Microscopic magnetic beads could quickly detect pathogens

Dynabeads are commercially available microscopic magnetic spheres which scientists use to isolate certain types of cells and proteins. Now, MIT researchers are developing a method of using the beads to quickly spot pathogens in drinking water or blood samples.

Utilizing current lab-based technologies, in which bacterial or viral cultures are grown, it may take several days to process samples of bodily fluids, water or other liquids. Needless to say, if pathogens are present in any of those substances, then the sooner that people know, the better.

That's where the Dynabeads come in.

Invented in 1976, the beads consist of a magnetic iron core covered in a polymer shell. That shell gets coated with different types of antibodies, which bind with specific target molecules in liquid samples to which the beads get added. By placing a magnet on the outside of a vial containing such a sample, scientists can thus gather together and analyze the target molecules, which are stuck to the Dynabeads.

That said, detecting the presence of pathogens in this fashion is still a rather time-consuming process. Led by professors Loza Tadesse and Rohit Karnik, a team at MIT is in the process of creating a work-around.

The scientists discovered that by utilizing a technique known as Raman spectroscopy, it's possible to detect Dynabeads within a liquid sample by the distinctive manner in which the beads scatter light. That unique "Raman signature" can be picked up in less than one second.

Karnik tells us that they are now developing a technology for separating free, unbound beads from those that are bound to pathogen cells. A portable device will then quickly and easily differentiate between the Raman signatures of the two. If the signature of pathogen-bound Dynabeads is detected, then users will know that the pathogen is present in the sample.

In lab tests performed so far, the process has already been used to detect Salmonella bacteria in water samples within just half a second.

"This is something that can be used to rapidly give a positive or negative answer: Is there a contaminant or not?" says Tadesse. "Because even a handful of pathogens can cause clinical symptoms."

Source: MIT