Original implementation of low-temperature SPS for bioactive glass used as a bone biomaterial

Eco-friendly synthesis of mesoporous bioactive glass ceramics and functionalization for drug delivery and hard tissue engineering applications

Hard tissue regenerative mesoporous bioactive glass (MBG) has traditionally been synthesized using costly and toxic alkoxysilane agents and harsh conditions. In this study, MBG was synthesized using the cheaper reagent SiO2by using a co-precipitation approach. The surface properties of MBG ceramic were tailored by functionalizing with amino and carboxylic groups, aiming to develop an efficient drug delivery system for treating bone infections occurring during or after reconstruction surgeries. The amino groups were introduced through a salinization reaction, while the carboxylate groups were added via a chain elongation reaction. The MBG, MBG-NH2, and MBG-NH-COOH were analyzed by using various techniques: x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy and energy-dispersive x-ray spectroscopy. The XRD results confirmed the successful preparation of MBG, and the FTIR results indicated successful functionalization. BET analysis revealed that the prepared samples were mesoporous, and functionalization tuned their surface area and surface properties. Cefixime, an antibiotic, was loaded onto MBG, MBG-NH2, and MBG-NH-COOH to test their drug-carrying capacity. Comparatively, MBG-NH-COOH showed good drug loading and sustained release behavior. The release of the drug followed the Fickian diffusion mechanism. All prepared samples displayed favorable biocompatibility at higher concentration in the Alamar blue assay with MC3T3 cells and exhibited the good potential for hard tissue regeneration, as carbonated hydroxyapatite formed on their surfaces in simulated body fluid.

High Boron Content Enhances Bioactive Glass Biodegradation

Derived Hench bioactive glass (BaG) containing boron (B) is explored in this work as it plays an important role in bone development and regeneration. B was also found to enhance BaG dissociation. However, it is only possible to incorporate a limited amount of B. To increase the amount of B in BaG, bioactive borosilicate glasses (BaG-B_x) were fabricated based on the use of the solution-gelation process (sol-gel). In this work, a high B content (20 wt.%) in BaG, respecting the conditions of bioactivity and biodegradability required by Hench, was achieved for the first time. The capability of BaG-B_x to form an apatite phase was assessed in vitro by immersion in simulated body fluid (SBF). Then, the chemical structure and the morphological changes in the fabricated BaG-B_x (x = 0, 5, 10 and 20) were studied. The formation of hydroxyapatite (HAp) layer was observed with X-ray diffraction (XRD) and infrared (IR) spectroscopy. The presence of HAp layer was confirmed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Enhanced bioactivity and chemical stability of BaG-B_x were evaluated with an ion exchange study based on Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and energy dispersive spectroscopy (EDS). Results indicate that by increasing the concentration of B in BaG-Bx, the crystallization rate and the quality of the newly formed HAp layer on BaG-B_x surfaces can be improved. The presence of B also leads to enhanced degradation of BaGs in SBF. Accordingly, BAG-B_x can be used for bone regeneration, especially in children, because of its faster degradation as compared to B-free glass.

Design of a Novel Trabecular Acetabular Cup and Selective Laser Melting Fabrication

The acetabular cups used in total hip arthroplasty are mostly made of dense metal materials with an elastic moduli much higher than that of human bone. This leads to stress shielding after implantation, which may cause aseptic loosening of the implant. Selective laser melting (SLM) technology allows us to produce tiny and complex porous structures and to reduce the elastic moduli of dense metals, thereby avoiding stress shielding. In the present study, rhombic dodecahedron porous structures with cell sizes of 1 mm, 1.5 mm, and 2 mm were designed. The strut diameter was changed to ensure that the porosity and pore size would meet the bone ingrowth requirements. Then, porous Ti6Al4V alloy specimens were printed using SLM, and compressive tests were carried out. The results showed that the compressive strength and elastic modulus values of the specimens with a cell size of 1.5 mm were in the range of 78.16-242.94 MPa and 1.74-4.17 GPa, respectively, which are in line with the mechanical properties of human cortical bone. Finite element analysis of a total hip joint model was carried out to simulate gait, and the surface of the trabecular acetabular cup was divided into 10 regions according to the stress distribution, with the stress interval in the range of 37.44-219.24 MPa. According to the compression test results, the gradient structure of Ti6Al4V alloy with different porosity was designed for trabecular coating. The gradient porous structure meets the mechanical requirements and is closer to the natural structure of human bone than the uniformly distributed porous structure.