Maximum information capacity of a three-dimensional hologram

This Letter is devoted to the problem of the maximum information capacity of a three-dimensional hologram with optimal utilization of the dynamic range of the storage medium. A hologram is treated as an object of information theory. Diffraction-limited holographic writing is analyzed on the basis of the reciprocal-lattice formalism. The calculation of the information capacity of the three-dimensional hologram is reduced to analysis of a set of multiplexed holograms each of which possesses a finite signal/noise ratio determined by the dynamic range of the holographic medium. The optimal number of pages which give the maximum information capacity with angular multiplexing is found. Pis’ma Zh. Tekh. Fiz. 23, 37–43 (September 26, 1997)     

Assessment of cell viability in a three-dimensional enzymatically cross-linked collagen scaffold

Microbial transglutaminase (mTGase) is an enzyme that introduces a covalent bond between peptide bound glutamine and lysine residues. Proteins cross-linked in this manner are often more resistant to proteolytic degradation and show increased tensile strength. This study evaluates the effects of mTGase mediated cross-linking of collagen on the cellular morphology, behaviour and viability of murine 3T3 fibroblasts following their seeding into collagen scaffolds. Additionally, cell mediated scaffold contraction, porosity and level of cross-linking of the scaffold has been analysed using image analysis software, scanning electron microscopy (SEM), colorimetric assays, and Fourier transform infrared spectroscopy (FTIR). We demonstrate that the biocompatibility and cellular morphology, when comparing cultures of fibroblasts integrated in mTGase cross-linked collagen scaffolds with the native collagen counterparts, remained unaffected. It has been also elicited that the structural characteristics of collagen have been preserved while introducing enzymatically resistant covalent bonds. This work was performed in the National Centre for Biomedical Engineering Science, Orbsen Building, National University of Ireland, Galway, Ireland.     

Surface topography and HA filler volume effect on primary human osteoblasts in vitro

HAPEX^TM, a bone analog material, with similar properties to cortical bone, has been studied in vitro with particular reference to the effect of surface topography. The stimulation of a favorable bone response by this composite depends on optimization of the hydroxyapatite (HA) content in relation to the material bioactivity without compromising the mechanical characteristics. In this study we have started to investigate the effects of surface topography on cell attachment and subsequent cellular behavior in relation to proliferation. Different volumes of HA (20% and 40%) were added to a high density polyethylene (HDPE) matrix to produce the test materials. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were used to examine cell morphology on HAPEX^TM, and the surface characteristics produced by different machining protocols. The measurement of cellular DNA and tritiated thymidine ([³H]-TdR) incorporation has been used to asses cell proliferation upon the materials. The results show that the material surface topography has a large influence on cell proliferation and attachment, and with a controled material topography the 40% vol HA/HDPE composite gives the greater biological response compared to the 20% vol HA/HDPE composite.     

Improved osteointegration and angiogenesis of strontium-incorporated 3D-printed tantalum scaffold via bioinspired polydopamine coating

Tantalum(Ta) is used in orthopedic implants because it has excellent biocompatibility. However, high elastic modulus, bio-inertness, and unsatisfactory osteointegration limits its wider use in clinical applications. Herein, a 3 D porous Ta scaffold with low elastic modulus was fabricated using selective laser melting(SLM). Strontium(Sr) was incorporated on the surface of the scaffold with the aid of polydopamine(PDA)to further improve its osteointegration ability. The prepared scaffolds exhibited a stable Sr ion release in 14 d. Rat bone marrow stem cells(BMSCs) showed improved early adhesion and spreading after Sr was incorporated on the porous Ta surface. The osteogenic behavior, including extracellular matrix mineralization(ECM), alkaline phosphatase activity(ALP), and expression of bone-related RNA, were all enhanced. Furthermore, the Sr-incorporated porous Ta scaffolds exhibited better angiogenic behavior, such as promoting migration, tube formation, and angiogenesis-related RNA expression abilities of human vascular endothelial cells(HUVECs). Additionally, histological images(HE, Masson and CD31 immunofluorescent staining) suggested that Sr-incorporated porous Ta scaffolds displayed enhanced osteointegration and angiogenesis after implantation in rat femur for 12 weeks. These findings prove that the PDA-based Sr-incorporated porous Ta scaffolds show promising use in orthopedic implants.     

