Since the total volume of a required Islet Sheet is less than that of any competing device, boosters can be administered without burdening the patient with literally extra pounds of material. If the functionality of an initial implant diminishes to a negligible level, the implant can be readily removed and replaced. With individually coated islets, once the implant has been made, there is no means of ever retrieving or removing it. Sequential implants continue to add massive quantities of material into the patient's body.

Not only is retrievability a virtuous property from a safety perspective, but it also affords great advantages in research and development. The most persuasive proof of a cure of diabetes is demonstration that on removal of the implant, the recipient subject returns to the diabetic state. Such a demonstration is possible only with a retrievable implant. More importantly, retrievability permits the unique opportunity to devise simple experiments to analyze requirements for various properties of the device.

For example, to determine the optimal thickness and permeability profile of the Islet Sheet coating, several Islet Sheets can be simultaneously implanted into a single animal. These several sheets can consist of coatings varying in thickness and permeability profile. After a period of time, the implants can be quantitatively retrieved. The extent of fibrosis, islet viability and functionality, and physical integrity can be quantified for each sheet formulation. Moreover, replicate sheets can be implanted in different sites within a single animal to determine optimal sheet properties as a function of implantation site. In this way, a single animal experiment can yield a wealth of highly relevant data. The results of such tests will be interpretable without ambiguity.

Because hundreds of thousands of islets are required to cure a diabetic patient, hundreds of thousands of individually coated islets must be implanted. In effect, the patient receives an implant of hundreds of thousands of separate devices. These many individual devices cannot be quantitatively retrieved in the event of some unforseen complication. Since a single Islet Sheet can contain hundreds of thousands of islets, only one or a few sheets need be implanted. This affords the option of emergency retrieval.