A novel method for the delivery of growth factor proteins from fibrin matrixes was developed. Nerve growth factor (NGF) fusion proteins contg. an exogenous transglutaminase substrate at the N-terminus of the protein were made recombinantly by E. coli. The NGF fusion proteins were covalently immobilized within fibrin matrixes during coagulation by the transglutaminase Factor XIIIa. Matrix bound NGF was found to enhance neurite extension by up to 50% vs. unmodified fibrin with NGF in the culture medium, and over 350% vs. fibrin without any NGF present. The magnitude of the enhancement of neurite extension depended on the dose of NGF immobilized. These results demonstrate that the NGF fusion protein was available to the cells in an active form even when it was covalently attached to the fibrin matrix. The materials investigated in this study may be useful in promoting peripheral nerve regeneration following transection due to trauma or surgery. This method can also be applied more generally to other growth factors and wound healing models of interest. [on SciFinder (R)]