Intraperitoneal stability of alginate–polyornithine microcapsules in rats: An FTIR and SEM analysis

Alginate–polycation microcapsule systems have been used over decades as delivery vehicles for cell and protein therapy. These systems have been unpredictable across a range of indications with questions resulting around the inherent stability of the alginate polysaccharide and failure mode of the delivery system. The current study focuses on such a system using 5 different alginates, 2 of which are commercially purified, which are crosslinked by polyornithine. Capsules formed by frequency-generated droplet formation were studied in the peritoneal cavity of Long-Evans rats over the course of 3 months by morphometry, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy of the surface. Individual capsule components were also investigated on FTIR and a relative stability index was generated by titration for comparison to explanted samples over time. Using these techniques, a distinct degradation pattern was noted and is compared between the 5 alginate sources.