Biodegradable polymer - hydroxyapatite nanocomposites for bone plate applıcations

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2010
Aydın, Erkin
Long bone fractures are fixed with bone plates to restrain movement of bone fragments. Fracture site must experience some pressure for proper healing. Bone plates are mostly made up of metals having 5 - 10 times higher elastic modulus than bones and most of the load is carried by them, leading to stress shielding and a bony tissue with low mineral density and strength. To avoid these problems, biodegradable polymer-based composite plates were designed and tested in this study. Poly(L-lactide) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biodegradable polymer composite fibers containing hydroxyapatite (HAP) nanoparticles were produced by extrusion and spinning techniques to reinforce the polymeric bone plates. The composite fibers were expected to mimic the natural organization of bone so that HAP nanorods aligned parallel to the loading axis of bone plate. Also, lactic acid was grafted on HAP surfaces and had a positive effect on the mechanical properties of the PLLA composites. A 50% (w/w) HAP nanoparticle content was found to increase tensile modulus value (4.12 GPa) ca. 2.35 times compared to the pure polymeric fiber with a reduction to one third of the original UTS (to 50.4 MPa). The fibers prepared were introduced to polymeric plates with their long axes parallel. Fiber reinforced bone plates were compression tested longitudinally and up to a 4% increase in the Young’s Modulus was observed. Although this increase was not high was not high probably due to the low fiber content in the final plates, this approach was found to be promising for the production of biodegradable polymeric bone plates with mechanical values closer to that of cortical bones. Biological compatibility of fibers was validated with in vitro testing. The osteoblasts attached and spread on the fibers indicating that bone fractures fixed with these could attract of bone forming osteoblasts into defect area and help speed up healing.

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Citation Formats
E. Aydın, “Biodegradable polymer - hydroxyapatite nanocomposites for bone plate applıcations,” Ph.D. - Doctoral Program, Middle East Technical University, 2010.