Novel Supramolecular Hydrogels as Artificial Vitreous Substitutes

The possibility of employing self-healing gels as potential artificial vitreous substitutes is being explored. Advancement of traditional synthetic hydrogels as vitreous substitutes is hindered by their fragmentation upon injection into the vitreous cavity leading ultimately to inflammation. Preliminary work involved developing first generation self-healing gels, using amphiphilic tri-block copolymers of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PPG-PEG-PPG) as the building block. Eight linear self-healing gels are synthesized by tethering an ureidopyrimidinone system to synthetically modified PPG-PEG-PPG via the formation of a bis-urea as a linker. The reversible nature of the hydrogen bonds permits alteration of their physical properties by changing the environment, yet retaining desirable characteristics. Despite low solubility in water, these polymers demonstrated associating behaviour under the investigated conditions, which is encouraging. Future generations of self-healing gels should involve the selection of a more hydrophilic core and/or star-like polymers to facilitate gel formation and strengthen the network.