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© 2001 SAGE Publications Requirements for Encapsulation Technology and the Challenges for Transplantation of Islets of LangerhansIslet Sheet Medical LLC,
Islet Sheet Medical LLC,
Islet Sheet Medical LLC, Requirements for successful cellular encapsulation are reviewed, with emphasis on the bioartificial pancreas. These requirements fall into three general categories: graft tissue viability, host response, and surgical practicality. Several design decisions, such as choice of materials, have ramifications on many requirements that must be simultaneously considered. Device dimensions are critical for allowing sufficient oxygen flux to the graft tissue. Host response to the materials used is varied. Some materials appear to promote new blood vessel growth, yet evidence distinguishing genuine neovascularization from ongoing fibrosis is scant. A neutral host response is supported by the authors' work, which additionally increases the possibility of device retrieval. The use of alginates for bioneutral encapsulation has mixed results, possibly because the polymer properties and the purity of the alginates are rarely characterized. Polycations, such as polylysine, have been applied to overcome shortcomings in polymer chemistry but have been shown to be unnecessary and possibly detrimental to host response. Microcapsules often suffer from incomplete coverage of cells, another issuethat is rarely addressed. Complete coverage is an absolute requirement for evasion of humoral immune destruction of the encapsulated tissue.
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