Although the gross mechanical properties of ageing tissues have been extensively documented, biological tissues are highly heterogeneous and little is known concerning the variation of micro-mechanical properties within tissues. Here, we use Scanning Acoustic Microscopy (SAM) to map the acoustic wave speed (a measure of stiffness) as a function of distance from the outer adventitial layer of cryo-sectioned ferret aorta. With a 400 MHz lens, the images of the aorta samples matched those obtained following chemical fixation and staining of sections which were viewed with fluorescence microscopy. Quantitative analysis was conducted with a frequency scanning or V(f) technique by imaging the tissue from 960 MHz to 1.1 GHz. Undulating acoustic wave speed (stiffness) distributions corresponded with elastic fibre locations in the tissue; there was a decrease in wave speed of around 40 ms-1 from the adventitia (outer layer) to the intima (innermost).

We develop a physical model to describe the kinetic behavior in cell-adhesion molecules. Unbinding of non-covalent biological bonds is decomposed into entropic and energetic controlled debonding. Such a treatment on debonding processes is a space decomposition of bond breaking events. Entropy controlled dissociation under thermal fluctuation is non-directional in a 3-dimensional space, and its energy barrier to escape may be not influenced by a tensile force but the microstates which can lead to dissociation are changed by the tensile force; An applied force effectively lowers the energy barrier to escape along the force direction. Such energetic effect will accelerate dissociate mainly along directions parallel to the loading direction. The lifetime of the biological bond, due to the superimposition of two concurrent off-rates, may grow with increasing tensile force to moderate amount and decrease with further increasing load, as debonding events dominated by entropy transit to those controlled by an applied force. We hypothesize that a catch-to-slip bond transition is a generic feature in biological bonds. The model also predicts that catch bonds in compliant molecular structure have longer lifetimes and may be activated at lower forces [1].

Lateral migration of vesicles (closed lipidic membranes) in a flow is characterized as a function of the relevant flow parameters and mechanical properties of the vesicles. We consider low Reynolds number flows, and migration is only due to viscous effects. Through experiments and simulations, we exhibit two different origins for such cross streamline migration: the presence of a wall, and a non1constant shear rate, as for instance in a Poiseuille flow. Such migration modifies the distribution of vesicles in a sheared polydisperse suspension; we present preliminary results proving that the hydrodynamic interactions between vesicles greatly modify the distribution of vesicles according to their sizes and deflation.

Computer Tomographic (CT) image data have become a standard basis for structural analyses of bony organs. In this context, regression functions between stiffness components and Hounsfields units (HU) from Computer Tomography, related to X-ray attenuation coefficients, are widely used for the definition of the (actually inhomogeneous and anisotropic) material behavior inside the organ. Herein, we suggest to derive the functional dependence of the fully orthotropic stiffness tensors on the Hounsfield units from the physical information contained in the X-ray attenuation coefficients: (i) Based on voxel average rules for the X-ray attenuation coefficients, we assign to each voxel the volume fraction occupied by water (marrow) and that occupied by solid bone matrix. (ii) By means of a continuum micromechanics representation for bone, which is based on voxel-invariant (species and whole bone-specific) stiffness properties of solid bone matrix and of water, we convert the aforementioned volume fractions into voxel-specific orthotropic stiffness tensor components. The micromechanics model, in combination with the average rule for X-ray attenuation coefficients, predicts a quasi-linear relationship between axial Young's modulus and HU, and highly nonlinear relationships for both circumferential and radial Young's moduli as well as for the shear moduli in all principal material directions. Corresponding whole-organ Finite Element analyses of a partially dentulous human mandible characterized by atrophy of the alveolar ridge show that volumetric strain concentrations/peaks within the organ are decreased when considering material anisotropy, and increased when considering material inhomogeneity.

