(335f) Cell Encapsulation Using Microfluidic Device
AIChE Annual Meeting
Wednesday, November 15, 2006 - 10:35am to 11:00am
Microencapsulation of living cells provides a new technology to over come various medical problems. Because the polymer membrane acts as an immunological barrier protecting the transplanted cells from immunorejection, the necessity of immunosuppressive drugs in xenotransplantations can be avoided. 20 years after proposed, the idea was successfully put into practice to immobilize xenograft islet cells to facilitate blood glucose control in small animal models. Cell encapsulation technology has been applied to a wide range of therapeutic treatments, such as diabetes, hemophilia, Parkinsons disease, cancer, and renal failure. The application of micromachining technology has increased rapidly in biotechnology in the last decade. By using hydrodynamic flow focusing, the diameter of the microcapsule formed is much smaller than conventional methods, with increase in surface-to-volume ratio, mechanical strength, and ability of nutrients diffusion. In addition, all the encapsulates are of uniform size. In the current study, we utilized various methods for preparing gel microcapsules via microfluidic devices. These methods have been applied for cell encapsulation. The firrst approach is internal gelation. Sodium alginate solution containing insoluble calcium carbonate powder were introduced as disperse phase and was broke up into droplets in continuous phase (mineral oil) using flow focusing technique. Then a secondary continuous phase containing acid was introduced to release calcium from insoluble salt in the droplet. Calcium ions will crosslink the alginate to initiate gelation. The second method to form gelled capsules is by droplet coalescence. It is known that inside microchannel, droplets with larger size move faster than droplets with smaller size. Different size droplets with alternative composition (sodium alginate and calcium chloride) were prepared using flow focusing method. Then they were introduced to a channel long enough to make them coalesce. Using this method, alginate gel droplets can be produced via a microfluidic device. The third method is making gelled droplets thermally. Agarose with low gelling temperature was used as disperse phase. After broke into droplets, they were collected in a vial placed inside an ice bath with temperature lower than 4 C to make droplet gelation. Fibroblast cells were added into agarose solution, cell enclosing capsules with uniform size can be made using this method.