A research team in China has engineered eye drops using exosomes extracted from pig semen to deliver a targeted drug payload to retinal tumours in mice, with treated animals showing suppressed tumour growth and preserved vision over a 30-day period.
Retinoblastoma is the most common intraocular cancer in children. While it is highly treatable in high-income countries, roughly 80% of cases occur in lower- and middle-income settings where delayed diagnosis and limited treatment options worsen outcomes. Current treatments intravitreal injections, systemic chemotherapy, and laser therapy require invasive delivery methods that can themselves cause damage to healthy eye structures, including vision loss. Getting a drug to the retina non-invasively means crossing multiple layers of tightly controlled tissue, a problem that has long constrained the development of eye-drop-based therapies for conditions at the back of the eye.
Exosomes small lipid-bound vesicles secreted by most cell types have been studied as drug delivery vehicles for their ability to cross biological barriers and their relatively low immunogenicity. Research on exosomes as carriers is, in the words of corresponding author Yu Zhang, “relatively mature,” with their potential for encapsulating therapeutic agents considered “theoretically feasible.” What was less explored was whether exosomes derived specifically from semen could traverse the layered barriers of the eye. The rationale came from a separate biological context: seminal exosomes are known to assist sperm in penetrating the female reproductive tract, suggesting they carry surface properties suited to breaching tight-junctioned tissue. As Zhang explained, the observation that exosomes “play a facilitative role in the penetration of physiological barriers in the female reproductive tract during sperm migration” led his team to investigate whether they could do the same in the eye.
Zhang and colleagues at Shenyang Pharmaceutical University isolated exosomes from pig semen selected because pigs are already widely used in biomedical research and their biological materials are generally acceptable for preclinical work. The team first tested these seminal extracellular vesicles (SEVs) on human corneal cells to confirm they could open and close the tight junctions between surface cells of the eye, which is the primary barrier to posterior segment access.
The researchers then engineered a therapeutic formulation. They loaded the exosomes with what they describe as a “nanozyme system” a combination of carbon dots, manganese dioxide, and glucose oxidase designed to generate reactive oxygen species inside tumour cells, disrupting cellular processes and triggering cell death. To increase selectivity for retinoblastoma cells over healthy tissue, they modified the outer surface of the exosomes with folic acid molecules. Retinoblastoma cells express substantially higher levels of folate receptors than surrounding healthy cells, making folic acid a recognised targeting handle.
The resulting formulation, labelled FA-SEVs@CMG, was applied as eye drops to mice carrying retinal tumours. A control group received drops containing the nanozyme components without exosome packaging. The researchers also conducted a 30-day safety evaluation in rabbits.
In the mouse tumour model, animals treated with the full FA-SEVs@CMG formulation showed suppressed tumour growth at the 30-day mark, with visual function assessed as comparable to tumour-free control animals. In the control group receiving the nanozyme components without exosome packaging, tumours continued to grow and spread to other parts of the eye, which the researchers attributed to the components’ inability to penetrate the ocular barrier. In the rabbit safety trial, the drops were tolerated over 30 days, with minor corneal irritation reported as the only observed side effect. The paper reports that the exosomes reached the posterior eye segment via both corneal and conjunctival routes and that their barrier penetration was attributable in part to epidermal growth factor expression on their surface.
The authors describe this as establishing, in their words, “the first SEV-based platform for noninvasive posterior segment delivery,” and characterise it as a potential approach for treating posterior ocular diseases more broadly. Chunxia Zhao, a drug delivery and nanomedicine researcher at the University of Adelaide who was not involved in the study, noted that the capacity to traverse similarly guarded biological interfaces including the blood-brain barrier and mucosal barriers could extend the approach to other disease contexts. These observations are Zhao’s extrapolations, not claims made in the paper itself. Zhang has indicated he intends to continue investigating semen-derived exosomes from other animal sources, including cattle, but acknowledged that human clinical application remains distant, stating there is “still a long way to go before” human trials.
This is preclinical work conducted in mouse and rabbit models. The findings have not been tested in humans, and it is not known whether the delivery mechanism, efficacy profile, or safety data would translate to human patients. The nanozyme components carbon dots, manganese dioxide, and glucose oxidase are not established clinical treatments; carbon dots in particular remain experimental in cancer therapy. The paper does not address manufacturing scalability or the regulatory considerations involved in deriving biological drug carriers from animal semen for clinical use. The observation period was 30 days, and no longer-term data on safety or tumour recurrence were reported.
References
Jiansong Zhao, Tian Yin, Yaxin Deng, Hongbing Liu, Mingli Wei, Chenxiao Chu, Xinxin Liang, Xiaoshuang Bi, Haibing He, Jingxin Gou, Xing Tang, and Yu Zhang. “Harnessing semen-derived exosomes for noninvasive fundus drug delivery: A paradigm for exosome-based ocular fundus therapeutics.” Science Advances, Vol. 12, eadw7275 (2026). DOI: 10.1126/sciadv.adw7275
