella Typhimurium to determine the analytical specificity and sensitivity/LOD of the GNPs. The results showed that the CE of the MNPs ranged from 99% to 100% and could capture as little as 1 CFU/mL. The LOD of the GNPs biosensor was 2.9 µg/µL. The GNPs biosensor was also tested on DNA from 38 naturally obtained bovine fecal samples. Out of the 38 fecal samples tested, 81.6% (31/38) were positive for Salmonella enterica spp., 65.8% (25/38) for C. jejuni, 55.3% (21/38) for L. monocytogenes, and 50% (19/38) for E. coli O157:H7. We have demonstrated that MNP and GNP biosensors can detect pathogens or their DNA at low concentrations. Ensuring food safety throughout the supply chain is paramount, given that these pathogens may be present in cattle feces and contaminate beef during slaughter.

Lemon essential oil nanoemulsions: Potential natural inhibitors against Escherichia coli

Lemon essential oil (LEO) is a common natural antibacterial substance, and encapsulating LEO into nanoemulsions (NEs) can improve their stability and broaden its application. Our study aimed to investigate the bacterial inhibitory effect of LEO-NEs against Escherichia coli (E. coli). Results showed that the minimum inhibitory concentration (MIC) of LEO-NEs was 6.25 mg/mL, and the time-kill curve showed that E. coli were significantly killed by LEO-NEs after 5 h of treatment at 1MIC. Flow-cytometry analysis showed that LEO-NEs adversely affected the cell-membrane depolarisation, cell-membrane integrity, and efflux pump function of E. coli. Confocal laser scanning microscopy demonstrated that 8MIC of LEO-NEs induced changes in the cell-membrane permeability and cell-wall integrity of E. coli. Proteomic results suggested that the mode of action LEO-NEs against E. coli was to enhance bacterial chemotaxis and significantly inhibit ribosomal assembly. They may also affect butyric acid, ascorbic acid and aldehyde metabolism, and sulphur-relay system pathways. In conclusion, LEO-NEs had potential application as a natural antibacterial agent for the control of E. coli in the food industry.

Magnetic Particle Spectroscopy for Point-of-Care: A Review on Recent Advances

Since its first report in 2006, magnetic particle spectroscopy (MPS)-based biosensors have flourished over the past decade. Currently, MPS are used for a wide range of applications, such as disease diagnosis, foodborne pathogen detection, etc. In this work, different MPS platforms, such as dual-frequency and mono-frequency driving field designs, were reviewed. MPS combined with multi-functional magnetic nanoparticles (MNPs) have been extensively reported as a versatile platform for the detection of a long list of biomarkers. The surface-functionalized MNPs serve as nanoprobes that specifically bind and label target analytes from liquid samples. Herein, an analysis of the theories and mechanisms that underlie different MPS platforms, which enable the implementation of bioassays based on either volume or surface, was carried out. Furthermore, this review draws attention to some significant MPS platform applications in the biomedical and biological fields. In recent years, different kinds of MPS point-of-care (POC) devices have been reported independently by several groups in the world. Due to the high detection sensitivity, simple assay procedures and low cost per run, the MPS POC devices are expected to become more widespread in the future. In addition, the growth of telemedicine and remote monitoring has created a greater demand for POC devices, as patients are able to receive health assessments and obtain results from the comfort of their own homes. At the end of this review, we comment on the opportunities and challenges for POC devices as well as MPS devices regarding the intensely growing demand for rapid, affordable, high-sensitivity and user-friendly devices.

Characterisation and Classification of Foodborne Bacteria Using Reflectance FTIR Microscopic Imaging

This work investigates the application of reflectance Fourier transform infrared (FTIR) microscopic imaging for rapid, and non-invasive detection and classification between Bacillus subtilis and Escherichia coli cell suspensions dried onto metallic substrates (stainless steel (STS) and aluminium (Al) slides) in the optical density (OD) concentration range of 0.001 to 10. Results showed that reflectance FTIR of samples with OD lower than 0.1 did not present an acceptable spectral signal to enable classification. Two modelling strategies were devised to evaluate model performance, transferability and consistency among concentration levels. Modelling strategy 1 involves training the model with half of the sample set, consisting of all concentrations, and applying it to the remaining half. Using this approach, for the STS substrate, the best model was achieved using support vector machine (SVM) classification, providing an accuracy of 96% and Matthews correlation coefficient (MCC) of 0.93 for the independent test set. For the Al substrate, the best SVM model produced an accuracy and MCC of 91% and 0.82, respectively. Furthermore, the aforementioned best model built from one substrate was transferred to predict the bacterial samples deposited on the other substrate. Results revealed an acceptable predictive ability when transferring the STS model to samples on Al (accuracy = 82%). However, the Al model could not be adapted to bacterial samples deposited on STS (accuracy = 57%). For modelling strategy 2, models were developed using one concentration level and tested on the other concentrations for each substrate. Results proved that models built from samples with moderate (1 OD) concentration can be adapted to other concentrations with good model generalization. Prediction maps revealed the heterogeneous distribution of biomolecules due to the coffee ring effect. This work demonstrated the feasibility of applying FTIR to characterise spectroscopic fingerprints of dry bacterial cells on substrates of relevance for food processing.

