Development of bone replacement material via nanohydroxyapatite crystal growth on silk fibroin fiber

Abstract

The objective of this research is to propose a new way to fabricate a composite material for future bone replacement development via growing apatite crystal on silk fibroin fiber. Apatite crystallization on silk fibroin fiber was prepared by precipitation reaction between Ca(NO3)2 solution and (NH4)2HPO4 solution adjusted pH by NH4OH solution. In this work, Effect of solution concentration and initial pH values was investigated on apatite crystals. Chicken eggshells were used as calcium source by heating sufficiently powdered eggshells at 1300 °C for 4 h to acquire CaO powders, made Ca(NO3)2 solution by dissolving in 65% HNO3 solution. Prepared Ca(NO3)2 solutions were adjusted concentration as 3 levels and were adjusted different pH values of 7, 8 and 9, respectively. For processing of apatite crystallization, silk fibroin fibers were immersed in Ca(NO3)2 solutions for 30 min. After that (NH4)2HPO4 solutions were added in silk fibroin fibers immersed in Ca(NO3)2 solutions. Reaction time was fixed about 1 min before cleaning to remove impurity precipitates on surface of silk fibroin fiber. Finally, apatite crystallization on silk fibroin fibers occurred. The obtained result can conclude morphologies of apatite crystals on silk fibroin fibers was sheets sphere and flower. Solution concentrations and initial pH values directly influenced on Ca/P ratio of obtained apatite crystals by Ca/P ratio increases as increased solution concentrations or increased pH values. Finally research, silk fibroin fibers were woven as two patterns of plain weave and twill weave and they were investigated Young’s modulus and tensile strength. The result indicates that Young’s modulus of silk fibroin fiber sheets woven as twill weave and as plain weave were about 616 MPa and 425 Mpa and tensile strengths of them weave were about 40 Mpa and 72 Mpa, respectively. The optimum condition of growing apatite crystals on silk fibroin fibers was sample of CP19. Design of silk fibroin fiber with plain weave was an optimum pattern for future biomedical applicaions.