The surface topology and composition of prosthetic implant materials affect cell responses and are therefore important design features. Plasma electrolytic oxidation (PEO) is a surface modification technique that can be used to produce oxidized surfaces with various surface properties. In this work, Ti-6Al-4V was PEO processed to give two surfaces with different morphologies but similar chemical composition. Surface characteristics were assessed using X ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, stylus profilometry and contact angle measurement.

In vitro culture of human foetal osteoblasts (HOB) was performed on the surfaces, to examine cell responses to them. Cellular proliferation, morphology and differentiation were examined, using the AlamarBlue assay, SEM imaging and an alkaline phosphatase (ALP) activity assay respectively. Additionally, the individual effects of oxides present in the PEO processed surfaces (rutile and anatase) on the cells were examined, by binding them in powder form to produce surfaces with similar morphology, but different composition.

Changes in the topology and chemistry of the surfaces affected osteoblast response. HOB proliferated more on the rougher PEO surface, and also displayed greater ALP activity. Also, cells responded differently to surfaces containing just rutile or anatase, indicating that the chemical phase of titanium oxide is of consequence for implant design.

Viscoelastic mechanical properties of biological cells are commonly measured using atomic force microscope (AFM) dynamic indentation method with spherical tips. Storage and loss modulii of cells are then computed from the indentation force-displacement response under dynamic loading conditions. It is shown in current numerical simulations that those modulii computed based on existing analysis can not reflect the true values due to the substrate effect. This effect can alter the indentation modulus by changing the geometric relations between the indentation displacement and the contact area. Typically, the cell modulii are significantly overestimated in the existing indentation analysis.

A statistical model is developed to study the loading-rate dependent mechanical response of biopolymer arrays. Using the kinetic Monte Carlo method, bundles of fibers are studied under load-controlled and displacement-controlled conditions.

Dentin is a load bearing multiphase composite composed of a ceramic phase, hydroxyapatite (HAP), a polymeric phase, collagen, and fluid filled porosity. In order to create better dentin replacements it is important to understand how applied load is naturally transferred between the phases during chewing and other stresses. To determine the apparent elastic modulus of HAP in dentin, applied stress over lattice strain in HAP, high energy wide angle x-ray diffraction measurements were performed on in situ loaded bovine dentin samples. It was determined that the average longitudinal apparent elastic modulus of HAP in dentin was 18.3±2.19GPa. This value is much lower than values predicted by the Voigt model when combined with volume fractions determined for the sample by thermo-gravimetric and chemical analysis. It has been determined that the decrease in apparent elastic modulus is most likely due to a decrease in the “bulk” elastic modulus of HAP due to nanometric effects.

The roles of minor organic layers in influencing the mechanical response of such biomineralized composites as mollusk shells and sponge spicules have been investigated. The mechanisms whereby such minor constituents govern energy dissipation in rigid biomineralized structures are discussed, and a rationale for new modes of toughening that may relate more generally to families of ceramic- or glass/organic composites is offered. New results of simple torsional tests conducted on spicule fibers of a hexactinellid sponge, Euplectella aspergillum (Euplectella a.), compared with those done on melt-drawn glass fibers, showed an enhanced ability to resist failure in torsion, whereas the glass fibers did not. This behavior was attributed to the presence of a very thin adhesive viscoelastic phase between the siliceous layers of the spicule fibers, combined with the architectural and surface features of the spicule fiber.