Understanding the Interactions of Collagen with Mineral in Bone:

Working Towards Developing a Realistic CompositeF.J. Harden1, I.R. Gibson2, R.M. Aspden

3 and J.M.S. Skakle11Department of Physics, SUPA, University of Aberdeen, Meston Walk, Aberdeen, AB24 3UE2School of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD

3 Musculoskeletal Programme, Institute of Medical Sciences, University of Aberdeen, Foresterhill, AB25 2ZD

Aims

• to review the existing literature on mineral-organic composites, focussing on the use of collagen;

• to study collagen in bone in situ to explore the mineral-collagen interaction;• to create and study new composite materials with similar features to bone.

What is bone and what are its functions?

� Bone is a light-weight, strong, living tissue.

� Bone contains its own cells and blood supply

surrounded by the interwoven bone structure.

� The bone extracellular matrix predominantly

consists of type I collagen (organic phase), and

hydroxyapatite (a mineral phase).

The main functions of bone are:

� to provide and maintain mechanical support

of the human body;

� to protect organs and vital tissues;

� to be a mineral reservoir around the body.

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Figure 1: Raman spectra of bone alongside Raman spectra of HA and

substituted-HA, both heated at 1000oC for 2 hours

Requirements of a bone-substitute material:

� Biocompatible

� Osteoconductive

� Osteoinductive

� Bone regenerative

Why research bone replacement materials?

� Growth of elderly population as a percentage of

total population.

� Greater expectations of quality of life.

� Degenerative bone diseases.

� Bone graft demand exceeds available supply.

X-ray Powder Diffraction (XRD)

Used to determine if a sample is pure and provides

information on crystallinity and particle size. It is useful

for the analysis of the mineral component in bone and

the synthetic analogues.

Future Work

• Formulation and analysis of HA-based composites.

• Mini-project on bone nodule formation.

• Neutron scattering on whole bone.

• Analysis of bone explants using Raman spectroscopy.

Raman Spectroscopy

The Raman spectrum obtained can give valuable

information on a material’s chemical composition. It can be

used for determining specific chemical groups in a material

easily, quickly and with little material preparation.

Figure 3: Comparison of whale bone and as-prepared HA

(at room temperature)

Figure 2: XRD comparison of heated bone, HA and substituted-HA

Materials

Hydroxyapatite (HA) based materials are widely used in orthopaedics and dentistry. Bone is a multi-substituted

calcium-phosphate apatite with several ionic substitutions. Hence, substituted-HA improves the bioactivity and bone

apposition rate of a replacement material, as it provides a closer bone-like inorganic chemical composition with the

addition of substituted elements.

Type I collagen is effectively the main element in the ‘building blocks’ of the bone matrix and is used as a biomaterial

to mimic the extracellular matrix.

as-prepared HA

Whale bone

substituted-HA heated at 1000oC for 2 hours

HA heated at 1000oC for 2 hours

Whale bone heated at 1000oC for 2 hours

matrix

Techniques include:

Raman Spectroscopy and X-ray Powder Diffraction.

Email: f.j.harden@abdn.ac.uk