UC Irvine

Age-related macular degeneration (AMD) is a leading cause of severe vision loss in the elderly and one of the major contributors to this disease is the structural and functional breakdown of the Bruch’s membrane, and because of this, retinal pigment epithelial (RPE) cells degenerate shortly after. The Bruch’s membrane is viscoelastic in nature and RPE cells are sensitive to those mechanical cues, therefore scaffolds that replicate this behavior may better support RPE health than purely elastic counterparts. Polyethylene glycol (PEG) offers an adjustable, biologically inert platform for this need, however most methods for implementing viscoelasticity into PEG hydrogels rely on complex reactions. This thesis presents a viscoelastic PEG hydrogel made by combining PEG-propionaldehyde and PEG-amine (5 kDa each), which then crosslinks through dynamic imine bonds while also going through physical chain entanglement during gelation. Elastic PEG diacrylate (PEGDA) hydrogels served as controls. Rheology test were performed on these hydrogels and it showed that PEGDA had a frequency independent modulus with no cross over between the G’ and G” values, while the PEG-propionaldehyde/ PEG-amine hydrogel displayed a clear crossover at approximately 0.3-0.5 rad/s, confirming viscoelasticity. Degradation tests were also performed and it showed that hydrogel stability depends on network maturity. This work overall serves as a simplified technique for producing viscoelastic PEG scaffolds for cells requiring a viscoelastic environment, such as RPE cells.