First analysis of ancient burned human skeletal remains probed by neutron and optical vibrational spectroscopy.

Burned skeletal remains are abundant in archaeological and paleontological sites, the result of fire or of ancient funerary practices. In the burning process, the bone matrix suffers structural and dimensional changes that interfere with the reliability of available osteometric methods. Recent studies showed that these macroscopic changes are accompanied by microscopic variations are reflected in vibrational spectra. An innovative integrated approach to the study of archaeological combusted skeletal remains is reported here, where the application of complementary vibrational spectroscopic techniques-INS (inelastic neutron scattering), FTIR (Fourier transform infrared), and micro-Raman-enables access to the complete vibrational profile and constitutes the first application of neutron spectroscopy to ancient bones. Comparison with data from modern human bones that were subjected to controlled burning allowed identification of specific heating conditions. This pioneering study provides archaeologists and anthropologists with relevant information on past civilizations, including regarding funerary, burial, and cooking practices and environmental settings.

Human bone probed by neutron diffraction: the burning process.

The first neutron diffraction study of human burned bone is reported, aiming at a comprehensive elucidation of the heat-induced bone diagenesis process. Chemical and crystallinity changes were probed in different types of bone (femur, humerus and tibia) upon heating to different maximum temperatures (from 400 to 1000 °C, under aerobic conditions). Fourier transform infrared spectroscopy has provided valuable complementary information. Noticeable crystallographic and domain size variations were detected, mainly between 700 and 900 °C, the high temperature interval (>700 °C) corresponding to an organized, highly symmetric inorganic bone matrix, virtually devoid of carbonates and organic constituents, while the lower range (<700 °C) revealed a considerably lower crystallinity associated with the presence of carbonates, lipids and collagen. This work contributes to a better understanding of heat-induced changes in bone and is therefore relevant for archaeology, biomaterials and forensic science.

Heat-induced Bone Diagenesis Probed by Vibrational Spectroscopy.

Complementary vibrational spectroscopic techniques - infrared, Raman and inelastic neutron scattering (INS) - were applied to the study of human bone burned under controlled conditions (400 to 1000 °C). This is an innovative way of tackling bone diagenesis upon burning, aiming at a quantitative evaluation of heat-induced dimensional changes allowing a reliable estimation of pre-burning skeletal dimensions. INS results allowed the concomitant observation of the hydroxyl libration (OHlibration), hydroxyl stretching (ν(OH)) and (OHlibration + ν(OH)) combination modes, leading to an unambiguous assignment of these INS features to bioapatite and confirming hydroxylation of bone's inorganic matrix. The OHlib, ν(OH) and ν4(PO43-) bands were identified as spectral biomarkers, which displayed clear quantitative relationships with temperature revealing heat-induced changes in bone's H-bonding pattern during the burning process. These results will enable the routine use of FTIR-ATR (Fourier Transform Infrared-Attenuated Total Reflectance) for the analysis of burned skeletal remains, which will be of the utmost significance in forensic, bioanthropological and archaeological contexts.

Crystal clear: Vibrational spectroscopy reveals intrabone, intraskeleton, and interskeleton variation in human bones.

OBJECTIVES: Vibrational spectroscopy is a valuable tool for the study of burned skeletal remains. Nonetheless, most investigations have been focused on a limited number of samples as well as on faunal bones rather than human bones. Conclusions based on those investigations may lack representativeness, namely about the intrabone, intra- and interskeleton variability of several chemometric indices. We aimed to investigate this issue on a large sample of human bones. MATERIAL AND METHODS: Powder samples were collected from 168 bones from four human skeletons. The sampling targeted 47 long bones, 72 short bones, and 49 tarsal bones as well as different bone regions in a total of 638 powder samples. Bones were experimentally burned in an electric muffle furnace for two hours to maximum temperatures ranging from 400°C to 1000°C. Another 623 burned samples were then collected totaling 1261 samples subjected to FTIR-ATR analysis. The CI, BPI, C/C, and OH/P indices were calculated. RESULTS: An important intrabone, intra- and interskeleton variation was observed, especially for the BPI. The CI, C/C, and OH/P indices revealed much less variation so site-specific sampling may not be as critical in these cases. Clear differences between our results and those from previous investigations were observed, namely on the temperature increment evolution of the CI and C/C indices. DISCUSSION: The relatively large heterogeneity, especially at the intrabone level, is possibly the consequence of microstructural bone differences. The dissimilarities observed between our investigation and other published studies are probably due to the fact that the samples used here came from human rather than faunal bones. Also, our samples were buried previously to the experimental burning so this may also partly explain our contrasting results, since previous research was mostly performed on fresh bone. Future inferences based on vibrational spectroscopy analyses should take into account the possible effect of all these sources.

Biomaterials from human bone - probing organic fraction removal by chemical and enzymatic methods.

Two different deproteination and defatting processes of human bone were investigated, by combined infrared and neutron techniques: a previously reported hydrazine extraction and a newly developed multi-enzymatic treatment. Complementary Fourier transform infrared total attenuated reflectance and inelastic neutron scattering spectroscopies were applied, allowing access to all vibrational modes of the samples. The effectiveness of the different experimental protocols for removing the organic constituents of bone (lipids and protein) was probed, as well as their effect on bone's structural and crystallinity features. The results thus gathered are expected to have an impact on bioanthropological, archaeological and medical sciences, namely regarding the development of novel biocompatible materials for orthopaedic xenografts.