Development of Hydrogel Biomaterials for Articular Cartilage Replacement

Aparna Jejurikar (2010). Development of Hydrogel Biomaterials for Articular Cartilage Replacement PhD Thesis, School of Chemistry and Molecular Biosciences, The University of Queensland.

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Author Aparna Jejurikar
Thesis Title Development of Hydrogel Biomaterials for Articular Cartilage Replacement
School, Centre or Institute School of Chemistry and Molecular Biosciences
Institution The University of Queensland
Publication date 2010-04
Thesis type PhD Thesis
Supervisor Dr. Lisbeth Grondahl
Dr. Gwendolyn Lawrie
A/Prof. Darren Martin
Total pages 184
Total colour pages 24
Total black and white pages 160
Subjects 06 Biological Sciences
Abstract/Summary Osteoarthritis is a painful degenerative condition that is a common affliction in young and older people. Pain management rather than a regeneration of a functional knee is the commonly accepted treatment of osteoarthritis today. Due to the inadequacies of current treatment options for osteoarthritis patients there has arisen an urgent need to develop an effective biomaterial to replace damaged articular cartilage. The demand is particularly strong for novel materials that can support the mechanical load to provide frictionless interfaces between the bones of the knee joint. In the proposed research project a novel approach to materials engineering was applied to develop an innovative alginate-based cartilage replacement biomaterial that possesses a structure uniquely mimicking the structural matrix of native articular cartilage. The interrelationship between matrix structure, crosslinking chemistry and properties is explored in detail. Of key interest are the physicochemical and mechanical properties of the hydrogel biomaterial which are optimized to match those of the native articular cartilage through detailed characterization and evaluation of material composition and properties. Ionically crosslinked alginate hydrogels can be formed in the presence of divalent cations such as Ca2+, Ba2+. The traditional method of immersing the membrane in a crosslinker solution for desired period of time was adopted. In addition, an alternative technique where the crosslinker solution is forced through the entire matrix of the membrane during crosslinking has been developed. Gravimetric studies showed that water uptake was mainly affected by the crosslinker ion present in the alginate matrix and less significantly by the crosslinking technique: Ca-alginate xerogels show a higher water uptake as opposed to Ba-alginate xerogels. Tensile tests showed that in Ca-alginate hydrogels prepared using pressure assisted diffusion technique both tensile modulus and tensile stress were doubled than in the hydrogels prepared using the immersion technique. The tensile stress of the Ba-alginate hydrogels were more than twice the value observed for the Ca-alginate hydrogels. The tensile modulus and tensile stress values for these hydrogels are orders of magnitude higher than those reported in the literature thus far. In comparison with the native cartilage tissue the Ca-alginate hydrogels displayed a slightly lower water content and compressive modulus but the tensile modulus of these hydrogels matched well with that of the tissue. A novel methodology to form alginate hydrogels using oxidized alginate (ADA) as a macromolecular crosslinker agent was developed. Optimization of the fabrication of the novel alginate hydrogels using acid catalysis produced hydrogels with a highly complex matrix structure. Hydrogels were produced using ADA of various degrees of oxidation and incorporated in various amounts. The physicochemical and mechanical properties of the hydrogels were dependent on the degree of oxidation and the amount of the ADA crosslinker. The water uptake by crosslinked hydrogels generally increased upon increasing the degree of oxidation of the macromolecular crosslinker. The covalently crosslinked hydrogels displayed a higher water content as compared to the ionically crosslinked hydrogels. Tensile tests also showed improvement in tensile properties upon increasing the degree of oxidation of ADA. However, due to the highly complex organization and structure of the matrix different trends in water uptake and mechanical properties of the hydrogels were observed upon incorporating ADAs with varying degrees of oxidation in varying amounts in the hydrogels. The water uptake and tensile properties of the hydrogels were similar to those of articular cartilage tissue. Composite alginate membranes using additives such as hydroxyapatite (HA) and layered double hydroxides (LDH) were synthesized. In addition to enhancing physical and mechanical properties of the hydrogels, composite hydrogels were synthesized to improve their mineralization properties and cellular compatibility. Stabilized HA particles were also synthesized by absorbing alginate on their surfaces at different times during HA synthesis. Investigation of the physicochemical and mechanical properties of the HA-alginate composite hydrogels showed no significant difference upon using various types of HA particles to produce composite hydrogels. Investigation of CaP mineral growth on the hydrogel surfaces showed that the HA-alginate composite hydrogels induced more mineralization in comparison with LDH-alginate composite hydrogels. Finally, substrate-dependent response of bone like SaOs-2 cells was investigated by seeding SaOs-2 cells on the HA-alginate composite hydrogel material. It was observed that incorporation of HA particles in the alginate hydrogel matrix enhanced cell attachment and specific growth rate. Although the HA-alginate hydrogels displayed poor compressive properties their water uptake, tensile properties, mineralization, and cellular compatibility properties were similar to those of the cartilage tissue. Alginate hydrogels with properties comparable with that of the cartilage in relation with water content, tensile properties, bioactivity, and osteoblast compatibility were successfully synthesized. However, the hydrogels exhibited poor compressive properties. Although, the alginate hydrogels produced in this study show potential as replacement material for cartilage repair in relation with water content and tensile properties, their compressive properties need to be enhanced.
Keyword articular cartilage
structure-property relationships
Tensile testing
Water Uptake
Additional Notes Colour pages 19, 24, 39, 59, 62, 66, 68-70, 81, 87, 92, 96, 115, 131, 134, 142, 156, 158, 159, 161, 162, 174, 182

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Created: Thu, 02 Dec 2010, 13:45:06 EST by Ms Aparna Jejurikar on behalf of Library - Information Access Service