Adhesion protein adsorption and bone cell growth on carbon nanotube composite materials
Bone growth on nano-structured materials is of paramount importance for designing better orthopedic prostheses. We have demonstrated here that surface energies and nano scale roughness are indeed important factors for determining adsorption of an important adhesion protein, fibronectin, and subsequent growth of bone forming cells, osteoblasts, on carbon nanotube composite materials. ^ For more meaningful and relevant quantification of surface roughness, effective roughness and normalized fibronectin adsorption was introduced. The results demonstrate that normalized fibronectin adsorption is strongly correlated with the effective roughness of surfaces. Rougher surfaces were shown to have higher surface energies, which also leads to greater adsorption. Most importantly, observed fibronectin adsorption is analyzed via a linear function of surface energy and surface roughness that describes the independent contributions of chemistry and physical roughness for fibronectin adsorption. ^ Furthermore, micro-aligned patterns of carbon nanotubes/nanofibers on plastic substrates of polycarbonate urethane or poly-lactic-co-glycolic acid were developed to determine subsequent cell adhesion and long term functioning of osteoblasts. Results showed direct evidence of both selective adhesion of osteoblasts and accelerated deposition of subsequent calcium phosphate crystals on micro-aligned patterns of carbon nanotube composite materials. ^ All experimental and theoretical analyses supported the importance of surface energy in terms of nano-roughness in mediating fibronectin adsorption, osteoblast adhesion, and even differentiation of osteoblasts. In such a manner, this quantitative study provides promising evidence for maximizing the surface responses for adhesion proteins and subsequent cell functioning by controlling surface properties in the nanoscale, providing direct information for designing better orthopedic materials. ^
Thomas J. Webster, Purdue University, Stephen M. Durbin, Purdue University.