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|Title: ||Fabrication and characterization of polymer-hydroxyapatite nanocomposites for bone tissue engineering|
|Other Titles: ||Gu zu zhi gong cheng ju he wu-qian ji lin hui shi na mi fu he cai liao de zhi bei yu biao zheng|
|Authors: ||Li, Kai ( 李凱)|
|Department: ||Department of Physics and Materials Science|
|Degree: ||Doctor of Philosophy|
|Issue Date: ||2010|
|Publisher: ||City University of Hong Kong|
|Notes: ||CityU Call Number: R857.M3 .L5 2010|
xv, 183 leaves : ill. 30 cm.
Thesis (Ph.D.)--City University of Hong Kong, 2010.
Includes bibliographical references.
|Abstract: ||Hydroxyapatite (HA) with a chemical structure of Ca10(PO4)6(OH)2 is a major
component and an essential ingredient of normal bone and teeth. Synthetic HA is
commonly used as a filler material for conventional polymer composites due to its
excellent biocompatibility and bioactivity. Polyethylene-HA composite (HAPEXTM)
filled with 40vol% HA microparticles has been used for orbital floor prosthesis, middle
ear implant and maxillofacial surgery. HAPEXTM is restricted to such orthopedic
applications due to its low mechanical strength. Accordingly, much effort has been
devoted to the development of polymer composites with good biocompatibility and
mechanical strength close to that of human cortical bones.
Recent advances in nanotechnology offer unique opportunities to develop
nanostructured materials for biomedical applications. Bone tissue is a natural
composite consisting of HA nanocrystals embedded in the collagen fibrils. The
incorporation of HA nanofillers into the polymer matrix can mimic closely the
structure of human bones. In this study, HA nanomaterials (nano-HA) of different
morphologies were synthesized using polymer assisted sol-gel and
micelle-hydrothermal techniques. The structure and properties of synthesized products
were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM),
transmission electron microscopy (TEM) and energy-dispersive X-ray analysis (EDX).
XRD and FTIR results indicated that the synthesized products exhibit typical
diffraction peaks and characteristic vibration bands of HA. Nano-HA synthesized from
the sol-gel method displayed spherical morphology with diameters ranging from 50-70
nm. And nano-HA prepared via micelle template synthesis had a rod-like feature.
Furthermore, simulated body fluid (SBF) immersion test revealed that both nano-HA
materials exhibit good bioactivity due to the ease of apatite layer formation on their
Commercially available HA nanorods (nHA) with an average aspect ratio of 6 were
selected as nanofillers for high density polyethylene (HDPE), polypropylene (PP),
polyamide-6 (PA6) and polyetheretherketone (PEEK). The main objectives of this
study were to investigate the structure, thermal and mechanical properties as well as
bioactivity of polymer/nHA nanocomposites. Nanocomposites with polymer matrices
based on HDPE, PP and PA6 were prepared by melt-compounding while the
PEEK/nHA nanocomposites were fabricated using thermal sintering process. Tensile
tests showed that the additions of low filler content improve the tensile modulus and
yield strength at the expense of tensile ductility and impact strength. However, the
tensile strength and stiffness of HDPE/nHA and PP/nHA nanocomposites are much lower than those of cortical bones. This is due to the low tensile strength of polyolefins.
On the other hand, PA6 and PEEK based nanocomposites exhibit tensile strength close
to that of cortical bones. The high tensile strength of PA/nHA nanocomposites derives
from strong interfacial interactions between the polymer matrix and nHA. The main
disadvantage of PA/nHA nanocomposites for orthopedic applications is the high
moisture absorption of PA6. Thus only PEEK/nHA nanocomposites with high
mechanical strength are promising load bearing materials to replace defective bones.
In vitro SBF immersion and osteoblast cell culture tests were used to assess the
bioactivity of polymer/nHA nanocomposites. In general, apatite mineral crystals and
mouse osteblasts can be deposited, attached and proliferated on these nanocomposites,
particularly for those with higher nanofiller content. These results imply excellent
bioactivity of the polymer/nHA nanocomposites.|
|Online Catalog Link: ||http://lib.cityu.edu.hk/record=b4086291|
|Appears in Collections:||AP - Doctor of Philosophy |
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