A micro-LED implant and technique for optogenetic stimulation of the rat spinal cord

Exp Neurol, 2021 · DOI: 10.1016/j.expneurol.2020.113480 · Published: January 1, 2021

Simple Explanation

This research introduces a small, implantable device using micro-LEDs to stimulate the spinal cord with light, a technique called optogenetics. The device is designed to be easily made and used in most research labs, even without specialized equipment, making it accessible for studying spinal cord function and potential therapies. The implant sits above the spinal cord and can trigger movements for at least six weeks without causing damage, offering a new tool to understand and treat spinal cord injuries.

Study Duration

6 Weeks

Participants

12 Long-Evans rats in the implant longevity study and 3 in the thermal safety study

Evidence Level

Not specified

Key Findings

1
The μLED implant can provide up to 50 mW/mm2 of light for optogenetic spinal stimulation.
2
Stimulation parameters such as pulse width and frequency significantly affect thermal characteristics in-vivo; lower pulse widths and frequencies resulted in smaller temperature increases.
3
The implant induced spinal activation for at least 6 weeks, making it a promising option for both acute and long-term stimulation studies.

Research Summary

This study presents a micro-LED (μLED) implant designed for long-term optogenetic stimulation of the rat spinal cord, emphasizing its simplicity in fabrication, implantation, and operation. The research identifies thermally safe optogenetic stimulation parameters by testing various conditions and measuring real-time temperature changes in-vivo, ensuring minimal tissue disruption. The implant demonstrates functionality for at least 6 weeks in awake, freely moving rats, inducing robust movements without causing significant physical or thermal damage to the underlying spinal cord.

Practical Implications

Accessible Research Tool

The μLED implant's ease of fabrication and use makes optogenetic spinal stimulation accessible to a wider range of laboratories, accelerating research in spinal physiology, pathophysiology, and therapeutic interventions.

Safe Stimulation Parameters

The identification of thermally safe stimulation parameters ensures the prevention of tissue damage during optogenetic stimulation, promoting reliable and ethical experimentation.

Long-Term Studies

The implant's long-term functionality (at least 6 weeks) enables researchers to conduct extended studies on spinal cord function and recovery, providing valuable insights for developing therapeutic strategies.

Study Limitations

1
Increasing scar formation between the implant and spinal cord can block light penetration over time.
2
Variability in movement thresholds occurred during the first and second week post-implant, likely due to continued progression of viral transduction.
3
The study mentions that the implants were tested in rats that had received a cervical contusion injury, limiting the ability to determine the effect of the implant on uninjured spinal cords.

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