Bacterial detection based on Förster resonance energy transfer

The huge economic loss and threat to human health caused by bacterial infection have attracted the public's concern, and there is an urgent need to relieve and improve the tough problem. Therefore, it is significant to establish a facile, rapid, and sensitive method for bacterial detection considering the shortcomings of existing methods. Förster resonance energy transfer (FRET)-based sensors have exhibited immense potential and applicability for bacterial detection given their high signal-to-noise ratio and high sensitivity. This review focuses on the development of FRET-based fluorescence assays for bacterial detection. We summarize the principle of FRET-based assays, discuss the commonly used recognition molecules and further introduce three frequent construction strategies. Based on the strategies and materials, relevant applications are presented. Moreover, some restrictions of FRET fluorescence sensors and development prospects are discussed. Suitable donor-acceptor pairs and stable recognition molecules are the essential conditions for sensors to play their roles, and there is still some room for development. Besides, applying FRET fluorescence sensors to point-of-care detection is still difficult. Future developments could focus on near-infrared fluorescent dyes and simultaneous detection of multiple analytes.

A Critical Review on Detection of Foodborne Pathogens Using Electrochemical Biosensors

An outbreak of foodborne pathogens would cause severe consequences. Detecting and diagnosing foodborne diseases is crucial for food safety, and it is increasingly important to develop fast, sensitive, and cost-effective methods for detecting foodborne pathogens. In contrast to traditional methods, such as medium-based culture, nucleic acid amplification test, and enzyme-linked immunosorbent assay, electrochemical biosensors possess the advantages of simplicity, rapidity, high sensitivity, miniaturization, and low cost, making them ideal for developing pathogen-sensing devices. The biorecognition layer, consisting of recognition elements, such as aptamers, antibodies and bacteriophages, and other biomolecules or polymers, is the most critical component to determine the selectivity, specificity, reproducibility, and lifetime of a biosensor when detecting pathogens in a biosample. Furthermore, nanomaterials have been frequently used to improve electrochemical biosensors for sensitively detecting foodborne pathogens due to their high conductivity, surface-to-volume ratio, and electrocatalytic activity. In this review, we survey the characteristics of biorecognition elements and nanomaterials in constructing electrochemical biosensors applicable for detecting foodborne pathogens during the past five years. As well as the challenges and opportunities of electrochemical biosensors in the application of foodborne pathogen detection are discussed.

An ultrasensitive dietary caffeic acid electrochemical sensor based on Pd-Ru bimetal catalyst doped nano sponge-like carbon

Caffeic acid (CA) is widely present in the human daily diet, and a reliable CA detection method is beneficial to food safety. Herein, we constructed a CA electrochemical sensor employing a glassy carbon electrode (GCE) which was modified by the bimetallic Pd-Ru nanoparticles decorated N-doped spongy porous carbon obtained by pyrolysis of the energetic metal-organic framework (MET). The high-energy bond N-NN in MET explodes to form N-doped sponge-like carbon materials (N-SCs) with porous structures, boosting the adsorptive capacity for CA. The addition of Pd-Ru bimetal improves the electrochemical sensitivity. The linear range of the PdRu/N-SCs/GCE sensor is 1 nM-100 nM and 100 nM-15 μM, with a low detection limit (LOD) of 0.19 nM. It has a high sensitivity (55 μA/μM) and repeatability. The PdRu/N-SCs/GCE sensor has been used to detect CA in actual samples of red wine, strawberries, and blueberries, providing a novel approach for CA detection in food analysis.

Advances of stable isotope technology in food safety analysis and nutrient metabolism research

Food quality, safety, and the regulatory metabolism of food nutrients in cells are primary factors in determining human health. However, residues of undesirable or hazardous compounds in food products and dysregulation in the nutrient metabolism inevitably occur occasionally. For years, chromatography-mass spectrometry technology has been recognized as an essential research tool in food analysis and nutrient metabolism research, and it is more accurate and robust when coupled with stable isotopes. In this study, we summarize the applications of stable isotope technology in the quantification of contaminant residues (pesticides, veterinary drugs, mycotoxins, polycyclic aromatic hydrocarbons, and other hazardous compounds) in foods and in the nutrients (glucose, lipids, amino acids and proteins) metabolism research. The aim of this review was to serve as a reference for providing effective analysis techniques for protecting food quality and human health, and to pave the way for the broader application of stable isotope technology.

