Crystallization of Calcium Deficient Hydroxyapatite Nanocrystals on Woven Silk Fibroin Fabric via Precipitation Process

A high bioactivity calcium deficient hydroxyapatite (Ca-def HAp) nanocrystal crystallized on a high strength woven silk fibroin (SF) fabric was characterized with the aim to utilize their advantages for the future bone implant applications. Apatite crystal was grown on SF fiber templates by precipitation reaction of Ca(NO₃)₂ prepared from chicken eggshells in (NH₄)₃PO₄ solutions, adjusted pH by NH₄OH solution. In the apatite crystallization process, (NH₄)₃PO₄ solutions prepared at different pH values were poured into the glass dishes containing SF fiber templates/Ca(NO₃)₂ solution, allowed reaction time of only a minute. The results had shown that, the Ca/P ratio of the crystals grown on SF fiber templates were increased through increasing in initial pH value of reaction. Its morphology had been changed from the plate-shaped to particle-shaped crystals. The plainwoven SF fabric was chosen as the suitable template to grow Ca-def HAp crystal for its much higher tensile strength (840 MPa), as compared to 470 MPa for the twill-woven SF fabric. The Cadef HAp nanocrystals on plain-woven SF fabric were confirmed the Ca/P ratio at 1.52 with X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The clusters size of smaller than 100 nm Ca-def HAp nanocrystals on plain-woven SF fabric also signified the high surface area of structure which are better for cell attachment, growth and differentiation. Accordingly, the overall result indicated that the composite of combining Ca-def HAp nanocrystals on plain-woven SF fabric had been successfully prepared by the rapid precipitation. The method offers a simpler setup and a shorter processing time and the Ca-def HAp on silk possess a higher tensile strength, suitable for development for future bone implant in the high load bearing regions.