No abstract

Objective. In this paper, we report on the development of an easy-to-fabricate three-dimensional Micro-Electrode Array (3D-MEA) specifically designed for brain-on-a-dish applications. Approach. The proposed device consists of pillar-shaped gold microelectrodes realized by electroplating directly on top of a standard MEA, making this approach highly versatile and convenient for batch fabrication. Moreover, with this simple technique, it is possible to obtain electrodes with a height of more than 100 µm onto different kind of substrates, ranging from glass to flexible plastic ones. Main results. This novel 3D-MEA structure has been validated with acute brain slices, successfully recording both epileptiform-like discharges (upon the administration of 4-AP), and electrically-evoked neuronal activity. The preliminary validation showed a substantial improvement in the signals amplitude with respect to both commercial and custom planar electrodes thanks to a better coupling offered by the peculiar shape of the three-dimensional electrodes. Significance. Beside the versatility of the fabrication approach, which allows to obtain 3D MEA devices onto both rigid and flexible substrates, the reported validation showed how the pillar approach can outperform standard planar MEA recordings in terms of signal amplitude. Moreover, thanks to the possibility of obtaining multi-level 3D structures within the same device, the proposed fabrication technique offers an interesting and flexible approach for the development of a new family of electrophysiological tools for 3D in vitro electrophysiology, in particular for acute brain slices and 3D neuronal cultures for brain-on-a-dish applications.

High quality attenuated intracellular action potentials from large cell networks can be recorded on multi-electrode arrays by means of 3D vertical nanopillars using electrical pulses. However, most of the techniques require complex 3D nanostructures that prevent the straightforward translation into marketable products and the wide adoption in the scientific community. Moreover, 3D nanostructures are often delicate objects that cannot sustain several harsh use/cleaning cycles. On the contrary, laser optoacoustic poration allows the recording of action potentials on planar nanoporous electrodes made of noble metals. However, these constraints of the electrode material and morphology may also hinder the full exploitation of this methodology. Here, we show that optoacoustic poration is also very effective for porating cells on a large family of MEA electrode configurations, including robust electrodes made of nanoporous titanium nitride or disordered fractal-like gold nanostructures. This enables the recording of high quality cardiac action potentials in combination with optoacoustic poration, providing thus attenuated intracellular recordings on various already commercial devices used by a significant part of the research and industrial communities.

Neuropathological models and neurological disease progression and treatments have always been of great interest in biomedical research because of their impact on society. The application of in vitro microfluidic devices to neuroscience-related disciplines provided several advancements in therapeutics or neuronal modeling thanks to the ability to control the cellular microenvironment at spatiotemporal level. Recently, the introduction of three-dimensional nanostructures has allowed high performance in both in vitro recording of electrogenic cells and drug delivery using minimally invasive devices. Independently, both delivery and recording have let to pioneering solutions in neurobiology. However, their combination on a single chip would provide further fundamental improvements in drug screening systems and would offer comprehensive insights into pathologies and diseases progression. Therefore, it is crucial to develop platforms able to monitor progressive changes in electrophysiological behavior in the electrogenic cellular network, induced by spatially localized injection of biochemical agents. In this work, we show the application of a microfluidic multielectrode array (MEA) platform to record spontaneous and chemically stimulated activity in primary neuronal networks. By means of spatially localized caffeine injection via microfluidic nanochannels, the device demonstrated its capability of combined localized drug delivery and cell signaling recording. The platform could detect activity of the neural network at multiple sites while delivering molecules into just a few selected cells, thereby examining the effect of biochemical agents on the desired portion of cell culture.