Raman microscopy of de novo woven bone tissue

The composition of the bone tissue initially formed during the early mineralization of calvarial bone is poorly understood. Calvarial de novo mineral deposition occurs rapidly; however, whether the mineral is first deposited as an amorphous calcium phosphate or some other calcium phosphate lattice is unclear. Raman microscopy offers the ability to distinguish differences in the mineral lattice through the positions and shifts in the bands of the bone tissue mineral constituents, particularly in the phosphate nu (1) stretch vibration (950-963 cm(-1)). The ratios of the mineral and organic matrix constituents throughout the sampled region can also elucidate the type of bone tissue deposited. The ability to examine intact specimens at high spatial resolution, without interference from water, is an important feature of Raman microscopy. Using postnatal murine calvaria. we show that the earliest mineral detected is a carbonated hydroxyapatite with other phosphate environments present at lower levels as well. We discuss the mineral composition changes with respect to the age of the mouse over the time period of 2 weeks using a sequence of calvarial sections: postnatal days 3, 7 and 14. We use two different data analysis techniques, factor analysis and center of gravity calculations, to elucidate these discrete changes.