Light-Activated Nanoparticles May Offer New Approach to Retinal Prostheses

Retinitis pigmentosa is a degenerative retinal disorder in which photoreceptors progressively die, reducing visual signals to the brain while leaving surviving inner retinal circuits underused. With restorative options limited, researchers are exploring ways to restore light responsiveness without surgery or genetic modification. One such approach uses newly developed injectable, light-sensitive nanoparticles designed to activate remaining retinal neurons and restore signaling toward the brain.

Developed by team led by Aarhus University (Aarhus, Denmark) researchers, the hollow graphitic carbon nitride nanoparticles measure roughly 300 nanometers in diameter and act as microscopic light receptors. Their structure, inspired in part by plant chloroplasts, is optimized to capture visible light. After injection into the eye, the particles settle near retinal nerve cells, positioning them to interact with surviving neurons. When illuminated, they trigger electrical and chemical events that can stimulate these nearby neurons to relay signals toward the brain.

Beyond the eye, the researchers examined how the material influences cellular signaling across scales. Using a tightly focused laser, they activated individual nanoparticles inside single cells and observed signals that propagated through the cell and into neighboring cells. In cardiac muscle cells, exposure to ordinary light‑emitting diode (LED) light influenced pacing and promoted more synchronous beating. These findings established a controllable, light-to-cell interface without genetic modification.

The most clinically directed tests targeted vision. In mice with advanced retinitis pigmentosa, injected nanoparticles accumulated on the retinal surface close to retinal ganglion cells that transmit information centrally. On illumination, the team detected activity in the visual cortex and recorded behavioral responses to light. In isolated pig retinal tissue, LED illumination activated ganglion cells only when nanoparticles were present.

The study, published in Nature Biomedical Engineering, did not restore normal vision but demonstrated measurable light‑evoked responses in severely degenerated retinas. The authors note that long‑term safety, delivery optimization, and durability in the eye require further investigation before any human testing. 

The work advances a seven‑year program that began at Aarhus University and has progressed from single‑cell activation to preclinical retinal responses. Collaborating institutions included the University of Chicago, the University of Eastern Finland, Aarhus University Hospital, and the University of Copenhagen. The team filed an international patent application in 2024 and, in 2025, launched the RetiNano project to develop a biocompatible, injectable photovoltaic retinal prosthesis.

“When we started, our fundamental question was whether we could create a material that could act as a wireless interface between light and living cells. We can now see that the particles are able to activate nerve cells in blind retinas. That brings us closer to our long-term goal of developing a new type of retinal prosthesis,” said Menglin Chen, associate professor at the Department of Biological and Chemical Engineering at Aarhus University.

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