title: Differences in infrared spectroscopic data of connective tissues in transflectance and transmittance modes.
abstract: Fourier transform infrared imaging spectroscopy (FT-IRIS) has been used extensively to characterize the composition and orientation of macromolecules in thin tissue sections. Earlier and current studies of normal and polarized FT-IRIS data have primarily used tissues sectioned onto infrared transmissive substrates, such as salt windows. Recently, the use of low-emissivity ("low-e") substrates has become of great interest because of their low cost and favorable infrared optical properties. However, data are collected in transflectance mode when using low-e slides and in transmittance mode using salt windows. In the current study we investigated the comparability of these two modes for assessment of the composition of connective tissues. FT-IRIS data were obtained in transflectance and transmittance modes from serial sections of cartilage, bone and tendon, and from a standard polymer, polymethylmethacrylate. Both non-polarized and polarized FTIR data differed in absorbance, and in some cases peak position, between transflectance and transmittance modes. However, the FT-IRIS analysis of the collagen fibril orientation in cartilage resulted in the expected zonal arrangement of fibrils in both transmittance and transflectance. We conclude that numerical comparison of FT-IRIS-derived parameters of tissue composition should account for substrate type and data collection mode, while analysis of overall tissue architecture may be more invariant between modes.
authors.affiliation: Department of Bioengineering, Temple University, Philadelphia, PA 19122, USA.
authors.forename: Arash
authors.initials: A
authors.lastname: Hanifi
authors.forename: Cushla
authors.initials: C
authors.lastname: McGoverin
authors.forename: Ya-Ting
authors.initials: YT
authors.lastname: Ou
authors.forename: Fayez
authors.initials: F
authors.lastname: Safadi
authors.forename: Richard G
authors.initials: RG
authors.lastname: Spencer
authors.forename: Nancy
authors.initials: N
authors.lastname: Pleshko
mesh_terms: D000818:Animals; D002356:Cartilage / Q000502:physiology*; D002417:Cattle; D051379:Mice; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013710:Tendons / Q000502:physiology*