Papers by Author: Saeed Hesaraki

Abstract: nanobioactive glasses are biocompatible and osteoconductive materials which can be mixed with solution of biocompatible polymers to make nanobiocomposite paste for hard and even soft tissue treatment. In this study, bioactive glass based on CaO-SiO₂-P₂O₅ system was produced via sol-gel technique and mixed with a solution phase. The solution phase was a 1:1 mixture of 3% hyaluronic acid solution and 3% sodium alginate solution in v/v. Rheological behaviors of the paste in rotation and oscillation modes were measured. For surface reactivity measurements, the paste was immersed in simulated body fluid (SBF) for different intervals and then characterized by SEM. The paste exhibited a superior injectability even from syringes with too narrow tips. It was a thixotropic fluid with shear thinning behavior. The results of surface reactivity revealed precipitation of apatite phase on the paste surfaces meanwhile an appropriate structural stability was observed against disintegration (anti-washout behavior). It seems that this biocomposite paste is an appropriate alternative for injectable bone substitute materials.

Abstract: In the present research, strontium containing nanobioactive glass (NBG-Sr) was synthesized by sol-gel method. The morphology was analyzed by transmission electron microscope (TEM). Different amounts (0.5 to 5 wt%) of NBG-Sr were then added to biphasic calcium phosphate (BCP). They were sintered at different temperatures, i.e., 1100, 1200 and 1300 °C and changes in physical and mechanical properties were investigated. A sharp decrease in pore volume was observed as the temperature increased. The maximum bending strength (~45 MPa) was achieved for BCP which was mixed with 3 wt% NBG-Sr and sintered at 1200 °C. This value was approximately the same when it was sintered at 1300 °C. The bending strength failed when both lower and higher amounts of 3 wt% NBG-Sr were utilized. Therefore, sintering of composites at 1200 °C was economically reasonable. The X-ray results showed that NBG-Sr additive did not change the phase composition of BCP when it was heat treated at 1200 °C. The attachment and proliferation of rat calvarium-derived osteoblasts on samples sintered at 1200 °C were also evaluated by scanning electron microscopy (SEM). Based on cell studies, all NBG-Sr-added BCPs supported attachment and proliferation of osteoblastic cells. Overall, biphasic calcium phosphate materials with improved mechanical and biological properties can be produced by using certain quantity of strontium-containing bioactive glass particles.

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: Nanocrystalline carbonated hydroxyapatite was produced through hydraulic conversion of calcium phosphate cement in simulated body fluid (SBF) and then heated in a microwave oven at 1000-1250 °C. The phase composition and microstructures were evaluated, before and after the thermal processing, using XRD and SEM, respectively. Total porosity and bending strength of the samples were also tested. Proliferation and morphology of osteoblastic cells on samples were evaluated using MTT method. Limited growth of apatite crystals was observed by the thermal treatment in which the samples exhibited a crystal size of ~ 150 nm at heating temperature of 1250 º. Based on the results, the microwave irradiation led to a little change in phase composition of carbonated apatite and slight amount of β-TCP phase was found together with large amount of apatite. The sample irradiated at 1250 °C formed more dense material having bending strength value up to 130 % that of unheated sample. The in vitro cell studies showed that the microwave irradiated samples could provide adequate cell proliferation and attachment.

Abstract: In this study, nanocomposites based on of β-tri calcium phosphate (β-TCP) and 2.5-10 wt% merwinite nanoparticles were prepared and sintered at 1100-1300°^c. The mechanical properties were investigated by measuring compressive strength and fracture toughness. Structural properties were evaluated by XRD, TEM and SEM analysis, and the in vitro bioactivity was studied by soaking the samples in simulated body fluid (SBF). The mechanical strength of the sintered samples were increased, by increasing the amount of merwinite phase up to 5 wt%, whereas it decreased when the samples were sintered at 1100 and 1200°^c. Nanostructured calcium phosphate layer was formed on the surfaces of the nanocomposites within 1 day immersion in simulated body fluid. Because of appropriate mechanical properties the composite is suggested to be used as substitute for hard tissue.

Abstract: In this research hydroxyapatite powder was synthesized by wet chemical method using calcium nitrate and diammonium hydrogen phosphate precursors at 2, 20, 50 and 90⁰ C. Phase composition, morphological aspects and particle size have been investigated using X-ray diffraction method (XRD), Fourier transform infra red spectroscopy (FTIR) and scanning electron microscopy (SEM). For the low synthesis temperature, products with low degree of crystallinity were obtained and the phases like calcium deficiency hydroxyapatite (CDHA) and hydroxyapatite were formed. In higher temperature ranges, higher degree of crystallinity was measured. For these samples, crystallite sizes estimated by scherrer formula and measured directly by SEM were found to be less than 100 nm. The synthesis temperature of 90°C has showed better results from crystallinity point of view. Considerable crystallinity of the powders produced in this research is almost comparable to that of conventional heat treatment used for enhancing the crystallinity.

Abstract: The present work was performed to improve the mechanical strength of porous calcium phosphate blocks by adding a little amount of montmorillonite mineral to the calcium phosphate composition. 3.5 wt % of the montmorillonite mineral was added to the slurry of precipitated hydroxyapatite and the porosity was produced by infiltration of a polymer template. After the firing process (1200 oC), the compressive strength, phase composition, morphology and dissolution behavior of the porous bodies were evaluated by appropriate techniques. It was found that the additive improved the mechanical strength but decreased the dissolution rate of the porous calcium phosphate body. Also the final composition of the porous block (i.e. hydroxyapatite, HA, and β- tricalcium phosphate, β-TCP) was not influenced through the presence of the additive. It is suggested that the montmorillonite mineral can improve the sintering performance of the HA and β- TCP.