A "miracle plaster" worked with New Zealand rabbits

The bioadhesive hydrogel GelCORE promises a lot for the future of ophthalmology. Now the gel has been tested on New Zealand rabbits.

Ophthalmology Blog
By Dr. med. Annabelle Eckert

The bioadhesive hydrogel GelCORE promises a lot for the future of ophthalmology. Now the gel has been tested on New Zealand rabbits.

This entry will focus on GelCORE, a bioadhesive hydrogel currently under development. This gel for corneal regeneration is being proposed as a type of "miracle plaster" for the eye surface; a kind of "safety lock" for an immuno-privileged organ that is almost immunologically defenseless when perforated. The eye is an organ worth protecting, as it gives us all the beautiful colorful impressions of our outside world. It helps us to communicate with our fellow human beings by recognizing and interpreting their facial expressions. We live in a society in which an ever-increasing amount of activity is done by information on monitors of any size. The human species is a visual one. In this world, 1.5 million people go blind every year due to corneal diseases or injuries. Not only do they lose the ability to orient themselves in space, but they also lose visual communication with their fellow humans.

A fulfilled promise that provides security

GelCORE passed the tensile test in the in vitro tests with great ease. It delivered what it promised in terms of adhesion strength in vitro. This promise could help the 1.5 million people a year that suffer corneal problems to stay in contact with their outside world and to perceive optical sensory impressions without difficulties. In addition to the transparency of the optical axis, it is also important that a bioadhesive hydrogel offers secure wound closure in order to prevent exogenous infections of the immune-privileged eye. It should thus be an invisible protective wall from the outside world. The in vivo and ex vivo tests on rabbits have yielded the necessary results to set the next step in the testing of GelCORE on humans.1

What happened to the New Zealand rabbits?

In a recent study, a small corneal defect was first inflicted on rabbits, followed by testing the bioadhesive hydrogel. The eyes were removed from the rabbits for ex vivo examinations. The eyes were examined by slit-lamp microscopy and anterior segment optical coherence tomography (ASOCT). The images obtained showed a transparent circular area where there was once a corneal defect 3 mm in diameter. The reason for this marvelous result, which was confirmed by optical coherence tomography, is the use of GelCORE. The ASOCT also shows that the former corneal defect had a depth of more than 50% of the cornea. This was now filled with the hydrogel and the surfaces merged seamlessly.1

GelCORE provides transparency

The in vivo experiments showed transparency in the area of the former corneal defect (1, 7 and 14 days after surgery). A gradual decrease of the fluorescein-positive sites in the wound area was observed by slit-lamp microscopy. The research group concluded that a reepithelialization of the defect had occurred. After 14 days, the 3 mm diameter corneal defect was completely healed.

Strength was again put to the test

Safety has been tested ex vivo with compression and tear tests. The gel showed a high adhesion strength. The adhesion of the hydrogel to the cornea was strong and therefore safe. Even after 28 days, there was no change in the thickness and surface texture of the hydrogel inserted into the corneal defect. Now all that is missing is a scientific confirmation that the new hydrogel is safe for the cornea.

Free passage through a non-toxic environment

The cytocompatibility of the GelCORE bioadhesive hydrogel was investigated in in vitro experiments. The research team attached particular importance to the fact that GelCORE is not cytotoxic. After all, the corneal cells are supposed to migrate into the “miracle plaster” and enable long-term regeneration. What seems to have a solid start, should also be permanent. The results of the two-dimensional cell culture with corneal fibroblasts and the scratch test for the in vitro examination of cell migration seem to give positive prospects. GelCORE is not cytotoxic and is a good basis for corneal degeneration.1

The hard truth to wrap up

Last but not least, of course, the final confirmation comes from the histopathological examination of the cryosections of the rabbit eyes. Here a strong adhesion between corneal tissue and the adhesive hydrogel was found. The formation of new non-inflammatory tissue within the former defect was also observed.Chapeau!

Reference:
1. Sani S.E. et al. (2019). Sutureless repair of corneal injuries using naturally derived bioadhesive hydrogels. Sci Adv. 2019 Mar 20;5(3):eaav1281.