Title

Hydroxyapatite/Poly(L-Lactic Acid) Fibrous Composites for Bone Tissue Engineering

Date of Completion

January 2011

Keywords

Chemistry, Polymer|Engineering, Materials Science

Degree

Ph.D.

Abstract

Human bone is a hybrid of hydroxyapatite (HA) and biopolymer nanofibrous composite. Thus, HA/biopolymer fibrous composites have been regarded as prospective candidates for bone tissue engineering. However, preparing HA/biopolymer fibrous composites mimicking the composition, structure, mechanical and biological properties of bone matrix has long been an attractive but challenging topic. In this work, different HA/poly(L-Lactide) (PLLA) micro- and nanofibrous composites were prepared and investigated for bone tissue engineering applications. ^ First of all, a HA/PLLA microfibrous composite was made by coating fibers with HA using a biomimetic method. To increase the coating content and enhance its bonding with the substrate, PLLA fibers were pre-treated with NaOH and NaOCl solutions at mild conditions. The etching treatment not only increased the roughness and the hydrophilicity of fibers, but also promoted HA coating formation on PLLA fiber surfaces. Influences of surface treatment and HA coating processes on the mechanical properties of PLLA and HA/PLLA fibers were also investigated systemically. ^ In addition, highly porous HA/PLLA nanofibrous composite scaffolds were prepared by incorporating either HA nano- or microparticles into PLLA nanofibers using an electrospinning technique. HA nanoparticles with different aspect ratios and variant levels of carbonate substitutions were synthesized using a wet precipitation method by adjusting the heating temperature and/or the initial ion concentration of the reaction system. Needle-shaped HA microparticles were prepared using a urea decomposition method. It was for the first time that needle-shaped HA nano- and microparticles were perfectly oriented along the long axe of electrospun nanofibers. All HA particles significantly enhanced the tensile modulus, strength and toughness of the corresponding scaffold, but to different extents. The biocompatibility and cell signaling property of selected nanofibrous scaffolds were evaluated by in vitro culture of rat osteosarcoma ROS17/2.8 cells on the scaffold surface. Cell morphology, viability and alkaline phosphatase (ALP) activity on these scaffold indicated their good potential for bone tissue engineering. ^