(142a) Comparisons of Methods to Bond Metal and Chitosan: a Biopolymer for Use as an Implant Coating

Implants are commonly made from
commercially pure titanium and from different types of metal alloys, which
include titanium combined with aluminum and vanadium and cobalt-chromium.  The bone cells that surround these implants
often times begin to leech away the metal ions needed for cellular
function.  This leeching causes a
loosening of the implant, which will eventually lead to surgery, in order to
replace the damaged implant.  Also, bare
metal does not allow for the proper attachment of bone cells in order to
stabilize the implant.  Osseointegration
is a necessary occurrence in order to properly stabilize and incorporate the
implant within the body.

One method to prevent biocorrosion,
along with increasing osseointegration, is to bond a biocompatible coating onto
the surface of the implant materials. 
Currently, several different methods are being used, which include
calcium phosphate [1] and chitosan, a de-acetylated form of chitin.  Chitin is the second most abundant form of
polymerized carbon found in nature [2] and is primarily found in the
exoskeletons of arthropods [3] and cell walls of fungi [4].  Chitosan, a biologically produced polymer,
is a catonic copolymer of glucosamine and N-acetylglucosamine [5] and considered
biocompatible because it can be degraded by specific enzymes [5].  Because of its biocompatibility, chitosan
has been tested as wound dressings, bone implants, and drug delivery systems
[5].  It may also work well as a coating
on metal implants, improving osseointegration of implants for craniofacial and
orthopaedic applications [3]. 

At Mississippi State University, we are
investigating three methods to bound chitosan to three different metals.  The chemical properties of the bonding
methods will be examined using x-ray photoelectron spectroscopy (XPS) and
Fourier Transform infrared spectroscopy (FTIR), while the crystalline structure
will be determined using (XRD).  The
differences in bond strength and film hardness will be examined using an nanoindentor.  Scanning Electron Microscopy (SEM) will then
be used to determine where the film failed due to the nanoindention and the
scratch tests.

[1]  Y. Yang, C.M.
Agrawal, K.H. Kim, H. Martin, K. Schulz, J.D. Bumgardner, J.L. Ong.  Journal of Oral Implantology, 29, 6,
270-277, 2003

[2]  G. Haipeng, Z. Yinghui, L. Jianchun, G. Yandao, Z. Nanming, Z.
Xiufang.  Journal of Biomedical
Materials Research, 52, 285-295, 2000

[3]  J.D. Bumgardner, R. Wiser, P.D. Gerard, P. Bergin, B. Chestnutt,
M. Marini, V. Ramsey, S.H. Elder, J.A. Gilbert.  Journal of Biomaterials Science: Polymer Edition, 14, 5,
423-438, 2003.

[4]  T. Mori, Y. Irie, S.I. Nishimura, S. Tokura, M. Matsuura, M.
Okumura, T. Kadosawa, T. Fujinaga.  Journal
of Biomedical Materials Research (Applied Biomaterials), 43, 469-472, 1998.

[5]  C. Jarry, C.
Chaput, A. Chenite, M.A. Renaud, M. Buschmann, J.C. Leroux.  Journal of Biomedical Materials Research
(Applied Biomaterials), 58, 127-135, 2001.