Papers by Keyword: Biomineralization

Abstract: Sea urchins mineralize Mg-calcite skeletons, both, within their exoskeletons as well as in their spines. In this study we have investigated sea urchin spines of the species Amblypneustes pachistus. The spines are round and consist of several wedges that extend from the base to the tip of the spine. The wedges are connected to each other by porous calcite. Rocking curves of the spines show a distribution of 0.5° of the 110 reflection, with the domains being misoriented by 0.1° to each other. In our EBSD system the average mean angular (MAD) deviation is 0.3°. This is higher than the signal that is needed for the detection of small misorientations of domains within a sea urcin spine. In order to increase the precision (not the accuracy) of the EBSD measurements several factors, such as geometric artifacts and charging of calcite were minimized. Handling of these factors and utilizing the subsequently described statistical approach allowed for the identification of different domains within the spines. It further allowed calculating the degree of misorientation between these domains. Our EBSD analyses and the subsequent evaluation of the data show that the wedges forming the spines of Amblypneustes pachistus are mosaic crystals. The misorientation of the wedges to each other increases from the base of the spine towards its tip. The here proposed method for increasing the precision of the angular resolution showed reproducibility on silicon of 0.05°.

Abstract: There has been much recent activity in the research area of nanoparticles and nanocrystalline materials, in many fields of science and technology. This is due to their outstanding and unique physical, mechanical, chemical and biological characteristics. Recent developments in biomineralization have demonstrated that nano-sized particles play an important role in the formation of the hard tissues of animals. It is well established that the basic inorganic building blocks of bones and teeth of mammals are nano-sized and nanocrystalline calcium orthophosphates (in the form of apatites) of a biological origin. In mammals, tens to hundreds of nanocrystals of biological apatite are found to combine into self-assembled structures under the control of bio-organic matrixes. It was also confirmed experimentally that the structure of both dental enamel and bones could be mimicked by an oriented aggregation of nano-sized calcium orthophosphates, determined by the biomolecules. The application and prospective use of nano-sized and nanocrystalline calcium orthophosphates for clinical repair of damaged bones and teeth are also known. For example, a greater viability and a better proliferation of various cells were detected on smaller crystals of calcium orthophosphates. Furthermore, studies revealed that the differentiation of various cells was promoted by nano-sized calcium orthophosphates. Thus, the nano-sized and nanocrystalline forms of calcium orthophosphates have the potential to revolutionize the field of hard tissue engineering, in areas ranging from bone repair and augmentation to controlled drug delivery devices. This paper reviews the current state of knowledge and recent developments of various nano-sized and nanocrystalline calcium orthophosphates, covering topics from the synthesis and characterization to biomedical and clinical applications. This review also provides possible directions of future research and development.

Abstract: This study describes biofilm formation as a non line-of-sight coating method on support materials such as polyurethane foam, porous glass, polypropylene (PP) and titanium alloy, using a Serratia sp., which can manufacture extracellular nanoscale scaffolded hydroxyapatite (HA) crystals via enzymatic cleavage of glycerol 2-phosphate (G2P) in the presence of CaCl2. Various microscopies and non-invasive magnetic resonance imaging were used to visualize the biofilm coating on the support surface. A novel micromanipulation technique was used to estimate the adhesive strength of native and HA-mineralized biofilms. The biofilm with HA was up to forty times stronger than that without HA. A coating of nano-HA (> 80 m) onto a biofilm-Ti disc was achieved.

Abstract: We have used zinc aluminate nanostructured films deposited by spray pyrolysis to determine its biocompatibility assessed by cells attachment and cell differentiation. Cell attachment onto zinc aluminate showed an increase of 53, 81 and 86% at 180, 300 and 420 minutes (p<0.05) when compared to controls. Mineralization was analyzed at 5 and 14 days of culture by scanning electron microscopy, microanalysis and atomic force microscopy. Our results showed in experimental culture a higher density of mineral-like tissue with small needle-shaped crystal and granular nanoparticles with preferential orientation when compared to controls. The composition of the mineral-like tissue deposited in zinc aluminate nanostructured material had a Ca/P ratio of 1.6, whereas control culture had a Ca/P ratio of 1.50. Our finding revealed that ZnAl2O4 promoted higher expression of type I collagen, bone sialoprotein, osteocalcin and alkaline phosphatase, suggesting that zinc aluminate provides a microenvironment that favors mineral formation and cell differentiation. Our results point to the potential use of ZnAl2O4 for the osteoinductive process in biomedical implants.

