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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.

Detection of foodborne pathogens using magnetic bead separation

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.

Sandwich hybridization DNA/RNA capture using magnetic beads

The vision of a cheese sandwich is actually quite useful when trying to understand the sandwich hybridization technique. In this analogy the cheese represents the single strand (ss) target DNA or RNA. The bread represents the oligonucleotide probe. For each target there are two oligonucleotide probes. The probes are synthesized to be perfectly complementary to the ends of the target ssDNA or RNA. Therefore, during an incubation period each oligonucleotide probe will bind to its specific end of the target DNA: one at the 5’ end and one at the 3’ end.

Using magnetic nanoparticles for molecular diagnosis of S. aureus

The bacteria Staphylococcus aureusis of major concern in modern healthcare.Once it spreads to a patient’s bloodstreamthe infection can lead to sepsis and death. Hospitalized patients are particularly vulnerable, especially those with weakened immune systems. Some strains of S. aureushavebegun to demonstrate antibiotic resistance. For these reasons it is important to identify and contain infection early; rapid detection of bacteria in patient sera is key. Traditional culture methods are time-consuming and require transportation of samples to offsite clinical laboratories.Development of a rapid point-of-care diagnostic tool is desirable, andthe magnetic nanoparticleis rapidly becoming the tool of choice.

First use biomagnetic separation to isolate the target molecule

Magnetic nanoparticles are fantastically customizable due to surface coatings and functional moieties, and are easily recoverable from solution. A functionalized nanoparticle will bind to its target after a short incubation time, and the conjugate can be isolated with the help of a magnetic separation rack. This technology allows for the rapid selection and concentration of a target molecule. Once the target molecules, in this case S. aureus bacteria, are isolated, further identification methods can be used. This is where a group of researchers working in Istanbul, Turkey became creative.

The grouphas engineered a S. aureus detection system using a mesoporous silica nanoparticle-oligonucleotide conjugate. The system’s limit of detection is 682 cells/mL, which indicates potential for use as a point-of-care diagnostic. The system detects Micrococcal nuclease (MNase), which is an enzyme specifically secreted by S.aureus. MNase degrades RNA or DNA, and is well known within the field to be a marker of S. aureus infection.

The system works as follows:

A sample of blood (1 mL) is mixed with magnetic nanoparticles coated with silica and functionalized to bind to S. aureus.
The nanoparticle-bacteria conjugate is isolated from solution by biomagnetic separation.
The isolate is heated to release MNase out of the bacteria and into solution
A non-magnetic mesoporous silica nanoparticle filled with fluorophore is added to the solution. The pores of this nanoparticle are sealed shut with oligonucleotides that are resistant to degradation by all nucleases except MNase. When the pores are capped the fluorophore is quenched and no fluorescence is visible.
If MNase is present in solution the oligonucleotide caps are degraded, the nanoparticle pores open, and the flurofores are released. The free fluorphores are no longer quenched, and a fluorescence signal is measured.

Recent advances in protein purification using biomagnetic separation - Part 2

Recent advances in protein purification using biomagnetic separation

The use of magnetic nanoparticles and biomagnetic separation to isolate proteins from solution is advancingover more traditional column-based methods. Magnetic nanoparticles provide a gentler and more rapid separation process compared to column-based methods, and often demonstrategreater yield. With a properly scaled separation rack the separation process can be monitored in real-time and calibrated across experiments.

DNA isolation from bacteria using charge-reversible magnetic nanoparticles

Magnetic bead cell separation for the detection of circulating tumor cells

Column-based magnetic activated cell sorting

Sepmag Q100 mL magnetic separation rack

Reversible and irreversible aggregation of magnetic particles

There are many variables to consider when designing a magnetic separation system and tailoring it to the experimental goal. Bead surface functionalization is one key component, and often receives the most attention because it is the most obvious point of control for assay specificity. However, it is easy to lose site of the fundamental mechanics of magnetic separation. When designing a magnetic separation protocol it is also important to consider the movement of the magnetic particles in the magnetic field gradient. Superparamagnetic particles will form chains when placed into a magnetic field, a key property to have high enough separation speed for practical purposes.