Multiple DNA cycle amplification for highly efficient detection of mercury pollution in food.

Mercury ion (Hg2+), a highly toxic metal pollutant, is widely found in the environment and can enter the human body through the food chain, causing various health issues. Sensitive and accurate methods for monitoring Hg2+ are highly desirable for ensuring food safety. Herein, we propose a self-sustainable multiple amplification system (MAS) for Hg2+ determination through the reciprocal activation between catalytic hairpin assembly (CHA) and rolling circle amplification (RCA). The thymine-encoded recognition element specifically recognizes Hg2+, triggering the exposure of the initiator. The initiator then motivates the mutual activation of CHA and RCA to accelerate the production of an exponentially amplified signal. The MAS method achieved a low detection limit of 11 pM. Due to its reliable target recognition and robust amplification efficiency, the MAS circuit facilitated the highly efficient and accurate analysis of low-abundance Hg2+ in milk and snakehead samples, thus providing a potentially new tool for food safety control.

A three-channel biosensor based on stimuli-responsive catalytic activity of the Fe3O4@Cu for on-site detection of tetrodotoxin in fish.

Tetrodotoxin (TTX), a lethal neurotoxin, poses a grave threat to human health. The available spectroscopic methods suffer from limitations such as complex procedures and inadequate on-site capabilities. In this study, we proposed a method using Fe3O4@Cu as a catalytic biosensor combined with SERS, colorimetry and image processing for TTX detection. Integrating the aptamer amplifies the specificity of the system and masks the catalytic activity of Fe3O4@Cu. The catalytic efficiency of Fe3O4@Cu in the H2O2-TMB reaction can quantify the concentration of TTX in the system. Consequently, oxidation of TMB (oxTMB) led to the generation and change of signals for SERS, colorimetry and image processing, enabling a three-channel quantitative detection of TTX. Under the optimal conditions, the detection limit of established SERS, colorimetry and image processing were 0.055, 2.127 and 0.243 ng/mL, respectively. This three-channel biosensor was applied to real samples, providing an accurate, stable and adaptable alternative for on-site TTX detection.

Sulfadiazine detection in aquatic products using upconversion nanosensor based on photo-induced electron transfer with imidazole ligands and copper ions.

Contamination of aquatic products with sulfonamide antibiotics poses a threat to consumer health and can lead to the emergence of drug-resistant bacteria. Common methods to detect such compounds are slow and require expensive instruments. We developed a sensitive sulfadiazine (SDZ) detection method based on the photoinduced electron transfer between UCNPs and Cu2+. The surface-modified upconversion nanoparticles bind to Cu2+ by electrostatic adsorption, causing fluorescence quenching. The quenched fluorescence was subsequently recovered by the addition of imidazole and SDZ to the detection system, which formed a complex with Cu2+. The sensor showed excellent linearity over a wide concentration range (0.05-1000 ng/mL), had a low limit of detection (0.04 ng/mL), was selective, and was not affected by common substances present in aquatic media. This indicates that the sensor has great potential for application in the detection of SDZ residues in aquatic products.

An electrochemiluminescent dual-signal immunosensor based on a Ru(bpy)32+-doped silica nanoparticle/copper nanocluster composite for okadaic acid detection.

In this study, a sensitive dual-signal electrochemiluminescence (ECL) immunosensor was developed for okadaic acid (OA) detection utilizing copper nanoclusters (CuNCs) and Ru(bpy)32+-doped silica nanoparticles (RuSiNPs). Interestingly, the CuNCs could simultaneously enhance both cathodic (-0.95 V) and anodic (+1.15 V) ECL signals of RuSiNPs, forming a dual-signal ECL sensing platform. Further, RuSiNPs@CuNCs were used as immunomarkers by covalently conjugating them with an anti-OA monoclonal antibody (mAb) to form probes. Finally, dual ECL signals of the immunosensor were fabricated and showed good linear relationships with OA concentrations in the range of 0.05-70 ng mL-1, having a median inhibitory concentration (IC50) of 1.972 ng mL-1 and a limit of detection of 0.039 ng mL-1. Moreover, the constant ratio of the cathodic and anodic ECL peaks achieved self-calibration of the detection signal and improved the reliability of the results. Finally, we successfully applied the ECL sensor to detect OA in spiked oyster samples.

Identification of prognostic biomarkers for cholangiocarcinoma by combined analysis of molecular characteristics of clinical MVI subtypes and molecular subtypes.

