[OPEN ACCESS] Fabrication of nanocellulose–hydroxyapatite composites and their application as water-resistant transparent coatings

Mai Ishikawa, Yuya Oaki, Yoshihisa Tanaka, Hideki Kakisawa, German Salazar-Alvarez and    Hiroaki Imai

J. Mater. Chem. B, 2015, Advance Article
DOI: 10.1039/C5TB00927H

Abstract
Nanosized composite rods ~300 nm in length and ~20 nm in width were produced by deposition of 22–77 wt% of a c-axis-oriented hydroxyapatite (HA) on cellulose nanocrystals (CNCs). The CNCs functionalized with sulphonic groups were covered with the HA nanocrystals through controlled nucleation and growth under a moderately supersaturated condition in a solution system based on a simulated body fluid. Water-resistant transparent coatings 2–4 μm thick were obtained via evaporation-induced assembly of CNC–HA nanocomposites by casting their suspension on a glass substrate and the subsequent growth of HA nanocrystals by vapour hydrothermal treatment. The composite coatings exhibited improved mechanical strength compared to that of crustacean exoskeletons, and potential for bone regeneration.