Papers by Keyword: Biomineralization

Abstract: The present world cannot be imagined without construction industry. On other hand we are not able to prevent impact of construction on the environment due to usage of its key component that is cement, which plays a greater role in the emission of greenhouse gases. Every tonne of Ordinary Portland Cement (OPC) that is produced releases on average a similar amount of CO₂ into the atmosphere, or in total roughly 6% of all man-made carbon emissions. One of the purposes of research should be to lower the amount of cement during construction without compromising the quality of building structure. Microbial metabolic activities often contribute to selective cementation by biomineralization. In the present study, a novel microbial based low energy green building material based on microbially induced calcium carbonate precipitation (MICP) has been reported that is known as “biocement”. Biocement has enormous potential and usage in building materials and structures with potential to partially replace the cement. The research demonstrates that production of biocement can enhance the durability of building structures in addition to have least impact on the environment.

Abstract: Natural bone ECM is a hierarchical nanocomposite made of an inorganic phase deposited within an organic matrix. In order to mimic the bone highly organized hybrid structure and functionality, strategies that allow assembling ceramic and polymer phase can be applied. To this aim, we investigated an in situ growth method able to nucleate a nanoHydroxyapatite (nHAp) phase into and around the interconnected porous structure of chitosan sponges. By increasing the calcium and phosphate concentration in the meta-stable solution used for the nHAp nucleation, the inorganic phase raised proportionally, in the range 10%-30% wt. In order to be compared with nHAp loaded scaffolds, pure chitosan samples have been produced by cross-linking biopolymer with arginine. Moreover, nHAp loaded samples, containing the 20 % wt of inorganic phase have been prepared by simply mixing low crystalline nHAp powders with the chitosan gel. The in situ nucleation method highlighted evident advantages in terms of nanophase distribution and mechanical performances with respect to a merely mixing procedure.

Abstract: Calcium carbonate (CaCO₃) was mineralized in N,N-dimethylformamide (DMF)-H₂O mixed solvents in the presence of polystyrene-b-poly (vinyl pyrrolidone) (PS-b-PNVP) block copolymer. The morphologies of PS-b-PNVP micelles and CaCO₃ crystals were characterized by TEM and SEM. By varying the volume ratio of DMF-H₂O, the CaCO₃ crystals with different morphologies and phases were obtained. It was convinced that the morphology of crew cut micelles played a key role in the morphological formation of CaCO₃.

Abstract: Phosphorites of the uppermost Neoproterozoic Doushantuo Formation were exposed at Weng'an, South China. Here, We report the origin of organic matter and paleoceanographic conditions of the fossil-bearing phosphorites at Weng'an, in terms of sedimentary facies, biomineralization and organic geochemistry, including the biomarker feature. GC-MS analysis showed that a normal alkane distribution pattern with a wide range of carbon atom numbers; Terpane, isoprenoids and steranes were detected in phosphorite. The biomarker implied that the sources of organic matters were the eukaryotes of phototrophic multicellular algae, protests and bacteria. Ph and Pr derivatived from Chlorophyll-a suggested that there may exist a photosynthetic process in palaeoocean. The result shows that phosphorite at Weng 'an generated from biomineralization. In summary, the evidence suggests microorganism were the major contributors to organic matter deposited as part of phosphorite, and exist biomineralization.

Abstract: In Nature, calcium carbonate biomineralizations are the most abundant mineralized structures of biological origin. Because many exhibit remarkable characteristics, several attempts have been made to use them as substitution materials for bone reconstruction or as models for generating biomimetic composites that exhibit tailored properties. CaCO₃ biomineralizations contain small amounts of amalgamate of proteins and polysaccharides that are secreted during the calcification process. They contribute to control the morphology of the crystallites and to spatially organize them in well-defined microstructures. These macromolecules, collectively defined as the skeletal matrix, have been the focus of a large number of studies aiming at synthesizing in vitro biomimetic materials, according to a bottom-up approach. However, recent proteomic investigations performed on the organic matrices associated to mollusc shells or to coral skeletons have quashed our hopes to generate, with only few macromolecular ingredients, biomimetic materials with properties approaching to those of natural biominerals. As a mean value, each matrix comprises a minimum of few tens of different proteins that seem to be strictly associated to calcium carbonate biominerals. Among the proteins that are currently detected, one finds RLCDs-containing proteins (Repetitive-Low-Complexity Domains), enzymes, proteins with protease inhibitors domains and at last, proteins that contains typical ECM (ExtraCellular Matrix) domains. Today, we still do not understand how the skeletal matrix works, and unveiling its complex functioning is one of the challenges for the coming decade, both from fundamental and applied viewpoints. Is it realistic to attempt generating abiotically, in a test tube at room temperature, biomimetic composites that mimic natural biomineralizations in their properties If so, and by supposing that we know the individual functions of all the components of the matrix, is there a minimal number of proteins required for producing in vitro calcium carbonate biomaterials that approximate natural biominerals These issues are of importance for the future research directions in biomaterials science.

