Density Gradient Medium for Cell Separation

Resume

This paper reports on a microfluidic system for cell separation employing countercurrent centrifugal elutriation (CCE), combined with density gradient media and branching input structures. In conventional CCE, the balance of centrifugal force and fluidic force is changed gradually with increasing flow rate and/or decreasing rotation speed, achieving the separation and recovery of cells based on their size, shape and/or density.

In the system presented, both the centrifugal force and driving force for conveying fluids are generated by rotating the device at the same time. We successfully separated microparticles and observed the retention behaviours of the cells in the separation chamber. The pump-integrated rotor systems required for conventional CCE are dispensed with by employing density gradient media, which significantly simplified the instruments and procedures.

Keywords: Elutriator, Cell separation, Centrifugal microfluidics, Density gradient

Introduction 

The separation or purification of particle samples based on size, shape, and/or density is often a crucial step in biological, environmental, and industrial preparations. CCE is a powerful method for continuous cell separation and has been applied to blood cell fractionation, stem cell purification, live/dead cell separation, cell cycle synchronization stages, and so on. In conventional CCE systems, cells loaded into the separation chamber are subjected to the centrifugal force generated by rotating a rotor in an outward direction and the force of fluid is pumped into the separation chamber in an inward direction.

By gradually changing the balance of these two forces, cells separate based on size, shape, and/or density. Therefore, conventional CCE systems require complicated instruments such as an integrated rotor with an adjustable displacement pump, and the devices cannot be disposable. Here we propose a simple CCE microfluidic system that employs density gradient media to achieve particle/cell separation without changing the rotation rate.