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

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The medical power of attraction

Chemistry World - London,UK

25 February 2009

http://www.rsc.org/Publishing/ChemTech/Volume/2009/04/medical_power_at

traction.asp

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.

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.

" This is a refreshingly brilliant approach for treating patients with

septicaemia "

- Tonse Raju, National Institutes of Health, Bethesda, US'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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