Biological evaluation of solid freeformed, hard tissue scaffolds for orthopedic applications

Hydroxyapatite (HA) lattices were made by extrusion freeforming, a rapid prototyping process, and sintered to produce hard tissue scaffolds for bone regeneration. These highly reticulated lattice structures can be built directly from a computer design file which decides and controls their macroscopic shape, pore structure and size distribution. They are therefore defect-specific and show potential in tissue engineering for non-load bearing sites.

Using a commercial human osteoblast-like cell line (HOS TE 85), biocompatibility was evaluated in an in vitro study. A high level of cell adhesion was evident by scanning electron microscopy on both convex and concave surfaces and the cell attachment was revealed at different depths into the scaffold. An AlamarBlue(R) assay was carried out to assess cell proliferation, which was further confirmed by quantifying total DNA concentration and total protein content.

The cell proliferation was significant and the pattern was comparable to that of the tissue culture control, ThermanoxTM. ALP activity and osteocalcin were quantified to evaluate the extent of cell differentiation, which confirmed the retention of the phenotype for the period studied. Mineralization of the matrix was determined via formation of nodules.

HA scaffolds are non-toxic, able to maintain cell viability and support cell growth, proliferation, differentiation, and nodule formation.