Core-shell designed scaffolds of alginate/alpha-tricalcium phosphate for the loading and delivery of biological proteins.

Development of scaffolds to load and deliver therapeutic molecules like growth factors greatly enhances tissue regenerative capacity. Here, we report the core-shell design of fibrous scaffolds made of alginate and α-tricalcium phosphate (Alg/α-TCP) for in situ protein loading and controllable delivery. Direct deposition of Alg/α-TCP solution through designed coconcentric nozzle in CaCl(2) bath allowed the generation of fibrous scaffolds. Through the process, in situ protein loading was possible and the core and shell composition was controlled. Feasibility of the designed scaffolds in loading and release of biological model protein cytochrome C (cyt C) was investigated. Scaffolding formed in CaCl(2) led to a considerable loss of cyt C in a crosslinking time-dependent manner, and the change in hardening conditions (Alg concentration, CaCl(2) concentration, and Alg/α-TCP ratio) was not as effective in reducing the protein loss. Subsequent release of cyt C from Alg scaffolds displayed a marked initial burst depending on crosslinking conditions, and shortening crosslinking time and decreasing CaCl(2) concentration lowered the initial burst. The α-TCP addition (up to 75%) resulted in more continual and sustainable release patterns. Composition change (α-TCP content) in core or shell significantly altered the release profiles, suggesting the possible designing core-shell configuration for target release patterns, such as dual-protein delivery. Additionally, the α-TCP incorporation significantly increased the mechanical stiffness to values much closer to those of hard tissues. Results indicate that coaxial deposited α-TCP/Alg fibrous scaffolds may be useful for designing proper growth factor delivery systems in hard tissue engineering.