Described is a spray-on hydrogel comprising water-soluble PEG polymers that cross-link in situ to form a hydrogel such that the cross-links are reversible. The hydrogel can be useful as a drug delivery composition, wound dressing or surgery adjuvant. Polyethylene glycol polymer and cross-linker solutions are sprayed simultaneously through a common orifice. Cross-linking via formation of thioether or disulfide bonds is initiated upon mixing, providing rapid gelation. The hydrogel components can be derivatized with RGD peptides or analogs thereof to promote retention in/on a body compartment such as the skin, surface of the eye, or a mucosa such as the vaginal mucosa. The cross-links are reversed using a reducing solution enabling easy removal of the hydrogel by dissolution. Processes for preparation of the cross-linker, RGD derivatized PEG and RGD-linked agents are also disclosed.
