User:Sousa.a.f/Magnetophoresis

1. Free-flow Magnetophoresis
Free-flow Magnetophoresis is a method that allows the separation of magnetic particles (MPs) in continuous flow. It consists in a microfluidic device with a separation chamber in which laminar flow is generated in the x-direction. Perpendicularly to the laminar flow, that is in the y-direction a magnetic field gradient is applied. By doing so, superparamagnetic particles usually composed by iron oxide material are deflected from their trajectory. Magnetophoresis can be used to control the motion of labeled cells with MP’s This is obtained by labeling the cells with specific antibodies that are previously immobilized in magnetic particles with different sizes, and so different magnetic momentum – this allows for immunomagnetic separation of different cells in an heterogeneous population

1.1. Magnetophoresis in Biological Research
In the life sciences research, lab-on-a-chip devices are very important because they present several advantages, since microfluidics reduces the time and cost associated to routine analysis while improving reproducibility. Besides to this, the use of non-reactive materials prevents contamination giving a friendly and sterile environment to biological species. Magnetophoresis in lab-on-a-chip devices is currently undergoing a rapid development, being a strong tool for biological research. Most of the biological samples under study are non-magnetic and are neither affected nor destroyed by the presence of a weak magnetic field gradient. Labeling those species with MP’s provides a versatile physical handle for manipulation of biological samples (figure 1).



Superparamagnetic particles are available with carboxyl groups or amino groups on their surface. Biomolecules such as DNA strands or antibodies can then easily be attached to the particle surface. When coated with, for example, an antibody, the particles can attach themselves to particular targeted cells (figure1). This allows for the Magnetic cell separation that has become a popular tool for the isolation of cells, especially rare cells, from a heterogeneous mixture. By applying an external magnetic field, the magnetically labeled cells or biomolecules can be deflected from their path. The separated magnetic particles carrying the biomolecules or cells of interest can then be used for downstream analysis and testing. This is of high interest due to the anticipated integration of such devices into micro total analysis systems. Magnetic separation of cells can be implemented as sketched in the figure, using a microfluidic channel with magnetic elements placed next to a wall. The figure shows the use of a permanent magnet that generates the magnetic field gradient perpendicularly to the fluid flow. Magnetic particles are dragged into this field and thus deflected from the direction of laminar flow, depending on their magnetic susceptibility. Non susceptible cells keep their trajectory.