Key Engineering Materials Vol. 587

Abstract: This paper examines challenges and opportunities for the field of bio-ceramics to achieve innovative solutions in two important areas of healthcare; regenerative medicine and personalized versus statistical-based diagnosis and therapy of individual patients. These opportunities are based upon use of new minimally invasive bio-photonics technology that can produce patient specific cell-based data to minimize costs, time and use of animals in developing and testing new bioactive ceramics. Changing the research culture is necessary to achieve significant improvements in the cost/benefit ratio of healthcare for aging populations. The approaches advocated in this paper have potential to achieve this cultural change.

Abstract: Inorganic component of bone is not hydroxyapatite but carbonate apatite. Although pure carbonate apatite (CO₃Ap) has not been prepared due to the limited thermal stability of CO₃Ap, dissolution - precipitation method using precursor block allows fabrication of pure CO₃Ap. Fabrication of CO₃Ap, cell response, tissue response and improvement of CO₃Ap will be discussed.

Abstract: Macroporous nanostructured calcium phosphate scaffold was produced at low temperature using freeze casting technique. Aqueous suspension of tetracalcium phosphate and dicalcium phosphate anhydrous was freeze-casted into cylindrical samples using an automated freeze casting device and subsequently freeze-dried. The sample was stored at 37 °C and 100% relative humidity for 24h, and then kept in simulated body fluid (SBF) for 7 days. The phase composition and microstructure of scaffold was characterized by X-ray diffraction and scanning electronic microscopy, respectively. Cell proliferation and attachment was also studied using Rat calvarium osteoblasts. The results showed a porous structure with total porosity of 75% and pore diameter ranging 50-150 μm and compressive strength of 5 ± 1 Mpa. The scaffolds had been composed of needle-like nanocrystals at the range of 40-100 nm. The XRD and FTIR data confirmed complete conversion of tetracalcium phosphate and dicalcium phosphate reactants into carbonate-substituted apatite phase due to the immersion process without any other impure phases. The results of cell studies revealed well attachment of osteoblasts on the pores and walls of the scaffolds as well as a time dependent proliferation and increased alkaline phosphatase activity. The produced scaffold has the requirements of an osteoinductive material but more in vitro and in vivo studies are required to prove this suggestion.

Abstract: The aim of the present work is to study the influence of the precipitation temperature in the synthesis of nanohydroxyapatite (n-HAp) on the properties of the resulting n-HAp powder for the fabrication of highly porous scaffolds for bone tissue engineering. The n-HAp powder was obtained by a wet precipitation technique starting from calcium nitrate tetrahydrate (Ca (NO₃)₂*4H₂O) and phosphoric acid (H₃PO₄) at different temperatures: 10°C, 37°C and 50°C. Highly porous scaffolds were fabricated using the three different powders by the sponge replica method and sintering at 1300°C. Combined X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses on powders indicated that on increasing the precipitation temperature the formation of pure n-HAp is accelerated, without significant changes in particles morphology and size. Scaffolds characterized by high porosity (89%) and good compressive strength (0.53 MPa for n-HAp prepared at 37°C) were obtained. XRD analyses on sintered n-HAp confirmed the thermal stability of the material. Therefore, the as-synthesized n-HAp powder can be successfully used for the fabrication of highly porous scaffolds as bone substitutes.

Abstract: Hydroxyapatite (HA) can be obtained by both synthetic and natural methods. The synthetic hydroxyapatite is the most commonly used type of HA and it is highly reliable. However fabrication of synthetic hydroxyapatite is complex and expensive. The production of natural hydroxyapatite is easy and inexpensive. In spite of being a biocompatible and bioactive material, hydroxyapatite has a limited usage as an implant material because of its weak mechanical properties. For this reason, HA based composites are required to supply improvement of strength and toughness of the implant materials without losing biocompatibility. In this study, HA composites were synthesized by using natural chicken hydroxyapatite (CHA) reinforced with 5 and 10wt. % commercial inert glass (CIG) powders. Then their physical, mechanical, microstructural properties were characterized. Finally, the most suitable CIG containing CHA composite for orthopedical applications was determined.

