Through photosynthesis, plants capture light and convert it into chemical energy. Humans, on the other hand, use light primarily to see.
But researchers are now finding ways to make mammalian cells (cells from a mammal, such as mice or humans) use some of the same light-driven chemistry.
In a 2026 study, scientists put photosynthesis-related material from spinach into mammalian eye cells and exposed them to light. This research sets out to determine if scientists can borrow a small part of the photosynthetic process and put it to work inside an animal cell.
Particularly to treat dry eye in humans.
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The Significance of Dry Eye
Dry eye is associated with low tear production, but the condition can be more serious than simply having too little moisture on the eye’s surface.
At all times, a healthy eye has a thin film of tears that are spread evenly thanks to blinking. When the tear film becomes uneven, the surface gets irritated and inflamed. This can increase oxidative stress, which happens because the normal amount of reactive molecules begins to outgrow what the body is capable of fixing.
Because of the damage this can cause, there is a desire for a solution that doesn’t just require adding tears via eye drops.
One possibility is to help the cells on the surface of the eye better handle the stress associated with dry eye, which is where photosynthesis comes in.
How Photosynthesis Can Help
Photosynthesis is the process plants use to turn sunlight into energy, and it comes in stages.
The first stage involves a part of the plant called thylakoids. When light hits the plant’s thylakoids, there is a reaction that produces molecules the cells can use for energy.
These molecules are:
- ATP, which provides usable energy for cells
- NADPH, which helps cells control damaging molecules.
NADPH is particularly relevant to the dry-eye research.
Producing those reactive molecules that get out of hand with dry eye is always happening, even in healthy eyes. When those molecules accumulate faster than the cell can control them, oxidative stress can damage proteins, membranes, and other cellular components.
NADPH helps support the systems cells use to keep these reactive molecules under control.
This leads researchers to an idea: mammalian cells might not be photosynthetic, but could we give the cells access to the light-dependent part that produces NADPH and ATP?
The LEAF System Uses Spinach to Power Eye Cells
In a 2026 study, researchers developed LEAF. It stands for “light-reaction enriched thylakoid NADPH-foundry,” which is to say that they isolated the tiny particles that create energy from light. In particular, they took it from spinach.
When exposed to light, these particles can:
- Capture light energy.
- Drive electron-transfer reactions.
- Produce NADPH and ATP.
- Support the cell’s antioxidant defenses.
- Reduce oxidative stress.
Then, they introduced it to mammalian cells.
How Did it Work?
When the researchers introduced LEAF into eye cells, the system remained functional and responded to light.
Researchers were not giving the eye cells the whole metabolism a plant uses. They were borrowing one specific part and using it for a different purpose.
Rather than using sunlight to manufacture food, the system uses light to generate molecules that may help an animal cell maintain its chemical balance.
The Treatment Improved Dry Eye Damage in Mice
The researchers then tested whether this could impact the eye’s response to dry eye.
In their experiments on cells from mice, LEAF treatment reduced oxidative stress and inflammatory activity in the cornea. The researchers also found improvements in corneal damage and tear production.
While it was not necessarily treating dry eye directly, it may have been helping the cells better cope with the processes that contribute to damage on the surface of the eye. This is significant because instead of replacing tears like a bandage or acting as a conventional anti-inflammatory, it is attempting to change the environment inside the cells.
The research is still at the preclinical stage, so human clinical trials will be necessary before we know whether this approach can become a treatment.
The Cells Did Not Become Capable of Photosynthesis
Plants use these light reactions to fuel their entire metabolic process. They essentially use photosynthesis to manufacture carbohydrates and sustain themselves.
That is not what is happening in the cells from mice.
The LEAF system is much more limited. It provides cells with a piece of photosynthetic machinery that can perform light-dependent reactions and generate useful molecules.
The animals could not use sunlight as a replacement for energy.
Light-Based Treatments for Dry Eye
The LEAF research is part of a larger interest in how light can influence human biology.
Another approach is known as photobiomodulation, which uses specific wavelengths of light to influence cells, instead of adding particles from plants.
Researchers have begun studying red and near-infrared light as a potential treatment for dry eye. A 2024 study, for example, reported improvements in several dry-eye measures following low-level light therapy.
The two approaches work very differently, but the underlying idea is similar: light may be capable of influencing cellular biology.
Animals Have Evolved Relationships with Photosynthesis Before
The idea of an animal making use of photosynthesis might seem strange, but isn’t unprecedented.
A known example being the sacoglossan sea slug.
These sea slugs eat algae and hold onto its chloroplasts inside their own cells. This process, known as kleptoplasty, allows the slugs to carry out photosynthesis for periods of time–although it’s not exactly the same process. It is thought to give the slug an additional energy source when food is scarce, but scientists are still studying how much energy they gather from the stolen chloroplasts.
Why Sea Slugs Matter to this Research
The slug has evolved a biological relationship with chloroplasts, while LEAF is an engineered system created by researchers.
Despite the difference, we can deduce the concept that an animal does not necessarily have to evolve its own ability for photosynthesis. It can be acquired from plants.
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