Key Engineering Materials Vols. 493-494

Abstract: In this study, we succeeded in preparation and characterization of two types of biocompatible polymer-coated inorganic nanoparticles (cupper and silicone oxide). As a biocompatible polymer, gelatin and poly(lactic acid) were used. For determination of their biodistribution, the obtained particles were administered to mice through the tail vein. After administration, the particles in some organs were determined with energy-dispersed X-ray spectrometer. The cupper nanoparticles were observed in the lung and kidney, while the silica particles were in the lung, liver and spleen. The distribution behaviors were quite different from non-polymer coated nanoparticles

Abstract: Hydroxyapatite nanoparticles were synthesized by preparing an aqueous solution comprising 0.5M Ca(OH)₂, 0.3M H₃PO₄ and 1M CH₃CHCO₂HOH (lactic acid) at pH of 3.7. KOH was added to the solution until pH=12 was reached, to precipitate hydroxyapatite. The incubation time ranged from 24 to 88 hours and the precipitates were then filtered on filter paper with the aid of a vacuum pump. The powders were synthesized with and without PVP addition. The powders were then sintered at 1100°C. Sintered and non sintered powders were characterized by scanning electron microscopy with field emission gun (FEG-SEM) and transmission electron microscopy (TEM) in order to assess particles morphology. Structural characterization was performed by X-ray diffractometry with Rietveld refinement. Albumin adsorption experiments were carried out on the powders with the aid of UV-VIS spectrometry. The results showed that the samples produced in the presence of PVP showed smaller particles when compared to non-dispersed samples. Albumin adsorption was more effective on the powders synthesized with dispersant.

Abstract: Hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) is one of the most important biomaterials used in bone regeneration therapies due to their chemical properties are very similar to the inorganic phase found in bone tissues. The direct observation of the ultrastructure of HA is very important in the comprehension of their nucleation and interactions with the molecules involved in bone formation. High-resolution Transmission Electron Microscopy (HRTEM) is a currently technique used for this task. However, the interpretation of the images is not straightforward and needs the use of softwares dedicated to high-resolution images simulations. This work presents the applicability of MEGACELL software in the analysis of HRTEM images of HA nanoparticles. MEGACELL is the most newly software, developed to construct nanocrystals models for HRTEM multislice simulations. The output files generated by MEGACELL are raw data format (.xyz), containing all the atomic positions, as well as input files compatible with JEMS (Java Electron Microscopy Software) format files. High-resolution images were acquired using a JEM 3010 URP microscope, with a LaB₆ thermionic electron gun operating at 300 kV, with a point-to-point resolution of 0.17 nm and a CCD Gatan 794SC multiscan digital camera, attached to the DigitalMicrographTM software for recording and image processing. Electron microscopy samples were prepared by dropping HA powder on copper TEM grids. HRTEM experimental images of HA particles, orientated along different zone axes, were interpreted applying the MEGACELL software to construct HA nanocrystal models and the multislice method to simulated them. MEGACELL improves the extraction of the ultrastructural features and facilitates a better interpretation of the phase-contrast images.

Abstract: Titanium dioxide is a material widely used in electronics industry and little explored in the biomedical area, which is the objective of this work. Nowadays one can find surgical instruments coated with thin films that have bactericidal properties when they are activated in the presence of ultraviolet light. For crystalline phase control TiO₂ was calcinated at 500°C. The crystallite mean size for sample calcinated at 500°C was 27nm. With the results of cytotoxicity it is possible to say that biomedical applications are possible. Electron microscopy images showed nanoparticles obtained by sol-gel process and the compounds were identified by FTIR analysis. Raman spectroscopy confirmed the existence of anatase titania phase and X-ray diffraction showed this material to be composed of a crystalline phase. X-ray fluorescence identified chemical contaminants.

Abstract: The regeneration potential of human bone is limited in the cases of repairing large bone defects, such as those associated with comminuted fractures or bone tumor resection. In most cases, autogenous and allogenic bones are used as bone grafts. However, the amount of both of them is severely limited. Nowadays, natural biomaterials are in question, like corals, cuttlefish, and various nacre species, or hydroxyapatite (HA) made from egg shells. The present work aims at preparing inexpensive nano-sized HA and whitlockite particles from various raw materials of natural-biological origin. Razor shells (ensis ensis) were collected from beaches of Thessaloniki in Greece. Each sample was reduced to particle size <100 µm and DTA/TG was employed to determine their exact CaCO₃ content. The suspended raw powders were put on a hotplate. The temperature was set to 80°C for 15 min. Then, equivalent amount of H₃PO₄ was added, drop by drop, into the solution. Different Ca/P ratios were tried. The reaction was ultrasonically assisted and continued for 8h. Then, to evaporate the liquid part, the mixture was put into an incubator at 100°C for 24 h and the resulting dried sediment was collected. The morphology of the produced powders was examined by SEM and revealed nano-sized particles. X-ray diffraction analysis indicated various Ca-phosphate phases, i.e. monetite and calcium phosphate hydrate. Thus, razor shells could be an alternative source for calcium phosphate ceramics production. In this study, long nacre shells were converted to various bioceramic structures with simple ultrasonic method without using hydrothermal method, which is carried out in a close vessel heated in a furnace and could cause accident if the vessel is worn. Chemical ultrasonic method is very safe and reliable method for bioceramic production from aragonite structures.

