Engineers from Pohang University of Science and Technology (POSTECH) in South Korea have replicated a structure of the human eye by 3D-printing an artificial cornea.

A team led by mechanical engineer Professor Dong-Woo Cho, collaborating with a range of scientists from across the country, 3D-printed an artificial cornea using a bio-ink made of decellularised corneal stroma and stem cells.

The cornea is the thin outermost layer of the eye that covers the pupil and provides protection from the external environment. The first layer admits light and therefore it needs to be transparent, move as the pupil moves, and have flexibility.

The researchers say that because their printed cornea is made of corneal tissue-derived bio-ink, it is biocompatible. Furthermore, 3D cell-printing technology recapitulates the corneal microenvironment, therefore its transparency is similar to the human cornea.

The human cornea is organised in a lattice pattern of collagen fibrils. The lattice pattern in the cornea is directly associated with its transparency, and many researches have tried to replicate the human cornea.

However, efforts to create an artificial cornea suitable for transplantation have encountered difficulties related, for example, to the use of cytotoxic substances in the body, as well as to producing a device with sufficient transparency and other functionality.

To overcome this challenge, the research team used shear stress generated in the 3D printing to manufacture the corneal lattice pattern and demonstrated that the cornea was biocompatible by using a corneal stroma-derived decellularised extracellular matrix bio-ink.

Throughout the 3D printing process, when ink in the printer passes through the nozzle, frictional force produces shear stress. Professor Cho and his team successfully produced a transparent artificial cornea with the lattice pattern of a human cornea by regulating the shear stress to control the pattern of collagen fibrils.

The research team also observed that the collagen fibrils remodelled along with the printing path create a lattice pattern similar to the structure of native human cornea after 4 weeks in vivo.

Jinah Jang, professor of creative IT convergence engineering at POSTECH, said: “The suggested strategy can achieve the criteria for both transparency and safety of engineered cornea stroma. We believe it will give hope to many patients suffering from cornea-related diseases.”

In the event that an individual has a severely damaged cornea, a corneal transplant is required. However, as of 2018, 2,000 patients throughout South Korea are still waiting for a cornea donation. On average, they wait six years or more for a donation.

For this reason, many scientists have put their efforts in developing an artificial cornea, with the existing artificial cornea using recombinant collagen or made of chemical substances such as synthetic polymer. According to experts, such devices, however, do not incorporate well with the eye or are not transparent after the cornea implant.

The research team behind the 3D printing cornea project include Professor Dong-Wong Cho, Professor Jinah Jang and Ms Hyeonji Kim at POSTECH, collaborating with Professor Hong Kyun Kim of Ophthalmology at Kyungpook National University School of Medicine. A report of their work has been published in Biofabrication.

In October 2018, scientists from China Pharmaceutical University and Southeast University in China developed contact lenses that change colour after releasing drugs into the eye, a visual indicator that could help doctors determine whether a medication is being delivered to its intended treatment site.