A new highly transparent injectable PHA-based thermogelling vitreous substitute
Transparency is an important criteria to application of biomaterials to the eye, and essential for use as a vitreous substitute. However, there is a lack of understanding on the features of transparent hydrogels and the boundaries of transparency for various hydrogel systems. In this paper, we tune the PHBHx content of biodegradable PHB polyurethane thermogels and show that the amount of hydrophobic PHBHx correlates with hydrogel cloudiness. We find that PHxEP-0.5 hydrogel shows high light transmittance, and suitable gel properties as a vitreous substitute. PHxEP-0.5 hydrogel is able to maintain transparency when implanted into rabbit eyes as opposed to a cloudy gel, and shows negligible inflammation and preservation of retinal structure over 6 months. In conclusion, we show that PHBHx-based thermogels can be tuned for transparency and are biocompatible in the rabbit eye. These results could be instructive for the design of a new generation of injectable transparent vitreous substitutes.