The hydroxyapatite, Ca10(PO4)6(OH)2, is a calcium phosphate materials with important
applications in the medicine and chemistry fields. Due to its excellent biocompatibility,
osteoconductivity and mechanical properties the hydroxyapatite has been used in biomedical
applications as bioceramics [1]. Hydroxyapatite provides bioactivity but is brittle, particularly in
highly porous scaffolds which may also exhibit low strength [2]. Therefore, dense or porous
polymer-hydroxyapatite composites have been investigated for synthetic bone graft substitutes
and bone tissue engineering scaffolds [3]. In this study, the porous cellulose acetate scaffolds
with different nanohydroxyapatite loadings were prepared via the dry-wet phase inversion
method by dispersing hydroxyapatite nanoparticles in the polymeric matrix. The calcined
hydroxyapatite prepared by the wet precipitation method has the crystal size smaller than 60 nm
and a high specific surface area of 69 m2/g. The unfilled and hydroxyapatite-filled cellulose
acetate scaffolds have an asymmetric structure consisting of two layers: the dense top layer
(active layer) supported by the porous sub-layer (substructure) as shown in Fig. 1. The crosssectional
SEM images revealed that hydroxyapatite nanoparticles were well dispersed in the
polyurethane matrix.

Fig. 1. The SEM images of scaffolds in the cross-section: a) pure cellulose acetate sample and b)
hydroxyapatite-filled cellulose acetate sample.
References:
[1] Dorozhkin, S. V. Calcium orthophosphates in nature, biology and medicine.In: Materials,
2009, 2, 399–498.
[2] Morgan, E. F.; Yetkinler, D. N.; Constantz, B. R.; Dauskardt, R. H. Mechanical Properties of
Carbonated Apatite Bone Mineral Substitute: Strength, Fracture and Fatigue Behavior. In:
Journal of Materials Science: Materials in Medicine, 1997, 8, 559–570.
[3] Mano, J. F.; Sousa, R. A.; Boesel, L. F.; Neves, N. M.; Reis, R. L. Bioinert, Biodegradable
and Injectable Polymeric Matrix Composites for Hard Tissue Replacement: State of the Art and
Recent Developments. In: Composites Science and Technology, 2004, 64, 789–817.