When food becomes contaminated with pathogens it is necessary to identify the contamination and remove that food from the supply line as soon as possible. When that food is perishable it becomes all the more important to act quickly, but this demands a rapid detection system. This “need for speed” automatically eliminates the traditional culture method from the list of potential detection techniques. A commonly used method for pathogen detection is to isolate the pathogen and concentrate it enough to be accurately amplified and detected by real time quantitative polymerase chain reaction (RTqPCR). However, the method used to capture and concentrate the pathogen needs to be rapid and efficient. Magnetic nanoparticles and magnetic bead separation techniques are the perfect technologies for the rapid isolation and concentration of pathogens.
Apolipoprotein-bound magnetic beads were used to capture pathogens
Two common foodborne pathogens are E. coli bacteria and the human norovirus. An apolipoprotein (ApoH)-modified magnetic nanoparticle was used to capture these pathogens. ApoHis protein in humanserum that increases in number when inflammation occurs.It has been shown to bind directly to a number of viruses and bacteria. It binds to LPS on gram-negative bacteria, and to surface proteins on gram-positive bacteria. This specific, but wide-spread recognition capacity makes ApoH a useful tool for detecting foodborne pathogens because multiple pathogens can sometimes co-contaminate a sample. ApoH allows for simulateous detection of a variety of bacteria and viruses. In this trial experiment the ApoH magnetic particles were used to detect E. coli, S. aureus, and human norovirus.
The pathogens are detectedby combiningmagnetic separation and RT-qPCR
The ApoH-bound magnetic particles were incubated in the serum to form pathogen-bead conjugates. A magnetic separation rack was used to isolate those conjugates from the serum.The concentrated solution of pathogen-bead conjugates was then treated with a lysis buffer to break apart the pathogens and release the nucleic acids. The magnetic beads were removed by magnetic separation and the remaining nucleic acid solution was analyzed by RT-qPCRusing primers specific to E. coli, S. aureus, and human norovirus.
Magnetic separation is an easy and convenient tool for the capture and concentration of a target. The use of a specific, but common protein such as ApoH to selectively bind bacteria and viruses is a good way to design a universal pathogen detection system. This rapid, culture-free method for the detection of foodborne pathogens could help keep the food supply clean and the public healthy.
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- Recent advances in protein purification using biomagnetic separation - Part 2