In Vitro and In Vivo Evaluation of a Three-Dimensional Porous Multi-Walled Carbon Nanotube Scaffold for Bone Regeneration

Carbon nanotubes (CNTs) have attracted a great deal of attention for the biological and medical science fields because of their characteristic physical and biological properties. In this study, we investigated the capacity of the 3D porous CNT scaffold (CNT porous block; CNTp) for bone regenerative medicine. Surface observations using a scanning electron microscope (SEM), crystal depositions on the surface of CNTps immersed in simulated body fluid (SBF), and evaluations of protein adsorption and controlled releasing were conducted to assess physical properties. The cell proliferation and cell morphology were observed using SEM and fluorescent microscopy. CNTps were implanted into critical-size mouse calvarial defects and evaluated for their osteoconductive ability and in vivo controlled release of recombinant human BMP-2 (rhBMP-2). Interconnected porous HA ceramics (IP-CHAs) were used for comparison. CNTps have multiporous structures with interporous connections with networks of multiwalled CNTs. Crystals containing calcium and phosphate were deposited in CNTps and on the surface of the CNT networks by immersing CNTps in SBF. CNTps adsorbed more significantly and released protein more gradually than IP-CHAs. Preosteoblasts seeded onto CNTps filled pores with stretched actin filaments and filopodia. Compared with IP-CHAs, CNTps showed significantly higher cell proliferation, better osteoconduction, and more bone generation with rhBMP-2. In this study, CNTps demonstrated good osteoconductive ability, cell attachment and proliferation capacity, and growth factor retaining ability. CNTps have the potential not only as artificial bones for the treatment of bone defects, but also as scaffolds for regenerative medicine using tissue engineering approaches