Simultaneous detection of three zoonotic pathogens based on phage display peptide and multicolor quantum dots

Quantum dots (QDs) attached magnetic beads (MBs) for on-chip efficient capture and detection of bacteria in ready-to-eat (RTE) foods

In this study, we established a versatile and simple magnetic-assisted microfluidic method for fast bacterial detection. Quantum dots (QDs) were loaded onto magnetic beads (MBs) to construct performance enhanced on-chip capture of bacteria. Escherichia coli (E. coli), as a model bacterium was studied. CdSe QDs were deposited onto the surface of Fe3O4 MBs through layer-by-layer self-assembly to enhance the loading of antibodies (Abs). MBs functionalized with anti-E. coli antibody molecules in a micropillar-based microfluidic chip were utilized to capture E. coli, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) was used for characterization of captured bacteria. This method was found capable of specifically isolating E. coli within the range of 1.0 to 1.0 × 109 CFU/mL, having a detection limit (LOD) of 10 CFU/mL. The average similarity score among mass spectra for the bacterial capture obtained in independent experiments is calculated as 0.97 ± 0.01 (n = 3), which shows this work's excellent reproducibility for bacterial capture. Bacterial growth on ready-to-eat (RTE) foods during its time of storage was successfully monitored. The present protocol has promising potential for microbial control and pathogen detection in the food industry.

QD-based fluorescent nanosensors: Production methods, optoelectronic properties, and recent food applications

Food quality and safety are crucial public health concerns with global significance. In recent years, a series of fluorescence detection technologies have been widely used in the detection/monitoring of food quality and safety. Due to the advantages of wide detection range, high sensitivity, convenient and fast detection, and strong specificity, quantum dot (QD)-based fluorescent nanosensors have emerged as preferred candidates for food quality and safety analysis. In this comprehensive review, several common types of QD production methods are introduced, including colloidal synthesis, self-assembly, plasma synthesis, viral assembly, electrochemical assembly, and heavy-metal-free synthesis. The optoelectronic properties of QDs are described in detail at the electronic level, and the effect of food matrices on QDs was summarized. Recent advancements in the field of QD-based fluorescent nanosensors for trace level detection and monitoring of volatile components, heavy metal ions, food additives, pesticide residues, veterinary-drug residues, other chemical components, mycotoxins, foodborne pathogens, humidity, and temperature are also thoroughly summarized. Moreover, we discuss the limitations of the QD-based fluorescent nanosensors and present the challenges and future prospects for developing QD-based fluorescent nanosensors. As shown by numerous publications in the field, QD sensors have the advantages of strong anti-interference ability, convenient and quick operation, good linear response, and wide detection range. However, the reported assays are laboratory-focused and have not been industrialized and commercialized. Promising research needs to examine the potential applications of bionanotechnology in QD-based fluorescent nanosensors, and focus on the development of smart packaging films, labeled test strips, and portable kits-based sensors.

Understanding the Role of M13 Bacteriophage Thin Films on a Metallic Nanostructure through a Standard and Dynamic Model

The dynamic and surface manipulation of the M13 bacteriophage via the meeting application demands the creation of a pathway to design efficient applications with high selectivity and responsivity rates. Here, we report the role of the M13 bacteriophage thin film layer that is deposited on an optical nanostructure involving gold nanoparticles/SiO₂/Si, as well as its influence on optical and geometrical properties. The thickness of the M13 bacteriophage layer was controlled by varying either the concentration or humidity exposure levels, and optical studies were conducted. We designed a standard and dynamic model based upon three-dimensional finite-difference time-domain (3D FDTD) simulations that distinguished the respective necessity of each model under variable conditions. As seen in the experiments, the origin of respective peak wavelength positions was addressed in detail with the help of simulations. The importance of the dynamic model was noted when humidity-based experiments were conducted. Upon introducing varied humidity levels, the dynamic model predicted changes in plasmonic properties as a function of changes in NP positioning, gap size, and effective index (this approach agreed with the experiments and simulated results). We believe that this work will provide fundamental insight into understanding and interpreting the geometrical and optical properties of the nanostructures that involve the M13 bacteriophage. By combining such significant plasmonic properties with the numerous benefits of M13 bacteriophage (like low-cost fabrication, multi-wavelength optical characteristics devised from a single structure, reproducibility, reversible characteristics, and surface modification to suit application requirements), it is possible to develop highly efficient integrated plasmonic biomaterial-based sensor nanostructures.

