Active Control of Dye Release for Neuronal Tracing Using PEDOT-PSS Coated Electrodes

Abstract

Penetrating neural probes comprising arrays of microelectrodes are commonly used to monitor local field potentials and multi-unit activity in animal brain over time frames of weeks. To correlate these recorded signals to specific tissue areas, histological analysis is performed after the experimental endpoint. Even if the lesion of the penetrating probe shaft can be observed, a precise reconstruction of the exact electrode positions is still challenging. To overcome these experimental difficulties, we developed a new concept, whereupon recording electrodes are coated with a poly (3, 4-ethylenedioxythiophene/ polystyrenesulfonate) (PEDOT/PSS)-based film. The conducting polymer acts as dye reservoir over several weeks and afterwards provides controlled delivery of neurotracers. This paper presents a recording electrode based on a PEDOT/PSS bilayer optimized for dye delivery and with reduced impedance. Controlled exchange of neurotracer dye is successfully demonstrated in vitro using spectrofluorometry and in neuroblastoma cell cultures. A second PEDOT/PSS capping layer on top of the dye reservoir lowers the passive leakage of dye by a factor of 6.4 and prevents a direct contact of the dye filled layer with the cells. Stability tests over four weeks demonstrate the electrochemical stability of the PEDOT coating, as well as retained functionality of the dye delivery system.

Potential of Photoelectric Stimulation with Ultrasmall Carbon Electrode on Neural Tissue: New Directions in Neuromodulation Technology Development

“…7). The PEDOT/SNP system presents a versatile platform for loading and releasing a wide range of drugs, including essential neurotransmitters such as glutamate, the inhibitory transmitter GABA, as well as dopamine (DA), 6,7-Dinitroquinoxaline-2,3-dione (DNQX), and bicuculline [89, 90, 92]. Thus, it holds promise for biochemical modulation using light-controlled, minimally invasive photoelectric electrodes to study the mechanisms of neural circuits involved in both normal and pathological cognition.…”

Applications of PEDOT in Bioelectronic Medicine

“…Electrochemical incorporation and in vivo delivery of the predrug for the anti-inflammatory corticosteroid dexamethasone has for example shown promise in alleviating biotic inflammatory reactions that occur postimplantation [15,18]. Similar systems have been suggested for other anti-inflammatory drugs, for example, tauroursodeoxycholic acid and prednisolone, for pharmaceutical use within cancer treatment as well as fluorescent molecules to mark positions of electrodes within tissue [16,52,53]. The ion conducting capabilities of PEDOT can furthermore be extended to allow transport of small charged drugs in channels integrated within the device itself [54,55].…”

Organic Bioelectronics for In Vitro Systems

“…Heizmann et al also produced a PEDOT:PSS-based electrode array designed to release dyes that can penetrate into SH-SY5Y cells upon oxidation of the PEDOT:PSS electrodes. 503 While this study does not represent an active recording of a neuronal or cardiac population, it does show the potential for tracking cells that have been recorded, which could be very useful if combined with some of the above technologies. Finally, a few devices have been manufactured that show great potential for application within the field of organic bioelectronics.…”

“…Both neuronal and cardiac cultures were applied to this device for successful recordings of each, indicating that different topologies and layers can be applied on top of MEA structures while maintaining recording efficacy. Heizmann et al also produced a PEDOT:PSS-based electrode array designed to release dyes that can penetrate into SH-SY5Y cells upon oxidation of the PEDOT:PSS electrodes . While this study does not represent an active recording of a neuronal or cardiac population, it does show the potential for tracking cells that have been recorded, which could be very useful if combined with some of the above technologies.…”