Master's Theses

Date of Award

2017

Document Type

Thesis

Department

Biomedical Engineering

First Advisor

Jean-Philippe Berteau

Second Advisor

Bingmei Fu

Third Advisor

Luis Cardoso

Keywords

bone, mineral phase, carbonate hydroxyapatite, bone mechanics, nanoscale imaging

Abstract

Bone tissue is a complex composite structure made up of a soft organic phase consisting of collagen I and non-collagenous proteins, and a hard inorganic phase consisting of mineral nanoplatelets. Given it’s compositional properties, bone is a unique stiff, tough, and strong biomaterial, making it exceptionally difficult to synthesize ex vivo. While the complete hierarchical structure may change with age and population, the basic building block components of mineralized collagen fibrils, are preserved. This study uses a model of intramuscular bone of the Atlantic herring fish, which present a simple structure, and no process of remodeling.

A multi-scale approach was developed to measure mechanical properties, mineral composition, mineral maturity or stoichiometric perfection, and distribution based on crystal thickness of 610 bone samples. Tensile modulus increased with tissue maturity marking an increased stiffness in mature populations. Calcium to phosphate ratio showed a correlated increase with stiffness and maturation along with carbonate content in the mineral component. Crystallinity ratio decreased with maturation confirming the presence of carbon substitutions with maturation. Finally, nanoscopic mineral crystal distribution resulted in thickening of crystals with maturation. This assessment of the mineral component, along with micro-mechanical tensile tests showed that the collagen-mineral interphase plays a key role in resisting load. These results contribute to a global understanding between biological components at the Nano scale and mechanical behavior at the macro-scale.

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