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Bone is a unique biological composite material made up of a highly structured collagen mesh matrix and mineral deposits. Although mineral provides stiffness, collagen’s secondary organization provides a critical role in bone elasticity. Here, we performed polarimetric analysis of bone collagen fibers using second harmonic generation (SHG) imaging to evaluate lamella sheets and collagen fiber integrity in intact cranial bone. Our polarimetric data was fitted to a model accounting for diattenuation, polarization cross-talk, and birefringence. We compared our data to the fitted model and found no significant difference between our polarimetric observation and the representation of these scattering properties up to 70µm deep. We also observed a loss of resolution as we imaged up to 70µm deep into bone but a conservation of polarimetric response. Polarimetric SHG allows for the discrimination of collagen lamellar sheet structures in intact bone. Our work could allow for label-free identification of disease states and monitor the efficacy of therapies for bone disorders.
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Evaluating the Efficacy of Collagen Isolation Using Stable Isotope Analysis and Infrared Spectroscopy
Stable isotope analysis of bone and dental collagen is one of the most common methods to investigate the ecology of modern and extinct human and animal populations. However, since bone and dentine are composite materials with both organic and mineral components, the mineral component must be removed prior to analysis. In this study we investigated the timing and efficacy of mineral removal from bone and dentine. We performed a series of time-step experiments that show that mineral removal can be quantified over short periods of time using Fourier Transform Infrared Spectroscopy (FTIR), and collagen alteration can be tracked using a combination of stable isotope analysis and elemental analysis. We tested our methods on three modern materials: mammalian bone, mammalian dentine, and shark dentine. Our results show: 1) mineral removal is a necessary step, as structural carbonate has a strong influence on stable isotope compositions; 2) demineralization using weak acid (0.1M HCL) does not appear to alter the elemental and isotopic compositions of collagen. Our methods can be used as a framework to evaluate the need-for and efficacy of other demineralization methods in use today including EDTA-demineralization and lipid removal.
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- PAR ID:
- 10390868
- Date Published:
- Journal Name:
- Journal of archaeological science
- ISSN:
- 0305-4403
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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