SINGAPORE — Scientists at the National University of Singapore developed eye drops containing photosynthetic machinery extracted from spinach leaves that enabled light-dependent steps of photosynthesis in mouse eyes. The treatment, called 'light-reaction enriched thylakoid NADPH-foundry' (LEAF), reduced dry eye symptoms in mice by decreasing inflammation, increasing tear production, and limiting corneal damage compared to saline-treated controls.

The LEAF eye drops were created by isolating thylakoid grana from spinach chloroplasts and encapsulating them. In mice with induced dry eye disease, five days of LEAF treatment produced improvements comparable to those seen with a commercially available dry eye medication. The system works by producing NADPH, an antioxidant that helps neutralize compounds that worsen eye inflammation.

David Tai Leong, a chemical engineer at the National University of Singapore who led the study, said the approach leverages a highly optimized natural system. "We are able to use a highly optimized photosynthetic machine, so we do not need huge amounts of the LEAF system." He added that the low concentration of chlorophyll keeps the drops transparent. "Because it's so low concentration, you can't see the green color. So we won't have green eyes like the Incredible Hulk."

The study was published on May 15 in the journal Cell. Leong’s team is now working to set up a clinical trial to assess the safety of LEAF eye drops in humans. The therapy is not yet approved for human use and requires further testing for long-term efficacy. If eventually approved, the drops would be activated by ambient light during normal daily activities.

Corey Allard, a cell biologist at Harvard Medical School who was not involved in the research, described the work as a "cool application" of engineering inspired by symbiotic relationships in nature. Dr. Xianfeng Lin, an orthopedic surgeon at Zhejiang University School of Medicine in China, noted that the eye is uniquely suited for such light-based strategies. "The eye is uniquely suited for this type of strategy, since light is already an intrinsic component of its normal physiological function." He added, "The work extends the role of light in the eye from being purely sensory to potentially contributing to local metabolic support and tissue repair."