A Fast Magnetic Fix for Sepsis?

In the micromagnetic-microfluidic blood cleansing device, saline collection fluid and contaminated blood with opsonized pathogens flow together without mixing under laminar conditions. As the fluids pass the external magnetic field concentrator, opsonized pathogens and excess beads are selectively pulled from the blood across theboundary between laminar streams and into the collection fluid where it exits as waste. A multiplexed, four-channel prototype can continuously cleanse over 80 percent of pathogens from contaminated human whole blood at a rate of 20 mL/hr in a single pass. (Illustration: Kristin Johnson and Chong Wing Yung, PhD, Children's Hospital Boston)  

Sepsis, an infection of the blood, can quickly overwhelm the body's defenses and is responsible for more than 200,000 deaths per year in the U.S. alone. Premature newborns and people with weakened immune systems are especially vulnerable. Since most existing treatments are ineffective, researchers in the Vascular Biology Program at Children's Hospital Boston have come up with a first line of defense -- using magnetism to quickly pull pathogens out of the blood.

Their blood-cleansing device, developed by Chong Wing Yung, PhD, a researcher in the laboratory of Don Ingber, MD, PhD, is described in the journal Lab on a Chip.

The system they envision will work like this: The patient's blood is drawn, and tiny magnetic beads, pre-coated with antibodies against specific pathogens (such as the fungus Candida albicans) are added. The blood is then run through a microfluidic system in which two liquid flow streams run side by side without mixing -- one containing blood, the other a saline-based collection fluid. The beads bind to the pathogens, and a magnet then pulls them (along with the pathogens) into the collection fluid, which is ultimately discarded, while the cleansed blood in reintroduced into the patient.

Tested with contaminated human blood, a device with four parallel collection modules achieved over 80 percent clearance of fungi in a single pass, at a flow rate and separation efficiency that would be viable for clinical applications. Yung and Ingber estimate that a scaled-up system with hundreds of channels could cleanse the blood of an infant within several hours.

"This blood-cleansing microdevice offers a potentially new weapon to fight pathogens in septic infants and adults, that works simply by removing the source of the infection and thereby enhancing the patient's response to existing antibiotics," says Ingber.

Yung, Ingber and physicians Mark Puder, MD, PhD, and Jay Wilson, MD. from the Department of Surgery at Children's Hospital Boston, with collaborators from Draper Laboratories, recently won a $500,000 grant from the Center for Integration of Medicine and Innovative Technology (CIMIT) to further the work. The next phase will be to test the device in an animal model.

The study was funded by CIMIT, with additional resources from Harvard University's Center for Nanoscale Systems (CNS) and the National Nanotechnology Infrastructure Network (NNIN) initiative.