Evaluation of nanofiber carbon and alumina for orthopedic/dental applications
Abstract
The purpose of the present in vitro study was to evaluate the cytocompatibility properties of novel materials possessing biologically-inspired geometries similar to components of physiological bone (hydroxyapatite crystals and collagen fibrils) for orthopedic or dental applications. Specifically, the influences of the geometry of carbon and alumina nanofibers on osteoblast (the bone-forming cell) adhesion, proliferation, and subsequent function was determined. For adhesion, results found that, indeed, a correlation was present between decreased nanometer fiber shape and increased osteoblast adhesion for both carbon and alumina. By delving into the mechanisms controlling osteoblast adhesion, the present study determined that the underlying reason for increased osteoblast adhesion was due to conformational (or bioactive) changes in fibronectin bound to the novel nanofiber materials. Specifically, on nanometer fiber materials with increased accessibility of RGD peptides (a bioactive region through which cell-membrane integrins bind), a subsequent increase in osteoblast adhesion was found. The present studies agreed with earlier findings that osteoblast adhesion was increased on materials with increased nanometer surface roughness (that is, smaller diameter carbon fibers in compacts, nanospherical alumina over conventional alumina, and nanofiber alumina over either of its spherical counterparts). Moreover, competitive cell (fibroblast, smooth muscle cell, and chondrocyte) adhesion was not affected by the diameter of the carbon fibers in compact form. In contrast, subsequent functions of osteoblasts (specifically, alkaline phosphatase activity and calcium deposition) were not dependent on nanometer fiber shape, but rather the presence of a more pronounced nanometer topography (which was present on the nanophase carbon fibers and nanospherical alumina compared to the conventional carbon fibers and nanofiber alumina, respectively). Upon further examination, these particular materials increased accessibility of heparan sulfate-cell binding regions in adsorbed fibronectin. In this manner, this study provided the first evidence that osteoblast differentiation, including deposition of a mineralized extracellular matrix was dependent on heparan sulfate-mediated osteoblast adhesion. For these reasons, the present study demonstrated that carbon and alumina nanophase materials have promise to serve as the next generation of orthopedic/dental materials with increased ability to bond to juxtaposed bone; this criteria is necessary for increased clinical efficacy of bone prosthetic materials.
Degree
Ph.D.
Advisors
Webster, Purdue University.
Subject Area
Biomedical research
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