New hydrogel suitable for eye surgery

Various retinal diseases, such as retinal detachment, require surgery to replace the vitreous. However, while gas and silicone oil have conventionally been used as substitutes for vitreous, these materials do not mix well with water and are not suited for long-term use.According to study co-author Associate Professor Tadamasa Sakai, hydrogels – elastic gels with high water content – are different as they mainly consist of water and are composed of substances similar to those found in soft tissues in our body. However, as Sakai explains, in the past they have also had drawbacks.“The downside of conventional hydrogels is that, after months and years, they start to absorb water and swell, irritate and exert pressure on the surrounding tissues, eventually causing damage,” Sakai said.{{quote-A:R-W:450-Q: Researchers believe it will eventually free patients from having to keep their head stabilised in a face-down position after vitreous surgery }}“We knew that swelling could be avoided by lowering the amount of polymers in the hydrogel, but lowering the concentration too much would require hours for the gels to form, thereby making th impractical for surgery.”To solve this probl, Sakai and his collaborators at the University of Tokyo and the University of Tsukuba developed a hydrogel with a low polymer concentration that could be introduced into a rabbit’s eye as a liquid, but was also capable of gelling within 10 minutes after injection to replace the vitreous.The scientists were able to accelerate the gelation rate by breaking the reaction into two steps: First they mixed two types of four-armed polymers to create highly branched polymer clusters in liquid; then the polymer clusters were prompted to aggregate once they were injected into the eyes.The hydrogel-implanted rabbits showed no signs of side effects, even after 410 days of treatment, suggesting that the body had not rejected the new material. There were also no significant differences in the swelling pressures of hydrogel-treated rabbits compared to those treated only with salt water.“Hydrogels are promising biomaterials, but their physical properties have been difficult to control. We wanted to show that these difficulties can be overcome by designing molecular reactions and I think we’ve been successful,” Sakai said.Researchers believe it will eventually free patients from having to keep their head stabilised in a face-down position after vitreous surgery, a procedure necessary for the currently injected silicone oil or gas bubbles to push the detached retina.The hydrogel’s properties may also make it suitable for treating a wide range of conditions, for example, as a space-filling gel to replace soft tissues damaged by trauma, tumors and degenerative diseases.