Cholangiocarcinoma (CCA) is widely noted for its high degree of malignancy, rapid progression, and limited therapeutic options. This study was carried out on transcriptome data of 417 CCA samples from different anatomical locations. The effects of lipid metabolism related genes and immune related genes as CCA classifiers were compared. Key genes were derived from MVI subtypes and better molecular subtypes. Pathways such as epithelial mesenchymal transition (EMT) and cell cycle were significantly activated in MVI-positive group. CCA patients were classified into three (four) subtypes based on lipid metabolism (immune) related genes, with better prognosis observed in lipid metabolism-C1, immune-C2, and immune-C4. IPTW analysis found that the prognosis of lipid metabolism-C1 was significantly better than that of lipid metabolism-C2 + C3 before and after correction. KRT16 was finally selected as the key gene. And knockdown of KRT16 inhibited proliferation, migration and invasion of CCA cells.

Upconversion fluorescence nanosensor based on enzymatic inhibited and copper-triggered o-phenylenediamine oxidation for the detection of dimethoate pesticides.

Pesticide residues in agricultural products pose a significant threat to human health. Herein, a sensitive fluorescence method employing upconversion nanoparticles was developed for detecting organophosphorus pesticides (OPs) based on the principle of enzyme inhibition and copper-triggered o-phenylenediamine (OPD) oxidation. Copper ions (Cu2+) oxidized the colorless OPD to a yellow 2,3-diaminophenazine (oxOPD). The yellow solution oxOPD quenched the fluorescence of upconversion nanoparticles due to the fluorescence resonance energy transfer. The high affinity of Cu2+ for thiocholine reduced the level of oxOPD, resulting in almost no fluorescence quenching. The addition of dimethoate led to the inhibition of acetylcholinesterase activity and thus prevented the formation of thiocholine. Subsequently, Cu2+ oxidized OPD to form oxOPD, which attenuated the fluorescence signal of the system. The detection system has a good linear range of 0.01 ng/mL to 50 ng/mL with a detection limit of 0.008 ng/mL, providing promising applications for rapid detection of dimethoate.

Rhizopus stolonifer and related control strategies in postharvest fruit: A review.

Rhizopus stolonifer is one of the main pathogens in postharvest storage logistics of more than 100 kinds of fruit, such as strawberries, tomatoes and melons. In this paper, the research on the morphology and detection, pathogenicity and infection mechanism of Rhizopus stolonifer was reviewed. The control methods of Rhizopus stolonifer in recent years was summarized from three dimensions of physics, chemistry and biology, including the nanomaterials, biological metabolites, light control bacteria, etc. Future direction of postharvest Rhizopus stolonifer infection control was analyzed from two aspects of pathogenic mechanism research and new composite technology. The information provided in this review will help researchers and technicians to deepen their understanding of the pathogenicity of Rhizopus stolonifer, and develop more effective control methods in the future.

Isothermal Reciprocal Catalytic DNA Circuit for Sensitive Analysis of Kanamycin.

Inappropriate use of veterinary drugs can result in the presence of antibiotic residues in animal-derived foods, which is a threat to human health. A simple yet efficient antibiotic-sensing method is highly desirable. Programmable DNA amplification circuits have supplemented robust toolkits for food contaminants monitoring. However, they currently face limitations in terms of their intricate design and low signal gain. Herein, we have engineered a robust reciprocal catalytic DNA (RCD) circuit for highly efficient bioanalysis. The trigger initiates the cascade hybridization reaction (CHR) to yield plenty of repeated initiators for activating the rolling circle amplification (RCA) circuit. Then the RCA-generated numerous reconstituted triggers can reversely stimulate the CHR circuit. This results in a self-sufficient supply of numerous initiators and triggers for the successive cross-invasion of CHR and RCA amplifiers, thus leading to exponential signal amplification for the highly efficient detection of analytes. With its flexible programmability and modular features, the RCD amplifier can serve as a universal toolbox for the high-performance and accurate sensing of kanamycin in buffer and food samples including milk, honey, and fish, highlighting its enormous promise for low-abundance contaminant analysis in foodstuffs.

Metal-organic framework-based multienzyme cascade bioreactor for sensitive detection of methyl parathion.

In this study, a cascade nanobioreactor was developed for the highly sensitive detection of methyl parathion (MP) in food samples. The simultaneous encapsulation of acetylcholinesterase (AChE) and choline oxidase (CHO) in a zeolitic imidazole ester backbone (ZIF-8) effectively improved the stability and cascade catalytic efficiency of the enzymes. In addition, glutathione-stabilized gold nanoclusters (GSH-AuNCs) were encapsulated in ZIF-8 by ligand self-assembly, conferring excellent fluorescence properties. Acetylcholine (ATCh) is catalyzed by a cascade of AChE/CHO@ZIF-8 as well as Fe(II) to generate hydroxyl radicals (·OH) with strong oxidizing properties. The ·OH radicals then oxidize Au(0) in GSH-AuNCs@ZIF-8 to Au(I), resulting in fluorescence quenching. MP, as an inhibitor of AChE, hinders the cascade reaction and thus restores the fluorescence emission, enabling its quantitative detection. The limit of detection of the constructed nanobioreactor for MP was 0.23 µg/L. This MOF-based cascade nanobioreactor has great potential for the detection of trace hazards.

