Methods for delivering GFs and cytokines to skin wounds. Direct delivery of rhGFs or cytokines is achieved via topical application or intradermal injection (left), with only short-term bioactivity, due to proteolysis and an ECM not able to support their action. Biomaterial-based delivery is achieved through the incorporation of rhGFs or cytokines into an ECM-like hydrogel, scaffold, sponge, or particle (right) that offers proteolytic protection and structural support for sustained bioactivity. ECM, extracellular matrix; NP, nanoparticles to list of abbreviations; rh, recombinant human. Color images are available online.