An Enhanced Lateral Flow Assay Based on Aptamer-Magnetic Separation and Multifold AuNPs for Ultrasensitive Detection of Salmonella Typhimurium in Milk

In this paper, a novel and ultrasensitive lateral flow assay (LFA) based on aptamer-magnetic separation, and multifold Au nanoparticles (AuNPs) was developed for visual detecting Salmonella enterica ser. Typhimurium (S. Typhimurium). The method realized magnetic enrichment and signal transduction via magnetic separation and achieved signal amplification through hybridizing AuNPs-capture probes and AuNPs-amplification probes to form multifold AuNPs. Two different thiolated single-strand DNA (ssDNA) on the AuNPs-capture probe played different roles. One was combined with the AuNPs-amplification probe on the conjugate pad to achieve enhanced signals. The other was connected to transduction ssDNA1 released by aptamer-magnetic capture of S. Typhimurium, and captured by the T-line, forming a positive signal. This method had an excellent linear relationship ranging from 8.6 × 102 CFU/mL to 8.6 × 107 CFU/mL with the limit of detection (LOD) as low as 8.6 × 100 CFU/mL in pure culture. In actual samples, the visual LOD was 4.1 × 102 CFU/mL, which did not carry out nucleic acid amplification and pre-enrichment, increasing three orders of magnitudes than unenhanced assays with single-dose AuNPs and no magnetic separation. Furthermore, the system showed high specificity, having no reaction with other nontarget strains. This visual signal amplificated system would be a potential platform for ultrasensitive monitoring S. Typhimurium in milk samples.

Label-Free Immunoassay for Multiplex Detections of Foodborne Bacteria in Chicken Carcass Rinse with Surface Plasmon Resonance Imaging

The frequent outbreaks of foodborne pathogens have stimulated the demand of biosensors capable of rapid and multiplex detection of contaminated food. In this study, surface plasmon resonance imaging (SPRi) was used in simultaneous label-free detection of multiple foodborne pathogens, mainly Salmonella spp. and Shiga-toxin producing Escherichia coli (STEC), in commercial chicken carcass rinse. The antibodies were immobilized on the same SPRi sensor chip as a label-free immunoassay. Their immobilization concentrations were optimized to be ranging from 0.25 to 1.0 mg/mL, and independent of pH values. This label-free immunoassay achieved 10⁶ colony-forming unit (CFU)/mL limit of detection for Salmonella, which was further improved to 1.0 CFU/mL with overnight bacteria enrichment. The injected samples with different bacteria, Salmonella Enteritidis, STEC, and Listeria monocytogenes, have been identified by the same biochip. Moreover, the SPRi signals revealed complex interference effects among coexisting bacteria species in heterogeneous bacteria solutions. This SPRi-based immunoassay demonstrates the great potential in high-throughput screening of multiple pathogenic bacteria coexisting in chicken carcass rinse. The reliability of antibody immobilization and cross-reactions of different antibodies on the same biochip are the major challenges of practical application of SPRi.

Use of IHF-QD Microscopic Analysis for the Detection of Food Allergenic Components: Peanuts and Wheat Protein

The aim of the study was to analytically evaluate quantum dots in immunohistofluorescence (IHF-QD) microscopic imaging as detectors of food allergens—peanut and wheat. The experiment was designed as two in silico experiments or simulations: (a) models of pastry samples were prepared with the addition of allergenic components (peanut and wheat protein components) and without the addition of allergenic components, and (b) positive and negative commercial samples underwent food allergen detection. The samples from both simulations were tested by the ELISA and IHF-QD microscopic methods. The primary antibodies (secondary antibodies to a rabbit Fc fragment with labeled CdSe/ZnS QD) were labelled at 525, 585, and 655 nm emissions. The use of quantum dots (QDs) has expanded to many science areas and they are also finding use in food allergen detection, as shown in the study. The study indicated that differences between the ELISA and IHF-QD microscopic methods were not observable among experimentally produced pastry samples with and without allergenic components, although differences were observed among commercial samples. The important value of the study is certainly the differences found in the application of different QD conjugates (525, 585, and 655). The highest contrast was found in the application of 585 QD conjugates that can serve for the possible quantification of present food allergens—peanuts and wheat. The study clearly emphasized that QD can be used for the qualitative detection of food allergens and can represent a reliable analytical method for food allergen detection in different food matrixes.

