Characterizing robocasting and freeze casting HA/TCP scaffolds in bone regeneration

Objective:

Biphasic calcium phosphate bioceramics consisting of hydroxylapatite (HA) and tricalcium phosphate (TCP) have received considerable attention as bone graft substitutes because of their excellent osteoconductivity comparing to other materials. Freeze casting and robocasting are very appealing candidate technologies for building ceramic scaffolds. However, the biocompatibility of HA/TCP scaffolds has not been extensively evaluated.

Method:

The scaffolds (5X5X3mm) made of HA/TCP (composition 60:40) by either robocasting or freeze casting were tested. Human bone marrow stromal cells (hBMSCs) were used to investigate the biocompatibility of these scaffolds. Cell attachment were examined using scanning electronic microscope (SEM) after cell seeding at 1, 4, 7 days. Proliferation of hBMSCs on the scaffolds was determined by MTT assays at day 1, 4, 7, and 10. Osteoinductivity ability was analyzed by culturing hBMSCs on the scaffolds in osteogenic induction medium in vitro. 

Result:

hBMSCs  attached on both scaffolds after day 1 and exhibited no difference. During early culture, from day 1 to day 4, no difference of proliferation rate was detected between freeze casting and robocasting scaffolds. After Day 7, hBMSCs proliferation rate slightly decreased on freeze casting. However, after cultured in induction medium, both osteocalcin and Runx2 expression were higher on freeze casting than robocasting by day 7. 

Conclusion:

Both robocasting and freeze casting HA/TCP scaffolds are biocompatible for hBMSCs attachment, proliferation, and differentiation. However, the specific parameters, such as porosity of the scaffolds and cell seeding procedures need to be optimized for future clinical applications.