Density CentrifugationBone is a heterogeneous tissue, that is, the proportions of hydroxyapatite and organic matrix varies. In application to bone, density centrifugation (D.C.) separates heterogeneous bone particles according to density thereby representing the degree of mineralization. More specifically, the low density fractions represent newly formed bone (which is less mineralized) while the high density fractions represent mature bone (more mineralized). Principle: Bone is ground (top right figure) and then the powder is sifted (bottom right figure) to achieve uniform particle size (<20 µm). The sample powder is then put through a series of centrifugations (spins) in solutions at specific densities. The particles of density greater than that of the solution will accumulate at the bottom of the tube (the pellet) while those with lower or equivalent densities will remain suspended in solution (the supernate). The supernate is adjusted to a lower density for the next spin and so on. This is repeated until no discernable powder accumulates at the bottom of the tube. Connective tissues are distributed over the following range: (collagen)1.35 - 3.15(apatite) g/ml, and heterologous bone localizes at approximately 2.00 g/ml. |
