Potential Bone Replacement Materials Prepared by Two Methods

Abstract

Natural and synthetic hydroxyapatite (HA) scaffolds for potential load-bearing bone implants were fabricated by two methods. The natural scaffolds were formed by heating bovine cancellous bone at 1325°C, which removed the organic and sintered the HA. The synthetic scaffolds were prepared by freeze-casting HA powders, using different solid loadings (20-35 vol.%) and cooling rates (1-10°C/min). Both types of scaffolds were infiltrated with polymethylmethacrylate (PMMA). The porosity, pore size, and compressive mechanical properties of the natural and synthetic scaffolds were investigated and compared to that of natural cortical and cancellous bone. Prior to infiltration, the sintered cancellous scaffolds exhibited pore sizes of 100 -300 µm, a strength of 0.4 -9.7 MPa, and a Young's modulus of 0.1 -1.2 GPa. The freeze-casted scaffolds had pore sizes of 10 -50 µm, strengths of 0.7 -95

Biomimetic Materials by Freeze Casting

“…3a), which consist of dense (5-10% porosity) concentrically oriented lamellar sheets that surround small vascular channels and lacuna spaces $10-50 lm in diameter. 31,92 Cancellous bone (Fig. 3b), on the other hand, is highly porous (75-85% porosity) and consists of trabecular struts that surround large pores $100-500 lm in diameter.…”

“…3b), on the other hand, is highly porous (75-85% porosity) and consists of trabecular struts that surround large pores $100-500 lm in diameter. 31,93 Figure 3c shows an artificial scaffold fabricated by freeze casting on a concentrically patterned surface that reflects the natural architecture of an osteon. 19 Figure 3d shows an artificial scaffold fabricated by a modified method that combines freeze gel casting and the polymer sponge technique, mimicking the trabecular architecture of cancellous bone.…”

“…92 Therefore, it is no wonder several research groups focus on freeze casting and subsequent polymer infiltration to fabricate hybrid inorganic-organic composites. [19][20][21][22][29][30][31]37,38 …”

“…[19][20][21][22] Figure 1e shows a schematic of this process. A variety of different polymer infiltration techniques includes polymer melt immersion, 23 polymersolvent evaporation, [24][25][26][27][28] in situ polymerization, [19][20][21][29][30][31][32] particle centrifugation, 33 and chemical vapor deposition. [34][35][36] In situ polymerization is the most popular method used to impregnate porous scaffolds with polymers.…”

“…20 There are a variety of potential applications for porous ceramics and hybrid composites fabricated by freeze casting. Biomimetic materials, such as structural composites [19][20][21][22][29][30][31]37,38 that may be useful as high-performance components in industries ranging from aerospace to automotive manufacturing and potential bone replacements 12,13,19,31, are most encouraging and are the primary focus of this article. Other potential applications for freeze-cast materials with complex shapes and designer microstructures include separation filters, insulators, sensors, electrodes, catalyst supports, fuel cells, and piezoelectric devices.…”