Purification of polymers used for fabrication of an immunoisolation barrier.

A multistep extraction procedure has been tested for purification of natural and semi-synthetic polymers used for fabrication of an immunoisolation barrier for implanting animal cells. This procedure, originally described by Klock et al. for alginates, has been adapted for other gelling polymers to remove pyrogens (endotoxins) and mitogens. Several other steps have also been tested, resulting in a new and simple procedure for polymer purification, giving satisfactory levels of contamination. Endotoxin levels have been quantified by means of chromogenic and gelclot LAL methods. A simple calculation of the endotoxin permissible levels shows that the quality of purified polymers exceeds FDA specifications for implantable polymers.