Division of Information Technology, Engineering and the Environment
Applied Centre for Structural and Synchrotron Studies
Applied Centre for Structural and Synchrotron Studies
ARC Linkage Grant
Clients: TGR
Biosciences, Portland Orthopaedics
Project duration: 2003-2005
Chief Investigators: Roger Smart, Sunil Kumar*, Nico Voelker
(Flinders Uni.), Mark deNichilo (TGR)
Description:
There is a considerable
amount of effort going into coating of metal implants for better
stability and osteointegration. Long-term fixation of titanium
(Ti)-based implants (both medical and dental) continues to be a
major challenge in biomaterials research. Chemical modification of
these implant surfaces is one of the major approaches being studied
for; the basic idea being enhanced adhesion of bone cells
(osteoblasts) at the implant surface, followed by controlled
deposition of bone by these cells. Various plasma-based techniques
have been used to coat Ti surfaces with hydroxyapatite (HA), calcium
phosphates, titania, etc., mainly focussed at achieving bonding at
the bone-implant interface through enhanced bioactivity.
The Biomaterials Research team at the
Ian Wark Research Institute
(IWRI) of UniSA has been working on a novel way of chemical
modification of implant surfaces for obtaining enhanced bone growth
on them; Ti implant surfaces are modified by generating functional
groups (such as hydroxyl, -OH) by employing the technique of plasma
(ionised vapour) modification/deposition.
The plasma processed hydroxylated silica-coated titanium
(Ti/SiO2:OH) screws have been used for dental implant trials in
sheep, suggesting enhanced bone growth (bone-implant contact
increase by about 50%) as compared to non-functionalised Ti
controls. Driven by these very significant results, we now plan to
use our plasma modified Ti surfaces for immobilisation of
biomolecules such as growth factors which are known potent mitogens,
with the major aim of studying these composite surfaces for possible
further bone-implant contact enhancement. We have already made some
progress in this direction; hydroxylated Ti (Ti-OH) surfaces
prepared by the plasma process have been shown to exhibit
significantly enhanced growth factor adsorption as compared to
non-functionalised Ti controls.
The use of nanophase bioceramics has also been suggested for
obtaining enhanced osteoblast adhesion on their surfaces through
increased adsorption of cell binding proteins such as vitronectin.
It is important to note that for the bone cells to attach to
adsorbed biomolecules, the latter must retain their bioactivity.
Therefore, the next logical, but more complex, step in this surface
modification process is to make use of specific molecular
recognition events occurring between the bone cells and the implant
surface. This can be achieved by introducing covalently tethered
bioactive molecules that trigger osteoblast growth via specific
ligand-receptor interactions.
In view of the above, the general aim of this project is to functionalise titanium surfaces by the plasma process in order to allow the subsequent covalent immobilisation of growth factors.
The specific aims of the proposed project are:
Covalent immobilisation of growth factors on pure and plasma processed surfaces of Ti and its alloys
Characterisation and quantitation of the immobilised growth factors; and
Subsequent in vitro bioactivity testing of the above surfaces for hard tissue (bone) growth.
We anticipate that this project will lead to the development of an implant material with enhanced biocompatibility and osteoadhesion.
The following specific outcomes are expected:
Establishment of Ti surfaces with optimised biocompatibility for hard tissue contact
Development of strategies for growth factor immobilization under retention of their bioactivity; and
Library of nanoscale
biomaterials that show optimised osteoadhesion and rapid healing
in vivo.
