The effects of charged substrates on the attachment of rat primary bone marrow stromal cells have been investigated using a novel cell culture chamber. Cells were cultured on the surfaces of a conductive and optically transparent indium tin oxide (ITO) coating. When a voltage was applied to the ITO electrodes, positive and negative charges were induced on the ITO electrodes. After 24 hours exposure to 0.8V, more cells attached to the anode than either the cathode or control both in presence or absence of serum in the culture medium. Protein desorption profiles also indicated that the enhanced attachment of cells to the anode was not controlled by the adsorption of serum proteins. The surface texture of ITO was analyzed using atomic force microscopy, the thickness by transmission electron microscopy, and crystallinity using glancing angle x-ray diffraction.

Calcium phosphate ceramic blocks of three different densities, porous, intermediate and dense, were prepared by tape casting (total = 18), and implanted in the femora of 9 Wistar rats for 1 to 3 weeks. Following fixation, the tissue was prepared for examination by scanning electron microscopy (SEM) of freeze fractured specimens, or back-scattered electron imaging (BSEI) of polymethylmethacrylate (PMMA) embedded, undecalcified, sections. The results demonstrated that while all ceramics were osteoconductive, the 93 % dense implants showed no evidence of bone bonding as judged by the plane at which specimens separated or cracked during preparation for microscopy. The porous ceramics, on whose surfaces both multinucleated cells and osteoid tissue were observed at all implantation times, exhibited less bone contact than the other two groups. Both SEM and BSEI showed that there was bone growth into the microporosity of both intermediate and porous ceramics, pore size range 1−2μ m, to a depth of about 6μm. The latter corresponds to the thickness of natural bone lamellae. In all implants examined, de novo bone formed on the ceramic surface by the initial production of a biological cement-line like interfacial extracellular matrix. The results clearly show that osteoconduction and bone-bonding are distinct mechanistic phenomena. While we assume the former to be a consequence of protein adsorption events culminating in anchorage of osteoblasts to the implant surface, the latter is the result of mechanical interdigitation of the extracellular matrix, produced by osteoblasts, with the microtopography of the implant surface.

Osteoblast cell differentiation and bone formation using rat calvaria cells were studied on the surface of a porous 3-dimensional polymer matrix of 50:50 poly (lactide-co-glycolide) (PLAGA)/ hydroxyapatite (HA). Cell proliferation was determined at 24 hr, 3, 7, 14, and 21 days. Exponential growth was observed during the first week and a steady increase in the population continued until 21 days after cells were seeded. Cell growth kinetics on PLAGA/HA showed an exponential pattern. Environmental scanning electron microscopy revealed the formation of multilayers of cells growing throughout the polymer matrices by day 7 and through day 21. Alkaline phosphatase (AP) activity was demonstrated after 21 days of culture on PLAGA/HA using a commercial diagnostic kit. Light microscopy observations of experiment cultures revealed active osteoblastic cells forming a characteristic mineralized matrix in the presence of β-glycerophosphate as a phosphate donor. Mineralization was not seen when the matrix alone was incubated with the reagent, indicating that the mineralization was due to the cells and not the HA in the matrix. These results suggested that the 3-dimensional PLAGA/HA matrix studied provided an excellent matrix for bone cell differentiation and mineralization in vitro and therefore may be a good candidate as a synthetic implant for bone regeneration.

Plasma-sprayed hydroxyapatite (PSHA) coatings are often used as the attachment vehicle for the femoral component of a total hip prosthesis. The key to successful hip replacement is the attachment of the femoral stem to the surrounding bone.

Within hours of implantation of PSHA-coated Ti-6AI-4V rods in canine bone, bone mineral deposits on the HA coating. These deposits take the form of globular networks of fibrous crystallites. The crystallinity of these deposits was confirmed via high-resolution transmission electron microscopy (TEM) and electron diffraction. We have also characterized the composition of these deposits using x-ray energy-dispersive spectroscopy (XEDS) in the scanning TEM. Finally, we have studied the morphology of the fiber-like crystallites by stereography in the TEM.

