Effect of magnetite nanoparticles on the biological and mechanical properties of hydroxyapatite porous scaffolds coated with ibuprofen drug.

Gelatin (GN) is a polymer, which is similar to the protein derived from collagen, an organic element in the bone. GN can incorporate into the mineral part of the bone, hydroxyapatite (HA). The HA bioceramic has properties very close to the natural bone characteristics. Therefore, in this research, bio-nanocomposite scaffolds made of the HA composed with magnetite nanoparticles (MNPs) are fabricated. For this purpose, the space holder technique is put to use using NaCl particles as the spacers. The HA-X%MNP (X = 0 wt%, 5 wt%, 10 wt%, and 15 wt%) scaffolds are coated via gelatin-ibuprofen (GN-IBO) in order to determine the capabilities of the scaffolds for compatibility and fibroblastic cells of the related tissue. The coated bio-nanocomposite scaffolds are characterized using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) tools. Then, the porosity and bioactivity of the prepared samples are tested in the simulated body fluid (SBF), and the associated compressive strength, fracture toughness, porosity and hardness are investigated. Also, the magnetic behavior of the scaffolds during the release of IBO in the phosphate buffer saline (PBS) is monitored after 21 days incubation. Finally, an analytical sandwich plate model is developed to analyze the vibrational response of an axially loaded plate-type HA-MNP bio-nanocomposite implants. The obtained X-ray diffraction (XRD) confirms the presence of IBO peaks after removing the samples from the PBS which proves the lower release speed of the sample containing 10 wt% MNPs. It is found that the interaction between IBO and HA affects the mechanical performance of the scaffolds. IBO release profiles present a burst release that depends on the HA content. The given results indicate that the manufactured scaffolds have good potentials for biological as well as hyperthermia applications in bone tissue engineering.

A novel magnetic bifunctional nanocomposite scaffold for photothermal therapy and tissue engineering.

In recent years, porous bifunctional scaffolds with hyperthermal and tissue regeneration functions play an essential role in the efficient cancerous bone tumors treatment. In this work, the nanocomposite scaffolds of gelatin (polymer phase) and akermanite (ceramic phase) were prepared by entrapping carboxyl-functionalized multi-walled carbon nanotube (MWNT) and embedding magnetic nanoparticles of iron oxide into the porous matrix as photothermal conversion agents. The obtained scaffolds and their components were characterized using FTIR, FESEM, TEM, EDS, DLS, and VSM analysis. The mechanical properties of the prepared scaffolds were also investigated. The swelling behavior of the scaffolds in PBS as well as biodegradation and protein adsorption capability were evaluated. The addition of nanoparticles into the gelatin/akermanite matrix efficiently increased the adsorption of bovine serum albumin on the surface of the composite scaffold and contrarily decreased its degradation rate in the presence of lysozyme. The prepared scaffolds exhibited a high photothermal performance using NIR laser with different power intensity and irradiation time. Finally, the biocompatibility of the scaffold was confirmed using G292 osteoblastic cells through MTT assays. It can therefore be concluded that synthesized scaffolds have a great potential in bone tissue engineering and probably treatment of tumor related bone defects.

Comparison of elastic properties of open-cell metallic biomaterials with different unit cell types.

Additive manufacturing techniques have made it possible to create open-cell porous structures with arbitrary micro-geometrical characteristics. Since a wide range of micro-geometrical features is available for making an implant, having a comprehensive knowledge of the mechanical response of cellular structures is very useful. In this study, finite element simulations have been carried out to investigate the effect of structure unit cell type (cube, rhombic dodecahedron, Kelvin, Weaire-Phelan, and diamond), cross-section type (circular, square, and triangular), strut length, and relative density on the Young's modulus, shear modulus, yield stress, shear yield stress, and Poisson's ratio of open-cell tessellated cellular structures. It was desired to see whether or not and to what extent each of the aforementioned parameters affect the mechanical properties of a porous structure. It was seen that the strut cross-section type does not have a considerable effect on the structure Young's modulus while its effect on the structure yield stress is significant. The strut length was not effective on the mechanical properties if the relative density was kept constant. It was also observed that the structure unit cell type and relative density have a considerable effect on the elastic properties. The highest and the lowest stiffness and strength belonged to the cube and diamond unit cell types, respectively. The rhombic dodecahedron structure with circular cross-section had a high yielding strength (second among all the cases) while its Young's modulus was relatively low. Therefore, it is the best choice for applications with low stiffness requirements, such as biomedical implants. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 386-398, 2018.

Mechanical Properties of Additively Manufactured Thick Honeycombs.

Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA) using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson's ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.