Co-delivery of a combination of more rapidly released GFs together with more slowly released factors may then permit engineered control of desired physiologic processes such as angiogenesis through use of this selective release sequence

concept. The Johnson et al. study [51] is an example that illustrates the usefulness of permeability enhancement, through nanotechnology techniques, for delivery of selleckchem tissue based therapeutic agents. Their efforts were to enhance the performance of a bioartificial pancreas to treat diabetes that uses microencapsulation as an immune barrier for transplanted Inhibitors,research,lifescience,medical islets of Langerhans. Unfortunately, the barrier also imposes oxygen diffusional limitations that can result in loss of viability and function. It is critical that the necessary amount of oxygen be delivered to encapsulated tissue after transplantation in order to maintain normal levels of Inhibitors,research,lifescience,medical insulin secretion. Without a solution that allows for effective oxygen delivery, transplantation of encapsulated tissue may never be successful. Their investigation included methods to reduce oxygen transport limitations by enhancing encapsulant oxygen permeability, for example, by combination of a highly concentrated perfluorocarbon

(PFC) nanoemulsion with alginate (PFC alginate). A theoretical reaction—diffusion model was used to predict the three-dimensional Inhibitors,research,lifescience,medical Inhibitors,research,lifescience,medical distribution of oxygen partial pressure in a spherical microcapsule and a planar slab containing islet tissue, from which the loss of cell viability and the reduction in insulin secretion rate are estimated. Numerical simulations were carried out for normal alginate and PFC alginate to examine the effect of surface

oxygen partial pressure, capsule Inhibitors,research,lifescience,medical diameter, slab thickness, and the size and density of dispersed islet tissue. Results show that hypoxic conditions can be reduced, thereby enhancing islet viability and substantially maintaining insulin secretion rate when the PFC nanoemulsion is incorporated in the encapsulation material for both geometries. The approach was also evaluated experimentally, and the ability to enhance these encapsulated tissue survival and function was successfully demonstrated, both in vitro and in vivo. Intact islets encapsulated in normal alginate and in PFC alginates having the composition described in the numerical predictions were used as model systems. Recovery of viable tissue after culture under various O2partial pressure conditions was expressed as the oxygen consumption rate (OCR)/unit volume of capsule divided by the same parameter measured immediately after encapsulation and before culture. When cultured at very low pO2, fractional OCR recovery was substantially greater with PFC alginate than with normal alginate.