How silk implants could help give clear vision
Millions of people around the world suffer from eye diseases that affect vision, including short-sightedness (myopia), blurry vision (presbyopia) and corneal disease. Myopia affects more than 35 % of the European population, while presbyopia affects essentially all individuals over the age of 45. Current treatments include surgery to add tissue or lenses, however these approaches can lead to complications, including rejection, corneal haze or shorter lifespans. No material has yet been found that meets the necessary mechanical properties and is transparent, biocompatible and versatile in order to overcome these challenges. Recent research has explored the use of an innovative material found in nature: the fibres of silkworm cocoons. Silk fibroin has emerged as a useful natural polymer for biomedical purposes. Silk-based biopolymers are biocompatible, stretchy and transparent, and come with fine-tunable properties, all the factors needed for a modern nature-based implant for the eye. Through the SILK-EYE project, which was funded by the European Research Council(opens in new window) (ERC), researchers have pioneered the development of new corneal implants and lenses made from silk. The work involved collaboration with researchers at the Wellman Center for Photomedicine(opens in new window) and Tufts University(opens in new window), and advanced earlier findings from a previous ERC-funded project, PRESBYOPIA, which developed intraocular lenses capable of reshaping under the action of ocular muscles, mimicking the function of a young crystalline lens. “These systems require materials that support both mechanical deformation and efficient light guidance,” explains Susana Marcos, professor of Research at the Spanish National Research Council(opens in new window) (CSIC). “Across these applications, silk fibroin emerged as a compelling platform.”
Creating a fabrication pipeline
Through SILK-EYE, Marcos and her colleagues developed a broad family of silk-fibroin-based materials, along with a complete fabrication pipeline, from cocoons to transparent membranes and inlays, tailored to each application. They designed corneal bandages that are biodegradable and can accelerate wound healing. The team also developed corneal inlays, which are engineered to allow the transport of nutrients while maintaining long-term stability. “These implants are also intended to correct refractive errors through a combination of mechanical response and refractive tuning,” adds Marcos. Beyond fabrication, the project ran extensive material characterisation, cell culture studies, laser-based material processing, and preclinical evaluation in rabbits. “The ultimate objective is clinical translation to humans,” says Marcos. “This will require additional preclinical work, followed by safety and efficacy trials.”
Improving the eyesight of European citizens
Testing showed how the team’s silk-fibroin–based corneal bandages significantly accelerate corneal wound healing and can be secured to the cornea without sutures. The high-silk-content corneal inlays also demonstrate long residency times and strong biocompatibility. Using state-of-the-art lasers, the researchers could also achieve consistent and substantial refractive index changes in their silk membranes. The project also advanced optomechanical designs and enabling systems for accommodating intraocular lenses. Marcos notes several aspects of the silk-based implants that make them highly promising, including ease of production, lower financial costs and greater sustainability, as they degrade naturally in the environment. The team will continue to develop the implants, evaluating the safety and efficacy of corneal implants in collaboration with researchers at the University of Valladolid(opens in new window). Parallel work with researchers at the University of Rochester(opens in new window) in the States, is investigating laser-induced refractive index changes in silk fibroin materials, which could enable fully customised ophthalmic lenses. “The conditions targeted by these implants are highly prevalent,” notes Marcos. “This makes the potential impact of alternative, scalable treatments particularly significant.”
