Investigation of microstructural features in regenerating bone using micro computed tomography

Processed Bamboo as a Novel Formaldehyde-Free High-Performance Furniture Biocomposite

We used an innovative approach involving hot pressing, low energy consumption, and no adhesive to transform bamboo biomass into a natural sustainable fiber-based biocomposite for structural and furniture applications. Analyses showed strong internal bonding through mechanical "nail-like" nano substances, hydrogen, and ester and ether bonds. The biocomposite encompasses a 10-fold increase in internal bonding strength with improved water resistance, fire safety, and environmentally friendly properties as compared to existing furniture materials using hazardous formaldehyde-based adhesives. As compared to natural bamboo material, this new biocomposite has improved fire and water resistance, while there is no need for toxic adhesives (mostly made from formaldehyde-based resin), which eases the concern of harmful formaldehyde-based VOC emission and ensures better indoor air quality. This surpasses existing structural and furniture materials made by synthetic adhesives. Interestingly, our approach can 100% convert discarded bamboo biomass into this biocomposite, which represents a potentially cost reduction alternative with high revenue. The underlying fragment riveting and cell collapse binding are obviously a new technology approach that offers an economically and sustainable high-performance biocomposite that provides solutions to structural and furniture materials bound with synthetic adhesives.

Synchrotron radiation techniques boost the research in bone tissue engineering

X-ray Synchrotron radiation-based techniques, in particular Micro-tomography and Micro-diffraction, were exploited to investigate the structure of bone deposited in vivo within a porous ceramic scaffold. Bone formation was studied by implanting Mesenchymal Stem Cell (MSC) seeded ceramic scaffolds in a mouse model. Osteoblasts derived from the seeded MSC and from differentiation of cells migrated within the scaffold together with the blood vessels, deposited within the scaffold pores an organic collagenous matrix on which a precursor mineral amorphous liquid-phase, containing Ca++ and PO₄^-- crystallized filling the gaps between the collagen molecules. Histology offered a valid instrument to investigate the engineered tissue structure, but, unfortunately, limited itself to a macroscopic analysis. The evolution of the X-ray Synchrotron radiation-based techniques and the combination of micro X-ray diffraction with X-ray phase-contrast imaging enabled to study the dynamic of the structural and morphological changes occurring during the new bone deposition, biomineralization and vascularization. In fact, the unique features of Synchrotron radiation, is providing the high spatial resolution probe which is necessary for the study of complex materials presenting heterogeneity from micron-scale to meso- and nano-scale. Indeed, this is the occurrence in the heterogeneous and hierarchical bone tissue where an organic matter, such as the collagenous matrix, interacts with mineral nano-crystals to generate a hybrid multiscale biomaterial with unique physical properties. In this framework, the use of advanced synchrotron radiation techniques allowed to understand and to clarify fundamental aspects of the bone formation process within the bioceramic, i.e. biomineralization and vascularization, including to obtain deeper knowledge on bone deposition, mineralization and reabsorption in different health, aging and pathological conditions. In this review we present an overview of the X-ray Synchrotron radiation techniques and we provide a general outlook of their applications on bone Tissue Engineering, with a focus on our group work. STATEMENT OF SIGNIFICANCE: Synchrotron Radiation techniques for Tissue Engineering In this review we report recent applications of X-ray Synchrotron radiation-based techniques, in particular Microtomography and Microdiffraction, to investigations on the structure of ceramic scaffolds and bone tissue regeneration. Tissue engineering has made significant advances in bone regeneration by proposing the use of mesenchymal stem cells in combination with various types of scaffolds. The efficacy of the biomaterials used to date is not considered optimal in terms of resorbability and bone formation, resulting in a poor vascularization at the implant site. The review largely based on our publications in the last ten years could help the study of the regenerative model proposed. We also believe that the new imaging technologies we describe could be a starting point for the development of additional new techniques with the final aim of transferring them to the clinical practice.

Magnetic Induction of Multiscale Anisotropy in Macroporous Alginate Scaffolds

Nano- and microscale topographical cues have become recognized as major regulators of cell growth, migration, and phenotype. In tissue engineering, the complex and anisotropic architecture of culture platforms is aimed to imitate the high degree of spatial organization of the extracellular matrix and basement membrane components. Here, we developed a method of creating a novel, magnetically aligned, three-dimensional (3D) tissue culture matrix with three distinct classes of anisotropy-surface topography, microstructure, and physical properties. Alginate-stabilized magnetic nanoparticles (MNPs) were added to a cross-linked alginate solution, and an external magnetic field of about 2400 G was applied during freezing to form the aligned macroporous scaffold structure. The resultant scaffold exhibited anisotropic topographic features on the submicron scale, the directionality of the pore shape, and increased scaffold stiffness in the direction of magnetic alignment. These scaffold features were modulated by an alteration in the impregnated MNP size and concentration, as quantified by electron microscopy, advanced image processing analyses, and rheological methods. Mouse myoblasts (C2C12) cultured on the magnetically aligned scaffolds, demonstrated co-oriented morphology in the direction of the magnetic alignment. In summary, magnetic alignment introduces several degrees of anisotropy in the scaffold structure, providing diverse mechanical cues that can affect seeded cells and further tissue development. Multiscale anisotropy together with the capability of the MNP-containing alginate scaffolds to undergo reversible shape deformation in an oscillating magnetic field creates interesting opportunities for multifarious stimulation of cells and functional tissue development.

