Glasses surface apatite formation

Figure 4.13 (a) Region of formation of apatite on Ca0-Na20-Si02 (CNS) glasses, (b) Mechanism of apatite formation at the surface of CNS glasses immersed in SBF. (After Kokubo (1997).)... 

It is known for various kinds of glasses and glass-ceramics that the essential requirement for them to bond to living bone is the formation of a biologically active bonehke apatite layer on their surfaces in the body. This boneUke apatite layer can be reproduced on their surfaces as a thin film. The mechanism of bonehke apatite formation on their surfaces is associated with their surface chemistry. These findings enable us to form apatite thin films even on surfaces of metals and organic polymers through the biomimetic approach. 

Ohtsuki, C Kushitani, H Kokubo, T Kotani, S Yamamuro, T. Apatite formation on the surface of Ceravital-type glass-ceramic in the body. J. Biomed. Mater. Res., 1991, 25, 1363-1370. 

A bioactive material is one that elicits a specific biological response at the interface of the material which results in the formation of a bond between the tissues and the material. A common characteristic of bioactive glasses, bioactive glass-ceramics, and bioactive ceramics is that their surface develops a biologically active hydroxy carbonate apatite (HCA) layer which bonds with collagen fibrils. The HCA phase that forms on bioactive implants is equivalent chemically and structurally to the mineral phase of bone. It is that equivalence which is responsible for interfacial bonding ". ... 

Nevertheless, in contrast to the bioglasses, in glass-ceramics A/W it has not been possible to find the amorphous silica layer, between the layer of CHA and glass-ceramics A/W, even not at level of high resolution transmission electronic microscopy. Nevertheless Kokubo and col., consider that the silanol groups formed on the surface of the glass-ceramic are the responsible for the CHA formation, because provides favourable sites for apatite nucleation and growth. 

Reprinted from M. Mozafari, M. Rabiee, M. Azami, S. Maleknia, Biomimetic formation of apatite on the surface of porous gelatin/bioactive glass nanocomposite scaffolds, Appl. Surf. Sci. 257 (2010) 1740-1749. with permission, (a) One day after immersion in SBF, small particles of apatite were created and started to grow up on the surface of scaffold samples. Furthermore, (b) after 14 days immersion in SBF, the apatite particles fully grew up and particles with plate-Uke structure were oriented perpendicularly to the surfaces of scaffolds and distributed over the entire surface. 

M. Mozafari, M. Rabiee, M. Azami, S. Maleknia, Biomimetic formation of apatite on the surface of porous gelatin/bioactive glass nanocomposite scaffolds, Appl. Surf. Sci. 257 (2010) 1740-1749. 

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