Density gradient centrifugation can utilize several types of blood, primarily to isolate specific cell populations. The types of blood most commonly used are peripheral blood, cord blood, and bone marrow aspirate.
Blood Types Used:
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Peripheral Blood: This is the most common source. It's readily accessible via a standard blood draw and contains a diverse population of leukocytes (white blood cells), making it suitable for isolating mononuclear cells (lymphocytes and monocytes).
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Cord Blood: Collected from the umbilical cord after birth, cord blood is rich in hematopoietic stem cells. It's frequently used in stem cell transplantation and research. Density gradient centrifugation is used to isolate specific stem cell populations.
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Bone Marrow Aspirate: This is a sample of liquid bone marrow, usually taken from the hip bone. It contains hematopoietic stem cells and other blood cell precursors. Density gradient centrifugation is used to separate different cell types for analysis and transplantation.
Purpose of Density Gradient Centrifugation:
Density gradient centrifugation separates cells based on their density. The blood sample is layered on top of a density gradient medium (e.g., Ficoll-Paque, Percoll). When centrifuged, cells migrate through the gradient until they reach a point where their density matches the density of the medium. This creates distinct bands of different cell populations. This method is particularly useful for isolating mononuclear cells from other blood components like red blood cells and granulocytes (neutrophils, eosinophils, basophils). The density difference allows for a clean separation.
Example
Imagine using peripheral blood. Red blood cells and granulocytes are denser than the Ficoll-Paque and pellet at the bottom of the tube, while the mononuclear cells (lymphocytes and monocytes) form a distinct layer at the interface between the plasma and the Ficoll-Paque. This layer can then be carefully collected for further use.
