Abstract: The disclosure relates to a composition that is liquid at a temperature below the body temperature of a mammal and that solidifies at or above the body temperature of the mammal. The composition includes a thermally-desolubilizable polymer interspersed with a polymeric component of extracellular matrix and an encapsulated form of an amine compound (preferably an aminated component of extracellular matrix) that is de-encapsulated in the body of the mammal. The polymeric component is able to form covalent bonds with amine moieties in the aminated component, in one or more tissues in the body of the mammal, or both. Upon injection of a liquid suspension of these components into the body of the mammal, the thermally-desolubilizable polymer condenses, entrapping the polymeric component. The polymeric component binds covalently with a tissue in the body, and the aminated component end-caps the remaining reactive moieties of the polymeric component, forming a matrix at the site of injection.