Direct Identification of Label-Free Gram-Negative Bacteria with Bioreceptor-Free Concentric Interdigitated Electrodes

This investigation demonstrates an electrochemical method for directly identifying unlabeled Gram-negative bacteria without other additives or labeling agents. After incubation, the bacterial cell surface is linked to the interdigitated electrode through electroadsorption. Next, these cells are exposed to a potential difference between the two electrodes. The design geometry of an electrode has a significant effect on the electrochemical detection of Gram-negative bacteria. Therefore, electrode design geometry is a crucial factor that needs to be considered when designing electrodes for electrochemical sensing. They provide the area for the reaction and are responsible for transferring electrons from one electrode to another. This work aims to study the available design in the commercial market to determine the most suitable electrode geometry with a high detection sensitivity that can be used to identify and quantify bacterial cells in normal saline solutions. To work on detecting bacterial cells without the biorecognition element, we have to consider the microelectrode's design, which makes it very susceptible to bacteria size. The concentration-dilution technique measures the effect of the concentration on label-free Gram-negative bacteria in a normal saline solution without needing bio-recognized elements for a fast screening evaluation. This method's limit of detection (LOD) cannot measure concentrations less than 102 CFU/mL and cannot distinguish between live and dead cells. Nevertheless, this approach exhibited excellent detection performance under optimal experimental conditions and took only a few hours.

Point-of-care CRISPR/Cas biosensing technology: A promising tool for preventing the possible COVID-19 resurgence caused by contaminated cold-chain food and packaging

The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused great public health concern and has been a global threat due to its high transmissibility and morbidity. Although the SARS-CoV-2 transmission mainly relies on the person-to-person route through the respiratory droplets, the possible transmission through the contaminated cold-chain food and packaging to humans has raised widespread concerns. This review discussed the possibility of SARS-CoV-2 transmission via the contaminated cold-chain food and packaging by tracing the occurrence, the survival of SARS-CoV-2 in the contaminated cold-chain food and packaging, as well as the transmission and outbreaks related to the contaminated cold-chain food and packaging. Rapid, accurate, and reliable diagnostics of SARS-CoV-2 is of great importance for preventing and controlling the COVID-19 resurgence. Therefore, we summarized the recent advances on the emerging clustered regularly interspaced short palindromic repeats (CRISPR)/Cas system-based biosensing technology that is promising and powerful for preventing the possible COVID-19 resurgence caused by the contaminated cold-chain food and packaging during the COVID-19 pandemic, including CRISPR/Cas system-based biosensors and their integration with portable devices (e.g., smartphone, lateral flow assays, microfluidic chips, and nanopores). Impressively, this review not only provided an insight on the possibility of SARS-CoV-2 transmission through the food supply chain, but also proposed the future opportunities and challenges on the development of CRISPR/Cas system-based detection methods for the diagnosis of SARS-CoV-2.

A Novel Gas Sensor for Detecting Pork Freshness Based on PANI/AgNWs/Silk

A novel, operational, reliable, flexible gas sensor based on silk fibroin fibers (SFFs) as a substrate was proposed for detecting the freshness of pork. Silk is one of the earliest animal fibers utilized by humans, and SFFs exposed many biological micromolecules on the surface. Thus, the gas sensor was fabricated through polyaniline (PANI) and silver nanowires (AgNWs) and deposited on SFFs by in-suit polymerization. With trimethylamine (TMA) as a model gas, the sensing properties of the PANI/AgNWs/silk composites were examined at room temperature, and the linear correlativity was very prominent between these sensing measures and the TMA measures in the range of 3.33 μg/L-1200 μg/L. When the pork sample is detected by the sensor, it can be classified into fresh or stale pork with the total volatile basic nitrogen (TVB-N) as an index. The result indicated that the gas sensor was effective and showed great potential for applications to detect the freshness of pork.

Determination of luteolin in Chrysanthemum tea with a ultra-sensitive electrochemical sensor based on MoO3/poly(3,4-ethylene dioxythiophene)/gama-cyclodextrin metal-organic framework composites

Chrysanthemum tea is a tranditional Chinese health drink, which contains luteolin, a flavonoid with vesatile health benefit activities. Herein, A sensitive electrochemical sensor based on composite materials consisting of MoO₃ nanorods, poly (3, 4-ethylene dioxyethiophene)(PEDOT), and γ-cyclodextrin metal-organic framework(CD-MOF) was prepared.The materials were characterized and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Due to the synergisticeffects of the materials, the sensor showed a wide linear range of 0.4 nM -1800 nM and a low detection limit (LOD) of 0.1 nM (S/N = 3) for luteolin under optimized conditions. Besides, the influences of some coexistent phenolic compounds and common metal ions on luteolin detection were evaluated and no significant interference was observed. Finally, the sensor was successfully applied to the detection of luteolin in real Chrysanthemum tea samples.