A highly sensitive microfluidic device has been developed to separate apoptotic cells. Apoptotic Jurkat cells were selectively labeled with magnetic beads (0.8 microm diam) using the C2A protein which recognizes phosphatidylserine. The cell mixture was flowed through a microfluidic channel and apoptotic cells were separated by a 0.3 T permanent magnet. Separations using our device showed 96% agreement with those of a commercial flow cytometer, indicating our device can be used to sort apoptotic cells in a miniaturized system.

The highly sensitive spin‐valve devices integrated with a microfluidic channel have been studied for cell counting in a chip‐cytometer. The presence or absence of a single magnetic bead was successfully detected by direct measurement of fringe fields emanating from magnetic beads using spin‐valve devices. The real‐time detection was also successfully confirmed by the direct measurement of magnetic fields generated from the magnetic beads passing an active sensing area of a spin‐valve device integrated with a microfluidic channel. Our results show the possibility of implementing a chip‐cytometer for biological applications using the highly sensitive spin‐valve devices integrated with a microfluidic device. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)