# High-power pulsed electrochemiluminescence for optogenetic manipulation of Drosophila larval behaviour

## TL;DR

A new high-power electrochemiluminescence method enables optogenetic control and imaging of fruit fly larvae behavior.

## Contribution

A biphasic pulse strategy achieves high-brightness, stable electrochemiluminescence for optogenetic applications.

## Key findings

- A biphasic voltage strategy produces over 100 μW mm−² optical power density for thousands of pulses.
- Optimized pulse trains enable prolonged high-brightness light with minimal power loss.
- ECL devices successfully triggered optogenetic responses in Drosophila larvae and allowed simultaneous imaging.

## Abstract

Electrochemiluminescence (ECL) produces light through electrochemical reactions and has shown promise for various analytic applications in biomedicine. However, the use of ECL devices (ECLDs) as light sources has been limited due to insufficient light output and low operational stability. In this study, we present a high-power pulsed operation strategy for ECLDs to address these limitations and demonstrate their effectiveness in optogenetic manipulation. By applying a biphasic voltage sequence with short opposing phases, we achieve intense and efficient ECL through an exciplex-formation reaction pathway. This approach results in an exceptionally high optical power density, exceeding 100 μW mm−², for several thousand pulses. Balancing the ion concentration by optimizing the voltage waveform further improves device stability. By incorporating multiple optimized pulses into a pulse train separated by short rest periods, extended light pulses of high brightness and with minimal power loss over time were obtained. These strategies were leveraged to elicit a robust optogenetic response in fruit fly (Drosophila melanogaster) larvae expressing the optogenetic effector CsChrimson. The semi-transparent nature of ECLDs facilitates simultaneous imaging of larval behaviour from underneath, through the device. These findings highlight the potential of ECLDs as versatile optical tools in biomedical and neurophotonics research.

Very high-brightness, prolonged electrochemiluminescence is achieved by combining an exciplex-formation mechanism with biphasic pulse modulation. Together this enables optogenetic behavioural manipulation and real-time imaging of Drosophila larvae.