Europium Nanoparticle-Based Lateral Flow Strip Biosensors Combined with Recombinase Polymerase Amplification for Simultaneous Detection of Five Zoonotic Foodborne Pathogens

The five recognized zoonotic foodborne pathogens, namely, Listeria monocytogenes, Staphylococcus aureus, Streptococcus suis, Salmonella enterica and Escherichia coli O157:H7, pose a major threat to global health and social-economic development. These pathogenic bacteria can cause human and animal diseases through foodborne transmission and environmental contamination. Rapid and sensitive detection for pathogens is particularly important for the effective prevention of zoonotic infections. In this study, rapid and visual europium nanoparticle (EuNP)-based lateral flow strip biosensors (LFSBs) combined with recombinase polymerase amplification (RPA) were developed for the simultaneous quantitative detection of five foodborne pathogenic bacteria. Multiple T lines were designed in a single test strip for increasing the detection throughput. After optimizing the key parameters, the single-tube amplified reaction was completed within 15 min at 37 °C. The fluorescent strip reader recorded the intensity signals from the lateral flow strip and converted the data into a T/C value for quantification measurement. The sensitivity of the quintuple RPA-EuNP-LFSBs reached a level of 10¹ CFU/mL. It also exhibited good specificity and there was no cross-reaction with 20 non-target pathogens. In artificial contamination experiments, the recovery rate of the quintuple RPA-EuNP-LFSBs was 90.6-101.6%, and the results were consistent with those of the culture method. In summary, the ultrasensitive bacterial LFSBs described in this study have the potential for widespread application in resource-poor areas. The study also provides insights in respect to multiple detection in the field.

Recent Advances on Peptide-Based Biosensors and Electronic Noses for Foodborne Pathogen Detection

Foodborne pathogens present a serious issue around the world due to the remarkably high number of illnesses they cause every year. In an effort to narrow the gap between monitoring needs and currently implemented classical detection methodologies, the last decades have seen an increased development of highly accurate and reliable biosensors. Peptides as recognition biomolecules have been explored to develop biosensors that combine simple sample preparation and enhanced detection of bacterial pathogens in food. This review first focuses on the selection strategies for the design and screening of sensitive peptide bioreceptors, such as the isolation of natural antimicrobial peptides (AMPs) from living organisms, the screening of peptides by phage display and the use of in silico tools. Subsequently, an overview on the state-of-the-art techniques in the development of peptide-based biosensors for foodborne pathogen detection based on various transduction systems was given. Additionally, limitations in classical detection strategies have led to the development of innovative approaches for food monitoring, such as electronic noses, as promising alternatives. The use of peptide receptors in electronic noses is a growing field and the recent advances of such systems for foodborne pathogen detection are presented. All these biosensors and electronic noses are promising alternatives for the pathogen detection with high sensitivity, low cost and rapid response, and some of them are potential portable devices for on-site analyses.

Fluorescent aptasensor for detection of live foodborne pathogens based on multicolor perovskite-quantum-dot-encoded DNA probes and dual-stirring-bar-assisted signal amplification

In this study, a fluorescent (FL) aptasensor was developed for on-site detection of live Salmonella typhimurium (S.T.) and Vibrio parahaemolyticus (V.P.). Complementary DNA (cDNA) of aptamer (Apt)-functionalized multicolor polyhedral oligomeric silsesquioxane-perovskite quantum dots (cDNA-POSS-PQDs) were used as encoded probes and combined with dual-stirring-bar-assisted signal amplification for pathogen quantification. In this system, bar 1 was labeled with the S.T. and V.P. Apts, and then bar 2 was functionalized with cDNA-POSS-PQDs. When S.T. and V.P. were introduced, pathogen-Apt complexes would form and be released into the supernatant from bar 1. Under agitation, the two complexes reached bar 2 and subsequently reacted with cDNA-POSS-PQDs, which were immobilized on MXene. Then, the encoded probes would be detached from bar 2 to generate FL signals in the supernatant. Notably, the pathogens can resume their free state and initiate next cycle. They swim between the two bars, and the FL signals can be gradually enhanced to maximum after several cycles. The FL signals from released encoded probes can be used to detect the analytes. In particular, live pathogens can be distinguished from dead ones by using an assay. The detection limits and linear range for S.T. and V.P. were 30 and 10 CFU/mL and 10²-10⁶ CFU/mL, respectively. Therefore, this assay has broad application potential for simultaneous on-site detection of various live pathogenic bacteria in water.

