Controlled release of substances bound to fibrin-anchors or of DNA

Fibrin sealants have been proposed as depot matrices for substances due to their biocompatibility, advantageous biological properties, and widespread use in wound healing. This study showed possibilities for a continuous and controlled release of pharmaceutically active substances out of a fibrin matrix. Substances of interest were linked to naturally occuring fibrin-anchors, (i) thrombin, (ii) fibronectin, and (iii) DNA. Fibronectin and thrombin bind fibrin by a specific binding moiety and DNA by charge. Fibrin clots were prepared from Tisseel Fibrin Sealant (Baxter AG, Vienna) by mixing 100 mg/ml fibrinogen, the substance of interest, and 4 U/ml of thrombin. Chemical crosslinking of proteins was performed with EDC using standard reaction conditions. Modification of proteins with biotin and PPACK was performed with N-hydroxysuccinimid activated compounds. With fibrin-anchors pharmaceutically active substances, i.e., tumor necrosis factor (TNF), albumin, and plasmid-DNA, were continously released over 10 days. In conclusion, the naturally occuring proteins fibronectin and thrombin with a fibrin binding moiety or DNA can be used as fibrin-anchors.