No abstract

Simple, rapid, and sensitive screening methods are the key to prevent and control the spread of foodborne diseases. In this study, a simple visual colorimetric assay using magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) was developed for the detection of Vibrio parahaemolyticus . First, the aptamer responding to V. parahaemolyticus was conjugated onto the surface of MNPs and used as a specific magnetic separator. In addition, the aptamer was also immobilized on the surface of AuNPs and used as a colorimetric detector. In the presence of V. parahaemolyticus , a sandwich structure of MNP–aptamer–bacteria–aptamer–AuNPs is formed through specific recognition of the aptamer and V. parahaemolyticus . The magnetic separation technique was then applied to generate a detection signal. Owing to the optical properties of AuNPs, a visual signal could be observed, resulting in an instrument-free colorimetric detection. Under optimal conditions, this assay shows a linear response toward V. parahaemolyticus concentration through the range of 10–10 6 cfu/mL, with a limit of detection of 2.4 cfu/mL. This method was also successfully applied for V. parahaemolyticus detection in spiked raw shrimp samples.

A simple one-pot synthesis of biocompatible and antifouling magnetite nanoparticles (Fe3O4NPs) was developed.

The traditional agglutination assays especially those based on polystyrene beads have been recognized as convenient tools for disease diagnosis despite their limited detection range and low sensitivity. Unlike other particles namely polystyrene beads, SiO2 and gold nanoparticles having insignificant magnetic properties, magnetic nanoparticles (MNPs) offer unique advantages as their magnetic properties for agglutination methods. In the presence of magnet, not only can they be used to enrich the samples, but also their aggregation can also be induced, providing sensitive and rapid measurements. This work aims to develop MNPs for aggregation-based biomolecular detection. The MNPs were surface-modified with PMAMPC via an in situ coating method, then biotin as the target-specific probe was immobilized. The biotin-conjugated PMAMPC-MNPs were used for capturing and detecting the complementary protein, streptavidin in human serum samples. With the magnetic-induction, the nanoparticles would aggregate in the presence of streptavidin, resulting in a short detection time even in undiluted human serum. The concentration range for the detection was 35 nM to 150 nM and the lowest concentration of detection was 35 nM or equivalent to 2.5 mg⸳mL-1. The fact that this is simple, rapid and instrument-free method for biomolecular detection broadens their potential use in a variety of diagnostic applications.