Ag@Au core-shell nanoparticle-based surface-enhanced Raman scattering coupled with chemometrics for rapid determination of chloramphenicol residue in fish.

The alarming increase in drug-resistant bacteria in fish resulting from the misuse of antibiotics poses a significant threat to ecosystems and human health. Therefore, the development of a reliable approach for detecting antibiotic residues in fish is crucial. In this study, a rapid and simple method for detecting chloramphenicol (CAP) residue in tilapia was developed using surface-enhanced Raman scattering (SERS) combined with chemometric algorithms. Silver and gold core-shell nanoparticles (Ag@Au CSNPs) were used as SERS nanosensors to achieve strong signal amplification with an enhancement factor of 2.67 × 106. The results demonstrated that the variable combination population analysis-partial least square (VCPA-PLS) model combined with the standard normal variable transformation pretreatment method exhibited the best predictive performance with a detection limit of 1 × 10-5 µg/mL. Thus, an SERS technique was established based on Ag@Au CSNPs combined with VCPA-PLS to rapidly detect CAP in tilapia.

Ultrasonic-Microwave extraction of glucoside alkaloids from potato peel residue and its antibacterial activity.

A new extraction and bacteriostatic ability of glucoside alkaloids in potato peel. To make better use of glucoside alkaloids, this experiment adopted ultrasonic microwave combined extraction of glucoside alkaloids from potato peel; then, the extracts of potato peel were subjected to bacteriostatic assays. The optimum experimental condition of response surface method was that the solid-liquid ratio was 1:18.00 g/mL, the ultrasonic power 505.00 W, the microwave time was 6.10 min and the ultrasonic time was 10.70 min. Under those conditions, the extraction amount of glucoside alkaloids was 292.91 mg/kg, which increased by about 28% compared with the QUEChERS method. The antibacterial activity of the obtained glucoside alkaloids was tested using five kinds of strains, and the results showed that Penicillium and Colletotrichum gloeosporioides were more sensitive. The results indicated that Ultrasonic-Microwave combined extraction was more efficient and convenient than that of QuEChERS method for glucoside alkaloids and related antibacterial compounds from potato peel.

G-Quadruplex/Hemin-Mediated Polarity-Switchable and Photocurrent-Amplified System for Escherichia coli O157:H7 Detection.

The contamination of food by pathogens is a serious problem in global food safety, and current methods of detection are costly, time-consuming, and cumbersome. Therefore, it is necessary to develop rapid, portable, and sensitive assays for foodborne pathogens. In addition, assays for foodborne pathogens must be resistant to interference resulting from the complex food matrix to prevent false positives and negatives. In this study, hemin and reduced graphene oxide-MoS2 sheets (GMS) were used to design a near-infrared (NIR)-responsive photoelectrochemical (PEC) aptasensor with target-induced photocurrent polarity switching based on a hairpin aptamer (Hp) with a G-quadruplex motif. A ready-to-use analytical device was developed by immobilizing GMS on the surface of a commercial screen-printed electrode, followed by the attachment of the aptamer. In the presence of Escherichia coli O157:H7, the binding sites of Hp with the G-quadruplex motif were opened and exposed to hemin, leading to the formation of a G-quadruplex/hemin DNAzyme. Crucially, after binding to hemin, the charge transfer pathway of GMS changes, resulting in a switch of the photocurrent polarity. Further, G-quadruplex/hemin DNAzyme enhanced the cathodic photocurrent, and the proposed sensor exhibited a wide linear range ((25.0-1.0) × 107 CFU/mL), a low limit of detection (2.0 CFU/mL), and good anti-interference performance. These findings expand the applications of NIR-responsive PEC materials and provide versatile PEC methods for detecting biological analytes, especially for food safety testing.

Preparation of a multilayer antibacterial film and its application for controlling postharvest disease in temperate fruit (including apple, pear, and peach) under ambient storage.

