Supercritical carbon dioxide processed resorbable polymer nanocomposite bone graft substitutes

• Published in: Acta biomaterialia Vol. 7; no. 9; pp. 3382 - 3389
• Main Authors: Baker, Kevin C., Manitiu, Mihai, Bellair, Robert, Gratopp, Carly A., Herkowitz, Harry N., Kannan, Rangaramanujam M.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-09-2011
• Subjects: angiogenesis; biocompatibility; Biocompatible Materials - chemistry; Bone graft; Bone Substitutes - chemistry; Bone tissue engineering; calcium; carbon dioxide; Carbon Dioxide - chemistry; clay; Compressive Strength; Humans; Lactic Acid - chemistry; mechanical properties; methodology; Nanocomposite; Nanocomposites; nutrient transport; osteoblasts; Osteoblasts - cytology; Polyesters; Polylactic acid; polymer nanocomposites; Polymers - chemistry; polystyrenes; Porosity; Scaffold; Surface Properties; tissue engineering; Tissue Engineering - methods; Nanocomposite; Bone tissue engineering; Scaffold; Bone graft; Polylactic acid
• ISSN: 1742-7061; 1878-7568
• DOI: 10.1016/j.actbio.2011.05.014

The development of synthetic bone graft substitutes is an intense area of research due to the complications associated with the harvest of autogenous bone and concerns about the supply of allogenic bone. Porous resorbable polymers have been used extensively in hard tissue engineering applications, but currently lack load-bearing capacity. Supercritical carbon dioxide (scCO
2) processing is used as a novel method to simultaneously impart a porous structure and disperse a nano-clay in a resorbable polymer matrix suitable for load-bearing applications. Porous resorbable polylactic acid (PLA)/cloisite clay nanocomposite constructs prepared using scCO
2 processing exhibit a 2.5-fold increase in compressive strength compared with pure polymer constructs. The resulting mechanical properties are comparable with human cancellous and cortico-cancellous bone. In addition to the significant improvements in mechanical properties, the nanocomposite constructs display a biocompatibility greater than that of polystyrene culture plate controls. Furthermore, calcium phosphate-rich deposits could clearly be seen on the surface of the constructs, as well as at the center of the cultured constructs, indicating that osteoblasts are able to penetrate the porous network of the nanocomposite constructs. Cellular infiltration of these constructs is important for their in vivo use as bone graft substitutes. The diameter of the pores suggests that these constructs would also support neovascularization, which is integral for nutrient transport.