Disclosed herein is a method for delivering cells or a therapeutic agent to a tissue site, the method involving (a) combining the cells or therapeutic agent with a soluble collagen to form a cell-collagen or therapeutic agent-collagen solution； and (b) administering the solution to the tissue site, whereby, upon contact with the tissue, the solution is converted to a gel. Also disclosed herein are the use of this method for treating tissue defects, and useful cell-collagen and therapeutic agent-collagen solutions.
