July 1, 2001
The need to encapsulate biological cells artificially so that they retain full biological activity while being transparent to the body's immune system is one of the great challenges facing bio-materials science. Researchers at the University of Chicago's MRSEC have made a breakthrough in the area of encapsulation processing which may lead to a new approach for treating diseases such as Insulin Dependent Diabetes Mellitus (the fourth largest cause of death by disease in the United States). In this disease, the Islets of Langerhans, which produce insulin, are damaged or destroyed.
One treatment for patients suffering from this disease is to transplant the entire pancreas. Another, much less invasive approach is to transplant isolated Islet cells that have been coated with a thin (approximately 10 micron) shell that is not recognized by the immune system of the body but is permeable to insulin, nutrients, electrolytes, oxygen, and metabolic waste. Since Islets are irregular in shape and size (100-300 micron) one must apply a coat to each one that will conform to its specific shape.
The MRSEC researchers have developed a technique based on the process of selective withdrawal of one fluid through another to manufacture such particle-specific coats. In essence, each cell is shrink-wrapped by a coat of pre-polymer which is subsequently polymerized. We have demonstrated the polymerization using photochemical, thermal, and chemical strategies. We have also prepared coatings based on hard plastics and on soft hydrogels that are better suited to bio/materials applications.
This schematic illustrates the method of selective withdrawal to confine one fluid as a tube within a second fluid. The photograph shows this method applied to a lower fluid of water that is drawn through an upper fluid of oil. The third figure is a confocal microscope image of a 200 micron bead taken around its equator. The bead is coated with a poly(ethylene glycol) that is labeled with a fluorescent dye.
Milan Mrksich*, Department of Chemistry; Sidney Nagel*, Department of Physics and Horacio Rilo, Department of Surgery; * denotes Senior MRSEC Investigator