New device to cleanse blood

Scientists have developed a blood-cleansing device which they say will be used in the future to remove bacteria and toxic substances from the blood of patients with sepsis, a life-threatening condition caused by bloodstream infections.

Researchers at Harvard University in the US, drawing inspiration from the architecture of the human spleen, have constructed a fluidic device that can clear more than 90 per cent of the bacteria from the blood of laboratory rats within five hours.

The device - the size of an iPhone5 and called ‘biospleen’ by its designers is intended for the treatment of sepsis, a key cause of mortality in intensive care units worldwide.

In sepsis, live and dead microbes in the bloodstream cause a build-up of toxic substances, which often leads to multiple organ failure and eventually death. Studies suggest that three to five among 10 patients with sepsis typically die even in state-of-the-art hospitals.

“The biospleen addresses the root problem in sepsis by removing the microbes and the toxins produced by bloodstream infections simultaneously,” the scientists said, describing their experiments in a research paper in the journal Nature Medicine.

“We don’t have to kill the microbes; the device just captures and removes them,” said Michael Super, a senior scientist and a research team member at the Wyss Institute for Biologically Inspired Engineering at Harvard.

The biospleen uses microscopic magnetic nanobeads coated with a genetically engineered human protein called opsonin to capture a variety of microbes. The magnets pull opsonin-bound microbes and the infection-related toxins from the blood.

In laboratory experiments, the device removed several species of bacteria and fungi as well as toxins from human blood while it flowed through the biospleen at 1.25 litres per hour.

In rats, the biospleen cleared more than 90 per cent of two species of disease-causing bacteria —Escherichia coli and Staphylococcus aureus — from the blood, reduced the levels of inflammation, and increased survival rates.

“The biospleen is intended to address a huge unmet medical need - at least six million people die of sepsis every year, especially in developing countries,” Michael said.

But the scientists caution that the device will need to undergo rigorous human trials before it can be used in hospitals.

“We still need to do large animal studies, so it could take another two years before human trials,” Super said.

“At this point in time, there is no specific proven treatment for sepsis,” said Palepu Gopal, intensive care specialist at Care Hospital, Hyderabad, who was not associated with the Harvard research efforts.

“The only drug we’ve ever had specifically for sepsis was withdrawn in 2011 after a large clinical study failed to show any survival benefits to patients who had received the drug. Today we use only antibiotics and supportive therapy,” said Gopal, who is also the secretary of the Indian College of Critical Care Medicine.

“While some companies have introduced blood-cleansing devices that have been used on patients with sepsis, there was no device yet that could also remove the offending micro-organisms,” Gopal said.

“If this new device lives up to its promise, it would be a significant advance in sepsis therapy,” Gopal said.

The emergence of drug-resistant microbes has complicated the medical war on sepsis. Doctors often lose sepsis patients because the bacteria teeming in the bloodstream do not respond to antibiotics. But the biospleen is expected to work irrespective of whether the microbes respond to drugs.