Fabrication and biological application of nano-hydroxyapatite (nHA)/alginate (ALG) hydrogel as scaffolds

We have fabricated tubular hydrogel scaffolds of nano-hydroxyapatite (nHA)/alginate (ALG) via a layer-by-layer (LbL) technique. Using Ca2+ as a crosslinker, nHA was assembled with ALG to form a hydrogel network. The inner diameter of scaffolds could be controlled from 0.5 mm to 7 mm by varying the assembled layer numbers of nHA/ALG pairs. By changing the nHA concentration, we can also control the crosslinking degree of the hydrogel network, and further change the mechanical properties, swelling behavior, permeability and diffusivity of the scaffolds. The elastic modulus of the hydrogel scaffolds was regulated from 0.98 +/- 0.05 MPa to 2.78 +/- 0.08 MPa as the concentration of nHA was changed from 50 mg mL(-1) to 300 mg mL(-1), which reached the requirements of avascular soft tissue. The diffusion coefficient was tuned from 23.84 x 10(-7) cm(2) s(-1) to 9.92 x 10(-7) cm(2) s(-1) for controlled mass transport in the hydrogel network. Moreover, human embryo skin fibroblast (ESF) culture experiments prove that nHA can improve cellular adhesion on the hydrogel surface. These results thus suggest that the assembled nHA/ALG hydrogel scaffolds are an attractive biomaterial for great potential application in soft tissue engineering.