Biomedicine

Microfiltering Sepsis

(Page 2 of 2)

  • Friday, May 23, 2008
  • By Jennifer Chu

Ingber modeled the design in theory after the spleen, which contains molecules that bind to pathogens, ferrying them out of the body as blood flows through.

So far, the team has been able to filter a volume of blood comparable to that found in a premature baby within two hours. The researchers are currently working to increase the device's capacity and efficiency, and they plan to use more pairs of channels to increase the filtration rate. The Center for Integration of Medicine and Innovative Technology (CIMIT) recently awarded the team a $500,000 grant toward further developing the technology, and Ingber plans to use the funds to set up animal studies in the next year.

"We're going to try this approach in rabbits, because they are the same size as preemies, who often have life-threatening sepsis," says Ingber. "And we're hoping that if we can demonstrate survival in rabbits, we can quickly go to patients."

Ultimately, Ingber envisions incorporating the microfluidic device into a cartridge form, which can be snapped into any conventional hemofiltration or dialysis system.

Jeffrey Platt, a professor of surgery at the University of Michigan Medical School, says that one challenge in using such a device is anticipating the specific pathogen involved in a given case of sepsis. There are multiple infectious agents, bacterial and fungal, that could trigger septic shock, and researchers would have to devise different magnetically coated solutions for each pathogen. However, Platt says, the device may effectively treat other conditions outside of sepsis.

"The concept underlying the device is novel and interesting, and might ultimately find other applications, such as removal of malignant cells or cholesterol particles from the blood," says Platt. "Whether in fact it would find one or another use depends on what may be found when it is tested in whole animal systems."

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nekote

139 Comments

  • 1362 Days Ago
  • 05/23/2008

What's the value of the microfluidics?

Please check the caption of the graphic.
Top image (actually the right image)?
blood flow from left to right (rather than top to bottom)?
Presence of a magnet in (bottom [image?]) actually left image?
Rotate pair of images counter clockwise, 90 degrees?


What is the value /purpose of the microfluidic channels?

Why not simply pass blood over / through surfaces coated with the key pathogen receptor molecules?  Like sticking flys to fly paper.

Alternatively, have those key pathogen receptor molecules on the surface of particles that can be filtered / channeled by their comparatively "large" size?  Or magnetism (if part of the particle is or can be induced to be magnetic)? Or other means of discriminating?

Such selective filtering methods could be quickly, easily and readily adapted to, say, existing pheresis machines (that remove / filter platelets from donors and return the remainder of the blood back to the donor) or dialysis machines?

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cyberpageman

53 Comments

  • 1362 Days Ago
  • 05/23/2008

Re: What's the value of the microfluidics?

I used to work on the magnetic separation of biological particles. A magnetic field is an easy way to separate magnetized particles from liquids.

As I understand the sepsis filtration, microfluidic channels are used because the pathogens have to diffuse out of the blood.  Diffusion is slow.  The microfluidic device compensates for the slow diffusion by using only a short pathlength over which the pathogens have to diffuse.  A micro device also has the advantage of requiring only a relatively small magnet to provide an efficient high-gradient magnetic field to pull the magnetized particles out of solution.

The pathogen-receptor-coated surface idea would work for a limited time, but would become saturated.  The microfluidic device provides a constant source of a fresh "surface" in the form of a stream of coated particles so saturation does not become a problem.

The Children's Hospital group have done a good job in developing their system.  Hopefully they will be able to scale it up so it will be useful clinically.

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nekote

139 Comments

  • 1361 Days Ago
  • 05/24/2008

Re: What's the value of the microfluidics?

How many grams of the pathogenic bad guys are going to be captured?  1 g?  100 g?

For a magnetic / size particle type method, I was thinking there would be a constantly added "drip" of particles mixed into the blood stream from the donor and that absolutely 100% of those particles would be removed, before the blood was returned to the donor.

For a surface coated method, one time use disposable media.  It would be best, of course, if there was some sort of (visual) indication of capture / utilization / "fullness".

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bkf11

10 Comments

  • 1357 Days Ago
  • 05/28/2008

Re: What's the value of the microfluidics?

Good question.
The advantage may be that the microfluidic device actually -removes- the pathogens from the blood stream so that toxins that the pathogen may be producing (constantly or upon its death) are not released into the bloodstream.
Just a guess!

Oh, and the image for the article is sideways - the right side seems to be what the caption refers to as "up".

Benjamin

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