Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Bachelor of Science in Mechanical Engineering

Degree Level

Undergraduate

Department

Mechanical Engineering

Advisor/Mentor

Nair, Arun

Abstract

When looking at bone at the nanoscale, it consists of a matrix of type I collagen and hydroxyapatite (HAP). Type I collagen is the most abundant protein in the body and together with the mineral HAP [Ca10(PO4)6(OH)2] is responsible for most of the structural integrity of bone. Collagen fibrils in bone contain HAP platelets of varying size dispersed between the collagen. The composition of the type I collagen is predicted to play a role in the mechanical properties of the interface. Our research looks at healthy heterotrimeric collagen and mutated homotrimeric collagen containing three identical chains. Both types of collagen are tested using Steered Molecular Dynamics (SMD) [1] in shearing and peeling directions along the hydroxyl (OH) surface of HAP. The Bell model is also applied to analyze the energy associated with rupturing collagen in shear. The results show that the force required to separate collagen from HAP is not affected by mutation, but the structure of the collagen considerably changes the distribution of hydrogen bonds between collagen-collagen and collagen-HAP interfaces. In shear, homotrimeric collagen forms between 20-40% fewer hydrogen bonds than heterotrimeric collagen. In both shearing and peeling, the number of collagen-water hydrogen bonds increases by roughly 100% before rupture. This research has led to the development of an HAP inspired structure. Currently 3D printed using ABS plastic.

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