Photosynthetic Eye Drops Derived from Spinach Reverse Corneal Damage in Preclinical Dry Eye Model
核心洞察
Researchers at the National University of Singapore developed LEAF (搜索), a nanosized thylakoid system extracted from spinach that produces NADPH when exposed to ambient light.
In a mouse model of dry eye disease (搜索), twice-daily LEAF (搜索) drops doubled NADPH levels, reversed corneal damage, and outperformed an approved therapeutic drug.
LEAF (搜索) reduced reactive oxygen species within 30 minutes of light exposure and boosted NADPH roughly 20-fold in tears from dry eye patients.
A team at the National University of Singapore has demonstrated that microscopic photosynthetic machinery extracted from grocery-store spinach can be transplanted into mammalian eye cells, where it harnesses ambient light to produce protective antioxidants and reverse corneal damage. The technology, called LEAF (搜索) (light-reaction enriched thylakoid NADPH-foundry), represents the first successful transplantation of plant photosynthetic machinery into mammalian tissue to generate biologically useful molecules powered entirely by visible light.
Dry eye disease (搜索) affects roughly 1.5 billion people worldwide, causing chronic pain, corneal scarring, blurred vision, and light sensitivity. The condition has been linked to depression, anxiety, and diminished quality of life. Current anti-inflammatory treatments are expensive, have limited availability, and can provoke uncomfortable systemic side effects with long-term use.
Breaking the Oxidative Stress Cycle
At the cellular level, dry eye disease (搜索) is driven by a self-reinforcing cycle of oxidative damage. Mammalian cells generate reactive oxygen species as byproducts of energy production. Under normal conditions, the antioxidant molecule NADPH neutralizes these damaging compounds. During inflammation, however, reactive oxygen species overwhelm cellular defenses and destroy the cell's ability to produce NADPH, triggering a death spiral that activates immune cells and perpetuates tissue damage.
"Trying to boost NADPH under these conditions is a losing battle," the researchers noted. Plants, by contrast, produce NADPH through photosynthesis via a completely different biochemical pathway—one that operates independently of the damaged mammalian machinery.
Engineering LEAF (搜索) from Spinach
The team's central innovation was developing a gentle chemical extraction method that isolates thylakoid grana—the stacked disc-like compartments inside chloroplasts that drive light-dependent photosynthetic reactions—while stripping away other chloroplast components that would otherwise degrade NADPH. The extracted thylakoids were repackaged with the surfactant Pluronic F127 to yield nanoparticles measuring approximately 400 nanometers across, roughly the size of a small bacterium.
"LEAF (搜索) could generate NADPH without exogenous cofactors and independent of mammalian metabolic control," according to a commentary published in Nature Biotechnology.
The system proved remarkably practical. LEAF (搜索) nanoparticles remained stable for two weeks at room temperature and up to one year at -80 degrees Celsius. Four independent batches manufactured in Singapore and China, each sourced from local spinach, demonstrated consistent efficacy.
Cellular and Clinical Evidence
In petri dish experiments, both macrophages and corneal cells—the two cell types central to dry eye disease (搜索)—readily internalized LEAF (搜索) particles. Within 30 minutes of ambient light exposure, reactive oxygen species levels dropped sharply. Pro-inflammatory macrophages shifted toward an anti-inflammatory state.
In tears collected from patients with dry eye disease (搜索), LEAF (搜索) boosted NADPH levels roughly 20-fold and reduced a damaging oxidative chemical by over 95 percent. Broader metabolic profiling showed that treated cells reverted to a healthier state. The photosynthesized NADPH supply, the team wrote, can "power antioxidant metabolism, promote cell repair, restore balance, and break the vicious cycle."
In a mouse model of dry eye disease (搜索), twice-daily LEAF (搜索) eye drops for five days doubled NADPH levels and reversed corneal damage, outperforming an approved chemical treatment. LEAF penetrated the animals' eyes within 30 minutes of administration. Notably, the plant-derived material did not trigger immune attacks in the eyes or in distant organs such as the liver and heart.
"This is an exciting finding as we have, for the first time, demonstrated that plant photosynthetic machinery can be transplanted into mammalian tissue to generate biologically useful molecules, powered entirely by the same light that enables our vision," said study author Kuoran Xing. "We, too, can have limited photosynthetic abilities."
Translation Potential and Future Directions
Because LEAF (搜索) "is derived from spinach, delivered as a simple eye drop, [and it] requires no external device or power source…we believe it has a strong potential for clinical translation," said study author David Tai Leong.
The eye's natural transparency to visible light makes it an ideal target for this approach. Beyond dry eye disease (搜索), the team is exploring whether LEAF (搜索) could be formulated as a cream to treat skin inflammation disorders using sunlight. They are also investigating methods to generate photosynthetic molecules in deeper organs and to support mitochondrial health.
"It is almost surreal when thinking of a possible future reality where human cells can have some limited but beneficial form of photosynthetic ability not only in the eye but elsewhere, too," Leong added.