Submitted to: Food Additives & Contaminants
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/18/2013
Publication Date: 5/8/2013
Publication URL: http://handle.nal.usda.gov/10113/57042
Citation: Meimaridou, A., Haasnoot, W., Shelver, W.L., Franek, M., Nielen, M.W.F. 2013. Multiplex immunoassay for persistent organic pollutants in tilapia: Comparison of imaging- and flow cytometry-based platforms using spectrally encoded paramagnetic microspheres. Food Additives & Contaminants: Part A. 30(5):843-852. Interpretive Summary: The presence of persistent organic pollutants in food is a problem that is of increasing concern as these toxic materials become more widely distributed in the environment and enter the food supply. The ever increasing variety of these compounds makes their determination more complex and expensive. Methods have been developed for the simultaneous determination of a number of these compounds, but these methods require sophisticated instruments that are expensive to operate and maintain. Furthermore, some instruments require complex, expensive sample cleanup procedure further adding to the cost of the analysis. This work describes the development of an analytical method capable of simultaneously determining three of the most common types of environmental contaminants that are of major food safety concern; namely: polychloro biphenyls (PCBs) from electric transformers and pesticides, polybromo diphenyl ethers (PBDEs) fire retardants from electronics or furniture, and polycyclic aromatic hydrocarbons (PAHs) from burning substances like charcoal. The new method has the advantage of being robust, simple and low cost. Coupled with this method was a QuEChERS (quick, easy, cheap, effective, rugged, and safe)-like extraction procedure modified from earlier work. This method uses a new imaging system that gives a response to the presence of the pollutant and the system is rugged and simpler to use than other detection systems of a similar capability to detect multiple contaminants simultaneously. The method worked well on 40 tilapia fillets, analyzed as blanks and each spiked with a mixture of relevant concentrations of the model compounds or a mixture of several POPs belonging to the three target groups (PCBs, PBDEs and PAHs). The results were compared with the conventional, but more complicated system and gave equivalent results demonstrating the new platform and extraction method works well for measuring pollutants in food samples.
Technical Abstract: 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. The new imaging superparamagnetic SEMs-based platform transports SEMs with considerably less fluid volume into a chamber. There SEMs are held in a monolayer with a magnet. LEDs are focused on the chamber to illuminate the SEMs instead of lasers, and analyzed by a CCD imaging detector, rather than a flow cytometer, 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 the rapid screening of POPs in fish.