Laser induced fluorescence reader for sandwichtype nanoparticle immunoassay to determine salinomycin

A unique laser-induced fluorescence reader was developed to detect various antibiotics in foods using a sandwich-type immunoassay platform. For the measurement, magnetic nanoparticles (MNPs) were synthesized in the size of 10-20 nm to be used for extraction of antibiotic target by magnetic separation and dye-doped silica nanoparticles (color balls) immobilized with antibody were synthesized in the size of 70-80 nm to be used as a probe for fluorescence detection. The reader system contains a diode laser irradiating from bottom to top for a long cell pathlength. In particular, this system was equipped with a ratiometric supplementary tool in order to compensate the particle loss during the sample pretreatment, which enhanced linearity and reproducibility. When it was demonstrated to determine salinomycin spiked in phosphate buffered saline solutions, detection limit of about <;10 pg/mL and excellent linear dynamic range with an improved linearity were obtained. For method and instrumental validation, the result was compared with that of enzyme-linked immunosorbent assay (ELISA). As a result, the developed fluorescence reading system provided a simplified analytical procedure and improved the detection limit more than 100-fold compared to ELISA.