Claudia Cea1 2 Emma Maggiolini3 Elisa Castagnola1 2 Elena Zucchini3 Surabhi Nimbalkar1 2 Stefano Carli3 Davide Ricci1 2 Luciano Fadiga3 4 Sam Kassegne1 2

1, San Diego State University, San Diego, California, United States
2, Center for Sensorimotor Neural Engineering, Seattle, Washington, United States
3, Istituto Italiano di Tecnologia, Ferrara, , Italy
4, University of Ferrara, Ferrara, N/A, Italy

We present a novel neural probe which allows not only intracortical electrical signal recording and neurotransmitter detection, but also is capable of simultaneously recording ECoG signals. The neural probe introduced here leverages the versatility of microfabrication process and our recent modular pattern transfer method to make probes that consist of a combination of glassy carbon (GC) surface and penetrating electrodes that are supported on a common polymeric substrate. This probe is hoped to offer a versatile platform that allows for the investigation of the correlation between neurotransmitter concentration, neuronal spiking activity, and also potentially ECoG signals.
For validation, both in vitro and in vivo characterizations of the devices have been performed. The electrochemical behavior of GC microelectrodes has been studied in a 0.9% NaCl aqueous solution through electrochemical impedance spectroscopy - to evaluate the magnitude and phase impedance giving insights of charge transport dynamics - and through cyclic voltammetry and power pulse technique - to quantify their capacitive charging and injection limit. The capability of the GC electrodes to detect neurotransmitters has been in vitro evaluated in PBS (Phosphate Buffer Solution) through Fast Scan Cyclic Voltammetry (FSCV), ramping the potential from -0.4V to 1.3V (Vs Ag/AgCl) and back at 400 V/s with a frequency of 10Hz. The GC electrodes were demonstrated to be capable of detecting Dopamine and Serotonin with very low detection limits and linear trends from 10 nM to 1 μM concentrations. The in vivo characterization has been accomplished by acute experiments, where the device was implanted in rats, and neural signal recordings, both simultaneous intracortical spikes activities at different locations and surface evocated potentials were documented.
In conclusion, the presented devices, giving the possibility to simultaneusly elaborate multiple informations from neural networks, offer significant advantages in a wide range of clinical applications for both the Central and Peripheral Nervous Systems.