We, too, can have limited photosynthetic abilities.
In Singapore, scientists have done something quietly extraordinary: they have taught human cells to borrow the sun-harvesting machinery of plants. Researchers at the National University of Singapore have developed LEAF, a spinach-derived technology that, when delivered as ordinary eye drops, reverses the cellular damage of dry eye disease — a condition that afflicts 1.5 billion people worldwide — by producing protective antioxidants using nothing more than ambient light. It is a reminder that the boundaries between kingdoms of life are more porous than we imagined, and that healing sometimes arrives not through conquest of disease, but through an unexpected act of kinship with the natural world.
- Dry eye disease is not a minor inconvenience — it scars corneas, causes chronic pain, and is linked to depression and anxiety in over a billion people whose current treatments are costly, side-effect-laden, and frequently abandoned.
- At the cellular level, the disease is a self-reinforcing trap: inflammation generates damaging molecules faster than the eye can neutralize them, creating a spiral of destruction that existing drugs only partially interrupt.
- NUS researchers broke the cycle by isolating the photosynthetic core of spinach chloroplasts and engineering it into nanoparticles small enough for corneal cells to absorb, effectively giving human tissue a limited ability to harvest light and produce its own antioxidants.
- In preclinical trials, LEAF eye drops restored near-healthy corneal conditions within five days, outperformed the leading prescription treatment Restasis®, and showed no toxicity or irritation over two months of safety testing.
- Clinical trials are now being planned, and the team is already looking beyond the eye — toward the retina, skin, and muscle — with strategies in development to deliver photosynthetic therapy even to organs that never see the light.
Somewhere in a laboratory at the National University of Singapore, researchers have been asking a question that sounds like science fiction: what if human eyes could borrow the sun-harvesting machinery of plants?
Dry eye disease affects more than 1.5 billion people globally. It scars the cornea, produces chronic pain, blurs vision, and has been linked to depression and anxiety. In the United States alone, its economic toll reaches $3.84 billion annually. The drugs that currently treat it work by suppressing inflammation, but they are expensive and trigger side effects severe enough that many patients stop using them.
At the cellular level, the disease is a trap. Inflammation generates reactive oxygen species — chemically aggressive molecules that damage tissue — faster than the eye can neutralize them with its natural antioxidant, NADPH. The result is a death spiral: more damage, more inflammation, more damage.
Associate Professor David Leong and his team approached the problem from an unexpected angle. They isolated thylakoid grana — the membrane structures inside spinach chloroplasts where photosynthesis occurs — and engineered them into nanoparticles roughly 400 nanometres across, small enough for corneal cells to absorb. The result was LEAF: Light-reaction Enriched thylAkoid NADPH-Foundry. Each particle is a miniature factory powered by the same ambient light already present in any room.
In laboratory tests, LEAF restored NADPH levels within 30 minutes of light exposure. In tear samples from actual dry eye patients, it increased NADPH roughly 20-fold and reduced a key cell-damaging oxidant by more than 95 percent. In preclinical trials with ophthalmologists from Zhejiang University, LEAF eye drops reversed corneal damage to near-healthy levels within five days — outperforming Restasis® — with no adverse effects found over two months of safety testing.
What makes the technology striking is its simplicity: no external device, no power source, no complex delivery system. It is spinach-derived, administered as ordinary eye drops, and powered by light. Clinical trials are now being planned. The team is already thinking further — toward the retina, skin, and skeletal muscle — and developing ways to deliver photosynthetic therapy to internal organs that never see the light at all.
Somewhere in a laboratory at the National University of Singapore, researchers have begun asking a question that sounds like science fiction: what if human eyes could borrow the sun-harvesting machinery of plants? The answer, published this week in the journal Cell, is that they can—and that this borrowed biology might heal one of the world's most widespread eye conditions.
Dry eye disease affects more than 1.5 billion people globally. It is not merely uncomfortable. The condition scars the cornea, produces chronic pain, blurs vision, and leaves sufferers sensitive to light. Studies have linked it to depression and anxiety. In the United States alone, the economic toll reaches $3.84 billion annually. The drugs that currently treat it—cyclosporine A and lifitegrast—work by suppressing inflammation, but they are expensive and often trigger side effects severe enough that patients abandon them.