The bone-implant bond strength to hydroxyapatite-coated cylindrical Ti-6A1–4V implants was evaluated in torsional tests using a canine model. Experimental hydroxyapatite (HA) coatings were deposited using pulsed laser deposition (PLD) under conditions that yield highly crystalline, phase-pure coatings on Ti-6A1–4V. Commercially available plasma-sprayed (PS) HA coatings of lower crystallinity and purity served as positive controls (for bone bonding) and uncoated polished and grit-blasted Ti-6A1–4V samples as negative controls. The torsional shear strength of the PLD HA-coated specimens implanted in cancellous bone was substantially lower than that of the PS HA-coated implants, at both 2 and 6 weeks post-implantation. Within statistical limits, the shear strength of the PLD HA-coated samples was similar to that of the polished Ti-6A1–4V control implants and lower than the grit-blasted Ti-6A1–4V control implants. Examination of PLD HA-coated samples after mechanical testing revealed many areas from which the coating had detached. Previous results from laboratory solubility studies showed that (a) PLD films released less calcium and phosphate than the PS controls, (b) rates of dissolution were much lower and (c) the PLD coatings contained fewer decomposition products. Taken with these previous findings, the present results suggest that the surface morphology and/or grain size of implants may be more important for bone bonding than the phase purity of hydroxyapatite coatings. Furthermore, the local chemical environment resulting from the dissolution of the more soluble phases present in the PS HA coatings may enhance bone bonding.

Although significant advances have been made to provide mechanically strong and nontoxic metals and alloys, biological integration of devices into natural tissues remains a problem. The Surface Induced Mineralization (SIM) and Void Metal Composite (VMC) processes produce a bioactive porous metal implant coating/device which may address many of the problems associated with conventional processing methods.

The VMC process produces materials which have cylindrical pores of uniform diameter which can completely penetrate the structure of the material. The pore diameter, orientation and interconnectivety are easily controlled

The SIM process uses the idea of nature's template-mediated mineralization by chemically modifying the implant to produce a surface which induces heterogeneous nucleation from aqueous solution. SIM produced bioactive coatings provide 1) control of the thickness and density of the mineral phase, 2) a way to coat porous metals, complex shapes and large objects, 3) the ability to coat a wide variety of materials, 4) potential choice for the phase of the mineral formed.

Siliceous materials are the principal components of Earth's crust and also have become key ingredients of modem technology. Recently, we have expanded our chemical characterization of complex silicates (e.g., framework [1] and sheet types [2]) to include studies of their interaction with select biocells [3,4]. It is becoming apparent that the surface chemistry of these silicates, and perhaps that of silica itself, plays a key role in the oft resulting cell pathogenesis, thus enhancing the value of further investigations with X-ray photoelectron spectroscopy. The present research describes the unique growth of Ehrlich (murine or rat tumor) cells on Sio and SiO2 wafers, and also on select seaentine silicates (such as chrysotile asbestos). Tbese growth studies were followed by both cell/silicate separations and unique freeze drying [3,4]. XPS examination at select stages discovered cell induced alterations in the Si, O, Mg and particularly Fe chemistry of the silicon based systems as well as corresponding changes in the cell chemistry. Many of these features were confirmed by atomic absorption spectroscopy.

The response of a range of porous Si films to acellular simulated body fluids has been monitored by SEM, EDX and FTIR analyses. Quite low levels of porosity are shown here to induce hydroxyapatite growth both on top of the film, and even on neighbouring areas of bulk Si, which in isolation have no such effect. The in-vitro demonstration of hydroxyapatite nucleation by a porous semiconductor could provide further insight into the phenomenon of bioactivity and help realise a broader range of bioactive materials.

A set of methods that can be used to create surfaces to accurately control biological reactions is described. These include strategies for inhibiting non-specific reactions, making highly organized surfaces, spatially arraying recognition moieties and characterizing complex surfaces.