An aptamer-based magnetic solid-phase extraction method was designed for the pretreatment of AFB1 from a Pixian Douban sample. It was developed based on aptamer–Fe3O4@SiO2–NH2 with subsequent ELISA validation, showing an efficient result.
A rapid, specific and visible detection method for Salmonella enteric serovar typhimurium (S. typhimurium) was developed based on a gold nanoparticle (AuNP) conjugated bifunctional oligonucleotide probe and aptamer. AuNPs were conjugated with bifunctional oligonucleotide probes and aptamer, then the target bacteria S. typhimurium cells were incubated with the conjugated AuNP. Since the aptamer had a higher affinity and specificity on binding with the cells and its configurations was therefore changed, AuNPs particles were released. These AuNPs particles would aggregate with NaCl and the color of the solution would turn blue from red. Under the optimal conditions, the correlation between the concentration of S. typhimurium and the intensity of the signals was observed to be linear within the range of 1.0 × 101∼1.0 × 106 cfu/ml (R2 = 0.9952), and the detection limit of the proposed method was observed to be 10 cfu/ml. This developed method offers the potential for rapid, sensitive, and visible detection of S. typhimurium in milk and shrimp samples.
Practical applications
The developed method in this study can be used for the detection of S. typhimurium in food samples such as milk and shrimp. Furthermore, the developed method can be easily modified for the simultaneous detection of S. typhimurium and other bacteria.
Cow milk is an important source of protein, but it is also a food that can cause allergies. In this research, a novel photoelectrochemical immunosensor based on CdWO4–CdS type-II heterojunction was constructed for the detection of allergen [Formula: see text]-lactalbumin ([Formula: see text]-Lac) in milk. CdWO4–CdS heterojunction was synthesized by one-step hydrothermal method. Compared with pure CdWO4, the CdWO4–CdS heterojunction significantly improved the photocurrent intensity. The polydopamine (PDA) was used as a crosslinking agent to couple basis materials and biomolecules. Ascorbic acid was used as an efficient electron donor to eliminate the photo-generated holes and inhibit the recombination of photo-generated electrons and holes. Under the optimum experimental conditions, the photocurrent intensity reduced linearly with the logarithm of [Formula: see text]-Lac concentration ranging from 0.001 ng[Formula: see text]mL[Formula: see text] to 10 ng[Formula: see text]mL[Formula: see text] and the limit of detection was 0.17[Formula: see text]pg[Formula: see text]mL[Formula: see text]. The constructed photoelectrochemical immunosensor exhibited excellent stability, selectivity and reproducibility, which provided a novel ideal for sensitive detection of [Formula: see text]-Lac and shed light on monitoring of other allergenic proteins in foods.
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