How do centrifuges separate cell nuclei from mitochondria?

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tubular centrifuge — centrifuge Figure 1: Tubular centrifuge

Centrifuges separate particles based on differences in their physical properties, such as size, shape, and density, by applying a sustained centrifugal force that effectively replaces gravity.1

To separate cell nuclei from mitochondria, a process of differential centrifugation is typically used. Because cell nuclei are generally larger and denser than mitochondria, they migrate toward the periphery of the spinning vessel more rapidly under a given centrifugal field.1

By controlling the duration and intensity of the centrifugation, you can allow the larger particles—the nuclei—to collect against the outer wall as sediment, while the smaller mitochondria remain suspended in the fluid. Once the nuclei have packed into the sediment, the remaining fluid containing the mitochondria can be drawn off for further processing or purification. If higher purity is required, the sediment can be resuspended and centrifuged again to remove any remaining smaller particles.1