Microfabricated Electroactive Surfaces for Cell Manipulation and Sorting

The ability to exercise precise spatial and temporal control over cell-surface interactions is an important prerequisite to the development of microdevices for diagnostic applications and multi-cellular constructs serving as in vitro mimics of native tissues.  Our laboratory is developing microfabricated electrically addressable surfaces for cell sorting and cell micropatterning applications.  These studies employ individually addressable microelectrodes that are modified with cell adhesive or non-adhesive molecules and then electrically stimulated; leading to selective adsorption or desorption of proteins and/or mammalian cells.  The switching of the properties of the microelectrodes can be achieved by the electrochemical desorption of protein-functionalized or non-fouling self-assembled monolayers. In one of the research projects, we are developing anti-CD4 antibody-modified gold electrodes for capturing CD4 T-cells and then, upon electrical activation of the microelectrodes, releasing both the antibodies and the T-cells from the electrodes.  This sorting mechanism will be employed for positive selection of specific leukocyte types from whole blood for rapid characterization and retrieval of the cells. 
Another application of "switchable" biointerfaces is to assemble multiple cell types on the surface for tissue engineering applications.  In this project we are working with optically transparent ITO electrodes that can be "switched" from non-fouling to cell-adhesive with precise spatiotemporal control. 
(Researchers involved on these projects: Sunny Shah, He Zhu, Jun Yan)

Cells on microelectrodes. (A) SEM micrograph of T-cells isolated on antibody-modified gold pads. Decreasing dimensions of gold pads can be used to isolate individual cells on electrode surfaces. (B) T-cell release from individually addressable gold electrodes.  The bottom electrode was activated resulting in T-cell sorting, while cells remained attached to the upper electrode that was not activated.    (C) Selective attachment of cells onto optically transparent ITO electrodes microfabricated on glass.  Different cell types are attaching to the upper and the middle electrodes as can be judged from differences in cell morphology.  The third electrode remains free and offers space for attaching another cell type.  This approach maybe used to create multi-phenotype cell cultures.