T cell activation on a single-cell level in dielectrophoresis-based microfluidic devices.

The gentle and careful in vitro processing of live cells is essential in order to make them available to future therapeutic applications. We present a protocol for the activation of single-T cells based on the contact formation with individual anti-CD3/anti-CD28 presenting microbeads in a lab-on-chip environment. The chips consist of microfluidic channels and microelectrodes for performing dielectrophoretic manipulation employing a.c. electric fields. The dielectrophoretic guiding elements allow the assembly of cell-bead pairs while avoiding ill-defined physical contacts with their environment. After overnight cultivation of the manipulated cells, 77% of the bead-associated T cells expressed the activation marker molecule CD69. Physiological stress on the cells was shown to be mainly due to the single-cell cultivation and not to the manipulation in the chips. The same approach could be useful for the in vitro regulation of stem cell differentiation.