Rapid and Visualized Detection of Virulence-Related Genes of Vibrio cholerae in Water and Aquatic Products by Loop-Mediated Isothermal Amplification

Vibrio cholerae can cause pandemic cholera in humans. The bacterium resides in aquatic environments worldwide. Continuous testing of V. cholerae contamination in water and aquatic products is imperative for food safety control and human health. In this study, a rapid and visualized method was for the first time developed based on loop-mediated isothermal amplification (LAMP) for detection of very important virulence-related genes ace , zot , cri , and nanH for toxins and infection process of V. cholerae . Three pairs of molecular probes targeting each of these genes were designed and synthesized. The one-step LAMP reaction was conducted at 65 o C for 40 min. Positive results were simply inspected by the production of light green color under visible light or green fluorescence under UV light (302 nm). Limit of detection (LOD) of the LAMP method ranged from 1.85-2.06 pg/reaction of genomic DNA or 2.50-4.00×10 2 CFU/reaction for target genes of cell culture of V. cholerae , which was more sensitive than standard polymerase chain reaction (PCR). Inclusivity and exclusivity of the LAMP method were 100% for all target genes. The method showed similar high efficiency to a certain extent in rapid testing of spiked or collected specimens of water and aquatic products. Target genes were detected by the absence from all water samples from various sources. However, high occurrences of nanH gene were observed in intestine samples derived from four species of fish and one species of shellfish, indicating a risk of potentially toxic V. cholerae in commonly consumed aquatic products. The results in this study provide a potential tool for rapid and visualized detection of V. cholerae in water and aquatic products.

Fluorescence Probe Based on Graphene Quantum Dots for Selective, Sensitive and Visualized Detection of Formaldehyde in Food

Graphene quantum dots (GQDs) have been successfully used as a highly sensitive probe for the sensing of formaldehyde (HCHO) in an aqueous solution. Through static quenching, the probe utilizes the interaction between HCHO and GQDs to trigger the “turn off” fluorescence response, and has good selectivity. The probe can detect HCHO in a pure aqueous solution, and it also can still detect HCHO in a complex environment with a pH range from 4 to 10. The concentration of HCHO and the fluorescence intensity of GQDs show a good linear relationship within the range of HCHO of 0–1 μg/mL, which was much more sensitive than previous reports. The limit of HCHO detection by GQDs is about 0.0515 μg/mL. In addition, we successfully applied it to the actual food inspection. It is proved to be a selective, sensitive and visualized method to check whether the concentration of HCHO in the foods exceeds the regulatory limit, which presents a potential application in food safety testing.

Smartphone Based Highly Sensitive Visualized Detection of Acid Phosphatase Enzyme Activity

With the rapid development of point-of-care (POC) technologies, the improvement of sensitive method featured with fast analysis and affordable devices has become an emerging requirement for the practical application. In...