Biomimetic growth of hydroxyapatite on super water-soluble carbon nanotube-protein hybrid nanofibers

We report here on a facile strategy for the creation of super water-soluble carbon nanotube (CNT)-protein hybrid nanofibers. Toluene-soluble CNTs were first synthesized by noncovalent functionalizing CNTs with a bifunctional linker, Z-glycine N-succinimidyl ester (Z-Gly-OSu), and then water-soluble CNT-protein hybrid nanofibers were created by phase-transferring the Z-Gly-OSu-functionalized CNTs from the toluene phase to protein aqueous solution. CNT-fibronectin (CNT-FN) and CNT-hemoglobin (CNT-HGB) hybrid nanofibers were successfully prepared in this work. Raman and XPS spectra confirmed the successful functionalization of CNTs with Z-Gly-OSu. TEM results indicated the formation of CNT-protein hybrid nanofibers. Biomimetic mineralization was conducted on the CNT-FN hybrid nanofibers and nanofiber film to explore the effects of protein and CNTs on the formation of hydroxyapatite (HA) crystals. SEM, Raman spectra, and TEM results indicated that the FN molecules promote the nucleation of crystalline nuclei and the CNT templates control the orientation of nuclei and the crystal growth of HA to form flake-like HA crystals.