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Published on: September 14, 2016
Polarized FT-IR microscopy of calcified turkey leg tendon
S J Gadaleta1, W J Landis, A L Boskey
1Department of Chemistry, Newark College of Arts and Sciences, Rutgers University, New Jersey 07102, USA.
Insights
Polarized FT-IRM reveals age-related changes in turkey tendon orientation. Older tendons show more aligned mineral components, indicating aging impacts tissue structure.
Area of Science:
- Biomineralization
- Materials Science
- Biophysics
Background:
- Tendon calcification involves mineral and matrix components.
- Understanding their orientation is crucial for tissue mechanics.
- Age-related changes in tissue organization are not fully understood.
Purpose of the Study:
- To assess mineral and matrix component orientation in turkey leg tendons using polarized FT-IRM.
- To compare young (<16 weeks) and old (>60 weeks) turkey tendons.
- To investigate age-related changes in tendon structural organization.
Main Methods:
- Polarized Fourier transform infrared microscopy (FT-IRM) was employed.
- Analysis of calcified, non-calcified, and transitional tendon regions.
- Spectra acquired in parallel and perpendicular polarization modes relative to collagen fiber axis.
Main Results:
- Both mineral (carbonate, phosphate) and matrix (collagen amide bands) components showed marked dichroism.
- Carbonate substitution sites (type A and B) exhibited distinct polarization behaviors.
- Older tendons displayed greater orientational effects and increased mineral orientation (anisotropy parameter A).
Conclusions:
- Polarized FT-IRM effectively assesses mineral and matrix orientation in calcified tissues.
- Aging leads to increased orientation of mineral components in turkey tendons.
- Age-related structural changes in tendon composition and organization are significant.
Abstract:
Polarized Fourier transform infrared microscopy (FT-IRM) was used to assess the orientation of mineral and matrix components of the normally calcified turkey leg tendon. Two groups of tendon, < 16 weeks of age (young) and > 60 weeks of age (old), were analyzed. Linear sequences from calcified, non-calcified, and transitional regions of the tendons were examined. Spectra collected in the "parallel polarization" mode were acquired with the electric vector of the infrared radiation parallel to the collagen fiber axis whereas spectra collected in the "perpendicular polarization" mode were acquired with the electric vector of the infrared radiation perpendicular to this axis. The v2 carbonate (850-890 cm-1) and v1, v3 phosphate (900-1180 cm-1) contours of the tendon mineral as well as the collagen amide I, II, and III bands of the extracellular matrix all displayed marked dichroism. The CO3(2-) ions substituted for PO4(3-) (878 cm-1, type B substitution) in the tendon mineral displayed parallel dichroism while the CO3(2-) ions substituted for OH (871 cm-1, type A substitution) in the tendon mineral displayed perpendicular dichroism. These orientational effects for both sites of carbonate substitution were greater in the older animals. The polarization properties of the v1, v3 phosphate contour were analyzed by use of an empirical anisotropy parameter (A), the value of which monitors the degree of orientation. This index significantly increased in the older animals indicating that aging produces a more highly oriented mineral. The amide I, II, and III contours of the collagen extracellular matrix also exhibited marked dichroism. The amide I component exhibits perpendicular dichroism while the amide II and III components exhibit parallel dichroism. The current study demonstrates the ability of polarized FT-IRM to assess the orientation of the mineral and matrix components of calcified tissue at the microscopic level.