Basic fibroblast growth factor (bFGF), a protein, plays a key role in wound healing and blood vessel regeneration. However, most negative effects in vivo, or in vitro result from the over dosage of bFGF. Furthermore, it needs to keep the bFGF from protein denaturant. Thus, this study aims to develop a new delivery system based on silica nanoparticles (SiO2 NPs) dispersed in collagen patch for delivery of the bFGF in a local and prolonged manner. In this research, SiO2 NPs are used to encapsulate bFGF through a modified water-in-oil micro-emulsion. The bFGF-loaded nanoparticles afterwards are dispersed in the collagen-based matrix through a EDC cross-linking step. The in vitro release kinetics of SiO2 NPs - encapsulated bFGF with and without collagen matrix have been monitored through ELISA. In addition, the cytotoxicity of SiO2 NPs is investigated by studying the viability of Human Umbilical Vein Endothelial Cells (HUVEC) under the different concentrations of SiO2 NPs. It has found the average diameter (d) for SiO2 NPs encapsulating bFGF is 45 ± 8 nm with a loading efficiency of 72.5±3%. The maximum concentration of bFGF locally released from SiO2 NPs impregnated collagen matrix can be monitored after 30 days, while bFGF released from SiO2 NPs can be detected in 20 days. The further prolonged releasing after the nanoparticle-encapsulated bFGF laden collagen matrix is possibly due to the interaction between the nanoparticles and collagen matrix. In addition, the biocompatibility of the SiO2 NP has been investigated. We found that SiO2 NPs at the concentration of 50 μg/ml can still keep the cell alive. The results indicate that the nanoparticle-laden collagen matrix can locally deliver growth factor in a prolonged manner. This new delivery system may benefit to blood vessel regeneration and potentiate greater angiogenesis.

Ti-6Al-4V alloy is an attractive biomaterial. The current work evaluates the microstructures of the solid and net-shape Ti-6Al-4V alloy produced by Electron Beam Melting (EBM) system using SEM/EDX and optical microscope. The microstructures are influenced by the cooling rate, processing parameters of the EBM system and re-heating of the existing layer during the melting of subsequent layers. Layer structure and columnar grains have been observed, with growing direction parallel to the built direction. The interior of these grains consists of alternating α / β phases. The β phase in the colonies resembles rod shape embedded in the α platelet. Along the grain boundaries more or less continuous α layers were observed. In comparison to solid samples uneven surfaces and pores were seen in the net shape structure. Microhardness evaluation of the EBM produced alloys was also carried out and compared with conventionally produced alloys.

Increase in modulus upon hydration in copolymers of desaminotyrosyl-tyrosine ethyl ester (DTE) and poly(ethylene glycol) (PEG) with iodinated tyrosines, poly(I2DTE-co-PEG carbonate)s, was investigated by varying the fraction and the molecular weight of the hydrophilic PEG component. Water, as expected, acts as plasticizer in polymer with PEG content < 15 wt% and > 30 wt%. But, water has the opposite effect in iodinated polymers with moderate PEG contents, between 15 to 20 wt%: it enhances the Young's modulus. The strength and modulus of hydrated poly(I2DTE-co-15%PEG2K carbonate)s increased by as much as fifteen fold upon hydration. While the decrease in the mechanical properties in most polymeric materials with diluents such water is due to the solvent-induced swelling, the increase in strength and modulus that is observed is most likely due to the reinforcing effect of the increased cross-linking efficiency of the hydrated PEG domains in the iodinated polymer.

Hydroxyapatite biomaterials production has been a major field in biomaterials science and biomechanical engineering. As concerns prediction of their stiffness and strength, we propose to go beyond statistical correlations with porosity or empirical structure-property relationships, as to resolve the material-immanent microstructures governing the overall mechanical behavior. The macroscopic mechanical properties are estimated from the microstructures of the materials and their composition, in a homogenization process based on continuum micromechanics. Thereby, biomaterials are envisioned as porous polycrystals consisting of hydroxyapatite needles and spherical pores. Validation of respective micromechanical models relies on two independent experimental sets: Biomaterial-specific macroscopic (homogenized) stiffness and uniaxial (tensile and compressive) strength predicted from biomaterial-specific porosities, on the basis of biomaterial-independent (‘universal') elastic and strength properties of hydroxyapatite, are compared to corresponding biomaterial-specific experimentally determined (acoustic and mechanical) stiffness and strength values. The good agreement between model predictions and the corresponding experiments underlines the potential of micromechanical modeling in improving biomaterial design, through optimization of key parameters such as porosities or geometries of microstructures, in order to reach desired values for biomaterial stiffness or strength.

