Fibrinogen is an attractive candidate for a wide range of regenerative treatments due to its bioactivity and FDA-approval.
Aim: We therefore sought to modify fibrinogen through covalent attachment of heparin. Heparin is desirable as it binds a significant number of growth factors, and its anti-coagulative properties play a role in limiting thrombotic events.
Methods: Heparin was conjugated to fibrinogen and thereafter quantified. The product was polymerised with thrombin at 37°C and characterised for delivery using rheology for viscoelastic properties, scanning electron microscopy for microstructure, viability assays, and thromboelastograms. Subsequently, growth factor entrapment and release were also assayed with ELISAs. The gel was further assessed in vitro with 3D endothelial spheroid assays.
Results Heparin conjugated fibrin was non-cytotoxic, formed softer and anti-thrombotic gels with 23 ± 5.3 Pa stiffness compared to normal fibrin at 50 ± 4.5 Pa and degraded slower. Furthermore, heparin was able to trap bFGF and VEGF and slow release it over 15 days. Subsequently, it promoted 3D spheroid sprouting in vitro.
Conclusion: A unique method of conjugating heparin to fibrinogen in a manner that maintains fibrinogen polymerisation is presented. It offers a natural and convenient drug delivery vehicle that mimics the extracellular matrix. In vivo evaluation is currently underway for neovascularization and clinical applications.