Selective comparison of gelling agents as neural cell culture matrices for long-term microelectrode array electrophysiology

In classic monolayer cell culture, the world is flat. In contrast, tissue-embedded cells experience a three-dimensional context to interact with. We assessed a selection of natural gelling agents of non-animal origin (l- and kappa-carrageenan, gellan gum, guar gum, locust bean gum, sodium alginate, tragacanth and xanthan gum) in serum-free medium at 1-4% (w/v) concentration for their suitability as a more natural 3D culture environment for brain-derived cells. Their biophysical properties (viscosity, texture, transparency, gelling propensity) resemble those of the extracellular matrix (ECM). Gels provide the neurons with a 3D scaffold to interact with and allow for an increase of the overall cell density compared to classical monolayer 2D culture. They not only protect neurons in cell culture from shear forces and medium evaporation, but stabilize the microenvironment around them for efficient glial proliferation, tissue-analog neural differentiation and neural communication. We report on their properties (viscosity, transparency), their ease of handling in a cell culture context and their possible use modalities (cell embedment, as a cell cover or as a cell culture substrate). Among the selected gels, guar gum and locust bean gum with intercalated laminin allowed for cortical cell embedment. Neurons plated on and migrating into gellan gum survived and differentiated even without the addition of laminin. Sodium alginate with laminin was a suitable cell cover. Finally, we exemplarily demonstrate how guar gum supported the functional survival of a cortical culture over a period of 79 days in a proof-of-concept long-term microelectrode array (MEA) electrophysiology study.