Porous Ceramics

The unique chemical composition and microstructure of porous ceramics enable the ceramic products used in a number of applications such as filtration of molten metals and hot corrosive gases, high-temperature thermal insulation, support for catalytic reactions, filtration of diesel engine exhaust gases, etc. These applications take advantage of special characteristics of porous ceramics such as low thermal mass, low thermal conductivity, controlled permeability, high surface area, low density, and high specific strength. In this chapter, we emphasize on direct foaming method, a simple and versatile approach that allows fabrication of porous ceramics with tailored microstructure along with distinctive properties. Foam stability is achieved upon controlled addition of amphiphiles to the colloidal suspension, which induce in situ hydrophobization, allowing the wet foam to resist coarsening upon drying and sintering

Natural Medicinal Drug Delivery from 3D Printed Scaffold and Surface Modified TI6AL4v Implants for Chemoprevention, Osteogenesis and Anti-inflammation for Bone Tissue Engineering Application

The objective of this research is to understand the role of natural medicinal compounds (NMCs) in bone tissue engineering application by modifying their release kinetics from the porous 3DP scaffold, evaluating their in vitro osteoblast (hFOB) proliferating and osteosarcoma (MG-63) preventing efficacy, and investigating their effect on osteogenesis, anti-inflammation and wound healing in rat distal femur model.Curcumin, although exhibit excellent antioxidant, anti-inflammatory, anticancer and osteogenic activities, suffers from extremely poor bioavailability. To enhance its bioavailability and to provide higher release, poly-(I? -caprolactone) (PCL), poly-ethylene-glycol (PEG) and poly-lactide-co-glycolide (PLGA) is used as the polymeric system to enable the continuous release of curcumin from the hydroxyapatite matrix for 22 days. The presence of curcumin in interconnected 3DP TCP scaffolds results in enhanced bone formation after 6 weeks in rat distal femur model. Complete mineralized bone formation increases from 29.6% to 44.9% in curcumin-coated scaffolds compared to control. In a follow-up study, we have further improved the bioavailability of curcumin by encapsulating it in a liposome, followed by the incorporation onto 3DP TCP scaffolds with designed porosity. Interestingly, liposomal curcumin released from the 3DP scaffold shows significant cytotoxicity towards MG-63 cells, while it promoted hFOB cell viability and proliferation. Presence of genistein, a soy-isoflavone shows a 90% reduction in vitro MG-63 cell viability and proliferation after 11 days, while, daidzein, another primary isoflavone, promotes in vitro hFOB cellular activities in both static and dynamic cell culture. In vitro H&E staining confirms controlled co-delivery of soy-isoflavones from the 3DP scaffold significantly reduces inflammatory cell recruitment at the surgery site after 24 hours of implantation in a rat distal femur model.Another more stable form of calcium phosphate, hydroxyapatite (HA) is utilized as a coating on metallic orthopedic implants for load-bearing applications. Coated implants are loaded with curcumin and vitamin K2, which enhances in vitro hFOB cell activities, while lowers in vitro MG-63 cell proliferation after 3, 7 and 11 days. Modified Masson Goldner staining of the tissue-implant section shows an improved contact between tissue and implant in dual drug-loaded HA-coated Ti implants compared to control implants in in vitro rat distal femur model

Regulation of Osteogenic Markers at Late Stage of Osteoblast Differentiation in Silicon and Zinc Doped Porous TCP

Calcium phosphates (CaPs) are one of the most widely used synthetic materials for bone grafting applications in the orthopedic industry. Recent trends in synthetic bone graft applications have shifted towards the incorporation of metal trace elements that extend the performance of CaPs to have osteoinductive properties. The objective of this study is to investigate the effects of silicon (Si) and zinc (Zn) dopants in highly porous tricalcium phosphate (TCP) scaffolds on late-stage osteoblast cell differentiation markers. In this study, an oil emulsion method is utilized to fabricate highly porous SiO2 doped β-TCP (Si-TCP) and ZnO doped β-TCP (Zn-TCP) scaffolds through the incorporation of 0.5 wt.% SiO2 and 0.25 wt.% ZnO, respectively, to the β-TCP scaffold. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) is utilized to analyze the mRNA expression of osteoprotegerin (OPG), receptor activator of nuclear kappa beta ligand (RANKL), bone morphogenetic protein 2 (BMP2), and runt-related transcription factor 2 (Runx2) at the later stage of osteoblast differentiation, day 21 and day 28. Results show that the addition of Si and Zn to the β-TCP structure inhibited the β to α-TCP phase transformation and enhance the density without affecting the dissolution properties. Normal BMP-2 and Runx2 transcriptions are observed in both Si-TCP and Zn-TCP scaffolds at the initial time point, as demonstrated by RT-qPCR. Moreover, the addition of both Si and Zn positively regulate the osteoprotegerin: receptor activator of nuclear factor k-β ligand (OPG:RANKL) ratio at 21-days for Si-TCP and Zn-TCP scaffolds. These results demonstrate the effects of Si and Zn doped porous β-TCP scaffolds on the upregulation of osteoblast marker gene expression including OPG, RANKL, BMP-2, and Runx2, indicating the role of trace elements on the effective regulation of late-stage osteoblast cell differentiation markers

Al2O3–TiO2/ZrO2–SiO2 based porous ceramics from particle-stabilized wet foam

Abstract The porous ceramics based on Al2O3–TiO2/ZrO2–SiO2 from particle-stabilized wet foam by direct foaming were discussed. The initial Al2O3–TiO2 suspension was prepared by adding TiO2 suspension to partially hydrophobized colloidal Al2O3 suspension with equimolar amount, to form Al2TiO5 on sintering. The secondary ZrO2–SiO2 suspension was prepared using the equimolar composition, and to obtain ZrSiO4, ZrTiO4, and mullite phases in the sintered samples, the secondary suspension was blended into the initial suspension at 0, 10, 20, 30, and 50 vol%. The wet foam exhibited an air content up to 87%, Laplace pressure from 1.38 to 2.23 mPa, and higher adsorption free energy at the interface of approximately 5.8×108 to 7.5×108 J resulting an outstanding foam stability of 87%. The final suspension was foamed, and the wet foam was sintered from 1400 to 1600 °C for 1 h. The porous ceramics with pore size from 150 to 400 μm on average were obtained. The phase identification was accomplished using X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetric analysis (TGA), and microstructural analysis was performed using field emission scanning electron microscopy (FESEM)