Islet encapsulation devices can induce a Foreign Body Response (FBR) due to the formation of a hardened avascular fibrotic capsule. This FBR is heightened when the device features a smooth surface as fibrous tissue is unable to adhere to the device, causing friction and thus instigating a substantial immunological reaction. This limits nutrient and oxygen diffusion causing islet death and ultimately implant failure. In this study we examine whether additive manufactured multiscale porous coatings promote optimal tissue integration and vascularisation for long-term functional islet encapsulation devices.
Devices exhibiting progressively more complex surface architectures (quantity of pores, microtexture and macrotexture) were implanted subcutaneously in rodents. Upon explant, analysis of fibrous capsule, angiogenic and macrophage response was performed. To validate scalability and functionality, devices were implanted in an STZ-induced diabetes pig model for two weeks before the blood glucose levels were measured in response to the infusion of insulin through the device.
SEM and MicroCT imaging demonstrated no tissue attachment and a noticeable void between the smooth surface devices and surrounding tissue. A significant increase in capsule thickness, vessel density and maturity were associated with complex surface architecture with no difference in macrophage populations. Bioavailability was equal when the same dose of insulin is delivered via the device vs subcutaneously in diabetic pig model.
Additive manufactured multiscale porous coatings on macroencapsulation devices can increase tissue integration and vascularity. These findings demonstrate scalability and functionality and the ability to resolve the immunological and diffusion limitations of current encapsulation devices.