Alp Yetisgin, PhD

Topical eye delivery is attractive because it’s simple and patient-friendly—yet most of a drop never reaches the target tissue. I keep asking a basic question: can polymersomes, with their thicker, tunable membranes, meaningfully change that equation without injections?

What polymersomes are (in plain terms)

Polymersomes are vesicles made from amphiphilic block copolymers: a watery core surrounded by a polymer membrane. Compared to liposomes, their membranes are thicker and more customizable. In theory, that lets us tune stability, permeability, and surface chemistry for the eye’s barriers rather than working around them.

What the evidence hints at (signals worth noticing)

• Some designs show movement across ocular barriers in ex vivo models after topical application.
• After intravitreal injection, certain polymersomes persist for weeks to months, implying sustained-release potential.
• Surface charge matters: anionic/neutral coatings diffuse better through the vitreous; strongly cationic systems tend to stick.
• Shape isn’t trivial—non-spherical assemblies can move differently in gels like the vitreous.

These aren’t “case closed” results; they’re “keep looking here” results.

What I’m still trying to understand

• Topical to posterior eye: Under what exact size/charge/shape window do polymersomes repeatedly reach the retina in vivo (not just ex vivo)?
• Biodegradation paths: Which chemistries clear cleanly from the vitreous, and on what timescales?
• Manufacturability: Which assembly routes give narrow size distributions and low residual solvent at practical ophthalmic scales?
• Clinical positioning: Where could polymersomes be genuinely better than existing depots or injections (not just “different”)?

Why this matters (beyond “cool nanotech”)

If we can reliably deliver drug to the right ocular compartment with fewer clinic visits, adherence improves, risks linked to frequent injections drop, and chronic diseases become more manageable. But “reliably” is the operative word—repeatability across labs and models is the bar.

What to watch next

• Surface chemistry that stays mild (anionic/neutral) in the vitreous.
• Tight size control in the ~70–120 nm range.
• Shape control beyond spheres (and how that translates to mobility and safety).

Further reading

• Yetisgin A.A., Sivakumar P.M., Cetinel S. Current state and potential of polymersomes as ocular drug delivery systems.
  Nanoscale (2025).
  
  DOI link