Spatiotemporally controlled microchannels of periodontal mimic scaffolds

Physiologic bioengineering of the oral, dental, and craniofacial complex requires optimized geometric organizations of fibrous connective tissues. A computer-designed, fiber-guiding scaffold has been developed to promote tooth-supporting periodontal tissue regeneration and functional restoration despite limited printing resolution for the manufacture of submicron-scaled features. Here, we demonstrate the use of directional freeze-casting techniques to control pore directional angulations and create mimicked topographies to alveolar crest, horizontal, oblique, and apical fibers of natural periodontal ligaments. For the differing anatomic positions, the gelatin displayed varying patterns of ice growth, determined via internal pore architectures. Regardless of the freezing coordinates, the longitudinal pore arrangements resulted in submicron-scaled diameters (~50 µm), along with corresponding high biomaterial porosity (~90%). Furthermore, the horizontal + coronal ([Formula: see text]) freezing orientation facilitated the creation of similar structures to major fibers in the periodontal ligament interface. This periodontal tissue-mimicking microenvironment is a potential tissue platform for the generation of naturally oriented ligamentous tissues consistent with periodontal ligament neogenesis.

Long-term biocompatibility and osseointegration of electron beam melted, free-form–fabricated solid and porous titanium alloy: Experimental studies in sheep

The purpose of the present study was to evaluate the long-term osseointegration and biocompatibility of electron beam melted (EBM) free-form–fabricated (FFF titanium grade 5 (Ti6Al4V) implants. Porous and solid machined cylindrical and disk-shaped implants were prepared by EBM and implanted bilaterally in the femur and subcutaneously in the dorsum of the sheep. After 26 weeks, the implants and surrounding tissue were retrieved. The tissue response was examined qualitatively and quantitatively using histology and light microscopic (LM) morphometry. Selected bone implants specimens were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-computed tomography (mCT). The results showed that both porous and solid implants were osseointegrated and high bone–implant contact was observed throughout the porous implant. In the soft tissue, the porous implants showed thinner fibrous encapsulation while no signs of intolerance were observed for either implant type. Taken together, the present experimental results show that FFF Ti6Al4V with and without porous structures demonstrate excellent long-term soft tissue biocompatibility and a high degree of osseointegration. The present findings extend earlier, short-term experimental observations in bone and suggest that EBM, FFF Ti6Al4V implants possess valuable properties in bone and soft tissue applications.

Long-term biocompatibility and osseointegration of electron beam melted, free-form-fabricated solid and porous titanium alloy: experimental studies in sheep

The purpose of the present study was to evaluate the long-term osseointegration and biocompatibility of electron beam melted (EBM) free-form-fabricated (FFF titanium grade 5 (Ti6Al4V) implants. Porous and solid machined cylindrical and disk-shaped implants were prepared by EBM and implanted bilaterally in the femur and subcutaneously in the dorsum of the sheep. After 26 weeks, the implants and surrounding tissue were retrieved. The tissue response was examined qualitatively and quantitatively using histology and light microscopic (LM) morphometry. Selected bone implants specimens were evaluated by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-computed tomography (mCT). The results showed that both porous and solid implants were osseointegrated and high bone-implant contact was observed throughout the porous implant. In the soft tissue, the porous implants showed thinner fibrous encapsulation while no signs of intolerance were observed for either implant type. Taken together, the present experimental results show that FFF Ti6Al4V with and without porous structures demonstrate excellent long-term soft tissue biocompatibility and a high degree of osseointegration. The present findings extend earlier, short-term experimental observations in bone and suggest that EBM, FFF Ti6Al4V implants possess valuable properties in bone and soft tissue applications.

Three-dimensional micro-computed tomographic imaging of alveolar bone in experimental bone loss or repair

BACKGROUND

Micro-computed tomography (micro-CT) offers significant potential for identifying mineralized structures. However, three-dimensional (3-D) micro-CT of alveolar bone has not been adapted readily for quantification. Moreover, conventional methods are not highly sensitive for analyzing bone loss or bone gain following periodontal disease or reconstructive therapy. The objective of this investigation was to develop a micro-CT methodology for quantifying tooth-supporting alveolar bone in 3-D following experimental preclinical situations of periodontitis or reconstructive therapy.

METHODS

Experimental in vivo bone loss or regeneration situations were developed to validate the micro-CT imaging techniques. Twenty mature Sprague-Dawley rats were divided into two groups: bone loss (Porphyromonas gingivalis lipopolysaccharide-mediated bone resorption) and regenerative therapy. Micro-CT and software digitized specimens were reconstructed three-dimensionally for linear and volumetric parameter assessment of alveolar bone (linear bone height, bone volume, bone volume fraction, bone mineral content, and bone mineral density). Intra- and interexaminer reproducibility and reliability were compared for methodology validation.

RESULTS

The results demonstrated high examiner reproducibility for linear and volumetric parameters with high intraclass correlation coefficient (ICC) and coefficient of variation (CV). The ICC showed that the methodology was highly reliable and reproducible (ICC >0.99; 95% confidence interval, 0.937 to 1.000; CV <1.5%), suggesting that 3-D measurements may provide better alveolar bone analysis than conventional 2-D methods.

CONCLUSIONS

The developed methods allow for highly accurate and reproducible static measurements of tooth-supporting alveolar bone following preclinical situations of bone destruction or regeneration. Future investigations should focus on using in vivo micro-CT imaging for real-time assessments of alveolar bone changes.

Quantitative morphometric evaluation of critical size experimental bone defects by microcomputed tomography

Our aim was to show that microcomputed tomography is a useful tool for acquiring high-resolution three-dimensional tomographic images to assess bone healing, the interface with materials, and the biocompatibility of bone substitutes. Acquired images can be used for non-invasive quantitative morphometric analysis of regenerating bone, leaving the option for conventional histology to be an adjunct used at defined intervals. The temporal characterisation of the mineralisation of bone potentially has a critical role in the understanding of the dynamics of mineralisation of healing bone. This has applications both for degradable and bioactive materials and for pharmaceutical products that act on bone. Formal validation of this promising new technique will be a critical part of continuing studies.