Oxygen adsorption on the (110) face of tantalum,niobium, molybdenum and tungsten single crystals

Preliminary surface studies using work function techniques are reported for the (110) face of the refractory metals tantalum, niobium, molybdenum and tungsten, both in the clean state and during the introduction of pure oxygen gas at room temperature. The conclusions of Haas et al from LEED measurements on the same group are substantiated. The surface potential changes as a function of exposure for tantalum and niobium are very similar but quite different from molybdenum and tungsten which are also similar. The latter show a two phase adsorption, both of which are electronegative, the former an initial electronegative phase followed by a pressure dependent electropositive phase. Solution of oxygen into the bulk probably takes place for tantalum and niobium to give rise to the electropositive state. Differences in atomic size are small for all four metals and thus the observed groupings are probably a consequence of chemical effects and similarities existing between members of groups VB and VIB.     

Quantitative analysis of three-dimensional fibrillar collagen microstructure within the normal,aged and glaucomatous human optic nerve head

The aim of this study was to quantify connective tissue fibre orientation and alignment in young, old and glaucomatous human optic nerve heads (ONH) to understand ONH microstructure and predisposition to glaucomatous optic neuropathy. Transverse (seven healthy, three glaucomatous) and longitudinal (14 healthy) human ONH cryosections were imaged by both second harmonic generation microscopy and small angle light scattering (SALS) in order to quantify preferred fibre orientation (PFO) and degree of fibre alignment (DOFA). DOFA was highest within the peripapillary sclera (ppsclera), with relatively low values in the lamina cribrosa (LC). Elderly ppsclera DOFA was higher than that in young ppsclera (p < 0.00007), and generally higher than in glaucoma ppsclera. In all LCs, a majority of fibres had preferential orientation horizontally across the nasal–temporal axis. In all glaucomatous LCs, PFO was significantly different from controls in a minimum of seven out of 12 LC regions (p < 0.05). Additionally, higher fibre alignment was observed in the glaucomatous inferior–temporal LC (p < 0.017). The differences between young and elderly ONH fibre alignment within regions suggest that age-related microstructural changes occur within the structure. The additional differences in fibre alignment observed within the glaucomatous LC may reflect an inherent susceptibility to glaucomatous optic neuropathy, or may be a consequence of ONH remodelling and/or collapse.     

Feasibility of three-dimensional macroporous scaffold using calcium phosphate glass and polyurethane sponge

Tissue engineering presents an alternative approach to the repair of a damaged tissue by avoiding the need for a permanent implant made of an engineered artificial material. A suitable temporary scaffold material that exhibits adequate mechanical and biological properties is required to enable tissue regeneration by exploiting the body’s inherent repair mechanism, i.e. a regenerative allograft. Synthetic bioresorbable polymers have been attracting attention as tissue engineering scaffolds. However, a number of problems have been encountered such as inflammatory responses and lack of bioactivity. Another good candidate for a tissue engineering scaffold is the calcium phosphates because of their good biocompatibility and osteointegrative properties. Their slow biodegradation is still remains problem, especially for the filling of large bony defects. In this study, we investigated the fabrication method of a three-dimensional reticulated scaffold with interconnected pores of several hundred micrometers using calcium phosphate glass in the system of CaO-CaF₂-P₂O₅-MgO-ZnO and a polyurethane sponge as a template. Calcium phosphate glass slurry was homogenously thick coated when the weight percentage of the calcium phosphate glass powder was 40% with 8 wt% of polyvinyl alcohol as a binder. Addition of 10 wt% dimethyl formamide as a drying control chemical additive into a slurry almost prevented the crack formation during drying. Sintering of the dried porous block at 850°C exhibited the densest microstructure as well as the entire elimination of the organic additives. Repeating the process significantly increased compressive strength of sintered porous body due to the thickening of the struts. To summarize, macroporous calcium phosphate glass can be fabricated with 500∼800 μm of pore size and a three-dimensionally interconnected open pore system. It is thought that this kind of biodegradable glass scaffold combined with osteogenic cells has potential to be studied further as a tissue-engineered bone substitute.     

Shannon number and information capacity of three-dimensional integral imaging

Integral imaging systems performance has been previously investigated with regard to different parameters such as lateral resolution, field of view, and depth of view. Those parameters are linked to one another, and, since the information capacity of an integral imaging system is finite, there are always trade-offs among them. We use the Shannon number and information capacity limit as figures of merit of integral imaging systems. The Shannon number and information capacity provide compact assessments of the system and are useful for analysis and design. The limitations on the Shannon number and the information capacity of an integral imaging system are determined by the recording and display media.     