At the cellular level, dry eye disease operates as a trap. Inflammation in the cornea generates reactive oxygen species, chemically aggressive molecules that damage tissue. Healthy eyes neutralize these molecules by producing NADPH, an antioxidant compound. But in inflamed eyes, the reactive oxygen species multiply faster than the eye can defend itself, creating what researchers call a death spiral—more damage triggering more inflammation triggering more damage.
Associate Professor David Leong and his team at NUS approached the problem sideways. They asked: could mammalian cells acquire a limited form of photosynthesis? The eye seemed like the obvious place to try. Unlike most organs, it absorbs visible light constantly. They turned to spinach. Using a patented extraction method, they isolated thylakoid grana—the membrane structures inside plant chloroplasts where photosynthesis actually happens—and stripped away the parts that would consume the NADPH they wanted to produce. What remained was LEAF: Light-reaction Enriched thylAkoid NADPH-Foundry. Particles roughly 400 nanometres across, small enough for cells to absorb, each one a miniature factory powered by the same light that lets us see.
In laboratory tests on inflamed corneal cells, LEAF restored NADPH levels within 30 minutes of light exposure. When tested in tear samples from actual dry eye patients, it increased NADPH roughly 20-fold and reduced hydrogen peroxide—a key cell-damaging oxidant—by more than 95 percent. In preclinical trials conducted with ophthalmologists from Zhejiang University, eye drops containing LEAF reversed corneal damage to near-healthy levels within five days. It outperformed Restasis®. Safety studies over two months found no adverse effects, no eye irritation, no toxicity.
What makes this work remarkable is its simplicity. LEAF requires no external device, no power source, no complex delivery mechanism. It is spinach-derived. It is administered as ordinary eye drops. It uses the ambient light already present in a room. Dr. Xing Kuoran, the study's first author, called it an exciting finding: for the first time, plant photosynthetic machinery had been successfully transplanted into mammalian tissue to generate biologically useful molecules. "We, too, can have limited photosynthetic abilities," he said.
The team is now planning clinical trials to move from preclinical success to human use. But they are already thinking beyond the eye. Oxidative stress—the same imbalance that drives dry eye disease—underpins inflammation across the body. LEAF-based approaches could eventually treat conditions affecting the retina, skin, and skeletal muscle. The researchers are even developing strategies to produce photosynthesized molecules in internal organs without requiring visible light to penetrate. The future they are imagining is one where human cells, in multiple tissues, possess some limited but genuinely useful form of photosynthetic ability. It is a future powered by sunlight and spinach.
Citas Notables
For the first time, plant photosynthetic machinery has been successfully transplanted into mammalian tissue to generate biologically useful molecules, powered entirely by the same light that enables our vision.— Dr. Xing Kuoran, first author of the study
LEAF harnesses ambient light to directly restore the molecule that dry eye disease depletes, requiring no external device or power source and using the light already used for vision.— Associate Professor David Leong
La Conversación del Hearth Otra perspectiva de la historia
Why the eye? Why not start with a simpler tissue?
The eye is one of the few places in the human body that naturally absorbs visible light all day. It made sense to work where light already flows.
And spinach specifically—was that arbitrary, or does spinach have something special?
Spinach's chloroplasts are well-studied and accessible. The team developed a mild extraction method that preserves the photosynthetic machinery without damaging it. Familiarity mattered.
The reactive oxygen species trap you described—that death spiral—sounds almost inevitable. How does LEAF actually break it?
By flooding the cell with NADPH, the antioxidant that the inflamed eye can't produce fast enough on its own. More antioxidant means the reactive oxygen species get neutralized before they can multiply further.
Five days to near-healthy corneas. That's faster than the existing drugs. Why haven't we seen this before?
Because it required thinking across disciplines—plant biology, nanotechnology, ophthalmology. Most researchers stay within their lane. This team didn't.
What happens when the light goes out? At night?
The NADPH production stops, but the antioxidants remain in the cell and continue working. The eye doesn't need constant photosynthesis, just enough to break the inflammatory cycle.
The sea slug that eats chloroplasts—that's not just a curiosity, is it?
No. It proved the concept was possible in animals. It asked the question: if one animal can do this, why not others? Why not us?
What's the real barrier to getting this into clinics?
Clinical trials. The preclinical work is solid, but you have to prove safety and efficacy in actual patients. That takes time and money. But there's no obvious reason it won't work.