PEG300 (Polyethylene glycol 300) is a water-miscible polyether widely used in biochemistry, structural biology, and medicine in addition to pharmaceutical and chemical industries. It serves as a kind of solubilizer, excipient, lubricant, and chemical reagent. PEG300 helps in the formation of hydrogels in situ upon mixing with silk. These PEG–silk hydrogels are of interest for many biomedical applications, such as anti-fouling and anti-adhesion.