Multielectrode biosensor chip for spatial resolution screening of 3D cell models based on microcavity arrays

Three-dimensional cell models represent the native in vivo situation more closely than two-dimensional cultures and are therefore preferred today for in vitro studies. In this context, there is a great demand for fast, non-invasive, real-time, and label-free methods that are capable for detailed analyses of three-dimensional cultures. To characterize heterogeneous cultures or to detect localized drug effects, a measurement method such as impedance spectroscopy in combination with microcavity arrays (MCAs) is desirable, which additionally offers spatial resolution. To overcome these limitations of the previously described MCA based on opaque silicon substrates and a square shape with four measurement electrodes imposed by the crystal structure, we used the selective laser etching (SLE) method to fabricate microcavities in fused silica and borosilicate glass without geometric constraints. We successfully developed MCAs with variable base including up to eight measurement electrodes in one cavity, which allows the increase in the number of electrode combinations to improve spatial resolution. In addition, we integrated a central cone electrode at the cavity bottom to extend the spatial resolution on the z-axis. To demonstrate the capability of the MCAs, we used MDA-HB-231 spheroids with an enclosed glass sphere to show that the heterogeneity of the model is evident in the relative impedance spectra. Analyses on various cell spheroids highlight the broad applicability of glass MCAs. In conclusion, our SLE-fabricated MCA clearly improve bioelectronic analyses of cellular changes in heterogeneous 3D models. Thus, bioelectronic analysis of electrophysiologically active cells and tumor biopsy samples could significantly benefit from our development.