Biological and mechanical characterization of chitosan-alginate scaffolds for growth factor delivery and chondrogenesis.

Chitosan-alginate (Ch-Al) natural polysaccharide blends have been used for wound healing, tissue engineering, and drug delivery due to their ability to form pH-dependent ionic chain-chain interactions. Yet, the biomechanical properties and growth factor (GF) release kinetics of Ch-Al, which are important in controlling the microenvironment during tissue regeneration, have not been fully explored. This study examines the compressive elastic modulus of many Ch-Al scaffold formulations and crosslinking conditions, and also the strain recovery after compressive deformation of Ch-Al scaffolds, both of which make Ch-Al an attractive composite for reproducing articular cartilage's resistance to and resiliency under compression. Cell viability, proliferation, and in vitro cartilaginous matrix production (collagen type II, glycosaminoglycans, aggrecan) without supplemental GFs are also investigated, demonstrating the polymer blend's inherent chondrogenic properties. Additionally, this study explores the ability of Ch-Al chain functional groups to control and extend GF delivery and minimize GF burst release, using model proteins BSA and histone at high loading dose and chondrogenic protein TGF-β1 at low loading dose in complete media. Expedited cartilaginous matrix synthesis on Ch-Al with low dose TGF-β1 release is evaluated, with Ch-Al supporting homogeneous matrix deposition and lacunae formation as early as 3 weeks due to Ch-Al's maintenance of GF bioactivity and sustained GF delivery. These results illustrate the potential to focus the formulational range of Ch-Al to provide enhanced mechanical performance and controlled, bioactive GF release to cooperatively promote cartilage regeneration.