Photostimulation for In Vitro Optogenetics with High‐Power Blue Organic Light‐Emitting Diodes

Abstract

Optogenetics, photostimulation of neural tissues rendered sensitive to light, is widely used in neuroscience to modulate the electrical excitability of neurons. For effective optical excitation of neurons, light wavelength and power density must fit with the expression levels and biophysical properties of the genetically encoded light‐sensitive ion channels used to confer light sensitivity on cells—most commonly, channelrhodopsins (ChRs). As light sources, organic light‐emitting diodes (OLEDs) offer attractive properties for miniaturized implantable devices for in vivo optical stimulation, but they do not yet operate routinely at the optical powers required for optogenetics. Here, OLEDs with doped charge transport layers are demonstrated that deliver blue light with good stability over millions of pulses, at powers sufficient to activate the ChR, CheRiff when expressed in cultured primary neurons, allowing live cell imaging of neural activity with the red genetically encoded calcium indicator, jRCaMP1a. Intracellular calcium responses scale with the radiant flux of OLED emission, when varied through changes in the current density, number of pulses, frequency, and pulse width delivered to the devices. The reported optimization and characterization of high‐power OLEDs are foundational for the development of miniaturized OLEDs with thin‐layer encapsulation on bioimplantable devices to allow single‐cell activation in vivo.

Segment-specific optogenetic stimulation in Drosophila melanogaster with linear arrays of organic light-emitting diodes

“…To avoid a strong drop in efficiency when driving the OLEDs at high brightness (socalled "roll-off") 21 , our devices are based on a fluorescent blue emitter molecule 22 . The electrical and optical performance of both large and microstructured OLEDs were very similar, but the power density of both was somewhat reduced compared to our earlier work 13,14,23 , which is due to the top-emitting device structure used here ( Supplementary Fig. 1).…”

Segment-Specific Optogenetic Stimulation in Drosophila melanogaster with Linear Arrays of Organic Light-Emitting Diodes

“…To avoid a strong drop in efficiency when driving the OLEDs at high brightness (so-called 'roll-off'), 16 our devices are based on a fluorescent blue emitter molecule. 17 The electrical and optical performance of both large and microstructured OLEDs were very similar, but the power density of both was somewhat reduced compared to our earlier work, 11,12,18 which is due to the top-emitting device structure used here (Supporting Fig. S1).…”

High Brightness, Highly Directional Organic Light‐Emitting Diodes as Light Sources for Future Light‐Amplifying Prosthetics in the Optogenetic Management of Vision Loss

“…These driving conditions were further informed by existing studies on light‐triggering of ChrimsonR‐tdT‐expressing RGCs and their recovery kinetics, and are comparable to the conditions used in the LED‐DMD‐based prosthetics employed in current clinical trials. [ 14,19 ]…”