Stability, reliability, and performance of organic light-emitting diodes and photodetectors in optogenetic studies

Abstract

Mapping neurons in the brain is important to understand the neuronal circuits involved in cognitive functions such as learning and memory formation. More importantly, understanding their dysfunction in neurological disorders and diseases could benefit patients that rely on better therapy interventions and techniques. To this aim, optogenetic tools, where light is used to control neuronal activity, and ultimately behavior, have revolutionized the field of neuroscience over the last 20 years. Current optogenetic approaches to investigate brain function involve the use of commercially available lasers and LEDs coupled to large implants, optical fibers or camera systems. Their use is usually associated with high cost, invasiveness and low spatial resolution. To address these limitations, organic electronic devices have been emerging as an alternative candidate for biocompatible, small-footprint, and high-resolution neural probes. In our own contribution to the field, we have demonstrated the successful detection of neuronal activity using organic photodetectors (OPDs) based on rubrene/C60, as well as direct optogenetic stimulation of neuronal activity using OLEDs based on Super Yellow. In this paper, we extend our previous work by demonstrating the stability and reliability of OPDs and OLEDs in optogenetics, and the effect of oxygen and encapsulation on the OPD/OLED performance. We also discuss the requirements for successful long-term neural recordings and determine the detection threshold for OPDs, (i.e. the required sensitivity to detect activity in a single neuron), as well as the minimum performance requirements in OLEDs to evoke neuronal activity.