Researchers are working on technology that is analogous to dialysis machines, but provides one of the functions of the spleen instead of the kidney. This sort of thing is a very early step on the road that eventually leads to machines capable of reproducing every necessary function of the body's major organs:
Taking advantage of recent advances in nanotechnology and microfluidics, researchers have made significant progress toward a device that could be used to rapidly remove pathogens from the blood of patients with sepsis, a potentially life-threatening condition that occurs when an infection is distributed throughout the body via the bloodstream. The new system effectively acts as an artificial spleen, filtering the blood using injectable magnetic nanobeads engineered to stick to microorganisms and toxins. After the beads are injected, blood is removed and run through a device that uses a magnetic-field gradient to extract the nanobead-bound germs. Then the blood is returned to the body.
[Researchers] looked to the human immune system - specifically, at a class of proteins in the blood that attach to potentially harmful microorganisms or toxins and mark them as targets for other immune cells. The group genetically engineered one such protein - known to bind to over 90 different pathogens, including bacteria, fungi, viruses, parasites, and toxins - so that it functions as a coating for magnetic nanobeads, giving them the ability to collect infectious agents in the bloodstream.
Following an injection of the beads, a patient's blood is run through an external device that contains a system of microfluidic channels, the design of which is inspired by the spleen. In the device, which the inventors call a "spleen-on-a-chip," contaminated blood flows through the channels alongside a saline solution. A magnetic-field gradient is then used to pull the nanobeads and their bound pathogens into that solution.