The objective of this study was to provide formulation of a new multilayer antibacterial film and to investigate the optimal use concentration of chitosan and carboxymethyl cellulose in the range from 0.5% to 2%, as well as its application for controlling postharvest disease in temperate fruit (apple, pear, and peach). The multilayer antibacterial film used chitosan (CS) and carboxymethyl cellulose (CMC) as polysaccharide macromolecule, lemon essential oil (LEO) as active agent, and ε-polylysine (ε-PL) as the main antibacterial ingredient. The results showed that the physical properties of the self-assembled film were adjusted by the electrostatic layer-by-layer (LbL) deposition. Fourier transform infrared (FT-IR) analysis and thermogravimetric (TGA) revealed that hydrogen bonds were generated during the self-assembly of CS-LEO/CMC-ε-PL film, resulting in changes in intermolecular interactions and thermal stability. Furthermore, compared with CS-LEO single-layer film, the multilayer film exhibited higher retention rate of LEO. In vivo test, the self-assembled film significantly inhibited the infection of postharvest pathogenic fungi including Penicillium expansum (P. expansum) and Alternaria alternata (A. alternata) on fruit. To summarize, the CS-LEO/CMC-ε-PL LbL self-assembly coating notably controlled postharvest pathogen rot on fruit, and reduced the loss of fruit during storage and transportation. Our results suggest that the polysaccharide-based edible coating prepared in this work may offer an alternative to synthetic waxes.

Screening-Capture-Integrated Electrochemiluminescent Aptasensor Based on Mesoporous Silica Nanochannels for the Ultrasensitive Detection of Deoxynivalenol in Wheat.

To prevent the contamination of cereals by mycotoxins, establishing a sensitive and rapid method for the detection of mycotoxins is essential. In this study, a screening-capture-integrated electrochemiluminescence (ECL) aptasensor based on mesoporous silica films (MSFs) was successfully prepared for the ultrasensitive and highly selective detection of deoxynivalenol (DON) in wheat. The narrow nanochannels of MSFs can realize size screening, thereby eliminating the influence of macromolecular substances and providing a pure environment for the signal probe (tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)32+)) to reach the indium tin oxide (ITO) conductive substrate, which significantly improves the anti-interference ability of the screening-capture-integrated ECL sensor. The aptamer (Apt) attached to the surface of the MSFs can specifically capture DON, and the resulting DON-Apt complex has a gated effect on the MSFs, triggering the inhibition of Ru(bpy)32+ in the electrolyte from reaching the ITO surface. Therefore, the ECL intensity of the sensor decreased with increasing DON concentration to achieve a quantitative detection of DON. Under optimized conditions, the linear range of the screening-capture-integrated ECL aptasensor was 0.001-200 µg/kg, and the detection limit was as low as 5.27 × 10-5 µg/kg (S/N = 3). In conclusion, this study developed a screening-capture-integrated ECL aptasensor that combines size screening and specific capture for the detection of DON in wheat, providing a new approach for the early detection of wheat mildew.

A Collection of RPA-Based Photoelectrochemical Assays for the Portable Detection of Multiple Pathogens.

Portable, ultrasensitive, and simultaneously quantitative detection of the nucleic acids of multiple foodborne pathogens is critical to public health. However, the current testing methods depend on costly equipment and tedious amplification steps. In this study, we propose a photoelectrochemical (PEC) biosensor combined with recombinase polymerase amplification (RPA) technology (RPA-PEC) for the rapid detection of multiple foodborne pathogens under irradiation of 980 nm light. In particular, two working surfaces were designed on homemade three-dimensional screen-printed paper-based electrodes. The genomic DNAs of Escherichia coli O157:H7 and Staphylococcus aureus was initiated by RPA on the corresponding electrode surfaces, thus forming a lab-on-paper platform. Using the formed DNA-PEC signaler, photocurrents were achieved at 37 °C after only 20 min of RPA. The detection performance was superior to that of conventional agarose gel electrophoresis, with detection limits of 3.0 and 7.0 copies/µL for E. coli O157:H7 and S. aureus, respectively. Our study pioneers a new RPA-PEC method for foodborne pathogens and provides directions for the construction of lab-on-paper platforms for the portable detection of multiple nucleic acids.

Boric acid group-functional Tb-MOF as a fluorescent and captured probe for the highly sensitive and selective determination of propyl gallate in edible oils.

