Kadhim Alamara

Micro-Raman spectroscopy shows how the coating process affects the characteristics of hydroxylapatite

The diversity in the structural and chemical state of apatites allows implant manufacturers to fine-tune implant properties. This requires suitable manufacturing processes and characterization tools to adjust the amorphous phase and hydroxyl content from the source hydroxylapatite. Hydroxylapatite was processed by high-velocity oxy-fuel spraying, plasma spraying and flame spraying, and primarily analyzed by Raman spectroscopy. Investigation of rounded splats, the building blocks of thermal spray coatings, allowed correlation between the visual identity of the splat surface and the Raman spectra. Splats were heat-treated to crystallize any remaining amorphous phase. The ν1 PO4 stretching peak at 950-970 cm(-1) displayed the crystalline order, but the hydroxyl peak at 3572 cm(-1) followed the degree of dehydroxylation. Hydroxyl loss was greatest for flame-sprayed particles, which create the longest residence time for the melted particle. Higher-frequency hydroxyl peaks in flame- and plasma-sprayed splats indicated a lower structural order for the recrystallized hydroxylapatite within the splats. Crystallization at 700 °C has shown potential for revealing hydroxyl ions previously trapped in amorphous calcium phosphate. This work compares Fourier transform infrared and Raman spectroscopy to measure the hydroxyl content in rapidly solidified apatites and shows that Raman spectroscopy is more suitable.

Development of scaffold building units and assembly for tissue engineering using fused deposition modelling

In tissue engineering (TE), a porous scaffold structure of biodegradable material is required as a template to guide the proliferation, growth and development of cells appropriately in three dimensions. The scaffold must meet design requirements of appropriate porosity, pore size and interconnected structure to allow cell proliferation and adhesion. This paper presents a methodology for design and manufacture of TE scaffolds with varying porosity by employing open structure building units and Fused Deposition Modeling (FDM) rapid prototyping technique. A computer modeling approach for constructing and assembly of three-dimensional unit cell structure is presented to provide a solution of scaffolds design that can potentially meet the diverse requirements of TE applications. A parametric set of open polyhedral unit cells is used to assist the user in designing the required micro-architecture of the scaffold with required porosity and pore size and then the Boolean operation is used to create the scaffold of a given CAD model from the designed microstructure. The procedure is verified by fabrication of physical scaffolds using the commercial FDM system.

The role of titanium dioxide on the morphology, microstructure, and bioactivity of grafted cellulose/hydroxyapatite nanocomposites for a potential application in bone repair

Fabrication and characterization of a novel 3D nanocomposite scaffold have been reported in this research. The purpose of developing this new 3D nanocomposite scaffolds is introducing an alternative treatment for bone tissue replacement. Outcomes confirmed that the morphology, microstructure and mechanical properties of synthesized 3D nanocomposite scaffolds closely mimics the properties of real bone tissue. The 3D nanocomposite scaffolds compose of nanoparticle hydroxyapatite which is embedded in the semi-IPN of polyacrylamide-grafted cellulose by free radical polymerization. TiO2 nanoparticles utilized as an auxiliary component. According to the SEM images the 3D nanocomposite were highly porous with maximum porosity of 87% inter connected with a pore size of around 70-130μm. The FTIR spectrum and XRD pattern confirmed the graft polymerization process and the presence of TiO2 in the structure of 3D nanocomposite structures. A tensile test instrument measured elastic modulus and compressive strength of the samples. Comparing to the trabecular bone tissue, the nanocomposite scaffold with the highest content of TiO2 revealed the adequate compressive strength of 4.1MPa. The in vitro swelling behavior of the scaffolds was determined in simulated body fluid for 72h. Results suggested that increasing the amount of TiO2 decreases the swelling behavior of the nanocomposite scaffolds. The cytotoxicity of the scaffolds was determined by MTT assays on L929 cells. The results of cell culture experiments showed that the scaffold extracts do not have cytotoxicity in any concentration. Our results suggested that the introduced 3D nanocomposite scaffolds have a great potential as a bone tissue substitute.

Microstructural evolution and micromechanical properties of thermally sprayed hydroxyapatite coating

ABSTRACT The effects of preheating and annealing processes on the micromechanical features of thermally sprayed hydroxyapatite (HA) coatings were investigated. The results indicated that subsequent heat treatment at 700°C for 60 min promotes the development of a crystalline HA coating. The EDS line scan showed that the oxygen content was homogeneous along the thickness direction from the coating surface to the titanium–HA interface, whereas the calcium and phosphorus concentration gradually decreased at 7 μm from the interface. From the roughness profiles, the coatings on preheated substrates gave lower roughness compared to the coatings at room temperature. According to the nanoindentation results, the sample preheated at 300°C after annealing at 700°C exhibited an elastic modulus of 108.1 ± 6 GPa and hardness of 5.97 ± 0.3 GPa, which were almost 3% lower and 171% higher than the bare substrate, respectively.