Abstract: This paper summarizes a TEDx Talk that the European physics professor Ille C. Gebeshuber, who has been living in South East Asia for nearly five years now, gave to a live audience of 800 in Kuala Lumpur, Malaysia, in July 2012. A similar talk is also given as an invited lecture at the 4^th International Conference of Bionic Engineering in China in August 2013. The talk highlights the importance of news ways of doing science and of doing engineering that are needed to successfully address the major challenges humankind is currently facing, and how a generalistic approach synergistically combining Eastern and Western thinking might help in this respect. Biomimetics is stressed as an integrated, generalist way of learning from living nature, and as best practice example for developing new approaches that are based on understanding rather than learning by heart, with memory, reason and imagination as pillars, bridging fields of specialization and of education and thereby blending the knowledge of single isolated scientists and specialist scientist networks to a wisdom of the whole, powerful enough to help us successfully address our major problems.

Abstract: The main objective of this work was to produce membranes of chitosan and collagen type I and check their ability to undergo “in vitro” calcification. The membranes of chitosan-collagen blends were characterized by TGA, infra-red spectroscopy and DSC. Samples of dense and porous membranes were immersed in solution SBF (Simulated Body Fluid) in order to verify their “in vitro” calcification. The membranes were observed by SEM. The production of chitosan-collagen membranes is possible, in dense and porous versions. We can conclude that the blend is less resistant to high temperatures, in comparison to pristine chitosan membranes shown in literature. Through the initial assays of calcification, we observe that it is possible to induce the calcium deposition on a chitosan-collagen membrane, as seen by SEM. Microscopy of fracture surfaces showed fibril structures, probably formed by collagen.

Abstract: Mine drainage waters are widely regarded as environmental pollutants, but they are also potential sources of valuable transition metals, such as zinc, copper and cobalt. This article describes the laboratory application of continuous flow modular bioreactor systems, one oxidative and the other reductive, for the selective precipitation of metals from metal-rich acidic mine waters.

Abstract: As a natural protein polymer, Bombyx mori silk fibroin (SF) has superior characteristics such as excellent mechanical properties, biocompatibility and biodegradation which make SF to be a potential candidate in the field of biomaterials. It has been reported that the mineralized SF can be used for bone repair and regeneration in the bone tissue engineering. In order to map out the growth process of hydroxyapatite (HAp) induced by SF in the mineralized buffer solution, the co-solution of SF and supersaturated simulated body fluid (1.5 SBF) was incubated at 37.2 °C for 7 days and observed by using TEM, DSC, DTA and TGA in this study. The TEM results indicated that nanoscale crystal nuclei were found along the surface of SF in the initial stage of mineralization and finally these crystals aggregated into three-dimensional network. DSC and DTA results showed that the thermal stability of HAp/SF was greatly improved by increasing incubation duration and that the phase transition of HAp occurred from metastable state to steady state. TGA results suggested the organic content of HAp/SF complex was about 21% which was similar to the natural bone.

Abstract: The differences of growth kinetic of urinary crystallites from patients with CaOxa stones and healthy subjects were compared. With the increase of crystal growth time (t), the size of urinary crystallites from patients increased constantly from 10±9 μm at t=1 h to 50±45 μm at t=72 h, but the number of urinary crystallites decreased gradually from 1820±610 ind./mm² at t=1 h to 220±98 ind./mm² at t=72 h, indicating that the formation process of crystallites in lithogenic urine was ascribed to growth control. In contrast, for healthy subjects, the number of crystallites increased from 1650±850 ind./mm² at t=1 h to 1800±830 ind./mm² at t=72 h. However, the particle size was slowly increased from 7±5 μm at t=1 h to 14±13 μm at t=72 h, while the sizes of most urinary crystallites were still less than 20 μm, indicating that the growth process of crystallites in healthy urine was dominated by nucleation control. The differences mentioned above are mainly attributed to that both the concentration and the activity of the inhibitors in healthy urine were higher than those in lithogenic urine, and the inhibitors in healthy urine can inhibit the growth and aggregation of urinary crystallites more effectively. This result can help to elucidate the renal-calculi formation mechanism.