Injected carbon nitride particles evoked cortical light responses in blind mice

Graphitic carbon nitride is a light-driven catalyst, and the particles are hollow spheres around 300 nanometres across whose structure captures visible light efficiently, a design borrowed in part from chloroplasts ^[10]. What follows in tissue is described only as electrical and chemical processes in the particle's immediate surroundings, close enough to change signalling in nearby cells ^[11][2]. Safety depends on those specifics. A material doing photochemistry beside a ganglion cell has to be characterised for what it produces and whether it keeps producing it in dim light.

Resolution is harder. In single-cell experiments, a precisely focused laser activated individual particles inside a cell, and the resulting signal travelled through that cell and on to neighbouring cells ^[12]. How far the signal spreads between neighbours sets how fine a pattern a future prosthesis could deliver, and the mouse readouts leave open how tightly light can be localised on the retina ^[3].

Ordinary LED light was enough in one of the other preparations. In cardiac muscle cells, LED illumination changed the cells' rhythm and made them beat more synchronously ^[13]. The move from a focused laser aimed at one particle to broad LED light matters because it decides whether an ordinary light source, and not a microscope, can drive the effect. Only a living eye can show what the particles do over weeks ^[15].

The approach depends on what retinitis pigmentosa leaves behind: the photoreceptors degenerate, while other retinal cells and their connections can remain intact ^[9]. "Instead of genetically modifying these cells, we use the nanoparticles to create a new connection between light and the nerve cells," said Menglin Chen, an associate professor at the Department of Biological and Chemical Engineering at Aarhus University ^[16][8]. Chen said that once the photoreceptors are lost, the options for restoring light sensitivity are still very limited ^[22].

The project began at Aarhus seven years ago, so around 2019 given the September 2026 date on the phys.org report, with the question of whether a microscopic solar cell could work inside the body ^[6][20][21]. Chen said the founding problem was whether the team "could create a material that could act as a wireless interface between light and living cells" ^[7]. The paper is in Nature Biomedical Engineering ^[5].

The phys.org account leaves out how many animals were tested, what the control conditions were, and the light intensities used ^[19]. The researchers say long-term safety and function need study in much greater detail before the technology could be tested as a treatment in people ^[18].