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Faster and more efficient methods of pathogen detection are in high demand. The traditional methods involve collection of patient blood or swab samples for multi-day cultures. These methods are time-consuming and require full laboratories with skilled technicians and sterile equipment. As such, they are not ideal for low-income areas or for rapid pathogen detection. There is a need for rapid pathogen technology and point-of-care diagnostic tools. Ideally, these technologies will come with a built-in validation protocol. Magnetic nanoparticles and molecularly imprinted polymers are good candidates for improved pathogen detection systems. An additional benefit to using magnetic nanoparticles is that the separation process is easy to quantitatively measure with a validation protocol.

 Magnetic nanoparticles for pathogen detection

Magnetic nanoparticles can be functionalized with antibodies that target bacterial pathogens in patient samples. When these functionalized nanoparticles are combined with fluorescent tags or quantum dots they can significantly speed up the diagnostic process. The  benefit of using magnetic particles is that they can be rapidly separated out of solution with a magnetic separation rack. The magnetic separation rack can come with validation software. The validation protocol first requires the operating technician to produce a standard curve for a particular separation volume. The standard curve provides baseline separation kinetics that can be expected for that sample volume. If any deviations from the standard curve are observed during sample separation, then the technician knows immediately and can correct the problem.

Upon completion of a successful magnetic separation, the particles can be analyzed for the presence or absence of fluorescence to determine if the target bound to the nanoparticles. This method is also known as a sandwich immunoassay. Another magnetic particle detection method utilizes quantitative polymerase chain reaction (qPCR) amplification of the target genetic material. The amplification of the genetic material is only possible if it is present in the first place. So, the magnetic nanoparticles are incubated with the patient sample before being isolated with a magnetic separation rack. The genetic material is isolated and amplified to determine if it is present in the patient sample. These two diagnostic strategies using magnetic nanoparticles are rapid and easy to scale down to a portable system. 

Free PDF guide:  "Validation of Magnetic Bead Separation Processes" 

Molecularly imprinted polymers for pathogen detection

The magnetic nanoparticle system works well as long as there is a known antibody that can be conjugated to the magnetic particle. However, this system won’t work as well in situations were there is no molecule with known affinity to the target. It would be great if we could make a pattern that perfectly matches any target pathogen. In fact, we can do this! Molecularly imprinted polymers make this possible. These polymers are actually formed around the target pathogen so they have the binding sites and cavities to perfectly match the target. The template molecule is removed to leave the imprinted polymer behind. These molecularly imprinted polymers can be attached to magnetic nanoparticles and used for pathogen detection in similar procedures as described above for immunoassays.

Uses for molecularly imprinted polymers for pathogen detection

Molecularly imprinted polymers have been used for the detection of influenza, dengue virus, Japanese encephalitis virus, HIV, hepatitis A virus, hepatitis B virus, adenovirus, picornaviruses, and Staphylococcus aureus bacteria. The ability to create a polymer with specificity to any template  means that molecularly imprinted polymers are a powerful technology for pathogen detection. Additionally, unlike conjugated biomolecules, these polymers have long-term stability. Molecularly imprinted polymers are a new technology with an exciting future. Perhaps they will work their way into new point-of-care technologies and help diagnose disease in resource-poor areas.

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Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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