Islet xenotransplantation

What would surgeons like from materials scientists?

Surgery involves the repair, resection, replacement, or improvement of body parts and functions and in numerous ways, surgery should be considered human engineering. There are many areas in which surgical materials could be improved, but surgeons are generally unaware of materials available for use, while materials scientists do not know what surgeons require. This article will review some of the areas where surgeons and materials scientists have interacted in the past and will discuss some of the most pressing problems which remain to be solved. These include better implant materials for hernia repair, breast reconstruction, the treatment of diabetes, vascular stenting and reconstruction, and electrical pacing devices. The combination of tissue engineering and nanomaterials has great potential for application to nearly every aspect of surgery. Tissue engineering will allow cells or artificial organs to be grown for specific uses while nanotechnology will help to ensure maximal biocompatibility. Biosensors will be combined with improved electrodes and pacing devices to control impaired neurological functions.

A new bioartificial pancreas utilizing amphiphilic membranes for the immunoisolation of porcine islets: a pilot study in the canine

We have developed a replaceable bioartificial pancreas to treat diabetes utilizing a unique cocontinous amphiphilic conetwork membrane created for macroencapsulation and immunoisolation of porcine islet cells (PICs). The membrane is assembled from hydrophilic poly(N,N-dimethyl acrylamide) and hydrophobic/oxyphilic polydimethylsiloxane chains cross-linked with hydrophobic/oxyphilic polymethylhydrosiloxane chains. Our hypothesis is that this membrane allows the survival of xenotransplanted PICs in the absence of prevascularization or immunosuppression because of its extraordinarily high-oxygen permeability and small hydrophilic channel dimensions (3-4 nm). The key components are a 5-10 microm thick semipermeable amphiphilic conetwork membrane reinforced with an electrospun nanomat of polydimethylsiloxane-containing polyurethane, and a laser-perforated nitinol scaffold to provide geometric stability. Devices were loaded with PICs and tested for their ability to maintain islet viability without prevascularization, prevent rejection, and reverse hyperglycemia in three pancreatectomized dogs without immunosuppression. Tissue tolerance was good and there was no systemic toxicity. The bioartificial pancreas protected PICs from toxic environments in vitro and in vivo. Islets remained viable for up to 3 weeks without signs of rejection. Neovascularization was observed. Hyperglycemia was not reversed, most likely because of insufficient islet mass. Further studies to determine long-term islet viability and correction of hyperglycemia are warranted.