Assessment of the load-bearing capacity of a primary pipeline

High-alloyed Cr-Ni-based two-phase stainless steel (SS) cast alloys are commonly used in nuclear power plants. The mechanical equipment in these facilities can contribute to a reduction in its resistance to stable crack growth as a result of extended operating times and high temperatures. The toughness of these materials strongly depends on their delta (δ) ferrite content, which spinodally decomposes into two phases with different ratios of Cr and Ni at a relatively low (slightly above 300 °C) temperature. This temperature is similar to the operating temperature of the vital parts, for example, the coolant system. The formation of two phases with the same crystal structure but different lattice parameters causes internal elastic stresses that result in a hardness increase and an impact-toughness decrease. The result is an increased risk of crack formation in the stress-concentration zones such as the critical regions of different welded joints (e.g. “L, T, K and X” shapes). The values of the critical stress intensity factor change according to its position along the crack contour. Therefore, the aim of our study was to assess the influence of the materials’ changes on the crack extension and the decrease of the primary pipeline’s bearing capacity by taking account of the increased temperature and time of operation for the given loading conditions. The SINTAP (European Structural Integrity Assessment Procedure) was used for this assessment.     

Construct of asymmetrical scaffold and primary cells for tissue engineered esophagus

Porous polymeric scaffolds have been widely employed as analogues of native extracellular matrix to create a living construct that would mimic the complexities of human tissue function in the field of tissue engineering. An asymmetrical porous 3-D substitute to be used as a scaffold for tissue engineered esophagus was fabricated using thermally induced phase separation (TIPS) method. The scaffold in which there are pores with 1–10 µm diameter on one side and ≥ 50–100 µm size on the other side and in the bulk was designed to mimic the mucosa constitute that is the most important functional layer of a normal esophagus. The cell and scaffold construct was evaluated using Hematoxylin and Eosin (H&E) staining as well as fluorescein diacetate (FDA) viable cell staining. It was found for the scaffold to be able to support the growth of primary esophageal epithelial cells on the side with micropores and fibroblasts in the scaffold bulk with large pores and good connectivity. A confluent layer of epithelial cells was observed throughout the surface with micropores, with multilayer of cells found at some locations. Clusters of fibroblasts were found on the other side as well as within the bulk of the scaffold.     

Adhesion formation of primary human osteoblasts and the functional response of mesenchymal stem cells to 330nm deep microgrooves.

The surface microtexture of an orthopaedic device can regulate cellular adhesion, a process fundamental in the initiation of osteoinduction and osteogenesis. Advances in fabrication techniques have evolved to include the field of surface modification; in particular, nanotechnology has allowed for the development of experimental nanoscale substrates for investigation into cell nanofeature interactions. Here primary human osteoblasts (HOBs) were cultured on ordered nanoscale groove/ridge arrays fabricated by photolithography. Grooves were 330nm deep and either 10, 25 or 100mum in width. Adhesion subtypes in HOBs were quantified by immunofluorescent microscopy and cell-substrate interactions were investigated via immunocytochemistry with scanning electron microscopy. To further investigate the effects of these substrates on cellular function, 1.7K gene microarray analysis was used to establish gene regulation profiles of mesenchymal stem cells cultured on these nanotopographies. Nanotopographies significantly affected the formation of focal complexes (FXs), focal adhesions (FAs) and supermature adhesions (SMAs). Planar control substrates induced widespread adhesion formation; 100mum wide groove/ridge arrays did not significantly affect adhesion formation yet induced upregulation of genes involved in skeletal development and increased osteospecific function; 25mum wide groove/ridge arrays were associated with a reduction in SMA and an increase in FX formation; and 10mum wide groove/ridge arrays significantly reduced osteoblast adhesion and induced an interplay of up- and downregulation of gene expression. This study indicates that groove/ridge topographies are important modulators of both cellular adhesion and osteospecific function and, critically, that groove/ridge width is important in determining cellular response.     

