**1. Introduction**

Type I diabetes (T1D) is a severe disease resulting from the destruction of the beta cells in the islets of Langerhans (islets) residing in the pancreas. The loss of beta cells leads to lack of insulin and increased glucose levels in the blood (hyperglycemia). If untreated, T1D 1 leads to permanent damage to small blood vessels which in turn causes blindness, kidney failure, heart failure and eventually premature death [1,2]. Even when treated with external insulin, blood glucose levels are not stable and fluctuate according to eating habits and insulin administra‐ tion. On the other hand, too much insulin can cause a dangerous drop in the blood glucose level (hypoglycaemia), which leads to confusion, loss of conscience and, if not immediately treated, sudden death.

Great efforts are made to develop a "closed loop" insulin pump that will secrete insulin when needed (after a meal) and sense the glucose level in order to stop secretion when glucose levels drop to normal levels. Islet implantation is another successful approach that utilizes donor's islets isolated from the pancreas to replace the missing islets of the patient. This approach, although promising, faces several obstacles that decrease its feasibility.


To approach these two fundamental problems, Beta-O2 Technologies had designed implant‐ able flat geometry device containing islets that were supplied with oxygen by immobilized and illuminated cyanobacteria. The implanted islets are partly protected from the attack of the immune system by a porous Teflon membrane. **Photosynthesis** was the source of the supply of oxygen, which is the focus of this chapter . Indeed, the designed device termed bioartificial pancreas contains battery-powered illumination module, photosynthetic organisms that produce oxygen and islets that produce insulin upon demand.

To create this "science fiction" bio-artificial pancreas device, a multidisciplinary approach was needed involving optics, material science, diffusion models, plant and islet biochemistry and other fields.
