Sutureless surgery advances with help of corneal glue

By Laszlo Dosa

WASHINGTON, DC - A new class of tissue adhesives known as biodendrimers may reduce or eliminate the need for sutures in most types of corneal surgery, reported US researcher Terry Kim MD at a Research to Prevent Blindness Foundation seminar.
The new glue shows promise for the repair of traumatic corneal wounds, surgical incisions from cataract surgery and corneal transplantation, and even LASIK surgery.

The compounds avoid the disadvantages of sutures, such as trauma to the cornea, uneven healing and astigmatism, infection, inflammation and scarring, Dr Kim said.
Developed by Duke University chemist Mark Grinstaff PhD, biodendrimers are made of a central core of polymer which branches radially outwards.

Biocompatible and biodegradable, the glue should not cause toxicity within the eye. Unlike alkyl-cyanoacrylate, the conventional 'super glue', which hardens as soon as it comes out of the tube, the biodendrimer does not begin to polymerise or harden until activated by an argon laser beam.

"You can apply this novel adhesive with much more control and ease than with conventional cyanoacrylate adhesives.
"In addition, you can control its polymerisation with an argon laser beam or other light source, giving it a major advantage over cyanoacrylate glue which polymerizes immediately upon contact with water or a moist surface," Dr Kim told EuroTimes.

Biodendrimers are easy to apply using a spatula to spread them over the wound. Another way of applying the glue is by putting it into a syringe and injecting it - a method Dr Kim expects will be adopted in future clinical trials.

That method allows precise delivery and is easy to control. This will be particularly useful for cataract surgery or corneal transplant incisions, or with LASIK flaps, where the surgeon can see the wound very clearly.

"That is what is nice about the cornea. It's right up front. We see the wound and the incision. It's very clearly visible and since the cornea is very accessible, we can get to it without complication and know where to put it exactly. For other areas of the eye, it may be a little more difficult," Dr Kim said.

Putting the glue in the wrong place would not be much of a problem because when it hardens it takes on a very smooth rubbery texture and remains in one piece.
If it is accidentally delivered into the anterior chamber of the eye, for example, the eye should degrade the glue with hopefully none or minimal inflammatory or toxic reaction.
It can also be removed by pulling it off in one piece after it hardens and should not pull the tissue along with it, he said.

The Duke University team initially tested the glue with enucleated human eyes obtained from an eye bank. The glue performed well in full-thickness and lamellar corneal wound models with no evident problems with wound sealing.

It successfully sealed linear and stellate corneal incisions as well as sutures. It also successfully sealed LASIK flaps.
Dr Kim expects to glean more information when he begins testing biodendrimers in an in vivo model.

He has chosen the chicken eye model because its cornea is very similar to the human cornea, with much of the same proteins and same corneal layers.
The in vivo testing should determine how this glue reacts with the surrounding tissue, how long the glue lasts, whether it causes toxicity or problems with inflammation, and how strong it works in the chicken eye. Clinical trials may begin in as little as two years.

"This is an entirely new technology for adhesives to replace sutures in ocular surgery which, for the first time, looks feasible and appears as though it will be compatible with the tissue. It should be easily applied in the operating room setting.

"The weakness is that he is just now beginning to apply it to a living animal model. So we'll have to reserve judgment. But overall, the work is extremely promising and it is the first time I have seen a new adhesive that actually looks as if it is going to be useful in the future," H. Dwight Cavanagh MD, PhD commented.

Fibrinogen tissue adhesives are also under study but they require the isolation of autologous fibrinogen, making them impractical in an emergency procedure. Moreover, the risk of infection rules out the use of donor fibrinogens, Dr Kim added.

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