Acceleration of segmental bone regeneration in a rabbit model by strontium-doped calcium polyphosphate scaffold through stimulating VEGF and bFGF secretion from osteoblasts

The development of suitable bioactive three-dimensional scaffold for the promotion of bone regeneration is critical in bone tissue engineering. The purpose of this study was to investigate in vivo osteogenesis of the porous strontium-doped calcium polyphosphate (SCPP) scaffolds for bone repair, as well as the relationship between osteogenic properties of SCPP scaffolds and the secretion of bFGF and VEGF from osteoblasts stimulated by SCPP. Besides, the advantages of scaffolds seeded with mesenchymal stem cells (MSCs) for bone repair were also studied. Firstly, the bone repair evaluation of scaffolds was performed on a rabbit segmental bony defects model over a period of 16 weeks by histology combined with X-ray microradiography. And then, in order to avoid the influence from the other factors such as hypoxia which emerge in vivo study and affect the secretion of VEGF and bFGF from host cells, human osteoblast-like cells (MG63) were seeded to SCPP, CPP and HA scaffolds in vitro to determine the ability of these scaffolds to stimulate the secretion of angiogenic growth factors (VEGF and bFGF) from MG63 and further explore the reason for the better osteogenic properties of SCPP scaffolds. The histological and X-ray microradiographic results showed that the SCPP scaffolds presented better osteogenic potential than CPP and HA scaffolds, when combined with MSCs, the SCPP scaffolds could further accelerate the bone repair. And the amounts of VEGF measured by ELISA assay in SCPP, CPP and HA groups after cultured for 7 days were about 364.989 pg/mL, 244.035 pg/mL and 232.785 pg/mL, respectively. Accordingly, the amounts of bFGF were about 27.085 pg/mL, 15.727 pg/mL and 8.326 pg/mL. The results revealed that the SCPP scaffolds significantly enhanced the bFGF and VEGF secretion compared with other scaffolds. The results presented in vivo and in vitro study demonstrated that the SCPP could accelerate bone formation through stimulating the secretion of VEGF and bFGF from osteoblasts, making it attractive for bone regeneration.     

In vitro response of primary rat osteoblasts to titania/hydroxyapatite coatings compared with transformed human osteoblast-like cells

The biocompatibility of titania/hydroxyapatite (TiO₂HA) composite coatings, at different ratio obtained by sol–gel process, was investigated studying the behavior of primary cultures of rat osteoblastic cells, isolated by femoral trabecular bone tissue. Moreover, the results have been compared with the response of human osteoblast-like MG63 cell line. Cytotoxicity of coatings was assessed by lactate dehydrogenase activity (LDH). The cellular behavior was analyzed by the cell proliferation (MTT test), cell morphology (SEM) and the biochemical markers evaluation of osteoblastic phenotype, such as alkaline phosphatase activity (ALP) and osteocalcin production. The results showed that TiO₂/HA coatings have no toxic effects and seemed to be a good support for cell adhesion and proliferation. Moreover, these materials allowed the differentiation of osteoblasts, stimulating the expression of alkaline phosphatase activity. The responses of the primary rat osteoblasts and human osteoblast-like MG63 cell line grown onto these coatings were similar in terms of proliferation and ALP activity. Differences were found considering the osteocalcin production. The results show that these coatings, thanks to their chemical composition and the deposition technique, are very promising for the potential orthopedic and dental applications.     

Correlation between temperature dependences of thermal expansivity and heat capacity up to the melting point of tantalum

Following the course of previously published series, this work studies in detail the correlation of the volumetric thermal expansion coefficient β(T) and the heat capacity C(T) of refractory tantalum. It is demonstrated that a clear correlation β(C) takes place in the lower temperature range and remains up to the metal melting point inclusively. Significant deviation from lower temperature linear behavior of the β(C) dependence occurs when the heat capacity reaches the classical 3R Dulong–Petit limit. The temperature dependence of differential Grüneisen parameter γ' ~ (?β/?С) is estimated.     

Crystallization of fluorescent quantum dots within a three-dimensional bio-organic template of actin filaments and lipid membranes

Biological molecules and molecular self-assemblies are promising templates to organize well-defined inorganic nanostructures. We demonstrate the ability of a self-assembled three-dimensional crystal template of helical actin protein filaments and lipids bilayers to generate a hierarchical self-assembly of quantum dots. Functionnalized tricystein peptidic quantum dots (QDs) are incorporated during the dynamical self-assembly of this actin/lipid template resulting in the formation of crystalline fibers. The crystal parameters, 26.5×18.9×35.5 nm3, are imposed by the membrane thickness, the diameter, and the pitch of the actin self-assembly. This process ensures the high quality of the crystal and results in unexpected fluorescence properties. This method of preparation offers opportunities to generate crystals with new symmetries and a large range of distance parameters.     

