Enhanced bone tissue formation by alginate gel-assisted cell seeding in porous ceramic scaffolds and sustained release of growth factor.

Increasing cell seeding efficiency in a tissue engineering construct can enhance cellular activity and tissue formation in vivo. Here, we demonstrate the use of alginate gel as a secondary phase material in 3D porous β-tricalcium phosphate scaffolds to improve cell seeding and provide controlled release of growth factors for bone tissue engineering. Cells were seeded in scaffolds in three ways: conventional seeding (CS), alginate gel-assisted seeding (GS), and alginate GS with bone morphogenetic protein-2 (BMP-2, GSB). In vitro study with MG-63 cells showed that cell seeding efficiency and cell population 1 week after seeding were significantly elevated in GS and GSB samples compared to CS samples. The GSB system demonstrated a sustained, steady release of BMP-2 over 2 weeks. In vivo, scaffolds seeded with rat mesenchymal stem cells were implanted ectopically into Sprague-Dawley rats for 8 weeks. GS and GSB samples exhibited improved osteogenic activity, with the GSB samples inducing the greatest osteocalcin and osteoid deposition. This study suggests that the alginate gel-assisted cell seeding increases seeding efficiency and allows for sustained release of growth factors. The use of the secondary phase polymer bolsters bone formation in vivo and has the potential for improving outcome in other tissue engineering applications.