Polyamide 4,6 membranes for the encapsulation of Langerhans islets: Preparation, physico-chemical properties and biocompatibility studies

Porous polyamide 4,6 membranes developed as semi-permeable and biocompatible membranes for the encapsulation of pancreatic islets were prepared by precipitation in water. Different membrane morphologies were obtained by varying the molecular weight of polyamide 4,6, the solvent evaporation time and the composition of the casting solution. Each membrane was submitted to differential scanning calorimetry and water flux measurements to study the total water content and the different kinds of water in correlation with its permeability performances. Their biocompatibility was first evaluated by a surface protein adsorption test. Of the various membranes, the one prepared by immersion in water after 5 minutes of solvent evaporation, of 15% KS200 polyamide 4,6 solution added with 1% of polyvinylpyrrolidone K30 seems to be the most promising. This membrane is characterized by a low adsorption of proteins, a high hydraulic coefficient and an asymmetric structure. Such a membrane represents a good candidate to be an efficient immunological barrier. It also exhibits good glucose and insulin diffusion properties. Moreover, rat islets cultivated on its surface were not affected by its presence and no important cell adhesion was noticed when implanted in mice. This membrane exhibits most of the properties suitable for the islet encapsulation with a view to developing a bioartificial pancreas.