Abstract: The production of nano-calcium phosphate, such as HA (hydroxyapatite), materials from synthetic chemicals could sometimes lead to a costly and tedious work. Sea creatures could be an alternative way to produce very fine and even nano-structured calcium phosphate materials. Nacres vastly consist of rich calcium carbonate and/or aragonite mater. With simple conversion methods, like hotplate stirring, various bioceramic structures could be produced suitable for thin film coatings with various methods, like pulsed laser deposition (MAPLE). This study is part of a bigger project which eventually and ultimately aims to produce nano-phases of calcium phosphate biocompatible bioceramics, which can be used for biomedical coatings. In this particular study, we focus at transforming chemically, using hotplate stirring method, local sea snail shells rapana thomasiana. Cleaned sea snail samples were provided from local markets in Istanbul. The shells were smashed down, ball-milled and the powder was sieved (<100 µm powder particles). Differential thermal analysis (DTA/TG) was employed to evaluate the exact CaCO₃ content of the shells. According to these results, the required volume of H₃PO₄ was added in order to set the molar ratio of Ca/P (during hotplate stirring) either 10/6 or 3/2 (these ratios correspond to HA and TCP, respectively). SEM and X-ray diffraction analyses were conducted. The SEM observations showed brick-like particles were formed with sizes <5 µm. From the X-ray diffraction analysis, predominantly monetite, which can be considered as a precursor of HA and TCP, was detected. The results of this study showed that to produce HA and other bioceramic phases, hot-plate stirring method is a reliable, fast, rapid and economic method when compared to other tedious HA production methods. Moreover, sea snail shells are very good candidate materials to produce fine powders with hotplate stirring method for various tissue engineering applications.

Abstract: We previously found that a positively charged Ti metal has a higher apatite forming ability in vitro than a non-charged Ti metal. For in vivo analysis using a rabbit model, two types of Ti metal were examined: porous Ti metals heat-treated subsequent to a mixed acid treatment (MHs) and porous Ti metals not heat-treated subsequent to the same mixed acid treatment (MOs). Although MHs and MOs had the same macro- and micro-structure, they had different surface charges. MHs, considered positively charged, had significantly higher bone ingrowth than MOs, considered charged zero. Similarly, MHs had significantly higher percentages of bone–implant contact than MOs at 3- and 6-week. A simple heat treatment made acid-treated porous titanium implants more osteoconductive. These results suggest that a positive charge obtained by a heat treatment enhances bioactivity of acid-treated titanium implants.

Abstract: Novel porous wollastonite microspheres for releasing silicate and calcium ions were prepared by electrospraying using a hydrolyzed alkoxide. Wollastonite formed in the microspheres by heating the electrosprayed precursor microspheres at 850 °C for 2 h. Numerous pores of 100-300 nm in diameter were newly formed at the surface of the microspheres. The size of porous wollastonite microspheres was determined to be 1-5 µm in diameter.

Abstract: It was demonstrated that microstructured surfaces improve cell spreading and bone ingrowth. Particularly, the surface roughness modulates the osseointegration of orthopaedic and dental implants. We have developed an innovative grit blasting process using Biphasic Calcium Phosphate, a Resorbable Biocompatible Blast Media (RBBM). PEEK is biocompatible but an inert material, involving no direct bone bonding. Implants coming from a rabbit experimental study, were processed for X-rays Micro tomography. Light microscopy and SEM were performed.It was demonstrated in this study that the surface treatment on PEEK improve the quality of bone architecture in direct contact with the sample surface, compared to the classical surface of PEEK. These data demonstrate that PEEK rough surface obtained by RBBM blasting maintain high biocompatibility and bone osteoconduction, and promote higher stability of the implant.

Abstract: Spherical nano-BaFe12O19 was prepared by Colloid template, layer-by-layer electrostatic self-assembly and heat treatment method. BaFe12O19/polyurethane (BF/PU) composite microspheres were prepared by Suspension in-situ polymerization. The Physical and chemical properties of the microspheres were analyzed by SEM, FTIR and TG-DSC, etc. The biocompatibility of microspheres was evaluated. Embolization experiments were performed in rete mirabile (RMB) of pigs. The results showed that BF/PU microspheres had a core-shell structure and good heat stability. The content of BaFe12O19 was 11.11wt% in microspheres. The density ofmicrospheres was 1.055g·cm-3, which was near to that of blood. The composite microspheres had agood biocompatibility and successfully embolized arteriovenous malformation (AVM) with different flow. BF/PU microspheres could be a new type of embolization material for cerebral AVM and has great potential as a therapeutic embolic agent.