A structural approach in the study of bones: fossil and burnt bones at nanosize scale

Abstract

We review the different factors affecting significantly mineral structure and composition of bones.Particularly, it is assessed that micro-nano-structural and chemical properties of skeleton bones change drastically during burning; the micro-and nano-structural changes attending those phases manifest themselves, amongst others, in observable alterations to the bones colour, morphology, microstructure, mechanical strength and crystallinity.Intense changes involving the structure and chemical composition of bones also occur during the fossilization process. Bioapatite material is contaminated by an heavy fluorination process which, on a long-time scale reduces sensibly the volume of the original unit cell, mainly the a-axis of the 2 hexagonal P63/m space group. Moreover, the bioapatite suffers to a varying degree of extent by phase contamination from the nearby environment, to the point that rarely a fluorapatite single phase may be found in fossil bones here examined.TEM images supply precise and localized information, on apatite crystal shape and dimension, and on different processes that occur during thermal processes or fossilization of ancient bone.complementary to that given by X-ray Diffraction and Attenuated Total Reflection Infrared spectroscopy. We are presenting a synthesis of XRD, ATR-IR and TEM results on the nanostructure of various modern, burned and palaeontological bones.

Potential of Bioapatite Hydroxyls for Research on Archeological Burned Bone

“…At 700 ºC, the infrared OH librational signal often appeared as a shoulder of the 630 cm -1 band, while ν(OH) was detected as a very weak band (Figure 4). This is in agreement with previous reported studies (37,41,61). In turn, Etok et al (74) and Wang et al (40) made the same observation at slightly lower burning temperatures (600 and 650 ºC, respectively).…”

“…700 to 1000 ºC. In the case of the OH lib signal, this general trend had been previously observed in other experiments(37,41,61,76), except for the one carried out by Reidsma et al(77) who were unable to detect any bands assigned to OH groups in their bovine bone samples. This was apparently not due to the specific taxonomic origin of the samples, since Snoeck et al(16) also used bovine samples in their experiment and were nonetheless able to observe the OH infrared signals.…”

“…Regarding the 603 cm -1 and 1035 cm -1 phosphate bands, both are affected by contaminants, as reported by Piga et al (13,41,58,78), the latter being particularly influenced by the presence of fluorapatite (at 1090 cm -1 ) and several other phosphate vibrational modes (such as ߥ 1 (HPO 4 2-…”

“…Human bone tissue is composed of an organic matrix (25%, mostly type I collagen), water (10%) and an inorganic component (65%) (38)(39)(40). The latter is known as bioapatite, a non-stoichiometric form of hydroxyapatite (12,41), of chemical formula Ca 10 (PO 4 ) 6-x (OH) 2-y (CO 3 2-) x+y . In vivo, carbonates may substitute phosphate (type B substitution) and/or hydroxyl (type A substitution) groups (42)(43)(44).…”