Cost-effective affinity support for the rapid separation of bacteria from complex food matrices

Advancements in molecular biology have facilitated the ability to detect microbes of interest in low abundance within complex samples. Although these technologies are extremely powerful, they typically accommodate only very small volumes of liquid samples as inputs; making sample volume a critical constraint for many molecular methodologies. Because testing volumes are often restricted to the microliter range, methods that concentrate target microbes can broaden the applicability of these detection devices. Immunomagnetic separation (IMS) is an example of a sample preparation method capable of selectively concentrating targets; utilizing magnetically-sensitive materials coated with biorecognition elements to isolate targets of interest. While the commercial availability of micron-sized, conjugation-ready, superparamagnetic particles has amplified the success of IMS for interrogating samples <10 mL, querying of large sample volumes with these particles is often financially restrictive if performed routinely. Therefore, a cost-effective alternative that can be employed for large-volume samples is presented. Here, a low-cost coating allows the conjugation of antibodies to the surface of inexpensive permanent magnets; ultimately creating an economical solid support for the selective capture of microorganisms in both buffer and ground beef homogenate (a complex food matrix). The broad utility of this method was further demonstrated by capturing either E. coli O157:H7 or Salmonella enterica through a simple antibody substitution. Novel techniques aimed at releasing target cells from the magnet via UV-light were also investigated, although the results were not definitive. Overall, expansion of IMS to large-volume food samples using this simple and economical solution could transform downstream detection capabilities in diagnostic applications.