Biomaterials as surgical tools - Annual Report 2018

8 April, 2019

More than 250 corneal transplants are performed each year but the number is limited to donor numbers and there are not enough. Synthetic or naturally derived surgical substrates offer a solution.

The dream is to construct and repair what nature has taken billions of years to design — the eye, or at least parts of it. With this goal clearly in focus, MacDiarmid Institute Associate Investigator and University of Auckland lecturer, Dr Laura Domigan, is working in league with ophthalmic surgeons and specialists at the University of Auckland Faculty of Medical and Health Sciences, Dr Trevor Sherwin in particular.

Biomaterials may be used for surgical tools, such as adhesives, as well as for tissue engineering. Those derived from natural polymers like proteins have the advantage of being more biocompatible.

The cornea is the exquisitely composed tissue that covers the eye. It can tear and malfunction for a variety of reasons, and need replacing or repairing. Over 250 corneal transplants are performed in NZ every year, but as with all organ transplants, the number is limited by donors. There simply aren’t enough of them.

Dr Domigan is quietly confident of achieving her goals and is tackling the hurdles one by one. The material has to be strong enough, last for a certain amount of time, then degrade at the right rate, and must also be biocompataible.

The main protein component of eye lenses are crystallins, packed in such a way as to be transparent and diffract light. These crystallins can be produced recombinantly in the lab, but not in sufficient volumes. Instead, they are extracting them from hoki fish eyes, which are a waste by-product.

Whether repairing or replacing corneal tissue, the synthetic or naturally derived substrates must be able to influence future cell growth in the right direction. Dr Domigan has recently used crystallin proteins to formulate transparent biomaterials – namely thin films, gels and adhesives. Crystallin protein thin films can be prepared with a range of mechanical properties and degradation rates, and micro-patterned to direct cell growth. One application that is currently being explored for these films is as stem cell carriers for the treatment of limbal stem cell deficiency that results in significant pain and loss of visual acuity.

Surgeons also want ophthalmic adhesives that work quickly to repair corneal tears, and can be handled easily. Existing surgical adhesives are not transparent, and there can be scarring and toxic effects. Dr Domigan’s current work is focused on the tuning of degradation rates to match host cell infiltration, whilst maintaining adequate adhesive strength and curing time for surgical use. This is applied science with a capital A.

Dr Domigan was a MacDiarmid Institute PhD student, under the supervision of Professor Juliet Gerrard at University of Canterbury. Her postdoctoral research was at Tufts University, Boston, in a lab where they studied silk materials, renowned for their strength. When she returned to New Zealand in 2015, she contacted opthalmologists about her ideas for producing synthetic or naturally derived surgical products and implants. The subsequent partnership has involved the challenge of learning about eye anatomy in depth. Dr Domigan is a Health Research Council Emerging Researcher and has an MBIE Smart Ideas Grant.