Multiplex Immunoassay Development for Detection of Organic Pollutants in Fish

December 4th, 2013 / Cassie Bannister

Kelley Hotspring Fish Farm (Tilapia)
Kelley Hotspring Fish Farm (Tilapia) by USDA NRCS is licensed under Creative Commons License

Tilapia farming is a promising solution to the problem of declining fish stocks. As a species, tilapia thrives well in many different environments, and is therefore being increasingly farmed for human consumption in the United States and Europe.

Concerns have been raised about the safety of consuming tilapia due to the possible presence of persistent organic pollutants (POPs). Chemicals such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenyl ethers (PBDEs), which are harmful to human health, could potentially contaminate tilapia stocks.

Multiplex immunoassays can be used to test for the presence of POPs. Previously, a single immunoassay would be used to detect each type of POP individually, but new technologies allow for the development of custom assays, which can screen for all three types of POPs at once. In particular, a recently developed technique using Luminex® spectrally encoded microspheres (SEM) has been found to produce faster and more efficient results when testing for POPs in tilapia.

A recent study published in Food Additives and Contaminants1 describes how this 3-plex SEM-based immunoassay can be used to detect PCBs, PAHs, and PBDEs in tilapia fillets. If POPs are present in the fish fillet, they bind to capture molecules on the SEMs. The assay system developed in this study was read on the MAGPIX® instrument. It uses red and green light-emitting diodes (LEDs) to illuminate the SEMs, which are held in place using a magnet so that they can be imaged using a camera, to determine which POPs are present. This instrument is the most compact, portable, and inexpensive of the Luminex multiplex instruments. The market-leading platform, Luminex 100/200™ instrument uses lasers to illuminate SEMs in a fluidic stream. However, the 100/200 instrument is not as portable or compact as MAGPIX.

As a flexible and open multiplexing technology, Luminex xMAP® Technology is a valuable tool in the development of custom assays, which allow researchers and industry specialists to quickly and efficiently detect potentially harmful chemicals in food intended for human consumption.

In summary, the benefits of using a 3-plex SEMs-based imaging immunoassay to test for POPs in tilapia are as follows:

  • Lower cost assay
  • More portable system for easy usage in the field
  • Rapid and effective screening
  • MAGPIX yields similar results to the Luminex 100/200 instrument

Luminex multiplexing technology made the development of this system possible by allowing the development of a highly customized assay process. The researchers hope that the type of 3-plex system developed in this study could be used to screen for POPs in fish in order to quickly verify its safety. This method also has potential for future screening of POPs in other sample matrices including other fish species, refined vegetable oils, and environmental samples.

Learn more about Luminex multiplexing instruments.

>Interested in developing your own assays? The free xMAP Cookbook contains detailed methods and protocols to help you develop assays on the xMAP platform.

Download the xMAP® Cookbook


  1. 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. Taylor & Francis Online (Internet). Cited November 2013. Available from: