Device Uses Magnets to Remove Toxins From Blood

Scientists have invented a device that uses a magnet to extract bacteria, fungi and toxins from blood, potentially throwing a lifeline to patients with sepsis and other infections.

The external gadget—tested so far in rats but not yet on humans—could be adapted one day for stripping Ebola and other viruses from blood, the scientists claim.

Blood infections can be very difficult to treat, and can lead to sepsis, an often-fatal immune response. More than 50 percent of the time, physicians cannot diagnose the cause of an infection that has prompted sepsis, and so they resort to antibiotics that attack a broad range of bacteria. This approach is not always effective, and can lead to antibiotic resistance in bacteria.

In search of a way to clear any infection, a team led by Donald Ingber, a bioengineer at the Wyss Institute for Biologically Inspired Engineering in Boston, Mass., developed an artificial ‘biospleen’ to filter blood.

Acting much like a spleen, the invention uses magnetic nanobeads coated with a genetically engineered human blood protein called MBL, or mannose-binding lectin. The MBL binds to pathogens and toxins, which then can be “pulled out” with a magnet, the developers wrote in the journal Nature Medicine.

To test the device, Ingber and his team infected rats with either E. coli or Staphylococcus aureus and filtered blood from some of the animals through the biospleen. Five hours after infection, 89 percent of the rats whose blood had been filtered were still alive, compared with only 14 percent of those that were infected but not treated. The researchers found that the device had removed more than 90 percent of the bacteria from the rats’ blood. The rats whose blood had been filtered also had less inflammation in their lungs and other organs, suggesting they would be less prone to sepsis.

The researchers then tested whether the biospleen could handle the volume of blood in an average adult human — about five liters. They ran human blood containing a mixture of bacteria and fungi through the biospleen at a rate of 1 litre per hour, and found that the device removed most of the pathogens within five hours.

That degree of efficacy is probably enough to control an infection, Ingber said. Once the biospleen has removed most pathogens from the blood, antibiotics and the immune system can fight off remaining traces of infection — such as pathogens lodged in the organs, he said.

“This treatment could be carried out even before the pathogen has been formally identified and the optimal antibiotic treatment has been chosen,” noted Ingber. “We potentially could treat patients with this bio-spleen during the most infectious, viraemic phase of the [Ebola] disease and reduce the amount of virus in their blood.”

Ingber says that the biospleen could also help to treat viral diseases such as HIV and Ebola, in which survival depends on lowering the amount of virus in the blood to a negligible level. His group is now testing the biospleen on pigs.

Nigel Klein, an infection and immunity expert at University College London, says that the biospleen could also allow diagnosticians to collect samples of a pathogen from the blood and then culture it to identify it and determine what drugs will best treat it. As blood transfusion and filtration are already common practices, he expects that the biospleen could move into human clinical trials within a few years.