In vitro immunoisolative properties of microfabricated biocapsules

Transplantation of cells with specific functions is a promising therapy for a wide variety of diseases including diabetes, Parkinson's, and hemophilia. Such transplanted cells, however, are sensitive to both cellular and humoral immune rejection as well as damage by autoimmune activity, without chronic immunosuppression. This study investigates whether microfabricated silicon-based biocapsules, with uniform membrane pore sizes in the tens of nanometer range, can provide immunoprotection of transplanted cells by blocking the passage of IgG through the biocapsule. By utilizing microfabrication technology, biocapsules can be fabricated with membranes having precisely controlled and uniform pore sizes, allowing one to optimize parameters specifically for the encapsulation of specific hormone-secreting cell types. The permeability of IgG was studied in microfabricated biocapsules with various pore sized membranes. In addition, immunoisolative characteristics were monitored by assessing viability and functionality of islets within biocapsules. The semipermeability of microfabricated biocapsules, along with their stability and biocompatibility, may provide an improved encapsulation device for immunoisolation of cell xenografts for hormone therapy, i.e. production of insulin by pancreatic islets in response to changing glucose levels.