Low-cost multichannel device for potentiometric recordings of neuronal culture's electrical activity through diamond-based microelectrode arrays

In the expansive realm of neuroscience, continual progress in unraveling the intricacies of the brain’s mechanisms stands as an indispensable foundation for addressing the complexities inherent in neurodegenerative disorders. Conditions such as Parkinson’s disease and Alzheimer’s present profound inquiries into our understanding of both normal and pathological brain physiology. Neurodegenerative diseases are characterized by the progressive degeneration of the structure and function of the nervous system; these conditions primarily affect neurons and then lead to a range of cognitive, motor, and behavioral symptoms. In order to evaluate the properties of neuron’s electrical activity in in vitro culture, the availability of devices able to combine low noise and high gain features, interfaced with advanced micro-electrode arrays is needed. This project involves the creation of a low-cost multi-channel device based on 60 independent channels interfaced with novel microelectrode arrays to acquire simultaneously the neuronal activity from multiple sites across the whole culture in a potentiometric configuration. The cells grow on the top of the innovative Micro graphitic Single Crystal Diamond Multi-electrode arrays (µG-SCD-MEAs), in a specific incubator at a controlled temperature and pressure. Diamond is considered as a great material for advancing biosensor technology, thanks to its biocompatibility, transparency, and chemical inertness. The device is composed by a motherboard interfaced with each of the 60 independent channels, in the center of which is placed the MEA with the culture. The motherboard is designed to take the signal from the neurons and input it to each channel. The single channel is composed by multiple amplifying and filtering stage. The first stage is the most critical and consist of an operational amplifier, specifically an LMP7721 known for its low-input bias current, low noise, and high CMRR. After that, the signal passes first through a low-pass filter with a cut-off frequency of 4kHz and then enters in another operational amplifier and in an integrated circuit which adds an offset of 1.8V in order to have an output value compatible with the dynamic of the ADC. Every stage of the channel is fundamental because of the high noiese and the low amplitude of the neuronal signal typically around tens of µV. Thanks to the presence of two multiplexer on the motherboard, we can switch through the channels and send the signal to the Nucleo Board’s ADC. Then, via USB, the signals reach the PC and they are ready for visualization and analysis. Preliminary tests conducted on a single channel, have validate the correct functioning of the board, with results able to satisfy the initial requirements. From these outcomes, it will be possible to expand the acquisition using all 60 channels. Given the promising preliminary outcomes, we will extend the device tests to 60 channels, allowing us to compare the board’s performance with existing products and start performing rigorous tests on the neuronal cultures.