Figure 4.

(a) Raman spectra of femoral rat bone, CO₃-AP; (b) ECM and collagen type I; (c)–(e) electron micrographs of ECM produced by rat osteoprogenitor cells, showing mineralized collagen fibre bundles (width 0.1–0.5 μm); (f) Raman image from an area of (e), which was subsequently imaged using the 960 cm⁻¹ ${\text{PO}}_4^{2-}$ band (1 pixel=0.5 μm). Scale bars in (c), (e) represent 5 μm and in (d) 1 μm.