Raman microprobe analysis of developing supraspinatus tendon insertions.

<p>Top row (A–C) shows a P7 insertion, middle row (D–F) a P14 insertion, and bottom row (G–I) a P28 insertion. Left column, A, D, G: 20 µm-thick sections stained with toluidine blue and according to von Kossa's method (scale bar = 50 µm). Note that despite the sharp front of mineralization in these figures suggested by the von Kossa staining, a graded mineralization from is evident from the Raman scans. Middle column B, E, H: magnified view of square region of interest shown in images in the left column (scale bar = 10 µm). The relative mineral concentration determined by the ratio of the heights of the 960 Δcm⁻¹ to 1003 Δcm⁻¹ Raman peaks (corresponding to the ν1 P-O stretching band of hydroxylapatite and the aromatic ring stretching band of phenylalanine in collagen, respectively) is indicated by the color gradient of the overlaid points. SS: supraspinatus tendon and H: humeral head. Right column C, F, I: baseline-corrected Raman spectra corresponding to points along a traverse from tendon (no mineral - dark blue) to bone (high mineral - red). The mineral peak (960 Δcm⁻¹) is indicated with a hollow arrow and the collagen peak (1003 Δcm⁻¹) is indicated with a black-filled arrow.