Browsing by Author "Brochu, Alice"

Total joint replacement surgeries are performed on thousands of patients every year, yet these implants are subject to failure following prolonged exposure to the harsh environment of the body as well as the complex loading patterns seen in biological joints. The generation of wear debris from both the articulating surfaces and the poly(methyl methacrylate) (PMMA) bone cement used to anchor the replacements in place serves to accelerate wear and subsequent failure of the device. Self-healing approaches that employ an encapsulated healing agent embedded in a catalyst-containing matrix have been developed to restore mechanical function to materials that undergo crack damage; following capsule rupture, and healing agent release and polymerization serves to halt microcrack propagation. However, existing encapsulated systems do not adhere to biomaterials constraints. In this work, interfacial polymerization of polyurethane (PUR) in an oil-in-water emulsion was used to achieve encapsulation of octylcyanoacrylate (OCA), a medical grade adhesive used in sutureless surgeries. The optimized encapsulation procedure was determined by studying the effects of solvent, surfactant, and temperature on the final product. The average size and size distribution, capsule shell thickness, percent fill and reactivity of encapsulated agent, and shelf life of these capsules were studied and are now suitable for incorporation into PMMA and assessment as potential healing agent systems.

Extending the functional lifetime of acrylic poly(methyl methacrylate) (PMMA) bone cement may reduce the number of revision total joint replacement (TJR) surgeries performed each year. We developed a system utilizing an encapsulated water-reactive, FDA-approved tissue adhesive, 2-octyl cyanoacrylate (OCA), as a healing agent to repair microcracks within a bone cement matrix. The proposed research tested the following hypotheses: (1) reactive OCA can be successfully encapsulated and the resulting capsules thoroughly characterized; (2) the static mechanical properties of the PMMA composite can be improved or maintained through inclusion of an optimal wt% of OCA-containing capsules; (3) PMMA containing encapsulated OCA has a prolonged lifetime when compared with a capsule-free PMMA control as measured by the number of cycles to failure; and (4) the addition of capsules to the PMMA does not significantly alter the biocompatibility of the material. Based on the experiments reported herein, the primary conclusions of this dissertation are as follows: (1) functional OCA can be encapsulated within polyurethane spheres and successfully incorporated into PMMA bone cement; (2) lower wt% of capsules maintained the tensile, compressive, fracture toughness, and bending properties of the PMMA; (3) inclusion of 5 wt% of OCA-containing capsules in the matrix increased the number of cycles to failure when compared to unfilled specimens and those filled with OCA-free capsules; and (4) MG63 human osteosarcoma cell proliferation and viability were unchanged following exposure to OCA-containing PMMA when compared with a capsule-free control.