Formation and osteoconductivity of hydroxyapatite/collagen composite films using a thermal substrate method in aqueous solutions

Abstract

We have studied the formation and carried out an in vivo evaluation of hydroxyapatite (HAp)/collagen and HAp/denatured collagen (gelatin) composite coatings on titanium substrates using a thermal substrate method. The coatings were formed on commercial pure titanium rods (diameter = 2 mm, length = 5 mm) and plates (thickness = 0.3 mm) using a thermal substrate method in aqueous solutions that contained 0.3 mM Ca(H2PO4)2, 0.7 mM CaCl2, and a concentration of acid-soluble collagen (Type I) of ∼432 mgdrn-3. The coating experiments were conducted at 40-140°C and pH = 8 for periods of 15 or 30 min. The coating temperature and collagen content in the solution influenced the surface morphology and collagen (or gelatin) content in the films. A coated rod was implanted in a 10-week-old male rat's tibia with a noncoated titanium rod being used as a control. The constructs were retrieved after a period of 14 d postimplantation and examined for new bone formation and for tissue response in the cancellous and cortical bone parts, respectively. HAp/gelatin composite films coated at > 60°C showed a slight improvement in osteoconductivity in the cortical bone. In contrast, there was no improvement in the cancellous bone, compared with HAp, which had no gelatin. However, the HAp/collagen composites showed a high osteoconductivity in the cortical bone region, and this increased with increasing collagen content in the films. There was the same tendency in the cancellous bone part. However, too higher a collagen content (40mass%) in the films gave rise to an obvious negative osteoconductive effect. © 2009 The Japan Institute of Metals.