Degree Type

Thesis

Date of Award

2008

Degree Name

Master of Science

Department

Materials Science and Engineering

First Advisor

Mufit Akinc

Abstract

This study aimed to develop a biomimetic approach to achieve the natural biomineralization of bone. Temperature and pH-sensitive self-assembling tri- and pentablock co-polymer templated Hydroxyapatite (Ca5(PO4)3OH) (HAp) nanocomposite hydrogels were synthesized, and enzyme-catalyzed urea decomposition was used to increase pH gradually and homogeneously. XRD, SEM, TEM and EDS analysis confirmed the formation of HAp. The hydrogels showed the existence of amorphous HAp. The inorganic phase exhibited thin sheet-like structure with a length of hundreds nanometers, and only 5-10 nm thick. Both high-resolution TEM and scanning TEM microimages, electron diffraction and SEM confirmed the nano-crystalline phase of HAp in dry state. The nano HAp sheets assembled to form clusters in the presence of polymer. The inorganic components account for 4-6 wt% of the total hydrogels. It is also proved by NMR that organic and inorganic components intimately associated with each other that formed nanocomposites. Samples prepared with Pluronic at 37oC showed smaller nanocomposite size than PAA.

It is also found that by the same urea-urease method without polymer, low inorganic ion concentrations (0.2M and 0.4M) and low temperatures (room T and 37oC), resulted in mainly calcium carbonate (CaCO3, calcite) whereas for higher Ca2+ and PO43- concentrations and temperatures (i.e., 1.0M and 1.5M at 60oC), HAp was the dominant phase. The urease activity has been confirmed to be affected by high concentration of buffer phosphate solution. Low phosphate concentration may facilitate the urea hydrolysis to release CO2 at a faster rate which reacts with Ca2+ to form CaCO3.

Copyright Owner

Mowen Li

Language

en

Date Available

2012-04-30

File Format

application/pdf

File Size

87 pages

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