US scientists have made a microfluidic device that cleanses blood of toxic pathogens.

Sepsis is a lethal disease caused by a microbial infection that saturates the blood and overwhelms the body's defences. Commonly caused by the fungi Candida albicans, it kills over 200 000 people in the US each year. Antibiotics are the most effective treatment but sometimes they can't cope with the quickly-multiplying pathogens. Donald Ingber, at Children's Hospital Boston and Harvard Medical School, and colleagues say their device rapidly reduces the number of pathogens in the blood so the antibiotics have fewer pathogens to kill.

A magnetic field gradient generated across the channels separates the fungi-bound beads from the blood

Ingber's device consists of four vertically stacked channels filled with flowing fungi-contaminated blood. He added magnetic microbeads coated with antibodies to the blood, which bound to the fungi. A magnetic field gradient generated across the channels continuously separated the fungi-bound beads from the blood. Ingber showed the device can clear 80 per cent of the fungi, 1000 times faster than other blood cleansing prototypes.

'We have integrated proven microfluidics and micromagnetic technologies to engineer a potentially effective, low-cost and portable blood cleansing system that can be applied worldwide to save human lives,' says Ingber. He adds that the patient's blood would be diverted out of their body, through the device for cleansing before being returned to the circulation, with simultaneous antibiotic treatment.

'This is a refreshingly brilliant approach for treating patients with septicaemia. The proof-of-principle is very convincing,' comments Tonse Raju, Medical Officer at the National Institutes of Health, Bethesda, US. 'However, major hurdles to be conquered are: effective cleansing when the blood flow rates are in the physiological range; removal of inflammatory products of sepsis that can perpetuate organ damage even in the absence of pathogens in the blood; and the problem of dealing with regions of the body where the organisms can reside without getting into circulation.'

Ingber says he is working on improving the device. 'We are currently developing a new process to increase the binding of magnetic beads to pathogens,' he explains. 'We are also developing new microfluidic designs that mimic the native architecture and function of the spleen, which is normally responsible for removing pathogens from the bloodstream. Prototypes demonstrate extremely high separation performance without the lost or dilution of circulating blood.'

Emma Shiells

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