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo.In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning.We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters.By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering.These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.The first two authors share first authorship.     

Low-temperature synthesis,pyrolysis and crystallization of tantalum oxide gels

Tantalum oxide gels in the form of transparent monoliths and powders have been prepared from hydrolysis of tantalum pentaethoxide under controlled conditions using different mole ratios of Ta(OC₂H₅)₅C₂H₅OHH₂OHCl. Alcohol acts as the mutual solvent and HCl as the deflocculating agent. For a fixed alkoxide water HCl ratio, the time of gel formation increased with the alcohol to alkoxide molar ratio. Thermal evolution of the physical and structural changes in the gel has been monitored by differential thermal analysis, thermogravimetric analysis, X-ray diffraction, and infrared spectroscopy. On heating to 400 °C, the amorphous gel crystallized into the low-temperature orthorhombic phase -Ta₂O₅, which transformed into the high-temperature tetragonal phase -Ta₂O₅ when further heated to 1450 °C. The volume fraction of the crystalline phase increased with the firing temperature. The -Ta₂O₅ converted back into the low-temperature phase, -Ta₂O₅, on slow cooling through the transformation temperature of 1360 °C, indicating a slow but reversible transformation.     

A novel poly-l-lactic acid scaffold that possesses a macroporous structure and a branching/joining three-dimensional flow channel network: its fabrication and application to perfusion culture of human hepatoma Hep G2 cells

In the development of large internal organ equivalents for use in humans, the organs themselves must be reorganized based on three-dimensional (3D) fabrication of biodegradable polymer scaffolds. To this end, appropriate design of the 3D structure—particularly with respect to the arrangement of a 3D flow channel network and macroporous structures for cell immobilization—is critical. In the present work, we therefore presented a new scaffold design based on a regular tetrahedron whose edge is 3.0 mm as a unit composing the entire shape and the 3D flow channel network of the scaffold. Such an advanced scaffold successfully fabricated through repeated layering/micromachining of macroporous PLLA/NH₄HCO₃ salt particle composite sheets followed by salt leaching and gas forming. This reliable production of a flow channel network over scaffolds is more promising than existing 3D microfabrication processes in which such networks are produced indirectly in the spaces remaining after fabrication. A preliminary short-term perfusion culture of Hep G2 cells demonstrated that, even in a small scaffold with a small volume of around 1.3 cm³, such a 3D flow channel arrangement is necessary to allow the cells to grow and function. Although the current dimensions of the design unit were not ideal, the basic design concept presented in this study shows great promise for use in the engineering of a large human organ equivalent.     

The response of primary rat and human osteoblasts and an immortalized rat osteoblast cell line to orthopaedic materials: comparative sensitivity of several toxicity indices

When studying the biocompatibility of orthopaedic biomaterials it isoften necessary to discriminate between responses which show mild cytotoxicity.It is therefore essential to use a very sensitive index of toxicity. We havecompared the sensitivity of four well-established indices of toxicity: totalcell protein content, leakage of lactate dehydrogenase (LDH), reducedglutathione content and the MTT assay, with that of a novel index, alkalinephosphatase (ALP) activity. Comparisons were made by detecting nickel chloridetoxicity in osteoblasts. ALP activity, the novel method, proved the mostsensitive index of toxicity and it provides a convenient automated assay forassessing the interactions of materials with osteoblasts. The responses tonickel chloride and to aqueous extracts prepared from carbon fibre reinforcedepoxy and polyetheretherketone (peek), two candidate materials for orthopaedicimplants, were compared in primary and immortalized rat osteoblasts, and !in primary human osteoblasts. Although the immortalized rat osteoblast cell line,FFC, was consistently the most sensitive cell type, the responses of the humancells and the FFC cell line were similar in terms of ALP activity throughout therange of nickel concentrations studied. Neither peek nor epoxy material extractsshowed a significant decrease in the MTT or ALP responses in any of the threecell types. Our data suggest that immortalized rat osteoblasts may provide anin vitro model system for screening the biocompatibility of orthopaedicpolymers.