Synthetic shorter analogues of the cell-penetrating peptide penetratin showed measurable ability to cross porcine corneal tissue, though none matched the full-length peptide.
All analogues penetratedEvery shortened penetratin variant showed measurable trans-corneal diffusion
What the researchers found
All synthesized penetratin analogues demonstrated measurable trans-corneal diffusion despite their hydrophilic nature and ~1.6 kDa size, though none achieved the penetration efficiency of full-length penetratin.
Why it matters
Eye drug delivery is challenging because the cornea blocks most molecules. Cell-penetrating peptides could carry drugs across this barrier without invasive procedures like injections.
The numbers in context
~1.6 kDa molecular weight; all analogs showed trans-corneal diffusion; none matched full-length penetratin (16 aa)
How the study worked
Synthesized fluorescently labeled short analogues of penetratin and its reversed sequence via mimotopic approach, then tested trans-corneal permeation ex vivo using freshly explanted porcine corneas. Structural analysis performed via circular dichroism.
Who was studied
Freshly explanted porcine corneas
What this study cannot tell us
Preliminary results only. Ex vivo porcine tissue may not fully replicate living human cornea. No therapeutic cargo was tested — only the peptide carriers themselves. No clear structure-activity relationship was established.
How to read the evidence
Preliminary — ex vivo testing on animal tissue with no therapeutic payload; early-stage proof of concept.
When this study was published
Published in 2020; this is early-stage work that likely requires further optimization before advancing.
The bigger picture
This work contributes to the broader effort of developing non-invasive eye drug delivery systems. If CPP carriers can be optimized, they could replace or reduce the need for eye injections in treating conditions like glaucoma, infections, or macular degeneration.
Questions still open
- Can these analogues carry actual drug molecules across the cornea, not just fluorescent labels?
- What happens to the peptides within corneal layers — do they distribute evenly or accumulate?
- Could combining shorter analogues improve penetration to match full-length penetratin?
Common questions
What is penetratin and why is it useful for eye drugs?
Why did they use pig corneas instead of human eyes?
Read the original research
Synthesis and Ex Vivo Trans-Corneal Permeation of Penetratin Analogues as Ophthalmic Carriers: Preliminary Results.
Pharmaceutics, 12(8)
Citation
Pescina, Silvia; Sala, Marina; Scala, Maria Carmina; Santi, Patrizia; Padula, Cristina; Campiglia, Pietro; Ostacolo, Carmine; Nicoli, Sara. (2020). Synthesis and Ex Vivo Trans-Corneal Permeation of Penetratin Analogues as Ophthalmic Carriers: Preliminary Results.. Pharmaceutics, 12(8). https://doi.org/10.3390/pharmaceutics12080728