Three-dimensional porous hydroxyapatite/collagen composite with rubber-like elasticity

A three-dimensional porous hydroxyapatite/collagen (HAp/Col) composite with a random pore structure was fabricated using freeze-drying processes; the self-organized HAp/Col nanocomposite with a weight ratio of 80.5:19.5, freeze-dried, was kneaded in 100 mM sodium phosphate buffer, frozen at -20 degrees C and freeze-dried. The cross-linkage of Col molecules was introduced dehydrothermally at 140 degrees C in vacuo. The porous composite had a porosity of 94.7% with pore sizes between 200 and 500 pm. The compressive stress for the wet porous composite in phosphate buffer saline (PBS) was gradually decreased during 20 days incubation with a small amount of weight loss. The cyclic and time-course compression tests showed good repeatability of stress and well-recovery of its height, and caused no collapse of the porous composite. The implantation of the porous composite in rat bone holes showed the biodegradable property and new bone formation occurred in the pores without inflammatory response. The porous composite fabricated has good flexibility and rubber-like elasticity, and is a promising bone regenerative material.