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Role of protein contaminants in the immunogenicity of alginates.

Alginate is widely used for cell microencapsulation and transplantation. There is a lack of standardization of alginate purity and composition. In a previous study, we compared different alginate purification methods and concluded that polyphenol and endotoxin contaminants were eliminated efficiently but residual protein contaminants persisted with all of the methods under evaluation. The objective of this study was to test the hypothesis that residual proteins play a role in the immunogenicity of certain alginate preparations. Using preparative size exclusion chromatography (SEC) and a large scale purification protocol that was derived from the findings obtained with SEC, we substantially decreased the protein content of alginate preparations. When implanted into mouse peritoneum, barium alginate beads made of alginates that were purified using SEC or the derived large scale protocol induced significantly less pericapsular cell adhesion than those made with control alginates. In conclusions, these results suggest that removing residual protein contamination may decrease the immunogenicity of certain alginate preparations. The measurement of proteins could be used as a screening method for evaluating alginate preparations.