ABSTRACT
There have been numerous attempts to replace organ function using cell transplantation including direct injections of dissociated cells into organs such as the liver, kidney or spleen.1'5 Subcutaneous and intraperitoneal routes have also been evaluated.6"10 More recent investiga tions have applied extracellular matrix polymers as structural supports for cell transplantation and immunoprotection.11,12 Potential medical applications of such ‘ artificial cells” or “tissue engineered” organoids include an extracorporeal bioartificial liver for detoxification,2 artificial red blood substitutes,13 the extracorporeal artificial kidney for hemodialysis,14 immunosorbents15 and drug delivery systems.16 The transplantation of immunoisolated (microencapsulated) cells represents another emerging area in biotechnology research and commercialization. Under such a scenario, the encapsulated cells, which could be a xenograft, would be hidden from the immune system of the body, but would still be able to respond to extracellular stimuli (e.g., blood glucose), with the required hormone, in the case of diabetes therapy insulin, secreted into the systemic circulation. Other applications of the microencapsulation concept include the encapsulation of genetically modified cells, which represents a novel approach to somatic gene therapy.17
