Hydroxyapatite pore size

The effect of including hydroxyapatite during the preparation of PHP was further investigated by comparing its performance with the unmodified polymers. In these experiments rat osteoblasts were seeded onto the surface of 40-, 60-, and 100- tm pore size polymers that were either unmodified or modified with hydroxyapatite and cell growth and migration assessed by histological analysis. 

Figure 7,15 Effect of pore size on DNA concentration as a function of time in culture of rat osteoblast cells in hydroxyapatite-coated polyHIPE polymer support, illustrating the dependence of cell proliferation rate on support pore size...

Kithne, J.H., Bartl, R., Frisch, B., Hammer, C., Jansson, V., Zimmer, M. 1994. Bone formation in coralline hydroxyapatite. Effects of pore size studied in rabbits. Acta Orthop Scand 65(3), 246-252. 

Porous hydroxyapatite granules with controlled porosity, pore size, pore size distribution and... 

Bone TE 4,4 -Dicyclohexylemethane diisocyanates (HMDI), PCL diol (Mw, 2000 Da), and ethylene glycol (EG) Porous composite scaffolds (PUR blended with hydroxyapatite) (porosity > 70%, pore size 100—400 pm) produced by polymer coagulation combined with salt leaching Ryszkowska et al. (2010)... 

Recently, a novel macroporous (surface area up to 1.5m cm ), zirconia-based cell carrier biomaterial (Sponceram Figure 10.5), which may be either partially or fully stabilized with Ca, Mg or Y, has been developed that can easily be coated not only with osteoconductive hydroxyapatite but also with the osteoinductive recombinant human bone morphogenetic protein, rhBMP-2. The pore size of this material is about 600 xm, and the porosity may be up to 85% (Roker et al., 2009). Subsequent cell proliferation studies performed in a bioreactor with preosteoblas-tic MC3T3-E1 cells showed that alkaline phosphatase (AP) activity attained a maximum level at day 5 in the presence of rhBMP-2. Likewise, a significant calcification of the extracellular matrix (ECM) occurred in the presence of rhBMP-2,... 

At relatively high supersaturations, compounds that include hydrophilic cations (such as Ca, Al, Fe, etc.) are likely to form highly hydrated amorphous precipitates via homogeneous nucleation and subsequent flocculation. A number of important crystalline compounds, such as hydroxyapatite or zeolites, are formed by phase transformation via amorphous and/or gel-like precursor phases. Thermal analysis techniques yield information on the amount of incorporated water, and mechanism and strength of bonding, and pore sizes of such amorphous and poorly crystalline materials. In some cases they have been successfully used to detect the initiation of phase transformation, such as the formation of ordered subunits of a quasicrystalline zeolite phase within amorphous alumosilicate precursors. 

Tsuruga, E., TaMta, H., Itoh, H., WaMsaka, Y., and Kuboki, Y. Pore size of porous hydroxyapatite as the ceU-substratum controls BMP-induced osteogenesis. /. Biochem. (Tokyo) 121 317-324,1997. 

Eggh P S, Muller W and Schenk R K, Porous hydroxyapatite and tricalcium phosphate cylinders with two different pore size ranges implanted in cancellous bone of rabbits a comparative histomorphometric and histologic study of bony ingrowth and implant substitution , Clin. Orthop. Rel. Res., 1988, 232, 127 38. 

Komlev, V. S. and Barinov, S. M. 2002. Porous hydroxyapatite ceramics of bi-modal pore size distribution. Journal of Materials Science Materials in Medicine 13 295-99. 

Hasegawa, M., Sudo, A., Komlev, V.S., Barinov, S.M. Uchida, A. (2004). High release of antibiotic from a novel hydroxyapatite with bimodal pore size distribution. J. 

Abstract— The aim of this study was to produce the absorbable BCP scaffolds from tricalcium phosphate (TCP) and hydroxyapatite (HA). The Naphthalene particles were used as pore forming agent. The conventional pressing and sintering were utilized to prepare disc shape samples. The sintering were carried out at the temperatures 1000,1100 and 1200 °C. The phase composition and chemical structure analyses were performed using XRD and FTIR experiments. The morphological aspects of scaffolds such as pore size and distribution and their interconnectivities were studied by SEM. 

Figure 1.4 SEM images of (a), (b) nanocomposite 30% nHA, scaffold 30% iiHA (c) before cell culture with interconnectivity (pore size 200-300 pm, 70% porosity) The arrows indicate interconnected pore structures (d) before cell culture and (e) after ceU culture. Reproduced from Torabinejad, B., et al., 2014. Synthesis and characterization of nanocomposite scaffolds based on triblock copolymer of L-lactide, e-caprolactone and nano-hydroxyapatite for bone tissue engineering. Materials Science Engineering. C, Materials for Biological Applications 42,199-210. Available at http //www.ncbi.nlm.nih.gov/pubmed/25063111 (accessed 25.09.14.).

The porosity features of ceramic materials prepared by directed ice crystallization are also useful for the development of biomaterials. Since the size of the pores can be varied by changing the crystallization conditions, the materials are suitable for the synthesis of ceramic scaffolds. The oriented character of the porosity leads to an anisotropy in the mechanical properties of such ceramics that is similar to the anisotropy of natural bones [132, 174—178]. The most significant progress in this direction was achieved by the development of hydroxyapatite (HAP) ceramics with a compression strength close to that of natural bone [179], and also by the development of tough AI2O3-PMMA layered nacre-like composites [180]. 

Osteoconductivity is the ability of a biomaterial to support the in-growth of bone cells, blood capillaries, and perivascular tissue into the gap between implant and existing bone. Efficient in-growth is supported by intercormected pores of 150-450 xm size. Hence, the development of such a pore system in plasma-sprayed hydroxyapatite coatings is of the utmost importance, as nonporous coatings may act like bioinert materials and their eventual substitution by bone is not guaranteed. 

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