Design, fabrication and characterization of glioelectronic devices for read-out of astrocytes in vitro and ex vivo.

Astrocytes, once considered passive, are now seen as key regulators of neural communication, managing ions and neurotransmitters at synapses. Though non-excitable, they signal via potassium (K+) and calcium (Ca2+) currents. Traditional microelectrode arrays (MEAs) are limited for astrocyte research. This work proposes MEAs enhanced with Zinc Oxide Nanorods (ZnO NRs) to improve astrocyte activity readout in vitro and ex vivo. For in vitro tests, ZnO NRs serve as both nanostructured electrodes and culture platforms for astrocyte growth, proliferation, and differentiation. ZnO was chosen for compatibility with low-temperature fabrication (80°C) on rigid (in vitro) and flexible (ex vivo) substrates. ZnO NR measure 600-900 nm in length and 150 nm in thickness, and support 70% cell viability while enabling astrocyte differentiation without organic promoters. Electrical tests show a 70% impedance reduction at low frequencies, and potassium stimulation confirms increased signal frequency, demonstrating effectiveness. For ex vivo tests, ZnO NRs were integrated into flexible MEAs, maintaining impedance reduction. Tests on an ischemia model using oxygen glucose deprivation (OGD) showed that nanostructured MEAs detected signals with greater sensitivity than standard electrodes, capturing increased event frequency during OGD. This study also optimized reduced graphene oxide (rGO) as a coating for ZnO NR electrodes. The process refined solution selection, deposition methods, and laser reduction parameters. UV laser reduction (30 ns) successfully converted GO to rGO without damaging ZnO NRs or polymeric substrates. The rGO coating preserved astrocyte biocompatibility while improving electrical properties, reducing impedance by up to 90% at low frequencies. This study also explores ZnO nanostructures for photoreactive surfaces to develop astrocyte research devices. A ZnO NR-P3HT composite improved photothermal activity by an order of magnitude while increasing surface potential and maintaining cell viability. Silver-coated ZnO NRs in surface-enhanced Raman spectroscopy (SERS) enhanced Raman signals for biological molecules, demonstrating potential for biosensing detection.