Biocompatibility of silicon-based arrays of electrodes coupled to organotypic hippocampal brain slice cultures

In this study we examined the passive biocompatibility of a three-dimension al microelectrode array (MEA), designed to be coupled to organotypic brain slice cultures for multisite recording of electrophysiological signals. Hip pocampal (and corticostriatal) brain slices from 1-week-old (and newborn) r ats were grown for 4-8 weeks on the perforated silicon chips with silicon n itride surfaces and 40 mum sized holes and compared with corresponding tiss ue slices grown on conventional semiporous membranes. In terms of preservat ion of the basic cellular and connective organization, as visualized by Nis sl staining, Timm sulphide silver-staining, microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) immunostaining, the sli ce cultures grown on chips did not differ from conventionally grown slice c ultures. Neither were there any signs of astrogliosis or neurodegeneration around the upper recording part of the 47-mum-high platinum-tip electrodes. Slice cultures grown on a separate set of chips with platinum instead of s ilicon nitride surfaces also displayed normal MAP2 and GFAP immunostaining. The width of the GFAP-rich zone (glia limitans) at the bottom surface of t he slice cultures was the same (similar to 20 mum) in cultures grown on chi ps with silicon nitride and platinum surfaces and on conventional insert me mbranes. The slice cultures grown on chips maintained a normal, subfield di fferentiated susceptibility to the glutamate receptor agonist N-methyl-D-as partate (NMDA) and the neurotoxin trimlthyltin (TMT), as demonstrated by th e cellular uptake of propidium iodide (PI), which was: used as a reproducib le and quantifiable marker for neuronal degeneration. We conclude that orga notypic brain slice cultures can grow on silicon-based three-dimensional mi croelectrode arrays and develop normally with display of normal subfield di fferentiated susceptibilities to known excito- and neurotoxins. From this i t is anticipated that the set-up, designed for recording of electrophysiolo gical parameters, can be used for long-term studies of defined neuronal net works and provide valuable information on both normal, neurotoxicological a nd neuropathological conditions. (C) 2001 Elsevier Science B.V. All rights reserved.