Design, synthesis, and evaluation of nanophase ceramics for orthopaedic/dental applications
Abstract
Clinical complications with conventional orthopaedic/dental implant devices are often due to insufficient bonding to juxtaposed bone; osseointegration provides mechanical stability to prostheses in situ , minimizes motion induced damage to surrounding tissues and is crucial to the clinical success of orthopaedic/dental implants. Ceramics have long been appreciated for their biocompatibility with bone cells and tissue, but, poor mechanical properties (such as ductility) have limited their wide use as orthopaedic/dental implants. The objective of the present in vitro study was to investigate, for the first time, various properties of nanophase (that is, novel material formulations with grain and pore sizes less than 100 nm) ceramics pertinent to orthopaedic/dental applications. Compared to conventional (that is, grain sizes greater than 100 nm) formulations of the same material, nanophase ceramics possess attractive mechanical and cytocompatibility properties. Specifically, nanophase ceramics demonstrated bending properties on the same order of magnitude as physiological bone; such properties are highly desirable for materials used as bone implants. Most important, the functions (such as adhesion, proliferation, synthesis of alkaline phosphatase, and deposition of calcium-containing mineral) of osteoblasts (the bone-forming cells) were selectively and significantly enhanced on nanophase ceramics. These results are most remarkable when contrasted to the observed decreased adhesion of fibroblasts (cells that contribute to fibrous encapsulation and callus formation events that lead to implant loosening and failure) on the nanophase alumina, titania, and hydroxyapatite tested. Investigation of the mechanism(s) of the observed, select, enhanced osteoblast adhesion (a crucial prerequisite for subsequent, anchorage-dependent-cell function) on all ceramic formulations tested in the present study revealed that the concentration, conformation, and bioactivity of vitronectin were important parameters mediating osteoblast adhesion exclusively on nanoceramics. Conformation of vitronectin that exposed epitopes (such as integrin-binding and heparan sulfate-binding sites) necessary for subsequent select osteoblast adhesion was enhanced on nanophase ceramics; these material formulations also promoted calcium and, subsequent, calcium-mediated vitronectin adsorption. By demonstrating that bioceramics can be designed and fabricated (through control of grain and pore size) to possess improved cytocompatibility properties for select osteoblast function, the results of the present study have made fundamental and groundbreaking contributions to the emerging fields of cellular/tissue engineering and nanophase material science. Undoubtedly, as this study demonstrated for the first time, nanophase ceramics have great potential to become the next generation, choice orthopaedic/dental biomaterial to enhance bonding to juxtaposed bone and, thus, increase implant efficacy.
- Publication:
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Ph.D. Thesis
- Pub Date:
- 2000
- Bibcode:
- 2000PhDT.......118W