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Osteoblast, fibroblast, and endothelial cell adhesion on nanophase (that is, materials with grain sizes less than 100 nm) alumina, titania, and hydroxyapatite (HA) was investigated using in vitro cellular models. Osteoblast adhesion was significantly (p < 0.01) greater after 4 h on nanophase alumina, titania, and HA than it was on conventional formulations of the same ceramics. In contrast, compared to conventional alumina, titania, and HA, after 4 h fibroblast adhesion was significantly (p < 0.01) less on nanophase ceramics. Examination of the underlying mechanism(s) of cell adhesion on nanophase ceramics revealed that these ceramics adsorbed significantly (p < 0.01) greater quantities of vitronectin, which, subsequently, may have contributed to the observed select enhanced adhesion of osteoblasts. Select enhanced osteoblast adhesion was independent of surface chemistry and material phase but was dependent on the surface topography (specifically on grain and pore size) of nanophase ceramics. The capability of synthesizing and processing nanomaterials with tailored (through, for example, specific grain and pore size) structures and topographies to control select subsequent cell functions provides the possibility of designing the novel proactive biomaterials (that is, materials that elicit specific, timely, and desirable responses from surrounding cells and tissues) necessary for improved implant efficacy.

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The present in vitro study investigated osteoblast adhesion on hydroxylapatite (HA) doped with either cadmium (Cd), zinc (Zn), magnesium (Mg), or yttrium (Y). Compared with any other dopant tested in the present study, osteoblast adhesion was significantly (p < 0.05) greater on HA doped with Y after 4 h; in addition, osteoblast adhesion increased with concentration (2-7 mol%) of Y in HA. The findings that HA doped with greater amounts of Y adsorbed higher concentrations of calcium and, subsequently, of vitronectin and collagen (proteins known to mediate osteoblast adhesion), but not of albumin, laminin, and fibronectin, may explain the observed enhanced adhesion of osteoblasts on these substrates. Interactions (i.e., adsorption and configuration/bioactivity) of vitronectin and collagen may have been promoted by increased porosity of doped HA. Through doping with Y, the present study provided the first evidence that HA can be synthesized and processed with improved cytocompatibility properties for osteoblast adhesion, and thus offered essential information for the design of novel proactive bioceramics. Proactive bioceramics which elicit specific, timely, and desired responses from surrounding cells and tissues are necessary for improving bonding of orthopaedic/dental implants to juxtaposed bone; such osseointegration will, undoubtedly, enhance implant efficacy.

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Hydroxylapatite (HA) was made containing magnesium, zinc, cadmium, and yttrium. Salts of these cations were added to precipitating HA; the precipitates were dried and sintered at 1100 degrees C for 1 h. Lattice parameters from X-ray diffraction spectra showed that these elements were incorporated into the apatite structure at a level of 2% added fraction of calcium in HA and up to 7% for yttrium. The densities of different substituted apatites were close to theoretical for pressed and sintered samples, which is evidence for low bulk porosity. The grain sizes of substituted apatites were smaller than those of pure HA except for cadmium-containing apatite. Surfaces of etched samples showed no second phases, whereas surfaces of unetched samples showed second phases and higher porosity than etched surfaces.

CaTiO(3) is a strong candidate to form at the interface between hydroxylapatite (HA) and titanium implants during many coating procedures. However, few studies have compared the cytocompatibility properties of CaTiO(3) to HA pertinent for bone-cell function. For this reason, the objective of the present in vitro study was to determine the ability of bone-forming cells (osteoblasts) to adhere on titanium coated with HA that resulted in the formation of CaTiO(3). To accomplish the formation of CaTiO(3), titanium was coated on HA discs and annealed either under air or a N(2)+H(2) environment. Materials were characterized by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), and atomic force microscopy (AFM). These characterization techniques demonstrated the formation of a nanometer rough CaTiO(3) layer as a consequence of interactions between HA and titanium during coating conditions. Results from cytocompatibility tests revealed increased osteoblast adhesion on materials that contained CaTiO(3) compared to both pure HA and uncoated titanium. The greatest osteoblast adhesion was observed on titanium-coated HA annealed under air conditions. Because adhesion is a crucial prerequisite to subsequent functions of osteoblasts (such as the deposition of calcium containing mineral), the present in vitro results imply that orthopedic coatings that form CaTiO(3) could increase osseointegration with juxtaposed bone needed for increased implant efficacy.