Cell adhesion and related phenomena on the surface-modified Au-deposited nervemicroelectrode examined by total impedance measurement and cell detachmenttests

Abstract

This study investigated alkanethiolate self-assembled monolayers (SAMs) of varied chainlengths adsorbed upon novel Au-coated microelectrodes, of which the surfaceproperties were quantitatively evaluated by surface characterization and 3T3fibroblast cell adhesion, total impedance and cell detachment tests. Thin-filmSAMs adsorbed upon Au/PI/Si provided a hydrophobic or passive surface withincreased water contact angle and initial total impedance. From cell adhesiontests, we can observe that the film formed as a dense-packed spacer resulted inincomplete cell sealing of 3T3 cells upon the surface-modified microelectrode.Thus the decrease in cell coverage rate and in the slope in association with totalimpedance as a function of cell–surface reaction time can be found. To studythe adhesion force of a comparable single cell attached upon varied modifiedsurfaces, a cell detachment test using a triangular probe tip of a well definedcantilever was carried out in medium containing fibroblast cells. Overall, both thepeak force and the work required to detach a comparable single cell from theanchoring domain corresponded well to the increased length of alkyl chains adsorbedupon Au/PI/Si. Both measurements on the SAM modified surfaces demonstratedmuch smaller values than those on the pristine Au/PI/Si surface. These resultsconcluded that a cell-repulsive characteristic was clearly formed on the SAMmodified microelectrode surface. The non-adhering properties of surface-modifiedmicroelectrodes should provide better sensitivity for neuromuscular stimulation as well asfor the recording of infinitesimal neural signals in future applications of neuralprostheses.