Bone substitute materials are very widely used in orthopaedics, craniofacial surgery and dental applications to repair damage caused to bones by injury or disease. If only a small area of bone needs to be replaced it can often be taken from elsewhere on the patient, but where large areas have to be reconstructed artificial bone scaffolds have to be used. These provide a framework into which the patient’s own bone can gradually grow, resorbing the scaffold material as it goes. Around 2.2 million bone grafts are done annually and the bone scaffold market is worth more than $7 billion in the US alone.
Certain ceramic materials are widely used for bone scaffolds but when used alone, they are quite brittle, especially when pore size is optimal for encouraging new bone growth. This leads to limitations in their use for repairing leg bones and in other load-bearing applications. A/Prof. Hala Zreiqat and her team from the University of Sydney are investigating a number of new scaffold materials. In recently published work, silk, and a type of biodegradable polyester, poly (?-caprolactone) (PCL), are being combined to strengthen ceramic bone-scaffold materials made of biphasic calcium phosphate (BCP).
The team successfully addressed the brittleness of the ceramic scaffold by coating it with PCL. They then further improved its bioactivity (since PCL is inert) with a silk coating. This familar natural polymer happens to bind particularly well to the PCL. The strength of the combination material under compression is approximately seven times that of the ceramic alone. The surface layer of silk is also responsible for improved growth of bone cells on the scaffold. This composite material appears to be a significant step forward in bone tissue engineering and regeneration applications, particularly at vitally important load-bearing sites.
This work has been enabled through scanning electron microscopy in the AMMRF at the University of Sydney.