A range of mineral content values and organization of the collagen and mineral phases are possible contributors to the significant variance demonstrated within the nanomechanical behavior of mineralized tissues. A combined approach using nanoindentation, to assess nanomechanical behavior, and X-ray diffraction, for analysis of crystallinity and composition, were used to investigate a range of modern and fossilized bone samples. This work provides new insight into the functional role of organization and composition of the mineral phase within heterogeneous, mineralized materials of biological origin. While the predominant influence on nanomechanical behavior is made by mineral volume fraction, the crystallinity was shown to play a significant role in the nanomechanical behavior of modern and fossilized bone samples. The interplay between material structure and function will ultimately help to elucidate the relative contributions of various factors to nanomechanical behavior and lead to improved development of biomimetic materials.

Submicron-sized hydroxyapatite (HAp) particles were loaded on the titanium plate by anodic oxidation over spark discharge voltage in HAp-containing bath. The biocompatibility and bioactivity were drastically improved by HAp deposition on the anodic oxide films. The affinity with living bone was the following order: anodized titanium plate with HAp > anodized titanium plate ≫ titanium. Bone-bonding strength between HAp-loaded titanium plate and living bone after 4 weeks' implant was much higher than that of anodized titanium plate.

In this study, fracture toughness of North American elk (Cervus elaphus canadensis) antler and bovine femur were measured using four-point bending tests on single-edge notched compact samples (ASTM C1421). Tests were conducted on crack growth directions longitudinal and transverse to the long axis of antler and bone in both dry and hydrated conditions to study the effects of fiber orientation and hydration. Fracture toughness results in the transverse orientation were much higher than that in the longitudinal orientation and increased with degree of hydration for both antler and bovine femur. The fracture toughness of antler was ∼ 50% higher than that of bovine femur. The highest fracture toughness value was obtained from the hydrated antler in the transverse orientation, which reached 10.31 MPa·m1/2 compared to that measured from bovine femur, which was 6.35 MPa·m1/2. The crack propagation and fracture surface were characterized using scanning electron microscopy. Toughening mechanisms, including crack deflection by osteons, uncracked ligament bridging, and microcracks formation, are observed and discussed. Comparisons between antler and bone are made.

Neointimal hyperplasia is a main cause for in-stent restenosis after stent-implantation and is triggered by inflammatory response to foreign materials. It can be inhibited if the stent is modified to have good blood compatibility by coating drug compounds. Low temperature plasma polymerization of 1, 2-diaminocyclohexane was performed to prepare more adhesive polymeric thin film onto the metallic stent. Then, the chemical grafting of α-lipoic acid (ALA) was carried out to improve blood compatibility of stent. Drugs containing carboxylic groups can be chemically grafted through the formation of amide bond in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide methiodide onto the DACH deposited stent surface. ALA grafted film showed good mechanical stability and blood compatibility.

Dental remineralization may be achieved by mediating the interactions between tooth surfaces with free ions and biomimetic peptides. We recently developed octuplet repeats of aspartate-serine-serine (DSS-8) peptide, which occurs in high abundance in naturally occurring proteins that are critical for tooth remineralization. In this paper, we evaluated the possible role of DSS-8 in enamel remineralization. Human enamel specimens were demineralized, exposed briefly to DSS-8 solution, and then exposed to concentrated ionic solutions that favor remineralization. Enamel nano-mechanical behaviors, hardness and elastic modulus, at various stages of treatment were determined by nanoindentation. The phase, microstructure and morphology of the resultant surfaces were characterized using the grazing incidence X-ray diffraction (GIXD), variable pressure scanning electron microscopy (VPSEM), and atomic force microscopy (AFM), respectively. Nanoindentation results show that the DSS-8 remineralization effectively improves the mechanical and elastic properties for demineralized enamel.

