The therapeutic value of many growth factors is often hindered by the narrow therapeutic index and sustained concentrations required for efficacy. Controlled release approaches provide a valuable tool to achieve these goals; however, growth factor stability must be maintained. Repifermin 1 is a truncated form of fibroblast growth factor-10, also known as keratinocyte growth factor-2, that exhibits promise in wound healing applications; however, controlled release formulation presents a challenge for this labile protein. Taking advantage of the heparin-binding motif of this class of biopharmaceuticals, Repifermin 1 was effectively stabilized and packaged in polyelectrolyte complexes. In the presence of dextran sulfate, the unfolding temperature of this growth factor was increased by $108C as confirmed by a variety of spectroscopic techniques. Dextran sulfate with bound Repifermin 1 was then complexed with several polycations (chitosan, poly-L-lysine, and polyethylenimine) resulting in the formation of $250 nm polyelectrolyte complexes that entrapped the protein with $70-80% efficiency. Release was controlled for more than 10 days and the mitogenic activity of Repifermin 1 on human umbilical cord vascular endothelial cells was significantly enhanced, whereas no effect was noted for free Repifermin 1 .