Electrochemical release of hepatocyte-on-hydrogel microstructures from ITO substrates

This paper describes a novel platform that utilizes micropatterning and electrochemistry to release cells-on-hydrogel microstructures from conductive indium tin oxide (ITO) substrates. In this approach, UV photopolymerization was employed to micropattern heparin-based hydrogels onto glass substrates containing ITO electrodes. ITO/glass substrates were first functionalized with acrylated silane to promote attachment of hydrogel structures. The surfaces containing hydrogel micropatterns were further functionalized with poly(ethylene glycol) thiol, rendering the regions around the hydrogel structures non-fouling to proteins and cells. After incubating surfaces with collagen (I), primary rat hepatocytes were shown to selectively attach on top of the hydrogel and not on surrounding glass/ITO regions. Electrical activation of specific ITO electrodes (-1.8 V vs. Ag/AgCl reference) was then used to release cells-on-hydrogel microstructures from the substrate. Immunostaining and reverse transcription polymerase chain reaction analysis of albumin, an important indicator of hepatic function, showed that the hepatocyte-on-hydrogel microstructures released from the surface maintained their function at levels similar to hepatocytes remaining on the culture substrate. In the future, switchable conductive substrates described here may be to collect cell samples at different time points and may also be used for harvesting cell-carrying vehicles for transplantation studies.