Dual-aptamers labeled polydopamine-polyethyleneimine copolymer dots assisted engineering a fluorescence biosensor for sensitive detection of Pseudomonas aeruginosa in food samples

To ensure the food security and protect public health, development of rapid and reliable approaches to detecting foodborne pathogens is of great significance. In this study, polydopamine-polyethyleneimine (PDA-PEI) copolymer dots are prepared via the self-polymerization of dopamine and cross-linking with branched PEI at room temperature. The PDA-PEI copolymer dots are very stable against photobleaching, extreme pH, as well as high ionic strength. They are used as a fluorescent probe to fabricate a biosensor for rapid and sensitive detection and quantification of Pseudomonas aeruginosa (P. aeruginosa). In the biosensor, dual-aptamers of P. aeruginosa are used to label PDA-PEI copolymer dots. Compared to single aptamer labeled PDA-PEI dots, the dual-aptamers labeled PDA-PEI dots endow the biosensor with enhanced sensitivity for target pathogen. The fluorescence biosensor demonstrates a wide linear response to P. aeruginosa in the concentration range of 10¹-10⁷ cfu mL^-1 with acceptable selectivity. The limit of detection is calculated to be 1 cfu mL^-1. The whole detection process can be finished in 1.5 h. The feasibility of the fabricated biosensor is verified by successful determination of P. aeruginosa in skim milk, orange juice, and popsicle samples. The biosensor provides an alternative and attractive platform for rapid and sensitive detection of bacteria in food products.

A comprehensive perspective of food nanomaterials

Nanotechnology is a rapidly developing toolbox that provides solutions to numerous challenges in the food industry and meet public demands for healthier and safer food products. The diversity of nanostructures and their vast, tunable functionality drives their inclusion in food products and packaging materials to improve their nutritional quality through bioactive fortification and probiotics encapsulation, enhance their safety due to their antimicrobial and sensing capabilities and confer novel sensorial properties. In this food nanotechnology state-of-the-art communication, matrix materials with particular focus on food-grade components, existing and novel production techniques, and current and potential applications in the fields of food quality, safety and preservation, nutrient bioaccessibility and digestibility will be detailed. Additionally, a thorough analysis of potential strategies to assess the safety of these novel nanostructures is presented.

Developments in Rapid Detection Methods for the Detection of Foodborne Campylobacter in the United States

The accurate and rapid detection of Campylobacter spp. is critical for optimal surveillance throughout poultry processing in the United States. The further development of highly specific and sensitive assays to detect Campylobacter in poultry matrices has tremendous utility and potential for aiding the reduction of foodborne illness. The introduction and development of molecular methods such as polymerase chain reaction (PCR) have enhanced the diagnostic capabilities of the food industry to identify the presence of foodborne pathogens throughout poultry production. Further innovations in various methodologies, such as immune-based typing and detection as well as high throughput analyses, will provide important epidemiological data such as the identification of unique or region-specific Campylobacter. Comparable to traditional microbiology and enrichment techniques, molecular techniques/methods have the potential to have improved sensitivity and specificity, as well as speed of data acquisition. This review will focus on the development and application of rapid molecular methods for identifying and quantifying Campylobacter in U.S. poultry and the emergence of novel methods that are faster and more precise than traditional microbiological techniques.

Nanotechnology: Review of concepts and potential application of sensing platforms in food safety

In recent years a number of new nanotechnology based platforms have been developed for detection of wide variety of targets including infectious agents, protein biomarkers, nucleic acids, drugs, and cancer cells. Nanomaterials such as magnetic nanoparticles, quantum dots, carbon nanotubes, nanowires, and nanosensors like giant magnetoresistance (GMR) sensors are used to quantitatively detect biomolecules with, experimentally, relatively good accuracy. There has been a growing interest in the use of magnetic fields in biosensing applications. Because biological samples have no ferromagnetic property and therefore there is no interference with complex sample matrix, detection of infectious agents from minimally processed samples is possible. Here, we provide a brief overview of the recent emergence of nanotechnology-based techniques for the detection and monitoring of foodborne diseases. In addition, the potential applications and future perspectives of nanotechnology on food safety are discussed. Ultimately, the review is expected to stimulate and provide directions to the development and application of nanotechnology-based tests for the early detection, and eventual control of foodborne diseases.