Researchers from Harvard’s Wyss Institute have developed a spleen-inspired device capable of rapidly filtering out pathogenic organisms and deadly toxins from the blood of patients. It’s hoped that one day, this blood-cleansing tool could be used to help individuals suffering from a life-threatening condition called sepsis.
Sepsis is the immune system’s overreaction to a bloodstream infection that triggers a cascade of systemic events in the body including inflammation and blood clotting. Even with intervention, some patients may experience organ failure which is often fatal. Doctors can treat patients with antibiotics but more than 50% of the time the causative agent cannot be identified, often because of time constraints, meaning that they have to resort to the “blanket coverage” approach of administering broad-spectrum antibiotics. Unfortunately, this is often an ineffective measure and has the undesirable side effect of encouraging antimicrobial resistance.
With the hope of improving patient outcome, Wyss Institute researchers set out to develop an external blood-cleansing device capable of filtering out a variety of organisms and the toxins they release from the blood without the need to first identify the infectious agent. The end result was “biospleen,” a microfluidic device based on the design of our own blood filtering organ—the spleen.
This device captures pathogens and toxins using magnetic nanobeads covered in a modified human protein called mannose-binding lectin (MBL). In the body, MBL plays a pivotal role in immunity because it is capable of recognizing and sticking to a broad range of infectious agents and is also able to distinguish them from self-molecules.
As blood flows through the device’s channels, a magnet pulls the beads and anything that they have latched on to out of the blood. Filtered blood is then returned back to the patient, much like what happens to patients on dialysis.
The team tested their device in a series of experiments, which are described in Nature Medicine. First, they used human blood that they contaminated with various pathogens. They found that biospleen was able to remove over 90% of the pathogens in the blood after five rounds of cleansing. While one device can only filter a maximum of one liter per hour, multiple devices can be hooked up at the same time to improve the rate of cleansing.
Next, the researchers tested biospleen on rats infected with two species of bacteria that are commonly associated with sepsis in humans—E. coli and S. aureus. Once again, they found that the device was able to remove 90% of the organisms from the rats’ blood. Furthermore, five hours after infection, 89% of the rats receiving treatment survived, whereas only 14% of the control group survived.
Finally, they injected rats with a bacterial toxin in order to mimic a type of shock called endotoxemic shock which is caused by toxic substances manufactured by certain species of bacteria. They found that the biospleen significantly improved survival rates after five hours of cleansing; 86% of the controls died, whereas only 11% of the mice receiving treatment perished.
The researchers believe that this device could also be useful in treating viral diseases such as HIV and Ebola, but they haven’t tested it on viral infections yet. The next stage is to use biospleen on larger animals; if it proves successful, they hope to move on to human trials.