Fabrication and mechanical and tissue ingrowth properties of unidirectionally porous hydroxyapatite/collagen composite

Abstract

This study investigated the effects of the three-dimensional (3-D) pore structure of a porous hydroxyapatite/collagen (HAp/Col) composite on their mechanical properties and in vivo tissue ingrowth. The unique 3-D pore structure, comprising unidirectionally interconnected pores, was fabricated by the unidirectional growth of ice crystals by using a cooling stage and a subsequent freeze-drying process. The unidirectional pores had a spindle-shaped cross section, and their size gradually increased from the bottom to the upper face. The porous composite showed an elastic property and anisotropic compressive strength for the pore directions. While the strength and modulus parallel to the pore axis were 1.3-and twofold higher than those of the porous composite with spherical pores formed randomly, the strength and modulus perpendicular to the pore axis showed the lowest values. The subcutaneous implantations revealed that when compared with the random pores, the unidirectional pores promote the ingrowth of the surrounding tissues into the pores.

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…This may lead to enhance the mechanical properties and osteointegration with improved biological and biochemical affinity to the host bone. Besides, the unidirectional porosity was found to have a positive influence on the ingrowth of the surrounding tissues into the pores of collagen/HA biocomposites [641].…”

Biocomposites and hybrid biomaterials based on calcium orthophosphates

“…Besides, porosity was found to have a positive influence on the ingrowth of the surrounding tissues into the pores of collagen/HA biocomposites. 771,772 Another approach is to mix bovine collagen with calcium orthophosphates. These biocomposites are marketed commercially as bone graft substitutes and can further be combined with bone marrow aspirated from the iliac crest of the site of the fracture.…”

Multifunctional materials for bone cancer treatment

“…119 Larger pores are unwanted, because the mechanical properties of the graft drastically decrease, while narrower pores limit cell penetration inside the graft. 120,121 Porosity and pore size can be controlled by different parameters, such as precursor concentration, drying conditions, presence of different components, etc. 13,22 Usually, COLL/HA composite materials with high porosity are obtained from diluted, mineralized collagen gel followed by freezedrying.…”