Preliminary research on biocompatibility of alginate-chitosan-polyethyleneglycol microcapsules

Background. To compare the biocompatibility of the alginate-polylysine-alginate (APA) microcapsule and the alginate-chitosan-polyethyleneglycol (ACP) microcapsute which newly developed in our laboratory. Methods. 1000 ACP microcapsules and APA microcapsules were implanted into the peritoneal cavity of Wister rats, and retrieved at 4 days and 3 weeks after implantation. The number of retrieved microcapsules and percentage of microcapsules with pericapsular fibrosis were recorded. 50, 100 and 200 of each kind of microcapsule mere co-cultured with human serum, the ability of complement activation of these microcapsules were recorded. Isolated rat islets were microencapsulated with ACP microencapsulates and APA microcapsulates, the amounts of secreted insulin were recorded when these encapsulated islet were serially cultured in Hank's solution containing 3.3mmol/L and 16.7mmol/L glucose. The unencapsulated islets were employed as control. Results. Four days after implantation, the number of retrieved microcapsules were: ACP microcapsule: 845 +/- 40.4; APA microcapsule: 807.6 +/- 45.7, while the percentage of percentage of microcapsules with pericapsular fibrosis were 16.4 and 65.68% (p<0.05). Three weeks after implantation, the number of retrieved microcapsules mere: ACP microcapsule: 715133; APA microcapsule: 367.5 +/- 105.6 (p<0.05), while the percentage of respective microcapsules with pericapsular fibrosis were 27.8% and 83.9% (p<0.05). The residual complement activity of human serum was much higher in the ACP activation group. As with unencapsulated islets, the ACP microencapsulated islets maintained the ability of constitutional insulin secretion and stimulated secretion when challenged with high concentration glucose. No significant difference was observed among groups. Conclusions. The ACP microcapsules possess better biocompatibility than AFA microcapsules.