The hardnesses of secondary cell wall laminae (SCWL) and compound corner middle lamellae (CCML) in wood were measured at indentation strain rates between approximately 7×10-4 s-1 and 20 s-1, using a new method called broadband nanoindentation creep. The wood was subsequently modified with ethylene glycol (EG) and the properties were re-measured. The SCWL and CCML responded differently to this modification: in the SCWL, hardness decreased uniformly by a factor of 3.7 ± 0.3 across all strain rates, whereas in CCML, the modification had a similar effect at low strain rates. However, at high strain rates, hardness was only lowered by a factor of 1.8. The EG modification also lowered elastic modulus of the SCWL and CCML, swelled the SCWL and CCML, and caused previously placed indents to disappear (CCML) or partly disappear (SCWL).

The underlying mechanisms of gecko adhesion have been investigated through modeling of the three-level hierarchical microstructures under gecko's toe [1]. At the bottom of hierarchy, we show that the peeling strength of a spatula pad for attachment can be 10 times larger than that for detachment. At the intermediate level of hierarchy, we show that the 10 times difference in the peeling strength of a spatula pad for attachment and detachment leads to a 100 times difference in adhesion energy at the level of seta. At the top of hierarchy, the attachment of a gecko toe is modeled as a pad under displacement controlled pulling, which yields an adhesive strength more than sufficient for gecko's body weight; On the other hand, the detachment is modeled as a pad under peeling, giving rise to a negligible peel-off force. The present study reveals that the hierarchical microstructures play critical roles in providing gecko with robust attachment and easy detachment.

A new method to fabricate superhydrophobic hard films is described. Surface texture of lotus leaf was replicated on an acetate film, on which a nanocrystalline (NC) Ni coating with a grain size of 30 ± 4 nm and a hardness of 4.42 GPa was electrodeposited. The surface texture consisted of conical protuberances with a height of 10.0 ± 2.0 0m and a tip radius of 2.5 ± 0.5 0m. An additional electrodeposition for 120 s and 300 s was used to locally modify the surface structure by depositing ‘Ni crowns' on the protuberances that increased their height to 14.0 ± 2.0 0m and their tip radius to 6.0 ± 0.5 0m. The modified structures were then treated with a perfluoropolyether (PFPE) solution, which provided a high water contact angle of 156°, i.e., comparable to the naturally superhydrophobic lotus leaf. The increased hydrophobicity as a result of surface structure and chemistry modifications was evident compared to a smooth NC Ni sample, which had a contact angle of 64°.

Iron is essential element for fundamental cell functions, catalyst for chemical reaction. Iron can be found in human body mainly in the form of ferritin - 5Fe2O3.9H2O.

57Fe Mössbauer spectrometry, X4ray powder diffraction, (XRD), X4ray fluorescence (XRF), scanning and transmission electron microscopy (TEM) were carried out for investigation of iron oxide particles in human spleens with diagnosis of hemosiderosis, hereditary spherocytosis, and reference sample.

Room temperature Mössbauer spectra of all investigated samples exhibit doublet4like features identified as Fe(III) predominantly in ferrihydrite and haem environments within the tissue. Low temperature Mössbauer effect measurements at 77 K revealed, however, no changes in the magnetic ordering of the investigated samples. A contribution of ferromagnetically split sextets is clearly seen for all investigated samples measured at 5K. Their occurrence indicates that part of the sample is magnetically ordered, i.e. below the blocking temperature of a superparamagnetic behaviour. The ratio of relative contents of doublet to sextet components suggests differences in the size of ferritin cores in the investigated samples. The hemosiderosis sample exhibits the largest ferritin core which, in turn, stores the highest amount of Fe and thus triggers this disease.

Additional structural characterization is obtained from powder XRD and XRF measurements. XRF results show presence of different chemical elements such as iron, sulphur, phosporus, chlorine, zinc, chromium, and bromine. TEM investigation reveals iron accumulation in macrophages of the human spleen. The size of the particles is around 5 μm.

The amount of chemical elements and pH in surrounding environments can influence iron oxidation status and may cause transformation of biogenic to abiogenic (toxic) character of ferritin.