Compositionally Modified Hydroxyapatite Nanocrystals for Polymer/Ceramic Scaffold Applications
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0897-J03-18.1
Compositionally Modified Hydroxyapatite Nanocrystals For Polymer/Ceramic Scaffold Applications Andrei V. Stanishevsky, Peserai Chinoda1, Shafiul Chowdhury, Vinoy Thomas, Aaron S. Catledge, and Derrick Dean2 Department of Physics, University of Alabama at Birmingham, Birmingham, AL 35294, USA 1 Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA 2 Department of Materials Engineering, University of Alabama at Birmingham, Birmingham, AL 35294, USA ABSTRACT The polymer/bioceramic composite materials attract much attention for the development of bioresorbable implants and tissue engineering scaffolds. Hydroxyapatite (HA) is the most commonly used bioceramic material due to its similarity to the major mineral component of the hard tissue. We synthesized carbonated and Mg-substituted HA nanocrystals with various concentrations of CO32- and Mg2+ ions by chemical precipitation in the range of the process temperatures from 25 oC to 100 oC. The HA nanocrystals were mixed with several polymeric materials (PCL, PLA, PVA, collagen) to fabricate bulk and nanofiber polymer/HA nanoparticle composites with the HA loading up to 80 % by weight. The HA nanocrystals and polymer/HA composites were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron and atomic force microscopy. Mechanical properties of the composites were investigated using nanoindentation technique. INTRODUCTION The growing need for resorbable bone substitutes [1] and implant fixation devices [2,3] require the development of materials that are both resorbable and bioactive [4], while mechanically similar to bone and stable for certain periods of time. Many natural (collagen, starch, chitin, and chitosan) and synthetic (e.g., polyglycolide (PGA), polylactide (PLA)) resorbable polymers have been used to repair cartilage and bone tissues. However, the mechanical strength, toughness, and elastic modulus of these polymers are lower than those of natural hard tissues. Addition of bioceramic particles to the polymeric materials can modify the mechanical and biological properties of the composite in a broad range [5-8]. One of most commonly used bioceramics is hydroxyapatite(HA) which is similar to the major mineral component of hard tissue. The biological behavior of HA is, among other factors, strongly affected by its crystallinity, presence of impurities, and surface morphology. It has been shown that a nanoscale grain size of synthetic HA and the presence of CO32- and Mg2+ ions show further stimulatory effects on bone growth. In the present study, we synthesized HA nanoparticles with different content of CO32- and Mg2+ ions, prepared several polymer/HA nanoparticle composites, and analyzed the structure, surface morphology, and mechanical properties of fabricated materials using X-ray diffraction (XRD), FT-IR spectroscopy, scanning electron (SEM) and atomic force (AFM) microscopy, and nanoindentation technique.
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EXPERIMENTAL DETAILS HA nanocrystalline particles were synthesiz
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