We present here two microfluidic lab-on-chip devices based on self-organization of magnetic beads for biological analyses. The first one is dedicated to Circulating Tumor Cells (CTC) sorting. Magnetic beads are self-organized on a magnetic ferrofluid pattern obtained by micro-contact printing. Magnetic beads, coated with an antibody directed against a cell membrane antigen, form a tridimensional array of columns. Experiences measure the yield and specificity of the cell separation. Also this system was used to culture lymphocytes. As clinical validation, this system was used to immunophenotype leukemia and lymphoma cells coupled with high resolution imaging. A second system has been used to infectious bacteria detection. A technological module for DNA preconcentration was demonstrated using closed packed magnetic beads. DNA was retained by electrostatic interaction at low pH and eluted at basic pH. The proof of principle of this system is established.
