A novel drug delivery system with a collagen-binding domain derived from C. histolyticum collagenase

The extracellular matrix (ECM) is an attractive target for localizing exogenous growth factors and other peptide signaling molecules as therapeutic agents. We have produced fusion proteins consisting of growth factor moieties and a collagen-binding domain (CBD) derived from a bacterial collagenase which we expected to act as an anchor to the collagen fibrils in vivo. The fusion proteins carrying the epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF) at the N-terminal of CBD (CBEGF and CBFGF) tightly bound to insoluble collagen and stimulated the growth of cultured fibroblasts as much as the unfused counterparts. CBEGF, when injected subcutaneously into mice, remained at the sites of injection for up to 10 days, but EGF was not detectable 24 h after injection. Although CBEGF did not exert a growth promoting effect in vivo, CBFGF, but not bFGF, strongly stimulated the DNA synthesis in stromal cells at 5 days and 7 days after injection. CBD may be used as an anchoring unit to produce fusion proteins which are nondiffusible and long-lasting in vivo.