Browsing by Subject "biomimetic"
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Item A tribological and biomimetic study of potential bone joint repair materials(2009-05-15) Ribeiro, RahulThis research investigates materials for bone-joint failure repair using tribological and biomimicking approaches. The materials investigated represent three different repairing strategies. Refractory metals with and without treatment are candidates for total joint replacements due to their mechanical strength, high corrosion resistance and biocompatibility. A composite of biodegradable polytrimethylene carbonate, hydroxyl apatite, and nanotubes was investigated for application as a tissue engineering scaffold. Non-biodegradable polymer polyimide combined with various concentrations of nanotubes was investigated as a cartilage replacement material. A series of experimental approaches were used in this research. These include analysis of material surfaces and debris using high-resolution techniques and tribological experiments, as well as evaluation of nanomechanical properties. Specifically, the surface structure and wear mechanisms were investigated using a scanning electron microscope and an atomic force microscope. Debris morphology and structure was investigated using a transmission electron microscope. The debris composition was analyzed using an X-ray diffractometer. Nanoindentation was incorporated to investigate the surface nanomechanical properties. Polytrimythelene carbonate combined with hydroxyapatite and nanotubes exhibited a friction coefficient lower than UHMWPE. The nanoindentation response mimicked cartilage more closely than UHMWPE. A composite formed with PI and nanotubes showed a varying friction coefficient and varying nanoindentation response with variation in nanotube concentration. Low friction coefficients corresponded with low modulus values. A theory was proposed to explain this behavior based on surface interactions between nanotubes and between nanotubes and PI. A model was developed to simulate the modulus as a function of nanotube concentration. The boronized refractory metals exhibited brittleness and cracking. Higher friction coefficients were associated with the formation of amorphous debris. The friction coefficient for boronized Cr (~0.06) under simulated body fluid conditions was in the range found in natural joints.Item Development of nano-scale and biomimetic surfaces for biomedical applications(Texas A&M University, 2006-10-30) Henry, James EdwardThe work described in this dissertation details the development of a biomimetic materials for use in sensors and therapeutics, based on new advances in material science. The sensors developed herein target neurodegenerative diseases. Two of the diseases, the transmissible spongiform encephalopathies (TSEs) and Alzheimer??????s disease (AD), are diseases associated with the abnormal folding of a protein, thus detecting the disease is dependent upon developing structure specific sensor technologies. Both sensors developed in this work take advantage of the unique optical properties associated with nanoscale metal particles, however they use different types of spectroscopies for optical detection of the presence of the disease associated abnormal protein, and different types of recognition elements that bring the disease associated proteins close to the nanoscale metal particles. In the case of TSEs, the recognition element was a commercially available antibody. In the case of AD, the recognition element was a molecular scale self-assembled surface. A therapeutic for AD was developed based on the molecular scale materials developed for the AD biosensor. Mathematical models were developed that facilitated the rational design of the biosensors described in this work that could also be used in future biosensor development.Item Studies of block copolypeptide synthesis, self-assembly, and structure-directing ability(Texas A&M University, 2007-04-25) Jan, Jeng-ShiungThe use of organic compounds as templates to assemble inorganic materials with structures over multiple length scales has received much attention due to the potential applications that can be developed from these materials. Many organisms synthesize organic/inorganic composites with exceptional control over morphology, physical properties, and nanoscale organization of these materials. Materials such as bone, nacre, and silica diatoms are excellent examples of the complex yet highly controllable hierarchically structured materials nature can form at ambient conditions. The ability to mimic these organisms through the design of supramolecular assemblies and use them to direct the growth of hierarchically structured materials has increased significantly in recent years. In this dissertation, block copolypeptide templated inorganic materials were synthesized and characterized using a wide range of analytical techniques. There are three major conclusions from this dissertation. First, the conformation of a polypeptide chain can be used to manipulate the porosity of oxide materials obtained. Second, individual supramolecular objects (vesicles) formed by block copolypeptides can be used as templates to form nanostructured hard materials. Third, polypeptide chemistry and solution conditions can be used to control both the morphology and porosity of the hard materials they assemble. This dissertation also describes preliminary work toward designing the block copolypeptides derivatives for biomimetic inorganic synthesis and gene delivery. This work includes the synthesis of these block copolypeptides derivatives and of the templated oxide materials. Some interesting silica materials such as porous silicas and silica nanocapsules were synthesized using double hydrophilic block copolypeptides derivatives as templates. Also, the preliminary work of using these block copolypeptides derivatives for gene delivery is included and shows these copolypeptide derivatives are potential delivery vehicles.Item Synthesis of Cell-responsive, Biodegradable Polyureas for Ligament Tissue Engineering(2011-08-08) Benhardt, Hugh AdamAn estimated 200,000 injuries to the anterior cruciate ligament (ACL) occur annually in the United States, with approximately 100,000 total ACL reconstructions performed each year. Due to inherent limitations with existing ACL reconstruction strategies, the development of tissue engineered ligaments is a key area of musculoskeletal research. Although great strides have been made in the scaffold design, current strategies are limited by the inability to replicate the mechanical behavior of native ligament tissue with synthetic polyesters or natural polymers. Poly(ester urethane)s have recently been investigated as possible scaffold materials because of their established biocompatibility, excellent mechanical properties, and exceptionally tunable structure. However, non-specific degradation makes it difficult to tailor polyurethane structure to complement ligament regeneration. In contrast, a biomaterial that features system-responsive degradation would integrate with native ligament remodeling and thus provide effective load transfer to newly formed tissue that is necessary to restore mechanical integrity. In this study, enzyme-labile peptide sequences were conjugated to ether-based polyols to form collagen-mimetic soft segments that feature cell-responsive degradation. Synthetic routes were first developed to functionalize these polyols with favorable end groups for peptide coupling. Upon successful conjugation, biodegradable soft segments were then incorporated into the structure of linear polyurea elastomers. By varying soft segment chemistry, soft segment molecular weight, and the hard to soft segment ratio, a library of cell-responsive, biodegradable polyureas was developed. This library can then be used to elucidate key structure-property relationships necessary to complement neotissue formation. Overall, synthesis of a novel biomaterial that combines the strength and tunability of synthetic elastomers with cell-responsive degradation will assist in the development of an improved tissue engineered graft for ACL reconstruction.Item The Interactions and Exchanges of Metal-bound Sulfur Containing Ligands with Various Transition Metals(2011-02-22) Foley, WilliamThe treble clef binding motif of the zinc finger metalloprotein utilizes N2S2 binding sites. Whereas other N2S2 metalloproteins function in catalytic roles, zinc fingers serve mostly a structural element, although there has been some evidence that the zinc finger protein can interact with exogenous metal ions in aggregate formation or ion exchange. The work presented within has been aimed at precedents for both of the latter in Zn2+. The use of zinc and cadmium dithiolate complexes as mono- and bidentate S-donor ligands to tungsten carbonyl complexes was explored and the ability of zinc and cadmium complexes to stably bind to W(CO)x (x = 4 and 5) was established. The reactivity of thiolate sulfurs within the bimetallic complexes was examined, gaining an understanding of zinc and cadmium N2S2. The characteristics of these complexes were examined via IR, UV-vis, elemental analysis, and x-ray crystallography spectroscopy. The ability of zinc to act as a scaffold for the synthesis of bisacetylbme-dach in the production and subsequent transfer of the same ligand to exogenous metal ion sources was investigated. Cu2+ and Cd2+ analogs to the Zn-1?-Ac2 were synthesized and their properties investigated with IR, elemental analysis, and UV-vis spectroscopy.