Abstract: The preparation of mesoporous silica coated hydroxyapatite (HAp) ceramics is reported. The adsorption of proteins onto hydroxyapatite (HAp) is important in a variety of oral or osseous biological events. HAp has been used as bone filler, and the protein adsorption onto HAp materials is of importance for the bond formation. HAp has been also used as the material for column packing of liquid chromatography to separate and refine proteins due to the adsorptive capabilities with respect to the HAp. Mesoporous silica (MPS) materials have been extensively studied as carriers of bio-molecules due to their potential practical applications in medical materials. Pore diameters of 1.5 30 nm of the periodic mesoporous materials are close to the diameters of target molecules and enclosure of the protein in a well-defined space may help to prevent denaturation. Previously, we reported the MPS coating on the porous hydroxyapatite (HAp) ceramics obtained by dip-coating method. Protein adsorption on the porous HAp with the MPS coatings was evaluated using UV-VIS spectrometry, and the quantity of BSA adsorbed onto the HAp ceramics with the MPS coatings is around 1.5 times high compared to that on porous HAp ceramics. In this study, the vapor-phase synthesis of MPS film on HAP ceramics was carried out to improve the protein adsorptive property of HAp ceramics. The quantity of adsorbed protein onto the HAp ceramic disc with MPS coatings is around 5 times high compared to that on HAp ceramic disc.

Abstract: In the present study, Zn-hydroxyapatite (Zn-HA) was synthesized, the powder was thermally treated at different temperatures and then characterized. The Zn-HA powder was characterized mainly by FTIR and XRD, but have been performed investigations like SEM, BET and size distribution. The addition of ZnO in hydroxyapatite causes alleged interactions with the existing groups in HA, which amend the corresponding signals to these groups in the IR spectra. X-ray diffractograms for samples (untreated and heat-treated) have been recorded and microstructural parameters for the all samples have been calculated. The obtained average sizes of the crystallites and the network tensions support the idea that Zn-HA powders are nanostructured. The SEM images and size distributions for Zn-HA indicate a cluster of crystals with nanometer-scale of the population-base. Was determined the adsorption-desorption isotherms for Zn-HA powder at 100 o C and 800 o C. The dates obtained from the analysis of particle size distribution indicates for the Zn-HA powder an size distribution for granules in the range from 0.05 to 0.3μm

Abstract: The present study reports the synthesis of carbonate apatite foam with fully interconnecting pores from βTCP foam by hydrothermal treatment in 1 mol·L^-1 disodium carbonate solution at 200°C. The βTCP foam were prepared; 1) using 3 mol% Mg as βTCP stabilizer, 2) using αTCP foam as a precursor by heat treatment at 900°C for 100 hours. The βTCP foam containing Mg could not transform to carbonate apatite foam completely. Meanwhile, the βTCP foam heat-treated at 900°C transformed to carbonate apatite after hydrothermal treatment for 10 days without morphological change. Compressive strength measurement indicated that the value of carbonate apatite foam derived from βTCP was significantly higher than that from αTCP.

Abstract: We reported the apatite-forming ability of CaO-SiO₂ spherical particles obtained through a sol-gel processing. In this study, we synthesized the CaO-SiO₂ containing silver (Ag) ions using silver standard solution to induce antibacterial property and evaluated the effects of Ag on their apatite forming ability in a simulated body fluid (SBF). The particles with 30CaO·70SiO₂ starting composition in Ag standard solution with range 0 to 500 ppm Ag content were synthesized through the sol-gel processing. The prepared 30CaO·70SiO₂ could be obtained as spherical particles with regardless of Ag contents. The prepared Ag-contained 30CaO·70SiO₂ particles formed apatite on their surfaces after soaking in SBF regardless of Ag contents. Consequently, Ag-contained 30CaO·70SiO₂ spherical particle could be obtained without decrease of its apatite forming ability.