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Multiplex immunoassay for persistent organic pollutants in tilapia: Comparison of imaging- and flow cytometry-based platforms using spectrally encoded paramagnetic microspheres

Anastasia Meimaridou, Willem Haasnoot, Weilin L. Shelver, Milan Franek, Michel W.F. Nielen
Food additives & contaminants 2013 v.30 no.5 pp. 843-852
additives, buffers, detectors, fish fillets, flow cytometry, food contamination, image analysis, immunoassays, lasers, optics, persistent organic pollutants, polybrominated diphenyl ethers, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, screening, solid phase extraction, tilapia (common name), vegetable oil
Recent developments in spectrally encoded microspheres (SEMs)-based technologies provide high multiplexing possibilities. Most SEMs-based assays required a flow cytometer with sophisticated fluidics and optics. A new imaging superparamagnetic SEMs-based alternative platform transports SEMs with considerably less fluid volume into a measuring chamber. Once there SEMs are held in a monolayer by a magnet. Light-emitting diodes (LEDs) are focused on the chamber to illuminate the SEMs - instead of lasers, and they are imaged by a charge-coupled device (CCD) detector, offering a more compact sized, transportable and affordable system. The feasibility of utilizing this system to develop a 3-plex SEMs-based imaging immunoassay (IMIA) for the screening of persistent organic pollutants (POPs) was studied. Moreover the performance characteristics of 3-plex IMIA were critically compared with the conventional 3-plex flow cytometric immunoassay (FCIA). Both SEMs technologies have potential for the multiplex analysis of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and polycyclic aromatic hydrocarbons (PAHs) in buffer and fish extract with insignificant differences in assay sensitivities. Furthermore, we developed a faster and simpler, modified QuEChERS (quick, easy, cheap, effective, rugged, and safe)-like generic POPs extraction from the tilapia fillet using sodium hydrogen carbonate as one of the salt additives and dispersive solid phase extraction (dSPE) as a clean-up. Finally, a preliminary in-house validation using 40 different blank and spiked tilapia fillet samples was performed in both systems and results obtained were critically compared. The lower-cost imaging SEMs-based system performed similar to the original flow cytometer and, in combination with the new quicker QuEChERS-like extraction, it has high potential for future rapid screening of POPs in several other sample matrices such as other fish species, vegetable refined oils and environmental samples.