This study reports the development of a Tb-metal-organic framework (Tb-MOF)-based fluorescent platform for the detection of propyl gallate (PG). The Tb-MOF using 5-boronoisophthalic acid (5-bop) as the ligand exhibited multiple emissions at 490, 543, 585, and 622 nm under an excitation wavelength of 256 nm. The fluorescence of Tb-MOF was selectively and significantly weakened in the presence of PG due to the special nucleophilic reaction between the boric acid of Tb-MOF and o-diphenol hydroxyl of PG, and the combined effect of static quenching and internal filtering. Furthermore, this sensor enabled the determination of PG within seconds in a wide linear range of 1-150 µg/mL, and with a low detection limit of 0.098 µg/mL, and high specificity against other phenolic antioxidants. This work provided a new route for the sensitive and selective determination of PG in soybean oil, thus was perspective to monitor and reduce the risk of PG overuse.

Construction of a self-sufficient DNA circuit for amplified detection of kanamycin.

Improper use of kanamycin can lead to trace kanamycin residues in animal-derived foods, which can pose a potential threat to public health. Isothermal enzyme-free DNA circuits have provided a versatile toolbox for detecting kanamycin residues in complicated food samples, yet they are always limited by low amplification efficiency and intricate design. Herein, we present a simple-yet-robust nonenzymatic self-driven hybridization chain reaction (SHCR) amplifier for kanamycin determination with 5800-fold sensitivity over that of the conventional HCR circuit. The analyte kanamycin-activated SHCR circuitry can generate numerous new initiators to promote the reaction and improve the amplification efficiency, thus achieving an exponential signal gain. With precise target recognition and multilayer amplification capability, our self-sustainable SHCR aptasensor facilitated the highly sensitive and reliable analysis of kanamycin in buffer, milk, and honey samples, thus holding great potential for the amplified detection of trace contaminants in liquid food matrices.

Non-destructive prediction of colour and water-related properties of frozen/thawed beef meat by Raman spectroscopy coupled multivariate calibration.

Freeze-thaw accelerated the colour deterioration of beef with the increase of colour b* and the decrease of colour a* values (P < 0.05). The maximum exudate loss reached 22 % after the seventh freeze-thaw. A strong correlation between the transversal relaxation time T21 and thawing loss may mean that T21 water contributed to the exudate loss during freeze-thaw. Afterwards, competitive adaptive reweighted sampling-partial least square (CARS-PLS) has the best prediction in thawing loss of frozen/thawed beef with correlation coefficients of prediction (Rp) of 0.971, and root mean square error of prediction (RMSEP) of 1.436. Besides, Uninformative variable elimination-partial least squares (UVE-PLS) showed good prediction effects on colour values (Rp = 0.932 - 0.994) and water content (Rp = 0.928, RMSEP = 0.582) of frozen/thawed beef. Therefore, this work demonstrated that Raman spectroscopy coupled with multivariate calibration has a good ability for non-destructive prediction in colour and water-related properties of frozen/thawed beef.

Insight into a Target-Induced Photocurrent-Polarity-Switching Photoelectrochemical Immunoassay for Ultrasensitive Detection of Escherichia coli O157:H7.

Sensitive, portable methods of detection for foodborne pathogens hold great significance for the early warning and prevention of foodborne diseases and environmental pollution. Restricted by a complicated matrix and limited signaling strategies, developing a ready-to-use sensing platform with ultrahigh sensitivity remains challenging. In this work, near-infrared (NIR) light-responsive AgBiS2 nanoflowers (NFs) and Cu2O nanocubes (NCs) were introduced to construct a novel target-induced photocurrent-polarity-switchable system and verified for the development of an all-in-one, ready-to-use photoelectrochemical (PEC) immunosensor. NIR-responsive n-type AgBiS2 NFs and p-type Cu2O NCs producing anodic and cathodic photocurrents were conjugated with monoclonal (MAb1) and polyclonal antibodies (PAb2), respectively. Using a sandwich-type immunocomplex bridged by Escherichia coli O157:H7, an efficient photocurrent-polarity-switching PEC system was formed on a paper-based working electrode (PWE). Owing to the spatial separation of the photogenerated carriers and the elimination of false-positive/negative signals by the polarity-switchable photocurrent, the proposed NIR PEC immunoassay for E. coli O157:H7 exhibits a considerably low detection limit of 8 colony-forming units/milliliter (CFU/mL) with a linear range from 25 to 5 × 107 CFU/mL. The platform includes a PWE with an automatic cleaning function and a portable PEC analyzer with smartphone-compatible Bluetooth capability, thus achieving point-of-care testing of E. coli O157:H7. The sensor was applied to the analysis of pork samples artificially contaminated with E. coli O157:H7, and the detection results were in good agreement with the plate counting method, a gold standard in the field. This work aimed to investigate the photoelectric activity of the NIR-responsive p/n-type composites and to provide a new signal-reversal route for the construction of an all-in-one ready-to-use PEC immunosensor for the detection of low-concentration biomolecules.