When smartphone enters food safety: A review in on-site analysis for foodborne pathogens using smartphone-assisted biosensors

Pathogens are one of the supreme threats for the public health around the world in food supply chain. The on-site monitoring is an emerging trend for screening pathogens during the food processing and preserving. Traditional analytical tools have been unable to satisfy the current demands. Smartphones have enormous potentials for achieving on-site detection of foodborne pathogens, with intrinsic advantages such as small size, high accessibility, fast processing speed, and powerful imaging capacity. This review aims to synthesize the current advances in smartphone-assisted biosensors (SABs) for sensing foodborne pathogens, and briefly put forward the problem that consist in the research. We present the role of nanotechnology and recognition modes targeting foodborne pathogens in SABs, and discuss the signal conversion platforms coupling with smartphone. The challenges and perspectives in SABs are also proposed. The smartphone analytics area is moving forward, and it much be subject to careful quality standards and validation.

Multiple fluorescence immunoassay for the simultaneous detection of Zearalenone and Ochratoxin A

A sensitive and accurate multiple fluorescence immunoassay for the simultaneous quantitative detection of Zearalenone (ZEN) and Ochratoxin A (OTA) in single spot based on multicolor quantum dots (QDs) labeling was developed for the first time. Two kinds of ZnCdSe/ZnS (core/shell) QDs with maximum emission wavelengths at 520 nm (green) and 610 nm (orange-red) were selected as marking materials, respectively. The anti-ZEN-mAb-QDs and anti-OTA-mAb-QDs were designed as the immune fluorescent probes. Fluorescence was measured at the same excitation wavelength and two different emission wavelengths to determine each target. The procedure for QDs-based multiple fluorescence labeled immunosorbent assay (M-FLISA) was developed. The 50% inhibition concentrations (IC₅₀) of ZEN and OTA were 0.034 and 1.175 ng/mL. Moreover, the limits of detection (LOD) for the simultaneous determination were 0.0239 and 2.339 ng/g for ZEN and OTA in maize, respectively. In addition, the recoveries ranged from 93.15 to 101.90% for ZEN and from 95.29 to 102.43% for OTA, with the coefficient variation (CV) of 2.70-8.86% and 3.51-6.22% respectively. There was good consistency between the M-FLISA and high performance liquid chromatography (HPLC) results, which confirmed that the M-FLISA was suitable for the simultaneous quantitative detection of various mycotoxins.

Biophotonic probes for bio-detection and imaging

The rapid development of biophotonics and biomedical sciences makes a high demand on photonic structures to be interfaced with biological systems that are capable of manipulating light at small scales for sensitive detection of biological signals and precise imaging of cellular structures. However, conventional photonic structures based on artificial materials (either inorganic or toxic organic) inevitably show incompatibility and invasiveness when interfacing with biological systems. The design of biophotonic probes from the abundant natural materials, particularly biological entities such as virus, cells and tissues, with the capability of multifunctional light manipulation at target sites greatly increases the biocompatibility and minimizes the invasiveness to biological microenvironment. In this review, advances in biophotonic probes for bio-detection and imaging are reviewed. We emphatically and systematically describe biological entities-based photonic probes that offer appropriate optical properties, biocompatibility, and biodegradability with different optical functions from light generation, to light transportation and light modulation. Three representative biophotonic probes, i.e., biological lasers, cell-based biophotonic waveguides and bio-microlenses, are reviewed with applications for bio-detection and imaging. Finally, perspectives on future opportunities and potential improvements of biophotonic probes are also provided.

A multicolor sensing system for simultaneous detection of four foodborne pathogenic bacteria based on Fe3O4/MnO2 nanocomposites and the etching of gold nanorods

Food safety problems attributed to foodborne pathogenic bacteria seriously endanger human health and cause substantial economic losses. Novel assays for rapid and sensitive identification of foodborne pathogenic bacteria are highly desired. In this study, a multicolor sensing system has been established for simultaneous determination of four foodborne bacteria by exploiting oxidase mimicking activity of aptamer-functionalized manganese dioxide-coated ferriferrous oxide (apt-Fe₃O₄/MnO₂) nanocomposites and oxTMB etching of gold nanorods (AuNRs). Apt-Fe₃O₄/MnO₂ nanocomposites were used as capture probes to recognize and capture specific bacteria. The captured bacteria blocked the catalytic sites of the magnetic conjugate, which inhibited the catalyzation of oxTMB and further reduced the etching of AuNRs. Consequently, the longitudinal shift of AuNRs decreased linearly with the increase of the concentration of bacteria ranging from 10 to 10⁶ CFU mL^-1. Instrumental detection limits for S. aureus, L. monocytogenes, E. coli O157:H7 and V. parahaemolyticus reached down to 1.3 CFU mL^-1, 1.2 CFU mL^-1, 1.3 CFU mL^-1 and 1.4 CFU mL^-1, respectively. And their visual detection limit was as low as 10 CFU mL^-1. The whole detection process only needs 40 min, suggesting that this method is promising in on-site detection of bacteria.