Abstract: In the present study, an Intelligent Multi-parameter Simulated Evaluation in vitro （IMSE system） was used to study the deposition properties of apatite formation on the surface of biphasic calcium phosphate porous ceramic (BCP) from static and dynamic r-SBF. Results showed that apatite formed on the surface of BCP from static and dynamic r-SBF differed between each other. In static r-SBF, ions were transferred by diffusion, which could not compensate the consuming of calcium ions, and mist apatite layer was formed on the surface of samples. But in the dynamic r-SBF, simulated fluid was adjusted precisely and flowed forcedly, the concentrations of ions were homogeneous; with the compensation of ions, calcium and phosphate were supersaturated, and the free energy of apatite formation was negative, bone-like apatite sheets were formed on the surface of samples.

Abstract: Papers reported that the pH value was rising slowly with the prolonging of soaking time when bioglass was studied into simulated body fluids, and it influenced the formation of apatite layer on the surface of bioglass obviously. An Intelligent Multi-parameter in vitro Simulated Evaluation （IMSE system） was used to study the bio-mineralization properties of 58S bioglass. The deposition of apatite formation on the surface of bioglass (BG) from dynamic r-SBF was studied systemically with IMSE system, which could control and stable such parameters as temperature, fluid rate, ion concentrations and pH value etc. precisely. Results showed that the rate of apatite formation was slowed down when pH value was stabled at about 7.35.

Abstract: Carbonated hydroxyapatite (CHA) and hydroxyapatite (HA) were prepared by the wet chemical method. The contact angle was measured to calculate the surface energy. The biomineralization process in SBF solution of HA and CHA were investigated in vitro. The cell attachment and proliferation behavior of CHA and HA were compared by the cell culture experiments. The results show that the polar component of surface energy of B-type CHA is higher than that of HA. Osteoblastic cells attach and proliferate very well on the surface, which indicates the excellent cell compatibility. The CHA have high bioactivity owing to rapid formation of hydroxyl-carbonate-apatite (HCA) mineralized layer on the biomaterial’s surface in SBF.

Abstract: In the coming decades, the need for reconstructive surgery of bones is predicted to increase with the ageing of the population as well as the increase of injuries needing traumatologic treatments. Therefore, there is still a constant search for tissue engineering and bone substitute materials. Xenografts, synthetic hydroxyapatitite, bioactive glasses and other bone substitutes have widely been studied. When bone defects are filled using bioceramics in granules, their utilization is limited to small size defects, because the injected granules do not give immediate support against the biomechanical loading of the bone. The aim of this study was to evaluate the preliminary biomineralization and the compression strength of experimental injectable bone cements modified with calcium ceramics. Our studies have focused on the development of injectable composites of bone cements, i.e. in situ curable resin systems containing impregnated Ca ceramics. The polymerized bone cement composites aspire to simulate as closely as possible the mechanical and structural properties properties of bone. The present compressive strength of our inorganic-organic bone cements are >65 up to ~180 MPa. These cements are slightly porous from their outermost surface and showed preliminarily osteoconductivity of some degree.

Abstract: Phosphorus containing biopolymers have been synthesized and studied as polymeric candidates for potential tissue engineering applications. The presence of phosphorus in the polymeric structure may improve the biocompatibility of polymers by enhancing their tissue contact. One aim of this study was to examine the chain extending reaction of poly(ε-caprolactone), PCL, using ethyldichlorophosphate as a coupling agent. A preliminary survey was done to find out whether the presence of phosphoester units in a rapidly degradable polymeric structure improves the Ca phosphate formation on PCL. Another aim of this study was to synthesize one kind of polyphosphazene, i.e. poly[bis(methacrylate)]phosphazene, PMAP. In addition, a preliminary biomineralization study for PMAP polymer was carried out. The results of the biomineralization studies indicated some bioactivity of both biopolymers.

Abstract: The sol-gel derived bioactive glass short fibers in the system CaO-P2O5-SiO2 was prepared using air-spray method. SBF immersion test indicated that the fibers possessed satisfactory bioactivity. SEM, XRD, FTIR analysis revealed that the morphologies and bioactivity of the fibers could be significantly influenced by the composition and viscosity of the solution. The fibers are very promising biomaterials for applications to bone restoration and tissue engineering as the bone defects fillers or additives for strengthening of the biomedical polymers.