Alp Yetisgin, PhD

When it comes to groundbreaking advancements in healthcare, the intersection of nanotechnology and biomaterials has unlocked unprecedented possibilities. Among these innovations, polymersomes—tiny vesicles created from self-assembling amphiphilic polymers—are emerging as powerful tools for targeted drug delivery. In this post, we’ll explore how polymersomes, specifically those crafted from hyaluronan-sphingosine (HA-Sph), are poised to revolutionize the treatment of ocular diseases.

The Challenge of Ocular Neovascularization

Ocular neovascularization, characterized by the abnormal growth of blood vessels in the eye, is a hallmark of vision-threatening conditions such as diabetic retinopathy and age-related macular degeneration. Current treatments, primarily anti-VEGF (vascular endothelial growth factor) agents, involve frequent injections into the eye—a process that is both invasive and expensive. Additionally, these treatments often suffer from poor bioavailability and limited efficacy in penetrating ocular barriers.

This is where polymersomes offer a transformative solution. By encapsulating therapeutic agents and facilitating their sustained, targeted release, these nanocarriers address the limitations of conventional therapies while promising a more patient-friendly approach.

What Are Polymersomes?

Polymersomes are nanoscale vesicles formed by the self-assembly of amphiphilic polymers. Structurally similar to liposomes, they offer enhanced stability, tunable chemical properties, and the ability to encapsulate both hydrophilic and hydrophobic drugs. These characteristics make polymersomes highly versatile for drug delivery applications.

The hyaluronan-sphingosine (HA-Sph) polymersomes developed in recent research exemplify the potential of these nanocarriers. By grafting sphingosine molecules onto hyaluronic acid chains, researchers have created a self-assembling system that combines the biocompatibility of hyaluronan with the bioactivity of sphingosine.

How HA-Sph Polymersomes Work

The innovation behind HA-Sph polymersomes lies in their dual functionality:

1. Targeted Delivery: Hyaluronic acid, a natural component of the eye’s vitreous humor, exhibits mucoadhesive properties that improve drug retention on the corneal surface. It also interacts with CD44 receptors found on ocular tissues, enabling targeted delivery.
2. Therapeutic Efficacy: Sphingosine, a bioactive lipid, inhibits the proliferation of human umbilical vein endothelial cells (HUVECs), effectively halting abnormal blood vessel growth. At the same time, it supports the health of retinal pigment epithelial cells, which are vital for maintaining vision.

Key Findings from Recent Research

Recent studies on HA-Sph polymersomes have yielded promising results:

• Size and Stability: These polymersomes exhibit spherical morphologies with sizes ranging from 97 to 162 nanometers, ensuring uniform distribution and stability.
• Sustained Drug Release: In vitro studies demonstrate that HA-Sph polymersomes gradually disintegrate, releasing sphingosine over time. This sustained release prolongs the antiangiogenic effect, reducing the need for frequent administrations.
• Antiangiogenic Effect: The polymersomes significantly inhibit HUVEC proliferation and reduce angiogenesis in tube formation assays. This confirms their potential to effectively combat ocular neovascularization.
• Ocular Penetration: Ex vivo studies using porcine eyes reveal that HA-Sph polymersomes successfully penetrate ocular barriers and reach the retina, making them suitable for topical application as eye drops.

Advantages of HA-Sph Polymersomes

Compared to existing treatments, HA-Sph polymersomes offer several advantages:

• Non-Invasive Administration: The ability to deliver drugs topically as eye drops reduces the reliance on invasive intravitreal injections.
• Enhanced Bioavailability: By overcoming ocular barriers, these polymersomes ensure higher drug concentrations at the target site.
• Patient Compliance: A less invasive and more effective treatment approach improves patient comfort and adherence.

Future Prospects

The development of HA-Sph polymersomes marks a significant milestone in nanomedicine. By combining the natural compatibility of hyaluronic acid with the therapeutic potential of sphingosine, these nanocarriers offer a novel approach to treating ocular diseases. As research progresses, polymersomes could pave the way for more effective, non-invasive, and patient-centric therapies, not only for eye conditions but for a wide range of healthcare applications.

While the results are promising, further studies are needed to explore the long-term safety and efficacy of HA-Sph polymersomes. Understanding the metabolism of sphingosine in ocular tissues and optimizing the dosage will be critical steps in translating this innovation from the lab to the clinic.

Further reads:

A. A. Yetisgin, S. Durak, O. Kutlu, S. Cetinel, Hyaluronan-Sphingosine Polymersomes for Treatment of Ocular Neovascularization: Synthesis and Evaluation. Macromol. Biosci. 2024, 24, 2300531. https://doi.org/10.1002/mabi.202300531

Yetisgin, A. A., Kutlu, O., & Cetinel, S. (2025). Designing blend polymersomes co-loaded with HRH peptide and sphingosine for the treatment of ocular neovascularization. Journal of Drug Delivery Science and Technology, 111, 107156. https://doi.org/10.1016/j.jddst.2025.107156

Yetisgin, A. A., Sivakumar, P. M., & Cetinel, S. (2025). Current state and potential of polymersomes as ocular drug delivery systems. Nanoscale, 17(24), 14458–14476. https://doi.org/10.1039/d5nr01273b