How does the structure of pullulan alginate composites change in the biological environment?

Alginate and pullulan are two polysaccharides with numerous applications in the field of biomedical sciences such as wound dressing, soft and hard tissue regeneration. These materials come into contact with the human body for various time intervals, depending on their intended use. In this study, alginate–pullulan composites were synthesized and assayed in vitro as follows: bioactivity, biodegradability, swelling ratio, and biocompatibility. After 2 weeks of immersion in simulated body fluid, calcium oxalate appeared on the surface of the composites near the apatite layer. The in vitro biocompatibility assay using human fibroblastic and osteoblastic cell lines showed encouraging results; therefore, the polymeric composite proved to be non-toxic and safe for further in vivo testing. This was also reinforced by cell proliferation, necrosis, apoptosis, and surface adhesion tests. The most promising results were obtained with the composite that was prepared using an alginate: pullulan weight ratio of 1:0.75. Applying this ratio caused cellular growth on the surface of the biomaterial. The applicability of composites was limited by the appearance of calcium oxalate. However, this phenomenon could be prevented by introducing an inorganic component into the alginate–pullulan composites, such as bioactive glass.