 Polyethylene glycol (PEG) hydrogels are biocompatible and proven to be tolerated in many tissue types, including the CNS.Mahoney and Anseth formed PEG hydrogels by photopolymerizing methacrylate groups covalently linked to degradable PEG macromers.Hydrogel degradation was monitored over time by measuring mechanical strength (compressive modulus) and average mesh size from swelling ratio data.