In this research, we report on the electrochemical tunability of patternable Glassy Carbon microelectrode probe structures for potential applications in bio-electrical signal recording and stimulation. The structures, made from lithographically patterned negative photoresist and subsequently pyrolyzed, have excellent electrochemical properties and electrochemical stability in biological fluids. Driven by the need of decreasing the damages and risks associated with neuroprosthetic implants, the present work focuses the tunability of glassy carbon electrochemical properties according to its fabrication parameters such as maximum pyrolysis temperature and pyrolysis time. Optimization of such parameters drastically changes the amount of charge delivered by the material in a biological solution simulating the extracellular fluid. Another important contribution of this study is the investigation of the stability of the electrochemical properties of the material in a long-term period of immersion in two different biofluids: Phosphate Buffered Saline (PBS) and a PBS with Hydrogen Peroxide (H2O2). The study shows how glassy carbon has the potential to become the future standard of care for neuroprosthetic devices, replacing current materials widely used in the fabrication of neural probes.